Conveners
Nuclear Astrophysics: NA 1
- Barry Davids (TRIUMF)
Nuclear Astrophysics: NA 2
- Annika Lennarz (TRIUMF)
Nuclear Astrophysics: NA 3
- Gavin Lotay (University of Surrey)
Nuclear Astrophysics: NA 4
- Almudena Arcones (TU Darmstadt)
Nuclear Astrophysics: NA 5
- Gabriel Martínez-Pinedo (GSI Darmstadt and TU Darmstadt)
Nuclear Astrophysics: NA 6
- Christopher Wrede (Michigan State University and Facility for Rare Isotope Beams)
Nuclear Astrophysics: NA 7
- Annika Lennarz (TRIUMF)
Nuclear reaction studies rely on three main physical components: the beam of nuclei provided by the facility, the detector systems used to measure the outgoing particles of interest, and the target. Target fabrication is thus a critical aspect of studying the reactions that power stars and probe the evolution of nuclear structure. The Jet Experiments in Nuclear Structure and Astrophysics...
Measurements of cross section and their extrapolation to stellar conditions are now routinely performed with accuracy of 5% or better. But the formation of 16O in the fusion of helium with 12C, in the 12C(a,g)16O reaction, is still not known with sufficient accuracy, in spite of the central role that this reaction plays in stellar evolution theory.
We developed [1] a new method to measure...
Astrophysical $S$ factors of $E1$ and $E2$ transitions of radiative $\alpha$ capture on $^{12}$C, $^{12}$C($\alpha$,$\gamma$)$^{16}$O, at Gamow peak energy, $E_G=0.3$ MeV, in the helium-burning process are estimated in cluster effective field theory (EFT). We construct an EFT for the reaction by choosing a separation scale as the breakup energy of $p$-$^{15}$N open channel and introduce...
Understanding the origin of elements in our universe is inevitable for modern nuclear physics. It is known that neutron-deficient stable isotopes, referred to as $p-$nuclei, are synthesized through the $p$-process triggered by photo-disintegration in supernovae. One of the major issues that remain unresolved is the anomalously large abundances for certain lighter $p-$nuclei in current...
The Gaseous Detector with Germanium Tagging (GADGET) was developed and operated at the National Superconducting Cyclotron Laboratory to measure weak, low energy, beta-delayed proton branches calorimetrically using the gaseous Proton Detector subsystem. The results constrain the strengths of the dominant resonances in key radiative proton capture reactions affecting the modeling of...
The Jinping Underground experiment for Nuclear Astrophysics (JUNA) takes advantage of the ultra-low background of the CJPL to conduct experiments for directly studying crucial reactions at stellar energies in the evolution of stars. In 2020, JUNA commissioned an mA level high current accelerator based on an ECR source, as well as high efficiency BGO and $^3$He detectors. These combination...
The origin of the elements in the universe is one of the long-standing problems in nuclear physics. In particular, the r-process attracts much attention since the hint of the heavy elements were detected after the gravitational wave was detected. To reveal the astrophysical conditions such as the neutron densities and the temperature, the nuclear physics parameters are highly demanded. Among...
The abundance of $^{26}$Al carries a special role in astrophysics, since it probes active nucleosynthesis in the Milky Way and constrains the Galactic core-collapse supernovae rate.
It is estimated through the detection of the 1809 keV $\gamma$-line and from the superabundance of $^{26}$Mg in comparison with $^{24}$Mg in meteorites. For this reason, high precision is necessary also in the...
Half of the elements heavier than iron are produced by a sequence of neutron captures, beta-decays and fission known as r-process. It requires an astrophysical site that ejects material with extreme neutron rich conditions. Once the r-process ends, the radioactive decay of the freshly synthesized material is able to power an electromagnetic transient with a typical intrinsic luminosity. Such...
The rapid neutron capture process ($r$-process) is responsible for creating more than half of the nuclei heavier than iron. Through a series of neutron captures, $r$-process facilitates the creation of neutron-rich nuclei up to the neutron drip line. A theoretical input for the description of this process requires knowledge of nuclear masses, neutron capture mechanisms, $\alpha$-decays,...
Nucleosynthesis by the rapid neutron-capture process (r-process) represents the cosmic origin of the heaviest elements (e.g., gold and uranium) beyond iron. Nuclear fission plays a key role in terminating the r-process path toward heavier elements and determining the final abundance pattern due to fission products. Additionally, fission serves as a heating source for kilonovae at late times...
The r-process nucleosynthesis (in explosive astrophysical events) is responsible for about half of the heavy elements observed in the universe. However, r-process outputs in the literature are difficult to replicate and vary across studies due to differences in nuclear mass models or initial conditions (e.g., seed nuclei). I will discuss why a thorough sensitivity analysis is required to...
Proton and alpha captures on unstable nuclei play a key role in determining the pathway of nucleosynthesis in explosive astrophysical environments, as well as energy generation throughout the cosmos. With remarkable advancements in radioactive ion beam technology, we are now able to study such reactions in terrestrial laboratories, and hence, have dramatically increased our understanding of...
In explosive astrophysical environments, such as novae, supernovae and neutron star mergers, a significant fraction of atomic nuclei are expected to exist in excited quantum states. These elevated levels participate in nucleosynthesis much in the same way as nuclear ground states and, as such, play an essential role in determining the abundance of chemical elements in our Galaxy. Due to the...
The role of nuclear isomers in astrophysical nucleosynthesis is gaining increased attention, as reactions on ground and isomeric states are both potentially important for determining the reaction rates and flow within the reaction network. A particular case is the odd-odd N=Z nuclides in the sd-shell, which play an important role in breakout from the CNO cycle in nova nucleosynthesis,...
The $R^{3}B$ (Reactions with Relativistic Radioactive Beams) experiment as a major instrument of the NUSTAR collaboration for the research facility FAIR in Darmstadt is designed for kinematically complete studies of reactions with high-energy radioactive beams. Part of the broad physics program of $R^{3}B$ is to constrain the asymmetry term in the nuclear equation-of-state and hence improve...
Using the relativistic mean-field model with the isoscalar- and isovector-meson mixing, $\sigma^{2}{\mathbf{\delta}}^{2}$ and $\omega_{\mu}\omega^{\mu}{\mathbf{\rho}}_{\nu}{\mathbf{\rho}}^{\nu}$, we present a new nuclear equation of state (EoS), which satisfies the large neutron skin thickness, $R_{\rm skin}$, of $^{208}$Pb and the small neutron-star radius, respectively reported by the PREX-2...
Type I X-ray bursts are the most common stellar explosions in our Galaxy, resulting from explosive hydrogen-helium burning. These bursts are triggered by thermonuclear ignition in the envelopes of accreting neutron stars within low-mass binary systems. Understanding the mechanisms behind these bursts requires knowledge of key nuclear reactions occurring in this stellar environment. However,...
One of the main questions in nuclear astrophysics is understanding how the elements heavier than iron are forged in the stars. Heavy element nucleosynthesis is largely governed by the slow and rapid neutron capture processes. However, a relatively small group of naturally occurring, neutron-deficient isotopes, the so called p nuclei, cannot be formed by either of those processes. These ~30...
Many important nucleosynthesis processes responsible for producing elements beyond iron are thought to be driven by ($\alpha$,n) reactions, for example the s-process and weak r-process. However, measurements of ($\alpha$,n) cross-sections present significant technical challenges, especially for reactions on radioactive nuclei or noble gases where targets are difficult or impossible to produce....
The formation of p-nuclei and their abundances are an important and ongoing study in nuclear astrophysical measurements. To understand and constrain theoretical models on the abundances of p-nuclei, further measurements of reactions on relevant nuclei and important branching points of the $\gamma$-process are needed. For this purpose the cross sections of (p,$\gamma$) and ($\alpha$,$\gamma$)...
Nuclear reactions induced by neutrons play a key role in several astrophysical scenario like primordial nucleosynthesis, s and r process and so on. From an experimental point of view, their reaction cross sections and reaction rates at astrophysically relevant temperatures are usually a hard task to be measured directly. Nevertheless big efforts in the last decades have led to a better...
Fusion reactions play an essential role in the energy production, the nucleosynthesis of chemical elements and the evolution of massive stars. Among these reactions, carbon burning is a crucial ingredient to understand the late stages of massive stars essentially driven by the 12C+12C reaction [1]. It presents prominent resonances at energies ranging from a few MeV/nucleon down to sub-Coulomb...
A precise determination of proton capture rates on oxygen is mandatory to predict the abundance ratios of the oxygen isotopes in a stellar environment where hydrogen burning is active. The $^{17}$O(p,$\gamma$)$^{18}$F reaction, in particular, plays a crucial role in AGB nucleosynthesis as well as in explosive hydrogen burning occurring in type Ia novae. At temperature of interest for the...
The NeNa-MgAl cycles are involved in the synthesis of Ne, Na, Mg, and Al isotopes. The 20Ne(p,γ)21Na (Q = 2431.68 keV) reaction is the first and slowest reaction of the NeNa cycle and it controls the speed at which the entire cycle proceeds. At the state of the art, the uncertainty on the 20Ne(p,γ)21Na reaction rate affects the production of the elements in the NeNa cycle. In particular, in...
An accurate understanding of the slowest reaction of the CNO cycle, the $^{14}$N(p,$\gamma$)$^{15}$O, is essential for estimating the lifetimes of massive stars and globular clusters. Additionally, it plays a crucial role in determining the CNO neutrino flux emitted by the Sun. Despite the significant efforts over the last twenty years, including pioneering underground measurements made by the...
One of the biggest questions in nuclear astrophysics regards the origin of heavy elements in the universe. The picture of traditional neutron-capture nucleosynthesis showed that two main processes contribute to elemental abundances heavier than iron, namely the slow (s) and rapid (r) processes. In recent years, observations and stellar evolution models of carbon-enhanced metal poor stars...
Indirect measurements are necessary to constrain cross sections and reaction rates of nuclear reactions that are inaccessible for direct measurement. One such indirect technique is the surrogate method. This method uses an alternate reaction channel to populate a nucleus of interest, and combines resulting experimental data with theory to constrain the (n,γ) cross section. Individual γ-decay...
Approximately half of the heavier-than-iron elements in the solar system today were made in the s-process. Of those elements, most between Iron and Strontium were made in massive stars. S-process nucleosynthesis in massive stars is driven by the reaction 22Ne(α,n)25Mg, the rate of which is enhanced by rotational mixing of 12C into the H-burning shell. However, 16O is a strong neutron poison,...
Fingerprints of the properties of exotic nuclei on nucleosynthesis observables have been used for decades to frame our picture of how the heaviest elements in our Solar System came to be. The abundance of elements in our Sun, as well as nearby metal-poor stars, hints at multiple neutron capture nucleosynthesis processes, the slow (s), intermediate (i) and rapid (r) neutron capture processes....
