Nuclear Theory·nucl-th
15 papers—9 primary·6 cross-listed
We discuss a constraint on the speed of sound, , derived from relativistic kinetic theory and show how it can be expressed in terms of the average sound speed, . This reformulation highlights the interplay between instantaneous and integrated stiffness of the equation of state and allows the kinetic-theory bound to be visualized as a restriction in the - plane.
This study investigates nuclear responses to two body external fields, interpreted as double phonon excitations, within the subtracted second random phase approximation (SSRPA) for 16O and 40Ca. To clarify the underlying characteristics of these modes, Hartree Fock(HF) and SSRPA with the diagonal approximation are first examined. The resulting strength distributions are nearly identical, indicating that residual interactions in the 1p1h sector contribute only weakly. This behavior contrasts with that of one body excitations, where coupling between 1p1h and 2p2h configurations is essential for generating collectivity. In the full SSRPA calculation, which incorporates the residual interaction among 2p2h configurations, the strength distributions are substantially modified. The double IS 0+ and 2+ modes show pronounced redistribution, with peaks shifted to lower energies and additional strength emerging at higher energies, whereas the double IV 1- mode shifts predominantly to higher energies due to a largely repulsive interaction, resulting in a resonance around twice the peak energy of the single giant dipole resonance. Analysis of single transition amplitudes reveals that low lying resonances are formed coherently through constructive neutron-neutron, proton-proton, and neutron-proton configurations, while high-lying resonances are dominated by neutron-proton configurations, reflecting their higher state density. These results demonstrate that double-phonon excitations cannot be described by simple folding of one-body responses; a fully microscopic treatment of 2p2h mixing, as provided by SSRPA, is essential.
W. Horiuchi🇯🇵 · Y. Suzuki🇯🇵 · R.B. Wiringa🇺🇸
Experiments using intermediate- to high-energy radioactive nuclear beams present numerous findings. Extracting important properties of physical observables relies on a firm theoretical analysis. Though Glauber theory is believed to work well, no convincing calculation has so far been done. We perform ab initio Glauber theory calculations of both elastic differential cross sections and total reaction cross sections for p+12C, 12C+12C, and 6He+12C systems. The wave functions of both 6He and 12C are generated by variational Monte Carlo calculations with spatial and spin-isospin correlations induced by realistic two- and three-nucleon potentials. Glauber's phase-shift function is computed by Monte Carlo integration up to all orders of nucleon-nucleon multiple scatterings. We show an excellent performance of the Glauber description to the selected data on the above systems. We also find that the cumulant expansion of the phase-shift function converges rapidly up to the second order for the above systems. This finding will open up interesting applications for the analysis of high-energy nuclear experiments.
W. Horiuchi · Y. Suzuki · R.B. Wiringa
The application of Glauber theory has been playing an increasingly important role with the study of unstable or exotic nuclei. Its adaptation to medium and high-energy nucleus-nucleus collisions is severely limited because one has to evaluate the matrix elements of multiple-scattering operators. The extraction of physical observables has been done using 'approximate' Glauber theory whose validity is hard to evaluate. We perform a full calculation of the matrix elements using Monte Carlo integration and analyze the elastic differential cross sections and the total reaction cross sections for p+12C, 4,6He+12C, and 12C+12C collisions. We use the variational Monte Carlo wave functions for 4,6He and 12C obtained by using realistic two- and three-nucleon potentials. We demonstrate the performance of the Glauber-theory calculations by comparing with available experimental data. We further discuss the accuracy of the conventional approximate methods in the light of the cumulant expansion for Glauber's phase-shift function.
I.A. Pshenichnov (1 and 2)🇷🇺 · S.D. Savenkov (1 and 2)🇷🇺 · A.O. Svetlichnyi (1 and 2) ((1) Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russia, (2) Moscow Institute of Physics and Technology, Dolgoprudny, Russia)🇷🇺
We investigate the production of secondary nuclei in the hadronic fragmentation and electromagnetic dissociation (EMD) of Ne beams at the LHC and Xe beams at NICA. For light nuclei at LHC energies, our calculations show that hadronic interactions are the dominant channel for nuclear transmutation. This contrasts with the previously established dominance of EMD in Pb-Pb collisions. For Ne-Ne collisions at TeV, we provide calculated cross sections and momentum distributions of produced nuclei such as He, C, N, and O. These results are essential for assessing potential contamination of the Ne-Ne event sample by collisions involving other nuclear species. Secondary nuclei will be also produced in the EMD of Xe beams at NICA, but they will not contaminate Xe-Xe data.
