Nuclear Theory·nucl-th

Tuesday·September 13, 2022

14 papers—7 primary·7 cross-listed

01
Microscopic aspects of $γ$ -softness in atomic nuclei
Nazira Nazir · S. Jehangir · S.P. Rouoof · G.H. Bhat · J. A. Sheikh · N. Rather · S.Frauendorf
The microscopic origin of the $γ$ -softness (fluctuations in the triaxiality parameter $γ$ of the nuclear shape) observed in atomic nuclei is studied in the framework of the triaxial projected shell model approach, which is based on the deformed mean-field picture with multi-quasiparticle configuration space. It is demonstrated that the coupling to quasiparticle excitations drives the system from a $γ$ -rigid to a $γ$ -soft pattern. As an illustrative example for a $γ$ -soft nucleus, a detailed study has been performed for the $^{104}$ Ru nucleus. The experimental energies and a large sample of measured $E 2$ matrix elements available for this nucleus are reproduced quite accurately. The shape invariant analysis of the calculated $E 2$ matrix elements elucidates the $γ$ -soft nature of $^{104}$ Ru.
nucl-thnucl-ex15 citations
02
Three-nucleon system: Irreducible and reducible contributions of the three-nucleon force
A. Deltuva · P.U. Sauer
The three-nucleon bound and scattering equations are solved in momentum space for a coupled-channel Hamiltonian. The Hamiltonian couples the purely nucleonic sector of Hilbert space with a sector in which one nucleon is excited to a $Δ$ isobar. The interaction consists of irreducible two-baryon and irreducible three-baryon potentials. The calculation keeps only the purely nucleonic one among the irreducible three-baryon potentials. The coupled-channel two-baryon potential yields additional reducible contributions to the three-nucleon force. The Coulomb interaction between the two protons is included using the method of screening and renormalization. Three-nucleon force effects on the bound-state energies and on observables of elastic nucleon-deuteron scattering and breakup are studied.
nucl-thPRC(2015)·11 citations
03
Measuring the speed of sound using cumulants of baryon number
Agnieszka Sorensen🇺🇸 · Dmytro Oliinychenko🇺🇸 · Larry McLerran🇺🇸 · Volker Koch🇺🇸
We show that the values of the first three cumulants of the baryon number distribution can be used to calculate the isothermal speed of sound and its logarithmic derivative with respect to the baryon number density. We discuss applications of this result to heavy-ion collision experiments and address possible challenges, including effects due to baryon number conservation, differences between proton and baryon cumulants, and the influence of finite number statistics on fluctuation observables in both experiment and hadronic transport simulations. In particular, we investigate the relation between quantities calculated in infinite, continuous matter and observables obtained in simulations using a finite number of particles.
nucl-thActa Phys.Polon.Supp.(2023)·5 citations
04
Nucleonic metamodelling in light of multimessenger, PREX-II and CREX data
Chiranjib Mondal🇫🇷 · Francesca Gulminelli🇫🇷
The need of reconciling our understanding of the behavior of hadronic matter across a wide range of densities, especially at the time when data from multimessenger observations and novel experimental facilities are flooding in, has provided new challenges to the nuclear models. Particularly, the density dependence of the isovector channel of the nuclear energy functionals seems hard to pin down if experiments like PREX-II (or PREX) and CREX are required to be taken on the same footing. We put to test this anomaly in a semi-agnostic modelling technique, by performing a full Bayesian analysis of static properties of neutron stars, together with global properties of nuclei as binding energy, charge radii and neutron skin calculated at the semi-classical level. Our results show that the interplay between bulk and surface properties, and the importance of high order empirical parameters that effectively decouple the subsaturation and the supersaturation density regime, might partially explain the tension between the different measurements and observations. If the surface behaviors, however, are decoupled from the bulk properties, we found a rather harmonious situation among experimental and observational data.
nucl-thastro-ph.HEnucl-exPRC(2023)·54 citations
05
Squeezed spectra and elliptic flow of bosons and anti-bosons with in-medium mass splitting
Yong Zhang🇨🇳 · Shi-Yao Wang🇨🇳 · Peng Ru🇨🇳 · Wei-Hua Wu🇨🇳
We study the impact of the in-medium mass splitting between bosons and anti-bosons on their spectra and elliptic flow. The in-medium mass splitting may cause a separation in the transverse momentum spectra, as well as a division in the elliptic flow between bosons and anti-bosons. The magnitude of this effect becomes greater as the in-medium mass splitting increases. With the increasing rapidity, the splitting effect of the spectra increases and the splitting effect of the elliptic flow decreases. These phenomena may provide a way to differentiate whether the influences on boson and anti-boson in the medium are consistent.
