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Simple hidden sector theories can give rise to interacting dark matter involving multiple particle species and long-range interactions, such as atomic dark matter. These scenarios are highly plausible in their own right, but can be particularly motivated by modern solutions to the Hierarchy Problem such as the Twin Higgs. These dark matter models feature dissipative dynamics and bound state formation, giving rise to complex dynamics at all scales which is only now being explored in detail. I will outline the variety of exciting new astrophysical and cosmological signals that could be generated by such scenarios: formation of mirror stars and their signals in optical, X-ray, gravitational lensing or gravitational wave observations; direct detection of atomic dark matter with dark plasma screening effects in terrestrial experiments or stellar cooling; signals in precision cosmological observables; and combining full MHD N-body simulations of atomic dark matter with measurements of galactic structure to determine the forces active in the dark sector.
Several models that provide solutions to the Standard Model's open problems allow for the possibility of long lived particles (LLPs) with lifetimes, in some cases, in excess of $10^{3}$ seconds. It is proposed that charged LLPs produced at the Large Hadron Collider could interact with the ATLAS detector, eventually coming to rest and decaying. Other LLPs, such as neutral particles, may also exit ATLAS and decay in flight just outside the detector. We propose a low cost scintillating detector to be placed above the ATLAS detector to measure LLP signals as they decay within ATLAS during technical stops and other “beam off” times, thus minimizing Standard Model background. The same detector would provide a decay volume outside of ATLAS to detect LLP decays in flight during normal operation. To illustrate the efficacy of the proposed detector we simulate the production, interaction, and decay of long lived particles within select models.
We analyzed diphoton($e^+e^-$) and dielectron($\gamma\gamma$) invariant mass spectrums in ATLAS to search for periodic resonance signals which are the decay products of clockwork gravitons predicted by the clockwork model. The clockwork model attempts to answer the hierarchy problem through a novel particle-generating mechanism. The name clockwork follows from the mechanics of obtaining a hierarchically larger field from a smaller field, which can address the hierarchical pattern of quark and lepton masses. We are interested in clockwork graviton because it also offers a solution to the naturalness problem of the electroweak scale. There are two undetermined parameters that define the theory, in addition to the graviton, which are the Higgs-curvature $k$, and the 5D fundamental Planck scale $M_5$. Monte Carlo graviton samples with different $(k,M_5)$ are generated with $\textit{Pythia}$ and the detector responses to the graviton are simulated with the transfer method. We included a cascade of decay effect caused by the periodic mass feature, higher mass gravitons decays into lighter mass gravitons, and the process repeats with lighter mass gravitons forming a decay chain if kinematically allowed. A model-dependent $(k,M_5)$ Fourier analysis is performed for the clockwork graviton signals; also a model-independent analysis is performed to search for any deviation from the standard model in the frequency domain. We have set the first exclusion limits for the phase-space $(k,M_5)$ and are prepared to perform the unblinding studies.
The discovery of neutrino oscillations provided evidence of lepton flavour vi- olation. In this work, we carry out the background simulations in the leptoquark framework. Leptoquarks are bosons which carry lepton and baryon numbers, coupling leptons to quarks and mediating charged lepton flavour violation pro- cesses at tree-level. The goal of this work is to study charged lepton flavour violations at the EIC based on the real detector simulations concentrating on three main background events, Charged Current Deep Inelastic Scattering (CC DIS), Neutral Current Deep Inelastic Scattering (NC DIS) and Photoproduc- tion. The plan is to simulate higher statistics of these background events by using the Djangoh MC event generator for neutral and charged currents and Pythia8 for photoproduction while applying selection criteria on higher statis- tical input events compared to what was done before with ECCE.
Distinguishing between signal events and background events is the main issue in the integrating measurments of nuclear physics and particle physics experiments. Signal corrections can be accomplished either theoretically or experimentally. In the experimental approaches, a set of detectors called background detectors is implemented. In background detectors, the majority of particles generating the main signal are blocked and particles causing the background are detected.
The Measurement of a Lepton Lepton Electroweak Reaction (MOLLER) is an experiment that requires signal corrections to achieve precise measurements of parity-violating asymmetry (A_PV). MOLLER will measure A_PV in the scattering of longitudinally-polarized electrons from unpolarized target electrons to an accuracy of 2.4% using an 11 GeV beam in Hall A at Thomas Jefferson National Accelerator Facility (JLab). Required experimental corrections arise from background processes that are characterized by fractional dilution factors and background asymmetries. Pion dilution factors and asymmetries are a significant contribution to the experimental correction and will be measured in dedicated pion detectors optimized to maximize the signal from pions.
This talk will review the MOLLER experiment and detail the optimization processes for the pion detector system. It is followed by the verification of the results from the simulation through the cosmic test and a beam test at MAMI-B microtron at Mainz, Germany. We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC).
The US-based future Electron-Ion Collider is a novel tool to address some of the unexplained physics of nucleons, including how their constituents contribute to their properties like spin, mass, etc., by colliding highly polarized electron beams with polarized beams of protons or ions. The high-energy interactions between the electrons and protons help in understanding the internal structure of the proton and one needs to know the polarization of the electron beam used. This is possible using a Compton polarimeter, facilitating Compton scattering of this electron beam with a circularly polarized laser beam. The physical quantities measured in the scattering will correlate to the degree of polarization of the electron beam. My research involves the simulation of transverse and longitudinal polarization of the electron beam with more focus on the effect of transverse beam smearing on transverse polarization measurement. I also have extended the work to evaluate beam synchrotron radiation at different locations at the interaction point in the polarimeter. In this talk, I will be presenting some of the results obtained using the Monte Carlo method in Geant4 simulations.
I acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) for this research.
I will give an overview of pseudo-Dirac dark matter, a scenario where a small Majorana mass splits charged Dirac dark matter into two nearly degenerate states. A longtime favourite of model-builders, this dark matter candidate has a rich phenomenology that still has yet to be fully characterized. I will discuss a few mechanisms for producing this kind of dark matter in the early universe, and will show various ways in which this candidate will manifest itself in the subsequent cosmology, astrophysical systems, and terrestrial experiments.
There is strong evidence for the existence of Dark Matter. One possible form of Dark Matter is strongly self-interacting Dark Matter, or Strongly Interacting Massive Particles (SIMP), modelled after Quantum Chromodynamics (QCD). It should also be noted that, to date, no direct detection of any kind of dark matter has been made. Direct detection of dark matter at accelerators is a high priority and is part of the program for the MoEDAL experiment located at the LHC. The MAPP extension to the MoEDAL experiment focuses on searching for Mili-Charged Particles (mCPs), and Long-Lived Particles (LLP). In this talk, we will discuss meson-like SIMP, and its potential detectability at the MoEDAL MAPP experiment. In order to model this dark matter, we construct a Lagrangian describing dark-pions using an approach inspired by Chiral Perturbation theory, an effective field theory of QCD. To couple our model to the Standard Model, we include a vector portal term which kinetically mixes our dark gauge fields with standard model gauge fields. As part of our model, we also include a Wess-Zumino-Witten term, this term is important to control the overproduction of strongly self-interacting Dark Matter in the early universe. We focus on two processes: a Drell-Yan process involving a dark gauge field, which produces a pair of dark-pions, and photofusion of two dark photons to three dark-pions. Due to kinetic mixing, these dark-pions will have an effective electric charge that is a small fraction of that of the electron.