We study net-baryon number density fluctuations in isospin-symmetric matter near the nuclear liquid-gas phase transition using the parity doublet model. We analyze second-order susceptibilities of net-proton and net-neutron numbers and their correlations. We show that proton-neutron correlations are nontrivial and lead to qualitative differences between net-proton and net-baryon fluctuations. We further investigate factorial cumulants and demonstrate that the differences between baryon- and proton-number factorial cumulants are governed by proton-neutron correlations. Our results highlight the importance of interaction-driven correlations for interpreting fluctuation measurements near the liquid-gas critical endpoint.
Anand Rai🇮🇳 · Dani Rose J Marattukalam🇮🇳 · Prasanta Murmu🇮🇳 · Ashutosh Dwibedi🇮🇳 · Rishabh Sharma🇮🇳 · Sabyasachi Ghosh🇮🇳
We study the thermodynamic and transport properties of hot and dense quantum chromodynamic matter expected to be produced in low-energy heavy-ion collisions, using three different effective quantum chromodynamic frameworks: the Nambu--Jona-Lasinio model, the chiral effective model, and the hadron resonance gas model. We briefly outline the theoretical formulation of thermodynamic quantities and transport coefficients within these approaches, where quarks are treated with effective masses in the Nambu--Jona-Lasinio and chiral effective models, and hadronic degrees of freedom are employed in the hadron resonance gas model. The transport coefficients are evaluated using the Boltzmann transport equation in the relaxation-time approximation. Following the theoretical overview, we present a comprehensive analysis of the behavior of these quantities as functions of the baryon chemical potential or net baryon density. The Lorenz ratio is found to increase rapidly-indicating a strong violation of the Wiedemann-Franz law in the low- regime--while approaching the universal value at higher baryon chemical potentials or densities. The shear-viscosity-to-entropy-density ratio remains nearly constant at low but exhibits a gradual increase as grows. We also discuss the qualitative similarities of these trends with those observed in the electron-hole plasma of graphene, an emergent quasi-relativistic system characterized by massless energy-momentum dispersion.
A. Deur🇺🇸 · M. M. Dalton🇺🇸 · S. Širca🇸🇮
The Gerasimov-Drell-Hearn sum rule is a generic relation that has been used to make significant contributions to research in hadronic physics. It connects the spin-dependent cross-section for photoproduction off a particle to the squared ratio of the particle's anomalous magnetic moment and its mass, . Thus, for a nucleon embedded in a nucleus, the sum rule relates the cross-section to averaged quadratically over the nucleons comprising the nucleus. This quadratic averaging can be used to constrain the mechanism responsible for the medium modification of the nucleon. We also point out that the global properties of the embedded nucleon like its axial charge, mass or magnetic moment are observables measurable through sum rules.
Urban Vernik🇩🇪 · Kai Hebeler🇩🇪 · Achim Schwenk🇩🇪
Recently, new quark mass dependent three-nucleon (3N) forces have been identified, whose contributions in nuclear matter exceed expectations of Weinberg power-counting arguments. In this work, we investigate the impact of the most dominant new interaction term, characterized by the coupling , in ab initio calculations of medium-mass nuclei. For this, we combine the new interaction with established 3N interactions up to next-to-next-to-leading order (NLO) and next-to-next-to-next-to-leading order (NLO) in chiral effective field theory. We explore two fit strategies for the low-energy couplings. The first is based only on few-body observables, while the second also incorporates information from O. Generally, we find that the interaction has a significant impact on energies and radii, however mainly due to changes in the short-range couplings. Overall, we do not find systematic improvements in the reproduction of medium-mass nuclei when the additional interaction is included.
first authorsco-authorsvia INSPIRE