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Nuclear Theory·nucl-th

Wednesday·January 27, 2021

7 papers—2 primary·5 cross-listed

All7Primary2Cross-lists5
  1. 01

    Determining the temperature in heavy-ion collisions with multiplicity distribution

    Y. D. Song🇨🇳 · R. Wang🇨🇳 · Y. G. Ma🇨🇳 · X. G. Deng🇨🇳 · H. L. Liu🇨🇳

    By relating the charge multiplicity distribution and the temperature of a de-exciting nucleus through a deep neural network, we propose that the charge multiplicity distribution can be used as a thermometer of heavy-ion collisions. Based on an isospin-dependent quantum molecular dynamics model, we study the caloric curve of reaction Pd + Be with the apparent temperature determined through the charge multiplicity distribution. The caloric curve shows a characteristic signature of nuclear liquid-gas phase transition around the apparent temperature , which is consistent with that through a traditional heavy-ion collision thermometer, and indicates the viability of determining the temperature in heavy-ion collisions with multiplicity distribution.

    nucl-thhep-phnucl-exPLB(2021)·33 citations
  2. 02

    Soft pions and transport near the chiral critical point

    Eduardo Grossi🇺🇸 · Alexander Soloviev🇺🇸 · Derek Teaney🇺🇸 · Fanglida Yan🇺🇸

    During the expansion of a heavy ion collision, the system passes close to the critical point of QCD, and thus the fluctuations of the order parameter are expected to be enhanced. Our goal is to compute how these enhanced fluctuations modify the transport coefficients of QCD near the pseudo-critical point. We also make a phenomenological estimate for how chiral fluctuations could effect the momentum spectrum of soft pions. We first formulate the appropriate stochastic hydrodynamic equations close to the critical point. Then, working in mean field, we determine the correlation functions of the stress tensor and the currents which result from this stochastic real time theory, and use these correlation functions to determine the scaling behavior of the transport coefficients. The hydrodynamic theory also describes the propagation of pion waves, fixing the scaling behavior of the dispersion curve of soft pions. We present scaling functions for the shear viscosity and the charge conductivities near the pseudo-critical point, and estimate the absolute magnitude of the critical fluctuations to these parameters and the bulk viscosity. Using the calculated pion dispersion curve, we estimate the expected critical enhancement of soft pion yields, and this estimate provides a plausible explanation for the excess seen in experiment relative to ordinary hydrodynamic computations. Our results motivate further phenomenological and numerical work on the implications of chiral symmetry on real time properties of thermal QCD near the pseudo-critical point.

    nucl-thhep-phPRD(2021)·63 citations
  3. 03

    Lensing of Dirac monopole in Berry's phase

    Kazuo Fujikawa🇯🇵 · Koichiro Umetsu🇯🇵

    Berry's phase, which is associated with the slow cyclic motion with a finite period, looks like a Dirac monopole when seen from far away but smoothly changes to a dipole near the level crossing point in the parameter space in an exactly solvable model. This topology change of Berry's phase is visualized as a result of lensing effect; the monopole supposed to be located at the level crossing point appears at the displaced point when the variables of the model deviate from the precisely adiabatic movement. The effective magnetic field generated by Berry's phase is determined by a simple geometrical consideration of the magnetic flux coming from the displaced Dirac monopole.

    ↳ hep-thcond-mat.str-elnucl-thPRD(2021)·3 citations
  4. 04

    System size dependence of baryon-strangeness correlations in relativistic heavy ion collisions from a multiphase transport model