Many particle and rare-event search detectors use liquid scintillators as the detection method. A popular candidate for scintillation fluids are noble elements such as Liquid Argon (LAr). LAr detectors typically store their scintillators inside an acrylic vessel, which can be coated with various materials. A common coating is 1,1,4,4-tetraphenyl-1,3-butadiene (TPB) which is a wavelength shifter that converts the ultraviolet (UV) scintillation into visible wavelengths that are detectable by the photodetectors, such as photomultiplier tubes. In the DarkSide-20K experiment clevios is an another coating on the acrylic, and will act as the electrodes. Acrylic is known to fluoresce in visible wavelengths when excited by UV light, and previous studies indicate that the clevios will also fluoresce under similar conditions, both of which could be a source of background in the experiment. The amount of light received by the photodetectors from the fluorescence can be compared to TPB when they are excited by the same wavelength and intensity of UV light. This comparison produces the relative light yield of acrylic or clevios to TPB. The fluorescence properties of these materials are measured at various temperatures between 300K and 4K. This includes all of the operating temperatures of noble liquids, with particular interest in 87K as that is the operating temperature of LAr, which is the liquid scintillator used in DarkSide-20k. The fluorescence properties are determined by exciting the acrylic using external UV sources to mimic scintillation events. We present the status of the study to determine the fluorescence of clevios, comparing it to standard materials used in liquid scintillators, such as TPB. These results will show how much clevios will contribute to background signals that are found in future liquid scintillator detectors.
The PICO collaboration aims to use superheated bubble chambers for the direct detection of dark matter, particularly in the spin-dependent WIMP-proton regime. PICO-40L is the current generation dark matter detector that is currently in the final stages of construction 2km underground at SNOLAB. It will be anticipating first commissioning results and early physics results early next year. The results from PICO-40L are expected to lead to a new world leading limit or discovery of dark matter. They will also inform the design and operation of a much larger next generation detector, PICO-500, currently in the design & fabrication phase. This presentation will be a brief overview on the current status of the PICO experiment and the first physics results.
The NEWS-G experiment searches for low-mass dark matter candidates at SNOLAB in Sudbury, Ontario. The direct dark matter search is performed using a spherical proportional counter (SPC) filled with light atomic mass gases. NEWS-G3 is a proposed experiment that employs the same technology as the NEWS-G experiment to search for coherent elastic neutrino-nucleus scattering (CEνNS) at a nuclear reactor. NEWS-G3 will consist of a 60-cm high purity copper SPC implemented in a compact shield consisting of many different layers of material. One layer of shielding is an active muon veto system consisting of plastic scintillators coupled with a photomultiplier tube (PMT). In this presentation, I will present the current status of the NEWS-G3 experiment at Queen’s University and the commissioning of the muon veto system.
Many important questions in Quantum Chromodynamics (QCD) remain unanswered, despite decades of investigation. For example, we cannot adequately explain how the fundamental properties (mass, spin) of objects such as the proton and neutron emerge from their constituent quarks and gluons. Interactions and structure in nuclear matter are intricately connected, the observed properties of composite objects emerge from this complex system. To attempt to understand these complex, dynamic systems requires a facility with a unique set of capabilities, the upcoming Electron-Ion Collider (EIC). The EIC is the only new accelerator facility scheduled to be built anywhere in the world in the coming decade. In this talk, I will outline the unique features of this facility and the fundamental questions that it seeks to answer, with a focus on Canadian contributions to this upcoming facility.
The Electron-Ion Collider (EIC) is a new US$2 billion high-luminosity accelerator that is expected to be operational at Brookhaven National Laboratory, USA at the beginning of the next decade. One of the main goals of the EIC is to understand the origin of hadronic mass, this is the majority of visible mass (>99%) in the universe. From the little that we understand, we know that the mass of these systems is intricately connected to their internal structure. To understand this structure, and therefore these mass generation mechanisms, we can examine one of the simplest hadronic systems we know of, mesons. My research work involves the study of light mesons (in particular K+) through Deep Exclusive Meson Production (DEMP) reactions. I have recently upgraded a DEMP [1] event generator to investigate K+ structure studies at the EIC. In this talk, I will present an update on these ongoing K+ studies and the modifications to the DEMP event generator that were required to conduct this study.
[1] https://github.com/JeffersonLab/DEMPGen.
The Measurement Of a Lepton Lepton Electroweak Reaction (MOLLER) experiment anticipates new dynamics beyond the standard model. The measurements are acquired by the scattering of longitudinally polarized electrons off the unpolarized electrons using a set of detectors in Hall A at Thomas Jefferson National Accelerator Facility (JLab) in Newport News, Virginia USA. In the present study, the ability of High Voltage Monolithic Active Pixel Sensors (HVMAPS) in the Hall A’s Compton polarimeter is investigated to monitor the scattered electron profile. Monolithic active pixel sensors require an in-vacuum operation to allow low-momentum particles at high rates. To prevent damage, the electronics necessitate dissipating the heat and require a cooling system. The temperature measurement of the HVMAPS in vacuum is essential to understand the thermal properties of the pixel detector and cooling needs. This talk will review the continuous efforts towards the cooling strategies, structure modification, and other changes required to achieve in-vacuum operation. We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC).
The KaonLT/PionLT Collaboration probes hadron structure by measuring deep exclusive meson production reactions at Jefferson Lab. A set of high momentum, high resolution spectrometers in Hall C allow for precision measurements of cross sections at different kinematics, from which form factors and other observables can be extracted. One possible measurement from these reactions is the beam single-spin asymmetry. This asymmetry measures the fractional difference in yield caused by an electron of positive or negative helicity, and is caused by interference between longitudinally and transversely polarized virtual photons. Measuring the asymmetry probes the Generalized Parton Distributions (GPDs) of the proton, which describe its three-dimensional parton and spin structure. In this work, the asymmetry is studied for the $p + e \rightarrow e’+ \pi + n$ data from the recent KaonLT experiment. The asymmetry is calculated for a photon virtuality $Q^2$ in the range between 2 and 5.5 GeV$^2$, above the resonance region ($W$>2 GeV), and the dependence of the asymmetry on the four-momentum transfer to the target $t$ is determined. These results are then compared to theoretical models to determine what information can be extracted about the GPDs of the proton.
In perturbative QCD, processes involving quark scattering provide the simplest way of studying non-Abelian scattering amplitudes. To that end, in this talk I will discuss our calculation for the Form Factor of the Higgs boson production via light quark mediated Gluon Fusion process in the high energy/small quark mass limit, where the leading contribution comes in the form of large double logarithms for each power of the strong coupling constant (α_s). We reproduced the leading coefficient (Next-to-Leading order in quark mass (m_q)) for the asymptotic expansion of the form factor in the high energy approximation; and extended the analysis to next coefficient which is at Next-to-Next-to-Leading order (O(m_q^3)). Three distinct sources of diagrams contribute to this coefficient at this order; the complete analytic result for which is presented at three loops. We also present all order analysis in the large-N_c limit of QCD as well as for the opposite Abelian limit. Our results provide a universal estimate of the light quark effects at the higher orders for both the Higgs boson production and decay processes.
Deep Inelastic Scattering (DIS) is described by an exchange of virtual photons or, at high energies, the $Z^0$. The distinctive characteristic of DIS in contrast to many processes (such as $pp$ at the LHC or $pA$ at the RHIC) is that the kinematics are precisely computable from the leptonic (and hadronic) final state at all orders. DIS reconstruction has a strong dependence on the collision reconstruction quality and the underlying detector resolutions. The classical methods are an option for reconstruction with certain limitations, such as higher order QED radiation effects. Our approach is a neural network method for reconstruction which introduces smaller systematic errors in deep-inelastic scattering, since it has the advantage of weighting classical reconstructions and effectively utilizing information all over the available phasespace. This has been previously studied for the ZEUS experiment and applied to inclusive measurements with impressive results. The study involves using EIC simulations and collider data from ZEUS to apply the new method on the EPIC detector and extend it to exclusive measurements, which will be a novel approach.
SNOLAB is an epicenter of global astroparticle physics and underground science discovery and research. As one of the deepest, cleanest underground laboratory in the world, with first-rate scientists and staff, it is a location of choice for cutting edge experiments. In this talk I will highlight some of the exciting research conducted at SNOLAB and discuss potential future research directions.
The SuperCDMS SNOLAB experiment is a next-generation direct detection dark matter search experiment with an anticipated world-leading sensitivity to particles with masses $\leq 10 \text{ GeV/c}^2$. The experiment is currently under construction at SNOLAB in Sudbury, Ontario. The unique facility, located 2 km underground, offers abundant shielding against cosmic rays. The SuperCDMS experiment requires a low background environment. All materials surrounding the experiment are assayed as they could contain impurities that can decay radioactively and cause an interaction within the detectors. As a result, various isotopes in these enveloping materials will have their expected background simulated and estimated. Furthermore, contributions from neutrinos and cosmic rays whose spectra are calculated analytically can be taken into account. Background Explorer is a python/web toolkit used for book-keeping background estimations for the SuperCDMS experiment as well as other experiments, including the Cryogenic Underground TEst facility (CUTE) at SNOLAB and the Deep Underground Neutrino Experiment (DUNE). Background Explorer takes an input of components, simulation datasets, and assay data to construct background spectra and display results in a user-friendly web interface. This presentation will demonstrate the functionality of Background Explorer V2 and its validation against the previously estimated backgrounds for SuperCDMS.
As part of the Dark Matter search by SuperCDMS at SNOLAB, HVeV detectors are used to provide a mechanism of detecting eV-scale energies. HVeV detectors are typically made of high-purity silicon operating with a high bias voltage at sub-K temperatures. An excitation to the silicon generates electron/hole pairs that drift due to the bias voltage. The phonons produced by the drift are expected to be quantized to the fixed voltage and distance traveled by the electron/hole pair. However, statistical randomness and impurities in the silicon add additional artifacts that need to be considered. These include detector resolution and probabilities for impact ionization and charge trapping. Additionally, LED calibrations introduce additional artifacts such as non-quantized heating. We look at some of the potential explanations for this heating, and how they may affect previous and future runs at SNOLAB.
In the Fall of 2019, the NEWS-G experiment used its latest detector, a 140 cm diameter Spherical Proportional Counter (SPC) to search for low-mass dark matter at the Laboratoire souterrain de Modane (LSM), in France. Having the sphere filled with pure methane, hydrogen was used as the target to produce new limits on the spin-dependent cross-section around masses of 1 GeV.
This talk will first describe the commissioning at the LSM with the shielding used, the SPC detection principle and the new multi-anode sensor. It will then focus on the energy calibration using a UV laser and argon-37, as well as the background discrimination methods to remove alpha-induced events and electronic spike signals. The talk will conclude with a presentation of recent results from NEWS-G and the status of the current commissioning of the detector at SNOLAB.
In this talk I will present preliminary results regarding the application of machine learning techniques for noise removal on signals from spherical proportional counters (SPCs) with the NEWS-G experiment. In SPC detectors, a primary ionization, created by a particle interacting with the gas, drifts towards a central anode. When ions approach the anode, the electric field becomes strong enough to trigger secondary ionizations, resulting in an amplified detector signal. Evaluation of these techniques include tests on simulated pulses with added noise, and quantifying model effects on physics goals such as primary ion counting and energy resolution. Successful implementation of this technique will reduce errors on event measurements (energy, drift time, etc.) and lower the analysis threshold, thereby enabling the experiment to search for lower mass dark matter events.
The TUCAN collaboration aims to make a measurement of the neutron electric dipole moment (nEDM) with a precision of 10-27 e cm, an order of magnitude improvement over the current best limit. A non-zero nEDM would be explicit evidence for CP violation in the Standard Model. This, in turn, contributes to solving the longstanding baryon asymmetry problem. Such a measurement requires an immense effort with careful coordination between many different subsystems. This talk will introduce how the nEDM measurement is conducted, the challenges involved, how these subsystems work together to overcome these challenges, and the current state of these systems at TRIUMF.
The TUCAN EDM experiment at TRIUMF will use polarized, ultracold neutrons (UCNs) to search for the neutron electric dipole moment (nEDM). The discovery of a permanent nEDM would indicate the violation of time reversal symmetry, and thus charge-parity symmetry (given the CPT theorem). This would point to physics beyond the Standard Model of Particle Physics. To achieve the projected sensitivity of the experiment of $1 \cdot 10^{-27}e$cm, a stable and homogeneous magnetic field is required in the inner most experiment region. This is mainly achieved with the use of a magnetically shielded room (MSR). To preserve the polarization of the neutrons between the UCN source and the MSR, magnetic guiding fields must be applied throughout the neutron guides between these two sections. Any losses in neutron polarization will directly affect the statistical sensitivity of the nEDM search. In this presentation I will outline the requirements of the guiding fields based on adiabatic spin transport theory and show my current work towards designing and prototyping this critical subsystem.
The Multi-Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS) is a novel approach in performing high-resolution collinear laser spectroscopy (CLS) in a multi-reflection time-of-flight (MR-ToF) device. By trapping a 30-keV ion beam in-between the MR-ToF’s electrostatic mirrors and revolving it around a few thousand times through an optical detection region (ODR), significant gains in experimental sensitivity can be achieved compared to a single passage in conventional CLS. This increase will allow for studying exotic radionuclides that are produced with low yields at radioactive ion beam facilities such as ISOLDE at CERN or ISAC and ARIEL at TRIUMF, thus opening a new region of the nuclear chart to CLS experiments.
In order to fully benefit from the MIRACLS approach, the MR-ToF device requires cooled ion bunches with strict emittance requirements. This necessitates the use of a dedicated Paul trap tailored to match ion-bunch properties to the MR-ToF requirements.
In this presentation we will describe the MIRACLS concept, its science goals, and its current status with an emphasis on the recent commissioning of its Paul trap. Experimentally, the Paul trap is shown to provide ion bunches with temporal widths of 123 ns (FWHM), well matched to perform highly sensitive CLS of exotic radionuclides in the MIRACLS MR-ToF device.
As the heaviest known fundamental particle, the top quark plays a special role in many theories of new physics beyond the Standard Model. Reconstruction of top anti-top pair production to the best possible resolution is therefore crucial to enhancing our sensitivity to Beyond Standard Model effects in precision measurements and searches at the Large Hadron Collider (LHC), from improved mass resolutions for bump hunting to more diagonal unfolding matrices for differential cross-section measurements. As such, we’ve designed a deep neural network (TRecNet) that infers the four-vectors of the top and anti-top quarks from detector-level decay products in the semi-leptonic decay channel. The performance of TRecNet and several slight variations of the network are compared to traditional top reconstruction algorithms based on likelihood fits and are shown to improve upon both reconstruction efficiency and resolution.
The symmetry between matter and antimatter is one of the great unresolved questions in fundamental physics, as it underscores the discrepancies between the Standard Model and cosmological observations. Many experiments have been performed to compare the properties of antimatter to matter at great precision. However, gravitation has so far eluded these efforts due to the difficulty measuring such a tenuous force acting on energetic anti-particles. The advent of cryogenic, trapped antihydrogen atoms, first produced by the ALPHA experiment, has opened a new possibility.
The ALPHA-g experiment at CERN, which has just completed its first year of physics campaign in 2022, is designed to precisely measure the gravitational mass of antihydrogen atoms. The anti-atoms are confined in a vertical magnetic minimum trap, and released through precisely controlled openings in the field, at the trap’s bottom and top. Anti-atoms preferentially escape through the opening with the lowest potential energy, which is a sum of magnetic and gravitational potentials. By observing the magnetic field at which anti-atoms escape equally through both openings, their gravitational mass can be deduced.
Precise measurement of antihydrogen gravity hinges on controlling the trap field. For a 1% precision in gravity measurement, the field need to be controlled to within 1e-5 T in a O(1 T)-deep trap. Extensive effort is therefore expended in magnet design, construction and magnetometry to achieve such precision.
This talk will give an overview of ALPHA-g’s physics methodology, magnetic trap design and simulation results which predict the precision achievable in ALPHA-g.
ALPHA-g has completed a successful run in 2022 in the pursuit of measuring the gravitational mass of antihydrogen. This apparatus was designed to test whether antimatter follows Einstein’s Weak Equivalence Principle (WEP), where the acceleration due to gravity that a body experiences is independent of its structure or composition. A measurement of the gravitational mass of antimatter has never been done before, as previous experiments used charged particles, which meant the experiments were dominated by electromagnetic forces. The ALPHA-g apparatus uses electrically neutral antihydrogen atoms produced in a vertical Penning-Malmberg trap and trapped in a magnetic minimum trap. By measuring the antihydrogen annihilation positions after a controlled magnetic release of the atoms the gravitational mass of antihydrogen can be determined. Annihilation positions are reconstructed with a radial time projection chamber (rTPC) surrounding the trapping volume.
To accurately determine vertical annihilation positions, precise detector calibrations are needed. A laser calibration system was developed and used to gather drift time data in the rTPC, which results in vertical position information, and can be used to monitor changes in pressure, temperature, and magnetic field. In particular, we can calculate the Lorentz angle using the drift time, which is then used in reconstruction to accurately determine the annihilation positions. This results in precise measurements for the gravitational mass of antihydrogen.
In this talk I will discuss the laser calibration system for the rTPC and the results of the drift time data taken over the course of the 2022 run period. I will further discuss how these results are used in the reconstruction of antihydrogen annihilations.
Antimatter lies at the heart of many of the universe’s unanswered questions, but direct study of antimatter structures is technically difficult. ALPHA-g promises the first direct free-fall observation of the Earth’s gravitational force acting on anti-atoms, by precisely recording the annihilation positions of anti-hydrogen atoms after a controlled release from a magnetic trap. Reconstructing these annihilations is a unique challenge requiring a specialized detector system. Furthermore, due to low antihydrogen yield and the slow release timescale, the cosmic ray background provides a an additional obstacle which requires a secondary detector system to overcome. I describe the implementation of the ALPHA-g time projection chamber and “barrel scintillator” cosmic ray veto, and showcase their ability to meet these goals.
The Antihydrogen Laser Physics Apparatus (ALPHA) collaboration uses low energy antiprotons to produce, trap, and study the bound state of an antiproton and positron, antihydrogen. Hydrogen has been studied extensively through history and has many physical properties known to a high precision experimentally and theoretically. Therefore, comparisons between hydrogen and its antimatter equivalent offer highly sensitive tests of many fundamental symmetries. In a new venture, ALPHAg, the collaboration is attempting to observe the effect of Earth’s gravity on antihydrogen through a controlled magnetic release.
ALPHAg will store low field seeking antihydrogen in a vertical magnetic minima trap, two short solenoids providing vertical confinement will then be slowly ramped down. Due to the difference in height between the two solenoids the trapping potential is different at each end by mg∆h, given this potential difference antihydrogen will “fall” in a direction biased by g and annihilate. Since this potential difference is equivalent to a ~ 4.5 Gauss magnetic field variation, and with a background field changing from 17000 Gauss to 10000 Gauss during release, it is clear this is only achievable through careful design, control, and measurement of magnetic fields.
I will introduce a technique developed in ALPHA that determines the in situ magnetic fields by measuring the cyclotron frequency of an electron plasma. I will then lay out the necessary steps to display control and understanding of the magnetic environment by showing results of extensive mapping of the on-axis field of several magnets, and characterisations of field drifts in the experiment. Finally, I will discuss the prospects and challenges related to making a measurement in a dynamic magnetic field in preparation for a gravity measurement.
It has been known for many years that an electron and its antiparticle, the positron, may together form a metastable hydrogen-like atom, known as positronium or Ps. In 1946, Wheeler speculated that two Ps atoms may combine to form the positronium molecule (Ps$_2$) stable with respect to auto-dissociation. In 2007, the existence of Ps$_2$ was confirmed experimentally by David Cassidy and? Allen Mills at the University of California.
I will present a determination of the radiation-less and two photon decay rates of Ps$_2$. We employ a simple technique to compute the amplitudes and write the products of spinors in terms of gamma matrices, which reduces the computational time and provides more insights into the physics of a reaction. After testing the method with the well known problem of para-positronium (p-Ps) and positronium ion (Ps$^{-1}$), I will present decay rate calculation of Ps$_2\to e^-e^+$ and Ps$_2\to \gamma \gamma$, and demonstrate that the previously published results are incorrect.
Nuclei away from the line of stability have been found to demonstrate behavior that is inconsistent with the traditional magic numbers of the spherical shell model. This has led to the concept of the evolution of nuclear shell structure in exotic nuclei, and the neutron-rich calcium isotopes are a key testing ground of these theories; there have been conflicting results from various experiments as to the true nature of a sub-shell closure for neutron-rich nuclei around $^{52}$Ca. In November of 2019, an experiment was performed at the ISAC facility of TRIUMF; $^{52}$K, $^{53}$K, and $^{54}$K were delivered to the GRIFFIN gamma-ray spectrometer paired with the SCEPTAR and the ZDS ancillary detectors for beta-tagging, as well as DESCANT for neutron-tagging. Using this powerful combination of detectors, we combine the results to construct level schemes for the isotopes populated in the subsequent beta-decay. Preliminary results from the analysis of the gamma, beta, and neutron spectra will be presented and discussed in the context of shell model calculations in neutron-rich nuclei.
The term ‘island of inversion’ is used to refer to a region of the nuclear landscape in which deformed intruder configurations dominate nuclear ground states over the spherical configurations naively expected from the shell model. Theoretical models of the inversion mechanism can be tested through detailed studies of the nuclear structure of transitional nuclei, in which the normal and intruder configurations compete. One such transition occurs along the N = 20 isotones, where neutron-rich $^{32}$Mg is known to have a deformed ground-state configuration, while $^{34}$Si displays a normal ground state configuration. Previous studies of the intermediate N = 20 isotone $^{33}$Al have yielded conflicting results regarding its structure. In the present work, $^{33}$Al was studied through the $\beta$-decay of $^{33}$Mg to clarify these discrepancies. A low-energy radioactive beam of $^{33}$Mg was delivered at a rate of 10e3 ions/s by the Isotope Separator and Accelerator (ISAC-I) facility at TRIUMF. Data were collected with the GRIFFIN high-purity germanium $\gamma$-ray spectrometer coupled with the SCEPTAR plastic scintillator array and the ZDS (zero degree) $\beta$ particle detectors. The high efficiency of the GRIFFIN detector provided new $\gamma$-$\gamma$ coincidences to elucidate the excited state structure of $^{33}$Al, and the capability of GRIFFIN to detect weak transitions has provided more complete $\beta$-decay branching ratios for the decay chain. Results following the $\beta$-decay of neutron-rich $^{33}$Mg are presented. Approximately 10$^{8}$ $\gamma$-$\gamma$ coincidences were used to build level schemes for $^{33}$Al and $^{32}$Al. $\gamma$-gated time spectra were fit to calculate half-lives of $^{33}$Mg, $^{32, 33}$Al and $^{33}$Si. $\beta$ counts were used to calculate $\beta$-feeding to the levels of the scheme of $^{33}$Al, including the ground state. Clarification of $^{33}$Al level scheme, and expansion of $^{32}$Al are presented.
Clustering in nuclei provides an alternative description to their nuclear structure in addition to the Nuclear Shell Model. Although alpha ($^4$He nucleus) clusters are widely accepted to be essential to the understanding of the structure of light nuclei, such as the Hoyle state in $^{12}$C, it was experimentally observed in heavy nuclei only recently in $^{212}$Po. The observation showed that $^{212}$Po had mixed shell and cluster configurations, where the structure of $^{212}$Po could be explained by an alpha cluster coupled to the doubly-magic $^{208}$Pb core. In particular, the clustering structure resulted in enhanced $E1$ (electric dipole) transitions from non-natural parity states, which were measured using gamma-ray spectroscopy.
Another recent experiment at INFN Legnaro observed an excess cross section for the parasitic $^{122}$Sn($^{13}$C,$^9$Be)$^{126}$Te reaction. Because the fusion-evaporation cross section for this channel was negligible in PACE4 calculations, the $^{126}$Te was likely populated through an alpha transfer reaction which suggests alpha-clustering in its structure. In this experiment gamma rays were detected with the GALILEO array which is composed of 25 Compton-suppressed HPGe detectors while charged particles with particle identification were detected in the EUCLIDES $E-\Delta E$ $4\pi$ Si-ball array. Gamma-ray spectroscopy with coincidence techniques, such as particle-particle, particle-gamma, and gamma-gamma, is underway to extract previously unobserved transitions and levels in $^{126}$Te from this data set. Preliminary results from the Legnaro data, together with plans for a future experiment, will be presented and discussed.
Nuclear theories often operate under the assumption that the strong nuclear force is charge independent. As a result, it is expected that mirror nuclei, which are identical under the exchange of total number of protons and neutrons, will have similar nuclear structures when Coulombic contributions are considered. Under the assumption of charge dependence, protons and neutrons are grouped together as nucleons which differ only by their isospin quantum number. However, the charge dependence of the strong nuclear force creates isospin non-conserving interactions which give rise to quantities like Mirror Energy Differences (MED) in analogous excited states for mirror nuclei which cannot be accounted for by Coulombic forces. Building a deeper understanding of isospin non-conserving interactions and how they affect nuclear structure will allow for more robust predictive powers in nuclear theories.
In order to explore the charge dependence of the strong force, a stable 20Ne beam experiment to produce 55Co was conducted at TRIUMF, Canada’s national particle accelerator centre, with a complimentary radioactive 21Na beam experiment proposed for production of 55Ni. These experiments are conducted using TRIUMF’s TIGRESS for gamma-rays, SFU’s TIGRESS Integrated Plunger (TIP) for charged particle detection, 40Ca targetry, and the Doppler-Shift Attenuation Method (DSAM). The 55Ni experiment will also utilize TRIUMF’s ElectroMagnetic Mass Analyzer (EMMA) for measurement of the A, Z, and energy of residual nuclei to enhance selectivity of reaction channels.
This talk will discuss how the 55Co experiment was conducted, the preliminary analysis of the resulting data set, as well as the lessons that will be carried forward for the 55Ni experiment. In addition to investigating the charge dependence of the strong interaction, this data will be utilized to explore the f7/2 hole configurations in 56Ni and electromagnetic transition rates for excited states of 55Ni and 55Co.
Neutron rich Mg isotopes far from stability belong to a region known as the island of inversion where the single particle description of the shell model breaks down, and the predicted configuration of the nuclear states becomes inverted. Nuclei in this region also exhibit collective behaviour in which multiple particle interactions play a significant role in nuclear matrix elements. These matrix elements can be studied through electromagnetic transition rate measurements, which allow for tests of theoretical models using the well-understood electromagnetic transition operators.
In-beam reaction experiments performed at TRIUMF, Canada's particle accelerator centre, allow for precise measurements of nuclei far from stability. Using TIGRESS in conjunction with the TIGRESS Integrated Plunger (TIP) allows for the implementation of Doppler shift techniques to measure transition rates in excited states of nuclei produced in low cross section reactions.
In June 2021, an experiment was performed using TIGRESS and TIP to measure excited state lifetimes in 28Mg using both the Doppler Shift Attenuation and Recoil Distance Methods to be sensitive to both short- and longer-lived states. $^{28}$Mg nuclei were populated using the $^{12}$C($^{18}$O,2p) fusion-evaporation reaction, with charged particles detected using the TIP CsI(Tl) ball, and gamma rays detected using TIGRESS.
Event reconstruction using detector-specific time windows were applied to remove uncorrelated background, while particle identification of light-charged ions was performed using offline fitting of CsI(Tl) waveforms taken during data collection. The resulting spectra demonstrate the successful separation of reaction channels by particle content, essential for studying $^{28}$Mg, as well as show clear evidence of the Doppler effects used to measure excited state lifetimes. The current status of data analysis and the impacts on nuclear physics will be discussed in this talk.
The nucleus, made up of protons and neutrons, exhibits a shell-like structure consisting of orbitals described by quantum mechanics. This has been demonstrated by extensive experimental observables, which reveal that nuclei possessing specific "magic numbers" of neutrons or protons exhibit particular characteristics well described in the nuclear shell model. The tin isotopes, with a closed proton shell at Z=50, are an ideal testing ground for shell model calculations as the isotopic range extends from the doubly-magic 100Sn through 132Sn. The singly-magic nucleus 114Sn, with N=64, is situated in the neutron mid-shell between the N=50 and N=82 magic numbers. The known even-even isotopes of tin are described as possessing a spherical shape in their ground state, however, those isotopes situated in the neutron mid-shell gap also exhibit excited states with properties characteristic of deformed shapes. This phenomenon is also known as shape coexistence. Here the deformed shape arises via 2-particle 2-hole excitation across the Z=50 proton shell gap. This deformed shape gives rise to rotational intruder-bands identified by excited 0+ states presenting at low excitation energies. A recent experimental study of 116Sn suggested a reevaluation of the properties of these intruder bands, while key information on 114Sn remains missing. To investigate the characteristics of these intruder bands, the competing beta-decay and electron capture of 114Sb was exploited to populate excited states in 114Sn at TRIUMF's ISAC facility in 2019. The decay to excited states and subsequent decays by gamma-ray emission were measured using the GRIFFIN spectrometer and its suite of ancillary detectors. The experiment pursued a more in-depth understanding of the intruder configurations and their band-heads in 114Sn with an intention to draw parallels to the recent findings in the other mid-shell even-even tin isotopes. Here, the current state of analysis and recent findings will be presented.
Ever since the first measurements were made of these ghostly particles, neutrinos have been a constant fascination for physicists due to their unusual properties. One such peculiarity is that neutrinos can seemingly change flavours as they propagate — a phenomenon known as neutrino oscillation. The oscillation probabilities are determined by a set of fundamental parameters in the Standard Model. Decades of neutrino experiments designed to probe these parameters have narrowed down much of the phase space, yet many unanswered questions remain: Is there CP-violation in the lepton sector? Which neutrino is the lightest? Are there neutrinos beyond the three generations? The answers to these questions may hold the key to discovering physics beyond the Standard Model and understanding our universe, but answering them requires detectors much more powerful than those currently in operation. The successor of the T2K and Super-Kamiokande experiments, Hyper-Kamiokande, is a next generation experiment with a 260 kiloton water Cherenkov far detector, a more powerful neutrino beam and more capable near detectors. It has a broad and ambitious physics program which includes probing the last unknown neutrino oscillation parameters and the precision measurement of neutrino mixing. In this talk, I will begin with a brief introduction of neutrino oscillations and the history of discoveries. I will then describe the Hyper-Kamiokande experiment, its current progress and its physics potentials, and the challenges that must be overcome in order to realize them.
The nEXO experiment is a proposed neutrinoless double beta decay (0$\nu\beta\beta$) search in the isotope $^{136}$Xe. 0$\nu\beta\beta$ is a lepton number violating process, and a positive observation of this decay mode in any isotope would be a direct observation of physics beyond the standard model. Anticipated to be located 2 km underground at SNOLAB, nEXO aims to discover the Majorana nature of neutrinos with a half-life sensitivity to 0$\nu\beta\beta$ exceeding $10^{28}$ years at the 90% confidence level. To reach this sensitivity goal, nEXO employs 5 tonnes of liquid xenon in a time projection chamber (TPC), and performs a multi-parameter fit to the dataset including event-level information on: the total energy deposited in the xenon, the position of energy deposits, and the topology of detected ionization clouds.
Stringent radiopurity requirements necessitate a 1.5 kilotonne water shield in order to reduce background contributions from ambient external radiation entering the TPC. Photomultiplier tubes (PMTs) instrumented inside the water shield tank will measure the Cherenkov light from passing atmospheric muons and other secondary particles to allow the vetoing of so-called cosmogenic backgrounds from the 0$\nu\beta\beta$ dataset; this active shield is referred to as the Outer Detector.
This talk will overview nEXO’s Outer Detector, cosmogenic background mitigation strategies, and introduce a GPU-accelerated ray-tracing software (Chroma) to simulate Cherenkov photons in the water and optimize nEXO’s muon veto.
Silicon photomultipliers (SiPMs) are an excellent solid-state photon detection technology that is becoming increasingly popular in the field of particle and medical physics. The features of SiPMs that make them an ideal candidate for photon detection are their compact size, lightweight, high gain, low operating voltage, low dark noise, and insensitivity to the magnetic field. The nEXO (Enriched Xenon Observatory) is a future tonne scale experiment that will be looking for neutrinoless double beta decay in the 136Xe isotope. Many large future experiments like nEXO, ARGO, etc. will be using SiPMs in their photon detection system. Newly developed vacuum ultraviolet (VUV) sensitive SiPMs will be directly used for the readout of xenon scintillation photons (λ = 175nm) in the nEXO experiment. In this research project, VUV-SiPMs from two different vendors are characterized using current-voltage (IV) and pulse-level measurements performed at TRIUMF, from room temperature to liquid xenon temperature. These data are analyzed to extract the SiPM’s features like breakdown voltage, gain, dark noise rate and correlated noise probability. The results from IV and pulse analysis are compared. The method is proposed for rapid quality control of large numbers of SiPMs using IV measurements.
The SNO+ experiment is a multi-phase neutrino detector located at the SNOLAB underground physics laboratory in Sudbury, Ontario, Canada. Currently, the 12 m diameter acrylic vessel (AV) is filled with 780 tonnes of the liquid scintillator, linear alkylbenzene (LAB), doped with the fluor 2,5-diphenyloxazole (PPO) to a concentration of 2.2 g/L. The detector is viewed by approximately 9400 photomultiplier tubes (PMTs) and is surrounded by an additional shielding volume of 7000 tonnes of ultra-pure water. SNO+ has a myriad of physics goals, including the search for neutrino-less double beta decay ($0\nu\beta\beta$), refined measurements of the solar neutrino flux, and the potential for observing neutrinos in the case of a supernova event in the galaxy. A supernova releases 99% of its energy in the form of neutrinos, so any nearby supernova would produce a strong neutrino signal in neutrino detectors such as SNO+. This talk will cover the detection of supernova neutrinos in SNO+ as a liquid scintillator detector, and the potential of the water shielding volume to act as a water Cherenkov detector to provide additional directional information on a supernova event.
We present results of an analysis studying neutrino-nucleon interactions in the energy range between ~100 GeV - 1 TeV by measuring the inelasticity of these interactions with IceCube DeepCore. IceCube is a Cherenkov neutrino telescope consisting of an optical sensor array placed in ice 1.5 - 2.5 km below the geographic South Pole and covering a volume of roughly 1 km3. DeepCore is a densely instrumented sub-array inside IceCube, which allows us to detect and reconstruct neutrinos with energies from ~5 GeV to 1 TeV with greater precision. IceCube has previously reported inelasticity distribution measurement at 1 TeV- 100 TeV and this analysis extends this range to lower energies to fill in the gap with accelerator measurements of differential cross section. We use a low-background sample of fully contained muon-neutrino charged current events to fit the shape of flux-averaged inelasticity distribution. In this talk we will present an updated result taking into account contribution from neutrino induced charm production.
Bound-state $\beta$-decay ($\beta_b^-$-decay) is a radically transformative decay mode that can change the stability of a nucleus and generate temperature- and density-dependent decay rates. In this decay mode the $\beta$-electron is created directly in a bound atomic orbital of the daughter nucleus instead of being emitted into the continuum, so the decay channel is only significant in almost fully stripped ions during extreme astrophysical conditions. The $\beta_b^-$-decay of $^{205}$Tl$^{81+}$ could influence our understanding of the production of $^{205}$Pb, a short-lived radioactive (SLR) nucleus that is fully produced by the s-process in stars. In the context of the early Solar system, SLRs are defined by half-lives of 0.1-100 My and their abundance in meteorites can be used to constrain the formation of the Solar System [1]. Historically, it has been noted that thermal population of the 2.3 keV state of $^{205}$Pb in stellar conditions could dramatically reduce the abundance of s-process $^{205}$Pb by speeding up the EC-decay to $^{205}$Tl. This destruction of $^{205}$Pb is potentially balanced by the $\beta_b^-$-decay of $^{205}$Tl$^{81+}$ [2]. Currently, a theoretical prediction for the half-life of fully stripped $^{205}$Tl is used in stellar models, but given the importance of the $^{205}$Pb/$^{205}$Pb chronometer, a measurement of the $\beta_b^-$-decay for $^{205}$Tl$^{81+}$ was conducted at the GSI Heavy Ion Facility in March 2020. A $^{205}$Tl$^{81+}$ beam was stored in the Experimental Storage Ring, and the growth of $^{205}$Pb$^{81+}$ daughters with storage time was directly attributable to the $\beta^-_b$-decay channel. The authors will report a preliminary measured half-life and detail how this half-life can be used to more accurately predict the $^{205}$Pb abundance in the early Solar System.
[1] M. Lugaro, et al. Progress in Particle and Nuclear Physics, 102:1–47, 2018.
[2] K. Yokoi, et al. Astronomy and Astrophysics, 145:339–346, 1985.
Precision mass measurements of neutron-deficient $fp$-shell nuclei near N=Z are of interest to the nuclear physics community because they are relevant to several research areas. First is that these nuclei are situated along the reaction path of the rapid proton capture process (rp-process) which powers type I X-ray bursts. Precision mass values are required for the calculation of astrophysical reaction rates which constrain uncertainty of the mass flow, the burst light curve, and the burst ashes produced. Precision mass measurements in this region are also valued as probes for studying the properties of isospin-symmetry breaking in nuclei via the isobaric mass multiplet equation (IMME). Experimental data on IMME $b$ and $c$ coefficients are used to construct isospin non-conserving shell model Hamiltonians which provide a grounds for investigating isospin non-conserving interactions and also provide a baseline for mass extrapolations. Experimental data presently only enables evaluations of the $c$ coefficients up to the mid-$fp$-shell at A=60. We report on precision mass measurements of neutron-deficient, upper-$fp$-shell nuclei $^{74-76}$Sr performed at TRIUMF with TITAN's multi-reflection time-of-flight mass spectrometer. This mass measurement campaign constitutes a first-time direct measurement of $^{74}$Sr, a first-time measurement of $^{75}$Sr, and improved mass precision of $^{76}$Sr. We give preliminary results on the effects that the new mass data have on the rp-process flow, type I X-ray burst ashes, and the IMME $b$ and $c$ coefficients.
Nuclear pairing, i.e., the tendency of nucleons to form pairs, has important consequences to the physics of neutron star crusts and heavy nuclei. The usual pairing found in nuclei happens between identical nucleons and in singlet states, while recent investigations have shown that certain heavy nuclei might exhibit triplet and mixed-spin pairing correlations in their ground states. In this talk, I will present new investigations on the effect of nuclear deformation on these novel superfluids. Signatures of these pairing effects can be directly seen in nuclear experiments on spectroscopic quantities and two-particle transfer direct reaction cross sections. Indirectly, pairing correlations of nuclear superfluidity can be probed in cold-atomic experiments utilizing Feshbach resonances. On that note, preliminary results on phenomenological investigations of $s$- and $p$-wave pairing in cold-atomic gases will also be discussed.
The precision measurements of neutrino oscillation parameters and neutrino-nucleus scattering and also unprecedented sensitivity to physics beyond the Standard Model are the goals of the next generation of long-baseline neutrino experiments. To achieve this high precision and sensitivity, these experiments need a reduction of the uncertainties in neutrino flux calculations. New measurements of hadron-nucleus interaction cross sections are needed to reduce uncertainties of neutrino fluxes. EMPHATIC (Experiment to Measure the Production of Hadrons At a Testbeam In Chicagoland) is a low-cost, table-top-sized, hadron-production experiment located at the Fermilab Test Beam Facility (FTBF) that aims to measure hadron scattering and production cross sections that are relevant for neutrino flux predictions. In my presentation, I will show measurements of the differential cross-section as a function of scattering angle for kaon-carbon interactions with a single charged particle in the final state at beam momenta of 30 GeV/c. These results can be used in current and future long-baseline neutrino experiments, and demonstrate the feasibility of future measurements by the EMPHATIC spectrometer.
A high-precision half-life measurement for the radioactive isotope, 26Na, was performed at TRIUMF’s Isotope Separator and Accelerator (ISAC) facility. This is the first experimental test of the high-efficiency Gamma-Ray Infrastructure for Fundamental Investigations of Nuclei (GRIFFIN) spectrometer for performing high precision (± 0.05% or better) half-life measurements [1]. In this talk, I will discuss new results of the half-life obtained from gating on 1809-keV γ-ray photopeaks that include corrections for pile-up and deadtime losses. The results obtained from these techniques will be compared to a previous high-precision measurement of the that employed direct β counting [2].
KEYWORDS: radioactive isotope, half-life, deadtime, pile-up
References
A. B. Garnsworthy et al., Nucl. Instrum. Methods Phys. Res. A, vol. 918, 0168-9002, (2019).
G. F. Grinyer et al., Phys. Rev. C. vol. 71, 044309, (2005).
The development of the GPD formalism in the last 25 years is a groundbreaking advance in our understanding of the structure of the nucleon. Unifying the concepts of parton distributions and of hadronic form factors, they contain a wealth of new information about how quarks and gluons make up hadrons. For example, GPDs correlate different parton configurations in the hadron at the quantum mechanical level. A recent theorem allows the reaction amplitude to be factorized into a hard part, representing the interaction of the incident virtual photon probe with the parton, and a soft part containing the GPD, representing the response of the nucleon to this interaction. This factorization relies on several assumptions that may not be true at low four momentum transfer (Q^2) for meson production. This presentation will give the projected results of the recently completed Pion-LT experiment from Jefferson Lab Hall C. These results will test the validity of GPD factorization in the range of Q^2 = 1.45 GeV^2 to Q^2 = 8.5 GeV^2, and will have implications for several GPD extraction experiments currently planned.
One of the foremost goals of nuclear physics is to provide an understanding of how nuclei are assembled from the basic constituent building blocks of protons and neutrons. Preceding studies have attempted to achieve this by observing the excitation's of nuclei under fine-tuned experimental conditions with the most advanced detectors available on the planet. Nevertheless, this initiative continues to present as extraordinarily non-trivial in nature, as these complex nucleic systems exhibit unique characteristics and trends in different areas of the chart of nuclides, many of which are yet to be fully understood and parameterized. A prime example of one such characteristic is the behaviour of collective states within the context of the shell model, and how this feature evolves in different Z areas of the chart of nuclides. With Z = 44 and N = 56, 100Ru lies near the middle of the Z = 40 − 50 shell, and ergo investigation into the excited states of this nucleus stands to offer an increased understanding of the evolution of collectivity in the Z = 40 − 50 region. The experiment under discussion herein focuses on the study of 100Ru via a two-neutron transfer reaction experiment that was performed using the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratory, in Garching, Germany, in 2019. The experimental procedure employed the use of a 102Ru target which was bombarded with protons in order to effectively pick-up two neutrons from the target, resulting in the production of 100Ru. Removing a pair of particles from the system enables the study of the neutron-pair properties of the states observed in the reaction, which in turn renders a more robust understanding of the structure of 100Ru. Results of the analysis of this experiment will be discussed and their future significance will be highlighted.
Neutrons are subatomic particles with no net electric charge, which means that they generally can penetrate deeper into matter than other subatomic particles. The interaction between neutrons and matter can be used to gather information about bulk characteristics of materials by evaluating the scattered neutrons. This opens a whole assortment of possible physics knowledge that can be acquired from studying neutron-matter interactions. This technique can be applied to a variety of materials but is particularly well suited for studying lighter elements such as hydrogen-rich materials. Neutron scattering is versatile and is used both for studying structures as well as dynamics on different lengths and time scales. The neutron scattering response can be inelastic, quasi-elastic, or elastic depending on the finite energy transfer between the neutrons and the material. The inelastic signal can probe the periodic motions of the molecules in the sample with a finite energy transfer, while the elastic signal is suitable for acquiring structural information. The Quasi-elastic neutron scattering is well suited to gather quantitative information about the correlation times and length scales of the diffuse motion occurring in hydrogenous materials in different geometries.
Potassium-40 ($^{40}$K) is a naturally-occurring, radioactive isotope impacting understanding of nuclear structure, geological ages spanning timescales as old as the Earth, and rare-event searches including those for dark matter and neutrinoless double-beta decay. The long-lived $^{40}$K radionuclide undergoes electron capture decays to either the excited or ground state of its Ar daughter, of which the latter has previously not been measured, and estimates of its branching ratio are highly variable ($I_{\text{EC}^0}\sim (0-0.8)\%$). In many dark matter searches, $^{40}$K contamination produces a challenging 3~keV background from these electron capture decays in the expected direct-detection signal region, and the ill-known ground state contribution may affect interpretation of the DAMA/LIBRA dark-matter claim. In geochronology, the common omission of this decay branch impacts calculated ages. This rare third-forbidden unique decay additionally provides an estimate for the associated weak axial-vector coupling constant, the quenching of which affects calculated half-lives of neutrinoless double-beta decay. The KDK (``potassium decay") experiment has completed the first, successful measurement of this elusive $^{40}$K branch using a coincidence technique between a high-resolution silicon drift detector to observe X-rays, and a high-efficiency ($\sim 98\%$) Modular Total Absorption Spectrometer (Oak Ridge National Labs) to tag gammas, ultimately differentiating ground and excited state electron capture decays of $^{40}$K. With our measurement, the re-evaluated $^{40}$K decay scheme yields $I_{\text{EC}^0} = 0.098\% \stackrel{\mathrm{stat}}{\pm} 0.023\% \stackrel{\mathrm{syst}}{\pm} 0.010\%$. We report on the $^{40}$K analysis, the extensive applications of our measurement, and a complementary result for zinc-65.
