Born in Punjab (India) in December 1941, Balraj Singh is not only the single most prolific nuclear data evaluator and disseminator of nuclear structure and decay data with 148 evaluations in Nuclear Data Sheets -- 85 as the first and often only author -- plus other journals, but his upmost curiosity and dedication brought him to be one of the finest nuclear physicists, with an everlasting influence on many of us. Balraj passed away about a year ago on 9 October 2023 in Ottawa, Ontario (Canada) at the age of 81, and at Atomic Data and Nuclear Data Tables we would like to commemorate some of his scientific achievements.
The properties of dilute neutron matter are mostly determined by the s-wave two-body (2N) interaction, while three-body (3N) interactions are suppressed by the Pauli principle. In a previous work, we showed that it can be advantageous to use the renormalization group based effective interactions with cutoffs scaled with the Fermi momentum, especially at low densities. In that case, induced 3N interactions may become important. In this work, we compute the 3N interaction induced by the similarity renormalization group flow of the s-wave 2N interaction. We work in the momentum-space hyperspherical partial wave basis and investigate its convergence properties. Then we study the effect of the induced 3N interaction on the equation of state of dilute neutron matter. We observe that the cutoff dependence of the equation of state is strongly reduced when the effect of induced 3N interaction is included.
Calculations for electron capture rates on nuclei with atomic numbers between $Z=20$ and $Z=52$ are performed in a self-consistent finite-temperature covariant energy density functional theory within the relativistic quasiparticle random-phase approximation. Electron captures on these nuclei contribute most to reducing the electron fraction during the collapse phase of core-collapse supernovae. The rates include contributions from allowed (Gamow-Teller) and first-forbidden (FF) transitions, and it is shown that the latter become dominant at high stellar densities and temperatures. Temperature-dependent effects such as Pauli unblocking and transitions from thermally excited states are also included. The new rates are implemented in a spherically symmetric 1D simulation of the core-collapse phase. The results indicate that the increase in electron capture rates, due to inclusion of FF transitions, leads to reductions of the electron fraction at nuclear saturation density, the peak neutrino luminosity, and enclosed mass at core bounce. The new rates reaffirm that the most relevant nuclei for the deleptonization situate around the $N = 50$ and $82$ shell closures, but compared to previous simulations, nuclei are less proton rich. The new rates developed in this work are available, and will be of benefit to improve the accuracy of multi-dimensional supernova simulations.
In this paper, the inverse potentials for the resonant f states of {\alpha}-3H and {\alpha}-3He are constructed using the phase function method by utilizing an ab-initio approach. A combination of three Morse functions are joined smoothly to prepare the reference potential. While the regular Morse function captures the nuclear and Coulomb interactions at short and medium ranges, an inverse Morse function is chosen to obtain the Coulomb barrier that arises because of the long-range Coulomb interaction. This reference potential is representative of a large family of curves consisting of eight distinct model parameters and two intermediate points that define the boundaries that exist between the three regions. The phase equation is solved using the Runge-Kutta 5th order method for the input reference potential to obtain the scattering phase shifts at various center of mass energies. The model parameters are then adjusted using the genetic algorithm in an iterative fashion to minimize the mean square error between the simulated and expected phase shift values. Our approach successfully constructed the inverse potentials for the resonant f states of the {\alpha}-3H and {\alpha}-3He systems, achieving convergence with a minimized mean square error. The resonance energies and widths for the {\alpha}-3H system for the f-5/2 and f-7/2 states are determined to be [4.19 (4.14), 1.225 (0.918)] MeV and [2.20 (2.18), 0.099 (0.069)] MeV, respectively. For the f-5/2 and f-7/2 states of the {\alpha}-3He system, the resonance energies and widths are [5.03 (5.14), 1.6 (1.2)] MeV and [2.99 (2.98), 0.182(0.175)] MeV, respectively. Our ab-initio approach to solve the phase equation utilizing a combination of smoothly joined Morse functions effectively captures both short-range nuclear and long-range Coulomb interactions, providing an accurate model for nuclear scattering involving charged particles.
We include the $\Delta$--isobars in the equation of state (EOS) of neutron star (NS) and study its effects with various parameter sets of the RMF model. We compare our results with the NS's constraints from the mass-radius measurement of PSR J0348+0432, PSR J1614-2230, PSR J0030+0451, PSR J0740+6620, PSR J0952-0607, and tidal deformability of GW170817. We calculate the mass-radius profile and tidal deformabilities of the NS using 21 parameter sets of the RMF model.Analyzing the result with various parameters, it is clear that only few parameter sets can satisfy simultaneously the constraints from NICER and GW170817. NLD parameter set satisfy all the constraints of NICER and GW170817. For its strong predictive power for the bulk properties of the neutron star, we take NLD parameter set as a representative for the detailed calculation of effect of $\Delta$-isobar on neutron star properties. We demonstrate that it is possible that $\Delta$-isobar can produce at 2-3 times the saturation density by adjusting the coupling constants $X_{\sigma\Delta}$, $X_{\rho\Delta}$ and $X_{\omega\Delta}$ in an appropriate range. Bulk properties of the NS like mass-radius profile and tidal deformability is strongly affected by the interaction strength of $\Delta$-isobar. Our calculation shows that it is also possible that by choosing $X_{\sigma\Delta}$, $X_{\rho\Delta}$ and $X_{\omega\Delta}$ to a suitable range the threshold density of $\Delta^-$-isobar become lower than $\Lambda^0$ hyperon. For a particular value of $\Delta$-coupling constants, the $R_{1.4}$ decrease by 1.7 km. This manuscipt give an argumentative justification for allowing $\Delta$-isobar degrees of freedom in the calculation of the NS properties.
The recent observation of the compact star XTE J1814-338 with a mass of $M=1.2^{+0.05}_{-0.05}~{\rm M_{\odot}}$ and a radius of $R=7^{+0.4}_{-0.4}$ km, together with the HESS J1731-347, which has a mass of $M=0.77^{+0.20}_{-0.17}~{\rm M_{\odot}}$ and a radius of $R=10.4^{+0.86}_{-0.78}$ km, they provide evidence for the possible presence of exotic matter in the core of neutron stars and significantly enhance our understanding of the equation of state for the dense nuclear matter. In the present srtudy, we investigate the possible existence of neutral anti-kaons and negative charged kaons in neutron stars by employing the Relativistic Mean Field model with first order kaonic (${K^{-}}$ and ${\bar{K^{0}}}$) condensates. To the best of our knowledge, this represents a first alternative attempt aimed to explain the bulk properties of the XTE J1814-338 object and at the same time the HESS J1731-347 object, using a mixture of kaons condensation in dense nuclear matter. In addition, we compare our analysis approach with the recent observation of PSR J0437-4715 and PSR J1231-1411 pulsars, proposing that to explain all objects simultaneously, it is essential to consider two distinct branches, each corresponding to a different composition of nuclear matter.
In this work, we present an evaluation of subleading effects in the hadronic light-by-light contribution to the anomalous magnetic moment of the muon. Using a recently derived optimized basis, we first study the matching of axial-vector contributions to short-distance constraints at the level of the scalar basis functions, finding that also the tails of the pseudoscalar poles and tensor mesons play a role. We then develop a matching strategy that allows for a combined evaluation of axial-vector and short-distance constraints, supplemented by an estimate of tensor-meson contributions based on simplified assumptions for their transition form factors. Uncertainties are primarily propagated from the axial-vector transition form factors and the variation of the matching scale, but we also consider estimates of the low-energy effect of hadronic states not explicitly included. In total, we obtain $a_\mu^\text{HLbL}\big|_\text{subleading}=33.2(7.2)\times 10^{-11}$, which in combination with previously evaluated contributions in the dispersive approach leads to $a_\mu^\text{HLbL}\big|_\text{total}=101.9(7.9)\times 10^{-11}$.
Hadronic light-by-light scattering (HLbL) defines one of the critical contributions in the Standard-Model prediction of the anomalous magnetic moment of the muon. In this work, we present a complete evaluation using a dispersive formalism, in which the HLbL tensor is reconstructed from its discontinuities, expressed in terms of simpler hadronic matrix elements that can be extracted from experiment. Profiting from recent developments in the determination of axial-vector transition form factors, short-distance constraints for the HLbL tensor, and the vector-vector-axial-vector correlator, we obtain $a_\mu^\text{HLbL}=101.9(7.9)\times 10^{-11}$, which meets the precision requirements set by the final result of the Fermilab experiment.
We compute the linearised dispersion relations of shear waves, heat waves, and sound waves in relativistic ''matter+radiation'' fluids with grey absorption opacities. This is done by solving radiation hydrodynamics perturbatively in the ratio ''radiation stress-energy''/''matter stress-energy''. The resulting expressions $\omega \, {=} \, \omega(k)$ accurately describe the hydrodynamic evolution for any $k\, {\in}\, \mathbb{R}$. General features of the dynamics (e.g., covariant stability, propagation speeds, and damping of discontinuities) are argued directly from the analytic form of these dispersion relations.
The light, strange baryons have been studied through various approaches and attempted to be looked for rigorously in experiments. The screened potential has been applied to heavy baryon sector as well as meson systems in earlier works. Here, this article attempts to compare the results for linear and screened potential for light strange baryons. Also, the Regge trajectories depict the linear nature.
Tsallis nonextensive statistics is applied to study the transport coefficients of strongly interacting matter within the Polyakov chiral SU(3) quark mean field model (PCQMF). Nonextensivity is introduced within the PCQMF model through a dimensionless $q$ parameter to examine the viscous properties such as shear viscosity ($\eta$), bulk viscosity ($\zeta_b$), and conductive properties, including electrical conductivity ($\sigma_{el}$) and thermal conductivity ($\kappa$). Additionally, some key thermodynamic quantities relevant to the transport coefficients, like the speed of sound ($c_{sq}^2$) and specific heat at constant volume ($c_{vq}$), are calculated. The temperature dependence of the transport coefficients is explored through a kinetic theory approach with the relaxation time approximation. The results are compared to the extensive case where $q$ approaches 1. The nonextensive $q$ parameter is found to have a significant effect on all transport coefficients. We find that the nonextensive behaviour of the medium enhances both specific shear viscosity $\eta/s_q$ as well as conductive coefficients $\sigma_{el}/T$ and $\kappa/T^2$. In contrast, the normalised bulk viscosity $\zeta_b/s_q$ is found to decrease as the nonextensivity of the medium increases. We have also studied the transport coefficients for finite values of chemical potentials. The magnitude of $\eta$, $\sigma_{el}$, and $\kappa$ increases at lower temperatures while $\zeta$ is found to decrease for systems with non-zero chemical potential.
The work presented is devoted to developing the integrated hydrokinetic approach (iHKM) for relativistic nucleus-nucleus collisions. While the previous cycle of works on this topic focused on ultra-relativistic collisions at the top RHIC and different LHC energies, the current work addresses relativistic collisions at lower energies, specifically ranging from approximately 1 to 50 GeV per nucleon pair in the center-of-mass colliding system. The formation times for the initial state of dense matter in such collisions can be up to three orders of magnitude longer than those in ultra-relativistic collisions. This reflects a fundamentally different nature and formation process, particularly concerning the possible stages of initial state evolution, including thermalization (which may be only partial at very low collision energies), subsequent hydrodynamic expansion, and the final transition of matter evolution into a hadronic cascade. These stages, which are fully realized in ultra-relativistic reactions, can also occur within the energy range of BES RHIC, albeit with distinct time scales. This publication not only advances the theoretical development of iHKM (referred to, if necessary, as the extended version of integrated Hydrokinetic Model, iHKMe), but also provides examples of model applications for calculating observables. A systematic description across a wide range of experimental energies, which is preliminary yet quite satisfactory, for spectra, flow, and femtoscopy, will follow this work.
Understanding the strong interactions between baryons, especially hyperon-nucleon ($Y$-$N$) interactions, is crucial for comprehending the equation-of-state (EoS) of the nuclear matter and inner structure of neutron star. In these proceedings, we present the measurements of $p$-$\Xi^{-}$ ($\bar{p}$-$\bar{\Xi}^{+}$) correlation functions with high statistics in Isobar (Ru+Ru, Zr+Zr) and Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV by the STAR experiment. With the Lednick\'y-Lyuboshitz approach, the source size and strong interaction parameters of $p$-$\Xi^{-}$ ($\bar{p}$-$\bar{\Xi}^{+}$) pairs are extracted.
The yields and ratios of light nuclei in heavy-ion collisions offer a method to distinguish between the thermal and coalescence models. Ratios such as $\rm N_t \times N_p/N_d^2$ and $\rm N_{^3He} \times N_p/N_d^2$ are suggested as potential probes to investigate critical phenomena within the QCD phase diagram. The significantly larger datasets from STAR BES-II compared to BES-I, combined with enhanced detector capabilities, allow for more precise measurements. In this proceeding, we present the centrality and energy dependence of transverse momentum spectra and particle yields of (anti-)proton, (anti-)deuteron, and $\rm ^3He$ at BES-II energies ($\sqrt{s_{\rm NN}}$ = $7.7 - 27$ GeV), as well as the light nuclei to proton yield ratios and coalescence parameters $(B_2(\rm d)$ and $B_3(\rm ^3He))$.
The thermalization of quark gluon plasma created in relativistic heavy-ion collisions is a crucial theoretical question in understanding the onset of hydrodynamics, and in a broad sense, a key step to the exploration of thermalization in isolated quantum systems. Addressing this problem theoretically, in a first principle manner, requires a real-time, non-perturbative method. To this end, we carry out a fully quantum simulation on a classical hardware, of a massive Schwinger model, which well mimics QCD as it shares the important properties such as confinement and chiral symmetry breaking. We focus on the real-time evolution of the Wigner function, namely, the two-point correlation function, which approximates quark momentum distribution. In the context of the eigenstate thermalization hypothesis and the evolution of entropy, our solution reveals the emergence of quantum thermalization in quark-gluon plasma with a strong coupling constant, while thermalization fails progressively as a consequence of the gradually increased significance of quantum many-body scar states in a more weakly coupled system. More importantly, we observe the non-trivial role of the topological vacuum in thermalization, as the thermalization properties differ dramatically in the parity-even and parity-odd components of the Wigner function.
Perturbative Quantum Chromodynamics corrections and the colour superconductivity indicate that strongly interacting matter can manifest unique physical behaviours under extreme conditions. Motivated by this notion, we investigate the interior structure and properties of quark stars composed of interacting quark matter, which provides a comprehensive avenue to explore the strong interaction effects, within the framework of $f(Q)$ gravity. A unified equation of state is formulated to describe various phases of quark matter, including up-down quark matter $(2SC)$, strange quark matter $(2SC+s)$, and the Colour-Flavor Locked $(CFL)$ phase. By employing a systematic reparametrisation and rescaling, the number of degrees of freedom in the equation of state is significantly reduced. Utilising the Buchdahl-I metric ansatz and a linear $f(Q)$ functional form, $f(Q)=\alpha_{0}+\alpha_{1}Q$, we derive the exact solutions of the Einstein field equations in presence of the unified interacting quark matter equation of state. For the $2SC$ phase, we examine the properties of quark stars composed of up-down quark matter. For the $(2SC+s)$and $CFL$ phases, we incorporate the effects of a finite strange quark mass $(m_{s}\neq0)$. The Tolman-Oppenheimer-Volkoff equations are numerically solved to determine the maximum mass-radius relations for each phase. Our results indicate that the model satisfies key physical criteria, including causality, energy conditions, and stability requirements, ensuring the viability of the configurations. Furthermore, the predicted radii for certain compact star candidates align well with observational data. The study highlights that quark stars composed of interacting quark matter within the $f(Q)$ gravity framework provide a robust and physically consistent stellar model across all considered phases.
The rapid development of quantum computing technology has made it possible to study the thermodynamic properties of fermionic systems at finite temperatures through quantum simulations on a quantum computer. This provides a novel approach to the study of the chiral phase transition of fermionic systems. Among these, the quantum minimally entangled typical thermal states (QMETTS) algorithm has recently attracted considerable interest. The massive Thirring model, which exhibits a variety of phenomena at low temperatures, includes both a chiral phase transition and a topologically non-trivial ground state. It therefore raises the intriguing question of whether its phase transition can be studied using a quantum simulation approach. In this study, the chiral phase transition of the massive Thirring model and its dual topological phase transition are studied using the QMETTS algorithm. The results show that QMETTS is able to accurately reproduce the phase transition and thermodynamic properties of the massive Thirring model.
The formalism developed in Refs.\cite{Guo:2023ecc,Guo:2024zal} that connects integrated correlation function of a trapped two-particle system to infinite volume scattering phase shift is further extended to coupled-channel systems in the present work. Using a trapped non-relativistic two-channel system as an example, a new relation is derived that retains the same structure as in the single channel, and has explicit dependence on the phase shifts in both channels but not on the inelasticity. The relation is illustrated by an exactly solvable coupled-channel quantum mechanical model with contact interactions. It is further validated by path integral Monte Carlo simulation of a quasi-one-dimensional model that can admit general interaction potentials. In all cases, we found rapid convergence to the infinite volume limit as the trap size is increased, even at short times, making it potentially a good candidate to overcome signal-to-noise issues in Monte Carlo applications.
Studying hyper-nuclei yields and their collectivity can shed light on their production mechanism as well as the hyperon-nucleon interactions. Heavy-ion collisions from the RHIC beam energy scan phase II (BES-II) provide an unique opportunity to understand these at high baryon densities. In these proceedings, we present a systematic study on energy dependence of the directed flow ($v_{1}$) for $\Lambda$ and hyper-nuclei ($^{3}_{\Lambda}{\rm H}$, $^{4}_{\Lambda}{\rm H}$) from mid-central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3.2, 3.5, 3.9 and 4.5 GeV, collected by the STAR experiment with the fixed-target mode during BES-II. The rapidity (y) dependence of the hyper-nuclei $v_{1}$ is studied in mid-central collisions. The extracted $v_{1}$ slopes ($\mathrm{d}v_{1}/\mathrm{d}y|_{y=0}$) of the hyper-nuclei are positive and decrease gradually as the collision energy increases. These hyper-nuclei results are compared to that of light-nuclei including p, d, t/$\rm ^{3}He$ and $\rm ^{4}He$. Finally, these results are compared with a hadronic transport model including coalescence after-burner.
We determine the nucleon axial, scalar and tensor charges and the nucleon $\sigma$-terms using twisted mass fermions. We employ three ensembles with approximately equal physical volume of about 5.5~fm, three values of the lattice spacing, approximately 0.06~fm, 0.07~fm and 0.08~fm, and with the mass of the degenerate up and down, strange and charm quarks tuned to approximately their physical values. We compute both isovector and isoscalar charges and $\sigma$-terms and their flavor decomposition including the disconnected contributions. We use the Akaike Information Criterion to evaluate systematic errors due to excited states and the continuum extrapolation. For the nucleon isovector axial charge we find $g_A^{u-d}=1.250(24)$, in agreement with the experimental value. Moreover, we extract the nucleon $\sigma$-terms and find for the light quark content $\sigma_{\pi N}=41.9(8.1)$~MeV and for the strange $\sigma_{s}=30(17)$~MeV.