    D. F. Wang🇨🇳 · S. Zhang🇨🇳 · Y. G. Ma🇨🇳

    The system size dependence of baryon-strangeness (BS) correlations () are investigated with a multiphase transport (AMPT) model for various collision systems from , , , , , , and at RHIC energies of 200, 39, 27, 20, and 7.7 GeV. Both effects of hadron rescattering and a combination of different hadrons play a leading role for baryon-strangeness correlations. When the kinetic window is limited to absolute rapidity , these correlations tend to be constant after the final-state interaction whatever kind of hadrons subset we chose based on the AMPT framework. The correlation is found to smoothly increase with baryon chemical potential , corresponding to the collision system or energy from the quark-gluon-plasma-like phase to the hadron-gas-like phase. Besides, the influence of initial nuclear geometrical structures of -clustered nuclear collision systems of as well as collisions is discussed but the effect is found negligible. The current model studies provide baselines for searching for the signals of Quantum Chromodynamics (QCD) phase transition and critical point in heavy-ion collisions through the BS correlation.

    ↳ hep-phnucl-thPRC(2021)·6 citations
  5. 05

    Nuclear matter distributions in the neutron-rich carbon isotopes C from intermediate-energy proton elastic scattering in inverse kinematics

    A.V. Dobrovolsky (a)🇷🇺 · G.A. Korolev (a)🇷🇺 · S. Tang (b,1)🇩🇪 · G.D. Alkhazov (a)🇷🇺 · G. Coló (c)🇮🇹 · I. Dillmann (b,2)🇩🇪 · P. Egelhof (b)🇩🇪 · A. Estradé (b,3)🇩🇪 · F. Farinon (b)🇩🇪 · H. Geissel (b)🇩🇪 · S. Ilieva (b)🇩🇪 · A.G. Inglessi (a)🇷🇺 and 16 other authors

    The absolute differential cross sections for small-angle proton elastic scattering off the nuclei C have been measured in inverse kinematics at energies near 700 MeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR served simultaneously as a gas target and a detector for the recoil protons. The projectile scattering angles were measured with multi-wire tracking detectors. The radial nuclear matter density distributions and the root-mean-square nuclear matter radii were deduced from the measured cross sections using the Glauber multiple-scattering theory. A possible neutron halo structure in C, C and C is discussed. The obtained data show evidence for a halo structure in the C nucleus.

    ↳ nucl-exnucl-thNPA(2021)·21 citations
  6. 06

    Weak Kaon Production off the nucleon and Watson's theorem

    E. Saul-Sala🇪🇸 · J. E. Sobczyk🇩🇪 · M. Rafi Alam🇮🇳 · L. Alvarez-Ruso🇪🇸 · J. Nieves🇪🇸

    We have improved the tree-level model of Ref arXiv:1004.5484 [hep-ph] for weak production of kaons off nucleons by partially restoring unitarity. This is achieved by imposing Watson's theorem to the dominant vector and axial-vector contributions in appropriate angular momentum and isospin quantum number sectors. The observable consequences of this procedure are investigated.

    ↳ hep-phhep-exnucl-exnucl-thPLB(2021)·2 citations
  7. 07

    Impurities in a one-dimensional Bose gas: the flow equation approach

    F. Brauneis · H.-W. Hammer · M. Lemeshko · A. G. Volosniev

    A few years ago, flow equations were introduced as a technique for calculating the ground-state energies of cold Bose gases with and without impurities. In this paper, we extend this approach to compute observables other than the energy. As an example, we calculate the densities, and phase fluctuations of one-dimensional Bose gases with one and two impurities. For a single mobile impurity, we use flow equations to validate the mean-field results obtained upon the Lee-Low-Pines transformation. We show that the mean-field approximation is accurate for all values of the boson-impurity interaction strength as long as the phase coherence length is much larger than the healing length of the condensate. For two static impurities, we calculate impurity-impurity interactions induced by the Bose gas. We find that leading order perturbation theory fails when boson-impurity interactions are stronger than boson-boson interactions. The mean-field approximation reproduces the flow equation results for all values of the boson-impurity interaction strength as long as boson-boson interactions are weak.

    ↳ cond-mat.quant-gasnucl-thSciPost Phys.(2021)·20 citations

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first authorsco-authorsvia INSPIRE