Recent neutron-star merger observations have provided r-process abundance constraints, which has led to significant attention towards additional neutron-capture processes such as the i-process and n-process. Working between the rates and environmental neutron densities of the r-process and s-process, their reaction pathways and abundance contributions are not yet fully characterized. Operating in densities of 10$^{13}$ - 10$^{20}$ neutrons/cm$^{3}$, sensitivity studies have shown these intermediate neutron-capture processes to take reaction pathways through experimentally accessible n-rich nuclei, providing opportunities to constrain the capture rates that define them.
This contribution will review the β-Oslo analysis of $^{91}$Sr, taken with the SuN total absorption spectrometer at the NSCL in 2018. By measuring both γ-ray and excitation energies, a coincidence matrix was produced to perform the Oslo analysis, providing experimental information on the nuclear level density and γ-ray strength functions, two critical components in finding the neutron capture cross section. Since neutron capture rates are historically unconstrained by experimental work, this provides an opportunity to further reduce these uncertainties, better characterizing the contribution of $^{91}$Sr to these exotic capture processes.
One of the challenges faced while studying the nuclear many-body problem is the nature of the nucleon-nucleon interaction. The full details are described by the theory of Quantum Chromodynamics (QCD), but for realistic calculations approximate models must be used. Historically these have been phenomenological potentials fit to experimental data. However, in recent decades, models for the nucleon-nucleon interaction were produced from a power counting expansion in Chiral Effective Field theory (EFT). As a result, these modern nuclear interactions have an advantage over the phenomenological potentials, since they have a connection to the symmetries of the underlying theory of QCD.
To investigate the nuclear many-body problem, we employ an ab initio approach. Quantum Monte Carlo (QMC) consists of a family of powerful stochastic methods for solving the many-body Schrodinger equation. QMC methods provide very accurate results, at the cost of being computationally expensive. In addition to their accuracy, QMC methods have the benefit that we can build the appropriate physics, such as pairing, directly into them.
Combining these two tools, QMC methods and the Chiral-EFT derived nucleon-nucleon interaction, leads to something of a contradiction. The Chiral-EFT potential is designed to be used perturbatively at the many-body level, but this is almost never the case, due to the fact that combining a non-perturbative technique (QMC) with a perturbative potential is not a trivial problem. This work attempts to remedy this inconsistency. To show this, we explore a variety of low-density neutron matter systems that have a direct application to neutron-rich systems such as the inner crust of neutron stars.
As one moves away from stable isotopes and deeper into the neutron-rich region, the likelihood of β-delayed neutron (βn) emission decay increases. The ability to understand the neutron emission probabilities and the neutron energy spectrum can reveal highly sensitive detail of the nuclear structure that a conventional β-decay study using only γ-ray detection cannot. We propose to build the Detector Array for Energy Measurements of Neutrons (DAEMON) that will employ the time-of-flight technique to enable high-resolution energy measurements of the neutrons emitted following βn emission. The initial trials, performed at the University of Guelph, testing the rudimentary geometries of EJ200 plastic scintillators and various electronic parameters of silicon photomultiplier (SiPM) arrays for the foundation of DAEMON will be presented. Upon successful comparison of tests with gamma sources with simulations data, the DAEMON prototype will be tested with the monoenergetic neutron beam at the University of Kentucky Accelerator Laboratory. Used in conjunction with the GRIFFIN Decay Station at TRIUMF in Vancouver, BC, DAEMON will establish a frontier for βn studies currently non-existent at the facility and therefore initiating a road to strong international collaborations. From shaping the abundance curve of the astrophysical rapid neutron capture process, as well as controlling the neutron induced fission in nuclear reactions, the building of a neutron detector will address a broad arena of physics.
The response of the proton to elastic scattering events has long been known to be described via two functions of the squared momentum transfer $Q^2$: the Sachs electric and magnetic form factors $G_E\left(Q^2\right)$ and $G_M\left(Q^2\right)$, respectively. To understand this elastic structure of the proton there are two main observables which constrain the form factors: cross section data from elastic electron-proton scattering events, and polarization transfer measurements, which generate `polarization ratio' data. After taking into account tree-level radiative corrections, separate fits of the form factors to these data lead to fits which disagree significantly with one another. Higher vertex corrections, especially two-photon-exchange corrections, have been assumed to play a larger role than previously thought in order to explain this discrepancy. We present our global reanalysis which takes special care to treat normalization uncertainties in a most statistically rigorous manner, with additional work done to understand how to extend certain statistical methods only defined for linear models, to non-linear models. We find only minor differences to fits when normalization uncertainty is correctly accounted for. We also present a simultaneous global fit to the two-photon-exchange corrected cross section data and polarization ratio data.
As a fundamental interaction of the Standard Model, the electroweak production of a W boson in association with two jets in proton-proton collisions is of particular interest due to its sensitivity to vector boson fusion, a topic of high interest at the Large Hadron Collider as it’s study can yield valuable information about the anomalous triple gauge couplings. By employing a machine learning network using boosted decision trees,high dimensional data collected by the ATLAS detector at CERN can be reduced to a single dimension. Applying an extended likelihood fit to this reduced dimension will yield a total fiducial cross section measurement, providing additional information towards our goal of improved understanding of the triple gauge couplings.
I will present a constraint on the sterile-neutrino dark matter through neutrino self-interaction inside a core-collapse supernova. The environment inside a core-collapse supernova has similar features as the early universe era where the sterile-neutrino dark matter is dominantly produced. I will start by showing how a massive scalar mediated neutrino self-interaction can affect the cooling rate of a core-collapse supernova. Then I will present the effect on the cooling luminosity, including the contributions to the thermal potential in the presence of non-zero chemical potentials from the plasma species. We will see that the supernova cooling argument can set a useful constraint on the neutrino self-interaction parameter space.
I present a new, open-source, pure Python program, MUTE (MUon inTensity codE) (A. Fedynitch, W. Woodley, M.-C. Piro 2022 ApJ 928 27). MUTE combines the state-of-the-art codes MCEq (Matrix Cascade Equation) and PROPOSAL (PRopagator with Optimal Precision and Optimised Speed for All Leptons) to compute cosmic ray cascades in the atmosphere and the propagation of muons through matter in separate steps. It is efficient, precise, and flexible, as the most recent theoretical models can be changed in the code independently of each other. Using these tools, MUTE provides forward predictions for muon intensities in mines or under mountains deep underground and underwater laboratories, accurately characterising the uncertainties arising from hadron production models. MUTE can also provide full information about muon energy and angular spectra underground. The control of theoretical uncertainties allows us to accurately predict the total muon rates and their seasonal variations to calculate muon-induced backgrounds in underground Dark Matter and neutrino detectors.
Bubble chambers using fluorocarbons or liquid noble gases are promising technologies for detecting low-energy nuclear recoils from weakly interacting massive particles (WIMPs), a potential candidate for dark matter. In this study, we used molecular dynamics simulations to determine the energy threshold in superheated liquids and Monte Carlo simulations with SRIM to obtain the bubble nucleation efficiency of bubble chamber detectors. We aim to construct an accurate physics model to explain the discrepancy observed between experimental results and the current theoretical model. The new model combines the Lindhard theory, resulting in improved accuracy and a better prediction of the bubble nucleation efficiency and energy threshold. Our preliminary results are promising and will be presented against experimental data from C3F8 and xenon superheated liquid detectors.