Nuclear Theory·nucl-th

Thursday·January 30, 2020

10 papers—5 primary·5 cross-listed

01
Hyperon-nucleon three-body forces and strangeness in neutron stars
Dominik Gerstung🇩🇪 · Norbert Kaiser🇩🇪 · Wolfram Weise🇩🇪
Three-body forces acting on a $Λ$ hyperon in a nuclear medium are investigated, with special focus on the so-called hyperon puzzle in neutron stars. The hyperon-nucleon two-body interaction deduced from SU(3) chiral effective field theory is employed at next-to-leading order. Hyperon-nucleon three-body forces are approximated using saturation by decuplet baryons and are transcribed to density-dependent effective two-body interactions. These together are taken as input in a Brueckner-Bethe-Goldstone equation with explicit treatment of the $Λ N \leftrightarrow Σ N$ and $Λ N N \leftrightarrow Σ N N$ coupled channels. Single-particle potentials of a $Λ$ hyperon in symmetric nuclear matter and neutron matter are calculated. With parameters of the $Λ N N$ three-body force constrained by hypernuclear phenomenology, extrapolations to high baryon density are performed. By comparison of the $Λ$ and neutron chemical potentials at densities characteristic of the core of neutron stars it is found that the combined repulsive effects of two- and three-body correlations makes the appearance of $Λ$ hyperons in neutron stars energetically unfavourable, thus offering a possible solution to a longstanding question.
nucl-thEPJA(2020)·133 citations
02
Cross-conductivity: novel transport coefficients to constrain the hadronic degrees of freedom of nuclear matter
Jean-Bernard Rose🇩🇪 · Moritz Greif🇩🇪 · Jan Hammelmann🇩🇪 · Jan A. Fotakis🇩🇪 · Gabriel S. Denicol🇧🇷 · Hannah Elfner🇩🇪 · Carsten Greiner🇩🇪
In general, the constituents of the bulk matter produced in heavy-ion collisions carry, besides electric charge, multiple other conserved quantum numbers like baryon number and strangeness. Therefore, an electric field will not only generate an electric current but, at the same time, also currents in baryon number and strangeness. We propose that the impact of the electric field on these conserved currents should be characterized by additional transport coefficients, which we call cross-conductivities. In this paper, we introduce and present a calculation of these cross-conductivities from the Green-Kubo formalism within the transport code SMASH for different chemical compositions of hadron resonance gases. We find that the coefficients underlie an ordering in the active degrees of freedom and that thus the chemical composition of the system plays a crucial role. Further, we argue that in future comparisons of lattice QCD calculations with these findings, one could constrain which degrees of freedom and their corresponding charge properties are relevant for the QCD dynamics of the system.
nucl-thhep-phPRD(2020)·29 citations
03
Number of constituent quark scaling of elliptic flows in high multiplicity p-Pb collisions at $s_{N N} =$ 5.02 TeV
Wenbin Zhao🇨🇳 · Che Ming Ko🇺🇸 · Yu-Xin Liu🇨🇳 · Guang-You Qin🇨🇳 · Huichao Song🇨🇳
We briefly summarize our recent study on the number of constituent quark (NCQ) scaling of hadron elliptic flows in high multiplicity p-Pb collisions at $s_{N N} =$ 5.02 TeV. With the inclusion of hadron production via the quark coalescence model at intermediate $p_{T}$ , the viscous hydrodynamics at low $p_{T}$ , and jet fragmentation at high $p_{T}$ , our $H y d r o - C o a l - F r a g$ model provides a nice description of the $p_{T}$ -spectra and differential elliptic flow $v_{2} (p_{T})$ of pions, kaons and protons over the $p_{T}$ range from 0 to 6 GeV. Our results demonstrate that including the quark coalescence is essential for reproducing the observed approximate NCQ scaling of hadron $v_{2}$ at intermediate $p_{T}$ in experiments, indicating strongly the existence of partonic degrees of freedom and the formation of quark-gluon plasma in high multiplicity p--Pb collisions at the LHC.
nucl-thhep-phnucl-exNPA(2021)·2 citations
04
Hydrodynamic attractors for Gubser flow
Ashutosh Dash🇮🇳 · Victor Roy🇮🇳
The Boltzmann equation is solved in the relaxation time approximation using a hierarchy of angular moments of the distribution function. Our solution is obtained for an azimuthally symmetric radially expanding boost-invariant conformal system that is undergoing Gubser flow. The solution of moments that we get after truncating the infinite set of equations at various orders is compared to the exact kinetic solution. The dynamics of transition is described by the presence of fixed points which describes the evolution of the system from an early time collisionless free streaming to the hydrodynamic regime at intermediate times and back to free streaming at late times. The attractor solution is found for various orders of moments as an interpolation between these fixed points. The relation of moments to various approximations of relativistic viscous hydrodynamics is investigated.
nucl-thPLB(2020)·43 citations
05
Evolution of quasiperiodic structures in non-ideal hydrodynamic description of phase transitions
D. N. Voskresensky🇷🇺
Various phase transitions could have taken place in the early Universe, and may occur in the course of heavy-ion collisions and supernova explosions, in proto-neutron stars, cold compact stars, and in the condensed matter at terrestrial conditions. Most generally, the dynamics of the density and temperature at first- and second-order phase transitions can be described with the help of the equations of non-ideal hydrodynamics. In the given work some novel solutions are found describing the evolution of quasiperiodic structures that are formed in the course of the phase transitions. Although this consideration is very general, particular examples of quark-hadron and nuclear liquid-gas first-order phase transitions to the uniform k_0=0 state and pion condensate second-order phase transition to non-uniform k_0\neq 0 state in dense baryon matter are considered.
nucl-thhep-phUniverse(2020)·3 citations
06
Tony Skyrme and the Origins of Skyrmions
Ian J. R. Aitchison (SLAC National Accelerator Laboratory and Oxford University)🇺🇸
I first discuss the main motivations for Tony Skyrme's highly original program (1958-62) of making fermionic nucleons out of bosonic pion fields, as described in his Cosener's House talk in 1984. These include a dislike of point-like elementary particles, which he blamed for infinite renormalization, and a preference for extended objects distinguished by what we would now call topological quantum numbers. In this he was strongly influenced by William Thomson (Lord Kelvin), who was so impressed by Helmholtz's proof of the conservation of circulation ("Wirbelbewegung") in fluid vortices that he developed an entire theory of atoms as knotted vortices in the ether fluid. Skyrme liked mechanical models, as did Kelvin, and he grew up fascinated by the ingenuity of Kelvin's machine for predicting tides, an example of which stood in his grandfather's house. This seems to have been connected to his strong preference for bosonic fields, which have a classical limit, over fermionic fields which do not. I then sketch the progress of Skyrme's ideas in the series of six papers in the years 1958-62, which passed largely unnoticed at the time. I emphasize his remarkable intuition that the kink solution of the classical Sine-Gordon equation would be a fermion when quantized, and the novelty of his identification of the Skyrmion winding number with baryon number in the three-dimensional case. I end by briefly describing how Skyrme's work was dramatically related to QCD in 1983-4.
↳ physics.hist-phcond-mat.otherhep-phnucl-th3 citations
07
Low energy doubly-virtual Compton scattering from di-lepton electroproduction on a nucleon
Vladyslav Pauk🇩🇪 · Carl E. Carlson🇺🇸 · Marc Vanderhaeghen🇩🇪
We propose a new way to experimentally determine the subleading low-energy structure constant of doubly-virtual Compton scattering on a proton. Such empirical determination will reduce the theoretical model error in estimates of the hadronic correction to the muonic hydrogen Lamb shift. We demonstrate that the di-lepton forward-backward asymmetry in the $e^{-} p \to e^{-} p e^{-} e^{+}$ process, which can be accessed at electron scattering facilities, yields a large sensitivity to this so far unknown low-energy constant.
↳ hep-phnucl-thPRC(2020)·8 citations
08
The impact of isomers on a kilonova associated with neutron star mergers
Shin-ichiro Fujimoto · Masa-aki Hashimoto
We investigate the significance of isomers on a kilonova associated with neutron star mergers (NSMs) for the first time. We calculate the evolution of abundances and energy generation rates ( $ϵ ˙_{nuc}$ ) of ejecta from NSMs, taking into account $β^{-}$ decay through isomers. We find that for ejecta with electron fraction ( $Y_{e}$ ) of $0.2 - 0.3$ , $ϵ ˙_{nuc}$ is appreciably changed from those without isomers, due to the large change in timing of $β^{-}$ decay through the isomeric states of $^{123, 125, 127} Sn$ and $^{128} Sb$ . In particular, the effects of the isomers on $ϵ ˙_{nuc}$ are prominent for ejecta of $Y_{e} \sim 0.25$ , which could emit a fraction of an early, blue component of a kilonova observed in GW170817. When the excitation from a ground state to its isomeric state is important, the isomers of $^{129} Sb$ and $^{129, 131} Te$ also cause additional and appreciable change in $ϵ ˙_{nuc}$ . Furthermore, we demonstrate that larger amounts of lanthanide-free ejecta result in a better fit of an observed light curve of the kilonova in GW170817 if the isomers are taken into account.
↳ astro-ph.HEnucl-thMNRAS(2020)·24 citations
09
Review of proton and nuclear shape fluctuations at high energy
Heikki Mäntysaari🇫🇮
Determining the inner structure of protons and nuclei in terms of their fundamental constituents has been one of the main tasks of high energy nuclear and particle physics experiments. This quest started as a mapping of the (average) parton densities as a function of longitudinal momentum fraction and resolution scale. Recently, the field has progressed to more differential imaging, where one important development is the description of the event-by-event quantum fluctuations in the wave function of the colliding hadron. In this Review, recent developments on the extraction of proton and nuclear transverse geometry with event-by-event fluctuations from collider experiments at high energy is presented. The importance of this fundamentally interesting physics in other collider experiments like in studies of the properties of the Quark Gluon Plasma is also illustrated.
↳ hep-phhep-exnucl-exnucl-thRept.Prog.Phys.(2020)·103 citations
10
Confronting Experimental Data with Heavy-Ion Models: Rivet for Heavy Ions
Christian Bierlich🇩🇰 · Andy Buckley🇬🇧 · Christian Holm Christensen🇩🇰 · Peter Harald Lindenov Christiansen🇸🇪 · Cody B. Duncan🇩🇪 · Jan Fiete Grosse-Oetringhaus🇨🇭 · Przemyslaw Karczmarczyk🇵🇱 · Patrick Kirchgaeßer🇩🇪 · Jochen Klein🇮🇹 · Leif Lönnblad🇸🇪 · Roberto Preghenella🇮🇹 · Christine O. Rasmussen🇸🇪 · Maria Stefaniak🇫🇷 · Vytautas Vislavicus🇩🇰
The Rivet library is an important toolkit in particle physics, and serves as a repository for analysis data and code. It allows for comparisons between data and theoretical calculations of the final state of collision events. This paper outlines several recent additions and improvements to the framework to include support for analysis of heavy ion collision simulated data. The paper also presents examples of these recent developments and their applicability in implementing concrete physics analyses.
↳ hep-phhep-exnucl-exnucl-thEPJC(2020)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE