Short range correlated (SRC) N N pairs are pairs of nucleons with high relative momentum (prel > kF where kF 250 MeV/c is the Fermi momentum in medium to heavy nuclei) and lower center of mass momentum. The motivation for studying SRC pairs ranges from a desire to achieve a more comprehensive understanding of the many-body nuclear wave-function at high-resolution to searching for explicit QCD-dynamics effects within the nuclear medium, not to mention connections to many other open problems in nuclear physics. Exploring short-range correlations was one of the physics motivations for building CEBAF (now Jefferson Lab). Scientists used the high luminosity and high energy of this cutting-edge machine to find kinematics that cleanly showed the signals of short-range correlations. This paved the way in the last two decades for tremendous progress understanding these correlations. This paper reviews recent progress and highlights outstanding questions and areas that need further study.

In stars that lie on the main sequence in the Hertzsprung-Russel diagram, like our sun, hydrogen is fused to helium in a number of nuclear reaction chains and series, such as the proton-proton chain and the carbon-nitrogen-oxygen cycles. Precisely determined thermonuclear rates of these reactions lie at the foundation of the standard solar model. This review, the third decadal evaluation of the nuclear physics of hydrogen-burning stars, is motivated by the great advances made in recent years by solar neutrino observatories, putting experimental knowledge of the proton-proton chain neutrino fluxes in the few-percent precision range. The basis of the review is a one-week community meeting held in July 2022 in Berkeley, California, and many subsequent digital meetings and exchanges. The relevant reactions of solar and stellar hydrogen burning are reviewed here, from both theoretical and experimental perspectives. Recommendations for the state of the art of the astrophysical S-factor and its uncertainty are formulated for each of them. Several other topics of paramount importance for the solar model are reviewed, as well: recent and future neutrino experiments, electron screening, radiative opacities, and current and upcoming experimental facilities. In addition to reaction-specific recommendations, also general recommendations are formed.

The study of nuclear forces, in particular the interaction between nucleons in the spin singlet state \(^1S_0\), allows us to examine the concepts of charge independence and charge symmetry. This latter property implies that the interaction between two protons is identical to that between two neutrons, except for small effects due to the different mass and charge of the particles. These effects leave their fingerprints on the scattering lengths that characterize low-energy nucleon-nucleon interactions. Precise measurements of the neutron-proton (\(n\)-\(p\)), proton-proton (\(p\)-\(p\)), and neutron-neutron (\(n\)-\(n\)) \(s\)-wave scattering lengths are essential for understanding charge symmetry breaking and refining nuclear force models. \(^1S_0\) proton-proton (\(p\)-\(p\)) scattering length requires Coulomb effects to be theoretically removed; yet, the Coulomb-free \(p\)-\(p\) data strongly depends on various theoretical techniques to subtract the Coulomb contribution. In this study, Tumino et al. (2023) aimed at measuring the Coulomb-free \(p\)-\(p\) scattering length directly, namely, minimizing the model dependence uncertainty. It has been extracted from the \(p\)-\(p\) scattering cross section measured at center-of-mass energies below 1 MeV via the quasi-free \(p+d \to p+p+n\) reaction, applying the Trojan Horse Method. A Bayesian data-fitting approach employing the expression of the s-wave nucleon-nucleon scattering cross section yielded a \(p\)-\(p\) scattering length \(a_{pp} = -18.17^{+0.52}_{-0.58}|_{\mathrm{stat}} \pm 0.01|_{\mathrm{syst}} \, \mathrm{fm}\) and an effective range \(r_0 = 2.80 \pm 0.05_{\mathrm{stat}} \pm 0.001_{\mathrm{syst}} \, \mathrm{fm}\), to be compared with the values in the literature, \(a_{pp} = -17.3 \pm 0.4 \, \mathrm{fm}\) and \(r_0 = 2.85 \pm 0.04 \, \mathrm{fm}\) (Machleidt and Slaus, 2001). It is important to underscore that the Coulomb-free \(p\)-\(p\) scattering length in the literature is devoid of short-range physics, which should be incorporated for a meaningful comparison. Therefore, a model founded on universality principles was developed to interpret these findings. It incorporates the short-range interaction as a whole, including nuclear and residual electromagnetic effects, similar to how the s-wave phase shift \(\delta\) operates in describing low-energy nucleon-nucleon scattering data. The calculated scattering length including short-range physics, \(a_{pp} = -17.6 \pm 0.4 \, \mathrm{fm}\), is in very good agreement with the Trojan Horse data, while model dependence is negligible as, in the universality framework, results are almost insensitive to the details of the interaction. The comparison with the current accepted short-range \(a_{pp} \) and \( a_{nn}\) values suggests that differences in the masses of up and down quarks and their electromagnetic interactions have a smaller-than-expected impact within the context of charge symmetry breaking, while other contributions such as partial waves beyond \(^1S_0\), three-nucleon interactions and the difference between quark scalar densities in proton and neutrons may play a role, especially at higher energies. Abstract of the lecture delivered at Palazzo Grimaldi in Modica on January 10, 2025, on the occasion of the ceremony for the award of the Grimaldi Prize 2024.

One of the hot topics in hadron physics is the study of the new exotic charmonium states and the determination of their internal structure. Another important topic is the study of the magnetic field produced in relativistic heavy-ion collisions and its effects on observables. In this note, we show that we can use ultra-peripheral collisions to address both topics. We compute the cross section for the production of the D⁺D⁻ molecular bound state in photon-photon collisions and also the cross section for π⁰ production in the target induced by the magnetic field of the projectile. Both cross sections are sizeable, and their measurement would be very useful to elucidate the above-mentioned questions.

We explore the potential of conducting low-energy nuclear physics studies, including nuclear structure and decay, at the future Electron-Ion Collider (EIC) at Brookhaven. By comparing the standard theory of electron-nucleus scattering with the equivalent photon method applied to Ultraperipheral Collisions (UPC) at the Large Hadron Collider (LHC) at CERN. In the limit of extremely high beam energies and small energy transfers, very transparent equations emerge. We apply these equations to analyze nuclear fragmentation in UPCs at the LHC and eA scattering at the EIC, demonstrating that the EIC could facilitate unique photonuclear physics studies. However, we have also shown that the fragmentation cross-sections at the EIC are about 1,000 times smaller than those at the LHC. At the LHC, the fragmentation of uranium nuclei displays characteristic double-hump mass distributions from fission events, while at the EIC, fragmentation is dominated by neutron emission and fewer few fission products, about 10,000 smaller number of events.

The (RB)-B-3 (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 (RB)-B-3 is to constrain the asymmetry term in the nuclear equation-of-state and hence improve the description of highly asymmetric nuclear matter (e.g., in neutron stars). For a precise determination of the neutron-skin thickness - an observable which is directly correlated with the symmetry energy in theoretical calculations - by measuring absolute fragmentation cross sections, it is essential to quantify the uncertainty and challenge the reaction model under stable conditions. During the successful FAIR Phase-0 campaign of (RB)-B-3, we precisely measured the energy dependence of total interaction cross sections in C-12+C-12 collisions, for a direct comparison with calculations based on the eikonal reaction theory.

The particle production in photon-photon (γγ) interactions present in electron-ion collisions is investigated. We present calculations for the total cross sections and event rates related to the production of light mesons [η,η′,f0 and f2], charmonium [ηc and χc], and charmoniumlike [X(3915),X(3940),X(4140), and X(6900)] states, considering the Electron - Ion Collider, Electron - ion collider in China, Large Hadron electron Collider, and Future Circular Collider - electron hadron energies. Our predictions demonstrate that experimental studies of these processes are feasible and useful to constrain the properties of light mesons and quarkonium states and shed some light on the configuration of the considered charmoniumlike states. Published by the American Physical Society 2025

In this contribution we discuss the production of charmonium states in two and three photon fusion processes in nucleus - nucleus collisions at the CERN Large Hadron Collider (LHC) energies. In a previous work we showed that the experimental study of these processes is feasible and they can be used to constrain the theoretical decay widths and give information on the non c−c¯ component of these states. Here we discuss some points which were not addressed in that work.

A fundamental framework to describe nuclear matter as a function of pressure and nuclear isospin asymmetry is the nuclear Equation of State (EoS). Constraining the parameters of the EoS is one of the central issues in nuclear physics, especially since the slope parameter L has not yet been constrained well experimentally. It has been identified that a precise determination of the neutron-removal cross section in neutron-rich nuclei, which correlates with the neutron-skin thickness, would provide a more precise constraint on L. To this end, an experiment was performed at the (RB)-B-3 part of the FAIR Phase-0 program. The reactions are studied in inverse kinematics with neutron-rich tin isotopes in the mass range of A = 124-134 on carbon targets of different thicknesses. The reaction products have been measured at beam energies of 400-900 MeV/u in a kinematically complete manner. In this communication, the analysis of Sn-124 + C-12 at 900 MeV/u is presented. The charge-exchange reactions, resulting processes, and their role in the calculation of other reaction cross sections are discussed.

The Facility for Antiproton and Ion Research (FAIR) is in its final construction stage next to the campus of the Gesellschaft fur Schwerionenforschung Helmholtzzentrum for heavy-ion research in Darmstadt, Germany. Once it starts its operation, it will be the main nuclear physics research facility in many basic sciences and their applications in Europe for the coming decades. Owing to the ability of the new fragment separator, Super-FRagment Separator, to produce high-intensity radioactive ion beams in the energy range up to about 2 GeV/nucleon, these can be used in various nuclear reactions. This opens a unique opportunity for various nuclear structure studies across a range of fields and scales: from low-energy physics via the investigation of multi-neutron systems and halos to high-density nuclear matter and the equation of state, following heavy-ion collisions, fission and study of short-range correlations in nuclei and hypernuclei. The newly developed reactions with relativistic radioactive beams ((RB)-B-3) set up at FAIR would be the most suitable and versatile for such studies. An overview of highlighted physics cases foreseen at (RB)-B-3 is given, along with possible future opportunities, at FAIR. This article is part of the theme issue 'The liminal position of Nuclear Physics: from hadrons to neutron stars'.

We study the production of the dimuonium (also known as true muonium) in two and three photon fusion processes in nucleus--nucleus collisions at the CERN Large Hadron Collider (LHC) energies. A new formalism is introduced for the production process and valuable new information is extracted which will be helpful in proposals of future experiments. We explore the phase space constraints, the reaction mechanisms, and how the dimounium decay observables might be jeopardized by other physical processes. We show that the energies available at the large hadron collider at CERN might lead to the first identification of the dimounium in a terrestrial laboratory.

In this work we present a calculation of exotic charmonium production in ultraperipheral collisions, in which the exotic state is explicitly treated as a meson molecule. Our formalism is general, but we focus on the lightest possible exotic charmonium state: a D+D− molecular bound state. It was proposed some time ago, and it has been an object of experimental searches. Here we study the production of the open charm pair in the process γγ→D+D−. Then we use a prescription to project the free pair |D+D−⟩ onto a bound state at the amplitude level and compute the cross section of the process γγ→B (where B is the bound state). Finally, we convolute this last cross section with the equivalent photon distributions coming from the projectile and target in an ultraperipheral collision and find the AA→AAB cross section, which, for Pb−Pb collisions at sNN=5.02 TeV, is of the order of 3 μb. Published by the American Physical Society 2024

An accurate 28P($p$, gamma )29S reaction rate is crucial to defining the nucleosynthesis products of explosive hydrogen burning in ONe novae. Using the recently released nuclear mass of 29S, together with a shell model and a direct capture calculation, we reanalyzed the 28P($p$, gamma )29S thermonuclear reaction rate and its astrophysical implication. We focus on improving the astrophysical rate for 28P($p$, gamma )29S based on the newest nuclear mass data. Our goal is to explore the impact of the new rate and associated uncertainties on the nova nucleosynthesis. We evaluated this reaction rate via the sum of the isolated resonance contribution instead of the previously used Hauser-Feshbach statistical model. The corresponding rate uncertainty at different energies was derived using a Monte Carlo method. Nova nucleosynthesis is computed with the 1-D hydrodynamic code SHIVA. The contribution from the capture on the first excited state at 105.64 keV in 28P is taken into account for the first time. We find that the capture rate on the first excited state in 28P is up to more than 12 times larger than the ground-state capture rate in the temperature region of 2.5$ $K to 4$ $K resulting in the total 28P($p$, gamma )29S reaction rate being enhanced by a factor of up to 1.4 at $ $K. In addition, the rate uncertainty has been quantified for the first time. It is found that the new rate is smaller than the previous statistical model rates, but it still agrees with them within uncertainties for nova temperatures. The statistical model appears to be roughly valid for the rate estimation of this reaction in the nova nucleosynthesis scenario. Using the 1-D hydrodynamic code SHIVA, we performed the nucleosynthesis calculations in a nova explosion to investigate the impact of the new rates of 28P($p$, gamma )29S. Our calculations show that the nova abundance pattern is only marginally affected if we use our new rates with respect to the same simulations but statistical model rates. Finally, the isotopes whose abundance is most influenced by the present 28P($p$, gamma )29S uncertainty are 28Si, $^ $S, $^ $Cl, and 36Ar, with relative abundance changes at the level of only 3 to 4.

The accuracy of reaction theories used to extract properties of exotic nuclei from scattering experiments is often unknown or not quantified, but of utmost importance when, e.g., constraining the equation of state of asymmetric nuclear matter from observables as the neutron-skin thickness. In order to test the Glauber multiple-scattering model, the total interaction cross section of Image 1 on carbon targets was measured at initial beam energies of 400, 550, 650, 800, and 1000 MeV/nucleon. The measurements were performed during the first experiment of the newly constructed R3B (Reaction with Relativistic Radioactive Beams) experiment after the start of FAIR Phase-0 at the GSI/FAIR facility with beam energies of 400, 550, 650, 800, and 1000 MeV/nucleon. The combination of the large-acceptance dipole magnet GLAD and a newly designed and highly efficient Time-of-Flight detector enabled a precise transmission measurement with several target thicknesses for each initial beam energy with an experimental uncertainty of ±0.4%. A comparison with the Glauber model revealed a discrepancy of around 3.1% at higher beam energies, which will serve as a crucial baseline for the model-dependent uncertainty in future fragmentation experiments.

The investigation of many astrophysical processes is dependent upon an understanding of nuclear reaction rates. However, nuclear capture reactions of astrophysical interest occur at extremely low energies, taking place at the Gamow energy within the stellar environment. Hence, they are hard to study experimentally due to Coulomb repulsion. They may also involve compound resonances stemming from a delicate interplay of many quantum states in the colliding bodies. The multi-channel algebraic scattering (MCAS) method is one that addresses both of these challenges; it has a history of successfully modelling narrow compound resonance structures, incorporating as many channels as are important for a given problem, but is also proven in recreating the lowenergy, non-resonant elastic scattering cross sections needed for these astrophysics problems. We provide an overview of MCAS’ techniques of modelling elastic scattering reactions, how these may be extended to capture reactions, and current work in this area.

The Coulomb excitation of Sn-124,Sn-128,Sn-130,Sn-132,Sn-134 isotopes in the electric field of a Pb target have been studied using the (RB)-B-3 setup as a part of the FAIR Phase-0 program. The experiment was motivated by the possibility of using the nuclear dipole response to infer valuable information on the slope of the symmetry energy of the nuclear equation of state. Measurements were performed in inverse kinematics at relativistic energies of 750 MeV/u and 904 MeV/u. The analysis method and preliminary results for the decay channel with a single outgoing neutron for Sn-124 are reported.

The conventional Big Bang model successfully anticipates the initial abundances of ^2 H(D), ^3 He, and ^4 He, aligning remarkably well with observational data. However, a persistent challenge arises in the case of ^7 Li, where the predicted abundance exceeds observations by a factor of approximately three. Despite numerous efforts employing traditional nuclear physics to address this incongruity over the years, the enigma surrounding the lithium anomaly endures. In this context, we embark on an exploration of Big Bang nucleosynthesis (BBN) of light element abundances with the application of Tsallis non-extensive statistics. A comparison is made between the outcomes obtained by varying the non-extensive parameter q away from its unity value and both observational data and abundance predictions derived from the conventional big bang model. A good agreement is found for the abundances of ^4 He, ^3 He and ^7 Li, implying that the lithium abundance puzzle might be due to a subtle fine-tuning of the physics ingredients used to determine the BBN. However, the deuterium abundance deviates from observations.

We examine the results on the determination of the Coulomb-free 1 S_0 proton–proton (p–p) scattering length by analyzing the cross section of the quasi-free p + d → p + p + n reaction at center-of-mass energies below 1 MeV. This was achieved using a Bayesian data-fitting approach, yielding a p–p scattering length a_pp = -18.17^+0.52_-0.58|_stat± 0.01_syst fm and effective range r_0 = 2.80± 0.05_stat± 0.001_syst fm. We test the stability of the results against the upper energy cutoff and fitting data sets separately. A model based on the Eckart potential is introduced for an effective description in the universal window. In this model, the short-range interaction is considered as a whole, similar to how the s-wave phase-shift δ functions in describing low-energy nucleon–nucleon scattering data. Based on our analysis, we confirm that the obtained parameters accurately represent the characteristics of the short-range physics and the influence of the up-down quark mass difference on the charge symmetry breaking is less significant as initially anticipated. Additionally, we suggest evaluating the charge symmetry breaking of the short-range interaction rather than solely focusing on the nuclear interaction.

The unexplained disagreement in the dependence of spectroscopic factors (C2Sexp) on the binding energy obtained by nucleon knockout using different targets is still a puzzle that needs to be addressed. To find an explanation of this riddle through exclusive measurements using different targets. The exclusive measurements were performed by using a Ne17 beam with an energy of 500 MeV/u incident on C and CH2 targets. Through the standard theoretical approach, C2Sexp were derived from the analysis of the experimental data on proton ejection from the proton halo in Ne17 as well as from its core O15. For the C target, proton ejection from the proton halo gave C2Sexp about 37% smaller than for the H target. But when protons are ejected from the core of Ne17, C2Sexp are identical within statistical uncertainties. An explanation for the difference in C2Sexp could be the removal of both halo protons, a more important reaction pathway for the C target. The C2Sexp values obtained by analyzing the proton ejection from the core indicate that it is not affected by the interaction with the halo protons. Published by the American Physical Society 2024