nucl-thhep-phIJMPE(2023)·0 citations
06
Enhanced dilepton emission from a phase transition in dense matter
O. Savchuk🇩🇪 · A. Motornenko🇩🇪 · J. Steinheimer🇩🇪 · V. Vovchenko🇩🇪 · M. Bleicher🇩🇪 · M. Gorenstein🇺🇦 · T. Galatyuk🇩🇪
It is demonstrated that the presence of a phase transition in heavy ion collisions, at beam energies that probe dense QCD matter, leads to a significant enhancement of the dilepton yield per produced pion due to the extended emission time. In addition, the temperature of low mass dileptons shows a modest decrease due to the mixed phase. The emission of dileptons in the SIS18-SIS100 beam energies range is studied by augmenting the UrQMD transport model with a realistic density dependent equation of state, as well as two different phase transitions. This is achieved by extending the molecular dynamics interaction part of the UrQMD model to a density dependent interaction potential with a high density minimum leading to a phase transition and metastable coexisting high density states. Together with a high precision measurement these simulations will be able to constrain the existence of a phase transition in QCD up to densities of several times nuclear saturation density.
nucl-thhep-exhep-phnucl-exJ.Phys.G(2023)·29 citations
07
Effects of finite sizes of atomic nuclei on shear modulus and torsional oscillations in neutron stars
Hajime Sotani · Hajime Togashi · Masatoshi Takano
The shear modulus of neutron star matter is one of the important properties for determining torsional oscillations in neutron stars. We take into account the effects of finite sizes of spherical nuclei on the shear modulus and examine the frequencies of crustal torsional oscillations. The shear modulus decreases owing to the finite-size effect, which in turn decreases the frequencies of torsional oscillations. In particular, the finite-size effect becomes more crucial for oscillations with a larger azimuthal quantum number and for neutron star models with a weaker density dependence of nuclear symmetry energy. In practice, when one identifies the quasi-periodic oscillations from a neutron star, where the magnetic effect is negligible, with crustal torsional oscillations, the finite-size effect can be more significant at frequencies higher than $\sim 100$ Hz.
nucl-thastro-ph.HEMNRAS(2022)·6 citations
08
Holographic Schwinger-Keldysh field theory of SU(2) diffusion
Yanyan Bu🇨🇳 · Xiyang Sun🇨🇳 · Biye Zhang🇨🇳
We construct effective field theory for SU(2) isospin charge diffusion, based on holographic Schwinger-Keldysh contour arXiv:2008.01269. The holographic model consists of a probe SU(2) gauge field in a doubled Schwarzschild-AdS $_{5}$ geometry. Accurate to first order in derivative expansion, we analytically compute the effective action up to quartic order in hydrodynamical fields. The effective theory contains both non-Gaussianity for noises and nonlinear interactions between noises and dynamical variables. Moreover, the effective theory captures both thermal and quantum fluctuations, which perfectly satisfy dynamical Kubo-Martin-Schwinger (KMS) symmetry at quantum level. Interestingly, the dynamical KMS symmetry, which is crucial in formulating non-equilibrium effective field theory for a quantum many-body system, is found to have a nice holographic interpretation.
↳ hep-thhep-phnucl-thJHEP(2022)·14 citations
09
Bulk Viscosity of Relativistic $n p e μ$ Matter in Neutron-Star Mergers
Mark Alford · Arus Harutyunyan · Armen Sedrakian
We discuss the bulk viscosity of hot and dense $n p e μ$ matter arising from weak-interaction direct Urca processes. We consider two regimes of interest: (a) the neutrino-transparent regime with $T \leq T_{tr}$ ( $T_{tr} ≃ 5 \div 10$ MeV is the neutrino-trapping temperature); and (b) the neutrino-trapped regime with $T \geq T_{tr}$ . Nuclear matter is modeled in relativistic density functional approach with density-dependent parametrization DDME2. The maximum of the bulk viscosity is achieved at temperatures $T ≃ 5 \div 6$ MeV in the neutrino-transparent regime, then it drops rapidly at higher temperatures where neutrino-trapping occurs. As an astrophysical application, we estimate the damping timescales of density oscillations by the bulk viscosity in neutron star mergers and find that, e.g., at the oscillation frequency $f = 10$ kHz, the damping will be very efficient at temperatures $4 \leq T \leq 7$ MeV where the bulk viscosity might affect the evolution of the post-merger object.
↳ astro-ph.HEnucl-thParticles(2022)·38 citations
10
Exploration of trace anomaly contribution to proton mass based on light vector meson photoproduction
Chen Dong🇨🇳 · Jiyuan Zhang🇨🇳 · Jingxuan Bu🇨🇳 · Huifang Zhou🇨🇳 · Xiao-Yun Wang🇨🇳
In the quantum chromodynamics, the mass source of the proton is decomposed into four parts by the energy momentum tensor : quark energy term, gluon energy term, quark mass term and trace anomaly term. And the trace anomaly term is the most crucial contribution for studying the internal structure of the proton. In this work, under the definition of the vector meson dominant model, the trace anomaly contribution of the proton is extracted from the experimental datas of light vector mesons $ρ$ , $ω$ and $ϕ$ photoproduction at the near-threshold, which are ( $1.15 \pm 0.08$ ) $%$ , ( $2.70 \pm 0.04$ ) $%$ and ( $5.58 \pm 0.25$ ) $%$ , respectively. Eventually, the average trace anomaly contribution of the proton is ( $4.36 \pm 0.40$ ) $%$ , which only account for a small fraction of the total proton mass. The result of this work will provide theoretical information support for further study of proton internal structure.
↳ hep-phnucl-thEPJC(2023)·4 citations
11
QCD Phase Structure and Interactions at High Baryon Density: Continuation of BES Physics Program with CBM at FAIR
D. Almaalol🇺🇸 · M. Hippert🇺🇸 · J. Noronha-Hostler🇺🇸 · J. Noronha🇺🇸 · E. Speranza🇺🇸 · G. Basar🇺🇸 · S. Bass🇺🇸 · D. Cebra🇺🇸 · V. Dexheimer🇺🇸 · D. Keane🇺🇸 · S. Radhakrishnan🇺🇸 · A.I. Sheikh🇺🇸 and 32 other authors
We advocate for an active US participation in the international collaboration of the CBM experiment that will allow the US nuclear physics program to build on its successful exploration of the QCD phase diagram, use the expertise gained at RHIC to make complementary measurements at FAIR, and contribute to achieving the scientific goals of the beam energy scan (BES) program.
↳ nucl-exnucl-th38 citations
12
Empirical determination of the Bohr-Weisskopf effect in cesium and improved tests of precision atomic theory in searches for new physics
G. Sanamyan🇦🇺 · B. M. Roberts🇦🇺 · J. S. M. Ginges🇦🇺
The finite distribution of the nuclear magnetic moment across the nucleus gives a contribution to the hyperfine structure known as the Bohr-Weisskopf (BW) effect. We have obtained an empirical value of -0.24(18)% for this effect in the ground and excited s states of atomic Cs-133. This value is found from historical muonic-atom measurements in combination with our muonic-atom and atomic many-body calculations. The effect differs by 0.5% in the hyperfine structure from the value found using the uniform magnetization distribution, which has been commonly employed in the precision heavy-atom community over the last several decades. We also deduce accurate values for the BW effect in other isotopes and states of cesium. These results enable cesium atomic wave functions to be tested in the nuclear region at an unprecedented 0.2% level, and are needed for the development of precision atomic many-body methods. This is important for increasing the discovery potential of precision atomic searches for new physics, in particular for atomic parity violation in cesium.
↳ physics.atom-phhep-phnucl-exnucl-thPRL(2023)·17 citations
13
Accessing GPDs through the exclusive photoproduction of a $γ$ -meson pair
Goran Duplančić🇭🇷 · Saad Nabeebaccus🇫🇷 · Kornelija Passek-Kumerički🇭🇷 · Bernard Pire🇫🇷 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷
We consider the exclusive photo-production of a photon-meson pair with a large invariant mass, working in the QCD factorisation framework. Explicitly, we consider a $ρ$ -meson or a charged $π$ in the final state. This process gives access both to chiral-even GPDs and chiral-odd GPDs, which are not well-known experimentally, especially the latter ones. The computation is performed at leading order and leading twist. We discuss the prospects of measuring them in experiments, focusing on the kinematics at the JLab 12-GeV experiment, and pPb ultra-peripheral collisions at LHC. In particular, the latter gives access to the small $ξ$ regime of GPDs.
↳ hep-phhep-exnucl-exnucl-th2 citations
14
Gluon Transverse-Momentum-Dependent Distributions from Large-Momentum Effective Theory
Ruilin Zhu🇨🇳 · Yao Ji🇩🇪 · Jian-Hui Zhang🇨🇳 · Shuai Zhao🇺🇸
We demonstrate that gluon transverse-momentum-dependent parton distribution functions (TMDPDFs) can be extracted from lattice calculations of appropriate Euclidean correlations in large-momentum effective theory (LaMET). Based on perturbative calculations of gluon unpolarized and helicity TMDPDFs, we present a matching formula connecting them and their LaMET counterparts, where the latter are renormalized in a scheme facilitating lattice calculations and converted to the $MS$ scheme. The hard matching kernel is given up to one-loop level. We also show that the perturbative result is independent of the prescription used for the pinch-pole singularity in the relevant correlations. Our results offer a guidance for the extraction of gluon TMDPDFs from lattice simulations, and have the potential to greatly facilitate perturbative calculations of the hard matching kernel.
↳ hep-phhep-latnucl-thJHEP(2023)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE