Nuclear Theory·nucl-th

Friday·January 1, 2021

16 papers—8 primary·8 cross-listed

01
Jets as a probe of the quark-gluon plasma
Jasmine Brewer🇺🇸
The suppression and modification of high-energy objects, like jets, in heavy-ion collisions provide an important window to access the degrees of freedom of the quark-gluon plasma on different length scales. Despite increasingly precise and differential measurements of the properties of jets in heavy-ion collisions, however, it has remained challenging to use jets to make unambiguous and model-independent statements about the quark-gluon plasma. Here I will give a personal take on some origins of these challenges, including the difficulty of modelling and biases from jet selection that obfuscate the direct interpretation of jet modification measurements. I will discuss a few model studies that have helped to disentangle the source of non-intuitive effects in measurements, and finally highlight data-driven approaches as an interesting opportunity toward studying the quark-gluon plasma in a model-independent way using jets.
nucl-thPoS(2021)·3 citations
02
A Nonequilibrium Information Entropy Approach to Ternary Fission of Actinides
G. Röpke · J. B. Natowitz · H. Pais
Ternary fission of actinides probes the state of the nucleus at scission. Light clusters are produced in space and time very close to the scission point. Within the nonequilibrium statistical operator method, a generalized Gibbs distribution is constructed from the information given by the observed yields of isotopes. Using this relevant statistical operator, yields are calculated taking excited states and continuum correlations into account, in accordance with the virial expansion of the equation of state. Clusters with mass number $A \leq 10$ are well described using the nonequilibrium generalizations of temperature and chemical potentials. Improving the virial expansion, in-medium effects may become of importance in determining the contribution of weakly bound states and continuum correlations to the intrinsic partition function. Yields of larger clusters, which fail to reach this quasi-equilibrium form of the relevant distribution, are described by nucleation kinetics, and a saddle-to-scission relaxation time of about 7000 fm/c is inferred. Light charged particle emission, described by reaction kinetics and virial expansions, may therefore be regarded as a very important tool to probe the nonequilibrium time evolution of actinide nuclei during fission.
nucl-thPRC(2021)·12 citations
03
Skyrme-Hartree-Fock calculations of nuclear properties in the drip-point region of neutron star crust
Uwe Heinzmann · Igor Mishustin · Stefan Schramm
In the present paper we explore the neutron-drip region of cold non-rotating isolated neutron stars. We have performed extended nuclear-structure calculations for nuclei embedded in the electron gas. For modeling the outer crust we use a set of Wigner-Seitz cells, where every cell contains one nucleus surrounded by a cloud of relativistic electrons. Above the drip point a non-relativistic neutron gas occurs in the cell. These calculations are carried out within the Hartree-Fock approach in combination with Skyrme effective interactions. For every baryon density we have determined the configuration with a minimal total energy. The drip elements and corresponding drip densities have been determined for about 240 different parametrizations of Skyrme forces used in the literature. We demonstrate that the calculated drip-point densities depend essentially on the Skyrme parametrization used. Even the drip elements and the occupied shells in the drip region differ for different parametrizations. We have found that the number of neutrons building the neutron gas at the drip point also depends essentially on the Skyrme force chosen. Nevertheless, the number density of the neutron gas in the drip-region is more or less the same ( $\sim 1 0^{- 5} \frac{n e u t r o n s}{f m ^{3}}$ ). The drip densities obtained within our approach are generally lower than predicted earlier.
nucl-th0 citations
04
Inclusive Breakup Cross Sections in Reactions Induced by the Nuclides $^{6}$ He and $^{6, 7}$ Li in the Two-Body Cluster Model
L. A. Souza · E. V. Chimanski · B. V. Carlson
Calculations of inclusive $α$ particle production are performed to interpret reaction experimental data induced by the two-neutron halo $^{6}$ He and the isotopes $^{6, 7}$ Li on different target nuclei. We have implemented the zero-range post-form DWBA to compute the elastic and nonelastic breakup cross sections. Integrated cross sections, angular distributions and spectra are presented. Projectiles are approximated as two-body clusters, namely $^{6}$ He as $α$ +dineutron and $^{6}$ Li ( $^{7}$ Li) interpreted as $α$ +deuteron(triton). The São Paulo optical potential is employed in the calculation of the distorted wave functions for the incident channels, while standard phenomenological interactions are used for the fragment-target interactions. Calculations for $^{6}$ Li and $^{7}$ Li furnish a good description of the data, while the reaction involving $^{6}$ He is found to be a complicated case, where data interpretation is still considered a major obstacle. The present analysis identifies an overall large contribution from inclusive breakup emissions for all the cases studied.
nucl-thPRC(2021)·6 citations
05
Woods-Saxon-type of mean-field potentials with effective mass derived from the D1S Gogny force
A. Bhagwat🇮🇳 · M. Centelles🇪🇸 · X. Viñas🇪🇸 · P. Schuck🇫🇷
Analytic average mean-field potentials of the Fermi-function (Woods-Saxon) type for the whole nuclear chart with space-dependent effective mass are deduced from the D1S Gogny force. Those ready-for-use potentials are advertised as an alternative to other existing phenomenological mean-field potentials.
nucl-thPRC(2021)·7 citations
06
Fermions with long and finite range interactions on a quantum ring
A. W. Bray🇦🇺 · C. Simenel🇦🇺
Background: Idealised systems are commonly used in nuclear physics and condensed matter. For instance, the construction of nuclear energy density functionals involves properties of infinite matter, while neutron drops are used to test nuclear interactions and approximations to the nuclear many-body problem. In condensed matter, quantum rings are also used to study properties of electron systems. Purpose: To investigate the possibility to use quantum rings with systems of nucleons including many-body correlations. Methods: A quantum ring model of a finite number of same spin fermions is developed. Several attractive and repulsive interactions with finite and infinite ranges are considered. Quantum Monte Carlo calculations are used to provide exact ground-state energies. Comparisons with analytical Hartree-Fock solutions are used to get an insight into the role of correlations. Results: Hartree-Fock results with no breaking of space translational symmetry are able to describe many systems. However, additional spatial correlations are required in the case of dense systems with a strong short-range repulsion, or with attractive interactions in large rings. Conclusions: Self-bound systems of fermions with spatial correlations produced by basic features of the nuclear interactions can be described on a quantum ring, encouraging applications with realistic interactions, as well as investigations with higher dimensional geometries such as spherium.
nucl-thPRC(2021)·1 citation
07
Microscopic-Macroscopic Approach for Ground-State Energies Based on the Gogny Force with the Wigner-Kirkwood Averaging Scheme
A. Bhagwat🇮🇳 · M. Centelles🇪🇸 · X. Viñas🇪🇸 · P. Schuck🇫🇷
In the previous paper I \cite{bhagwat20} we have shown that self-consistent Extended Thomas-Fermi (ETF) potentials and densities associated with a given finite-range interaction can be parametrized by generalized Fermi distributions. As a next step, a comprehensive calculation of ground-state properties of a large number of spherical and deformed even-even nuclei is carried out in the present work using the Gogny D1S force within the ETF scheme. The parametrized ETF potentials and densities of paper I are used to calculate the smooth part of the energy and the shell corrections within the Wigner-Kirkwood semiclassical averaging scheme. It is shown that the shell corrections thus obtained, along with a simple liquid drop prescription, yield a good description of ground-state masses and potential energy surfaces for nuclei spanning the entire periodic table.
nucl-thPRC(2021)·6 citations
08
Self-consistent conversion of a one-component bulk viscous fluid to particles
Denes Molnar ((1) Purdue University, (2) Wigner Research Center for Physics, Budapest)
Comparison of heavy-ion experiments to fluid dynamics simulations requires the conversion of the fluid to particles. Extending the approach in Molnar & Wolff, PRC 95, 024903 (2017), this work presents self-consistent bulk viscous corrections from kinetic theory for a one-component system with isotropic $2 \to 2$ interactions. The phase space corrections are contrasted to the Grad ansatz and also to corrections obtained from the relaxation time approximation. In addition, the bulk viscosity of the system is calculated and compared with the Grad result, as well as the $ζ \propto (1 - 3 c_{s}^{2})^{2} η$ relation between shear and bulk viscosity near the conformal limit. The possible influence of various bulk correction choices on differential elliptic flow $v_{2} (p_{T})$ in heavy-ion collisions is also estimated.
nucl-thhep-ph0 citations
09
New fit of time-like proton electromagnetic form factors from $e^{+} e^{-}$ colliders
Egle Tomasi-Gustafsson🇫🇷 · Andrea Bianconi🇮🇹 · Simone Pacetti🇮🇹
The data on the proton form factors in the time-like region from the BaBar, BESIII and CMD-3 Collaborations are examined to have coherent pieces of information on the proton structure. Oscillations in the annihilation cross section, previously observed, are determined with better precision. The moduli of the individual form factors, determined for the first time, their ratio and the angular asymmetry of the annihilation reaction $e^{+} e^{-} \to p ˉ p$ are discussed. Fiits of the available data on the cross section, the effective form factor, and the form factor ratio, allow to propose a description of the electric and magnetic time-like form factors from the threshold up to the highest momenta.
↳ hep-phnucl-thPRC(2021)·35 citations
10
Nonrelativistic Effective Field Theory with a Resonance Field
J. B. Habashi🇺🇸 · S. Fleming🇺🇸 · U. van Kolck🇫🇷
We discuss shallow resonances in the nonrelativistic scattering of two particles using an effective field theory (EFT) that includes an auxiliary field with the quantum numbers of the resonance. We construct the manifestly renormalized scattering amplitude up to next-to-leading order in a systematic expansion. For a narrow resonance, the amplitude is perturbative except in the immediate vicinity of the resonance poles. It naturally has a zero in the low-energy region, analogous to the Ramsauer-Townsend effect. For a broad resonance, the leading-order amplitude is nonperturbative almost everywhere in the regime of validity of the EFT. We regain the results of an EFT without the auxiliary field, which is equivalent to the effective-range expansion with large scattering length and effective range. We also consider an additional fine tuning leading to a low-energy amplitude zero even for a broad resonance. We show that in all cases the requirement of renormalizability when the auxiliary field is not a ghost ensures the resonance poles are in the lower half of the complex momentum plane, as expected by other arguments. The systematic character of the EFT expansion is exemplified with a toy model serving as underlying theory.
↳ hep-phnucl-thquant-phEPJA(2021)·21 citations
11
Chiral separation effect catalyzed by heavy impurities
Daiki Suenaga🇯🇵 · Yasufumi Araki🇯🇵 · Kei Suzuki🇯🇵 · Shigehiro Yasui🇯🇵
We investigate the influence of Kondo effect, namely, the nonperturbative effect induced by heavy impurities, on the chiral separation effect (CSE) in quark matter. We employ a simple effective model incorporating the Kondo condensate made of a light quark and a heavy quark, and compute the response function of axial current to the magnetic field in static limit and dynamical limit. As a result, we find that the Kondo effect catalyzes the CSE in both the limits, and particularly the CSE in dynamical limit can be enhanced by a factor of approximately three. Our findings clearly show that the presence of heavy impurities in quark matter can play an important role in the transport phenomena of light quarks induced by a magnetic field.
↳ hep-phcond-mat.mes-hallnucl-thPRD(2021)·9 citations
12
Neutron - mirror neutron mixing and neutron stars
Zurab Berezhiani🇮🇹 · Riccardo Biondi🇮🇹 · Massimo Mannarelli🇮🇹 · Francesco Tonelli🇮🇹
The oscillation of neutrons $n$ into mirror neutrons $n^{'}$ , their mass degenerate partners from dark mirror sector, can have interesting implications for neutron stars: an ordinary neutron star could gradually transform into a mixed star consisting in part of mirror dark matter. Mixed stars can be detectable as twin partners of ordinary neutron stars: namely, there can exist compact stars with the same masses but having different radii. For a given equation of state (identical between the ordinary and mirror components), the mass and radius of a mixed star depend on the proportion between the ordinary and mirror components in its interior which in turn depends on its age. If $50% - 50%$ proportion between two fractions can be reached asymptotically in time, then the maximum mass of such "maximally mixed stars" should be $2$ times smaller than that of ordinary neutron star while the stars exceeding a critical mass value $M_{N S}^{max} / 2$ should collapse in black holes after certain time. We evaluate the evolution time and discuss the implications of $n - n^{'}$ transition for the pulsar observations as well as for the gravitational waves from the neutron star mergers and associated electromagnetic signals.
↳ astro-ph.HEastro-ph.GAhep-phnucl-thEPJC(2021)·63 citations
13
True Dynamical and Gauge Structures of the QCD Ground State and the Singular Gluon Fileds
Vakhtang Gogokhia🇭🇺 · Gergely Gábor Barnaföldi🇭🇺
We convincingly argue that the true dynamical and gauge structure of the QCD ground state is much more complicated than its Lagrangian exact gauge symmetry supposes to be. The dynamical source of these complications has been identified with the tadpole/seagull term, which renormalized version called, the mass gap. Its true dynamical role is hidden in the QCD ground state, but it is explicitly present in the full gluon self-energy. To disclose it the splintering between the transverse conditions for the full gluon self-energy and its subtracted counterpart has been derived. The equation of motion for the full gluon propagator on account of the mass gap was given, which allows to fix the dynamical and gauge structures by a newly-introduced generalized gauge. A novel non-perturbative analytical method, the mass gap approach was developed for QCD and its groud state as well. We have discovered a general, non-perturbative singular solution for the full gluon propagator valid in the whole gluon momentum range, while dominating at large distances over all the other possible solutions. It accommodates all the severe infrared singularities, which may appear in the QCD ground state due to the self-interaction of massless gluon modes. A corresponding non-pertubative multiplicative infrared renormalization program has been formulated. The resulting full gluon propagator prevents gluons to appear at large distances as physical states (confinement of color gluons). Our approach also explains the scale violation in the asymptotic freedom regime, and why the rising potential between heavy quarks is only linear one.
↳ hep-thhep-phnucl-th1 citation
14
Convergence of hydrodynamic modes: insights from kinetic theory and holography
Michal P. Heller🇩🇪 · Alexandre Serantes🇵🇱 · Michał Spaliński🇵🇱 · Viktor Svensson🇵🇱 · Benjamin Withers🇬🇧
We study the mechanisms setting the radius of convergence of hydrodynamic dispersion relations in kinetic theory in the relaxation time approximation. This introduces a qualitatively new feature with respect to holography: a nonhydrodynamic sector represented by a branch cut in the retarded Green's function. In contrast with existing holographic examples, we find that the radius of convergence in the shear channel is set by a collision of the hydrodynamic pole with a branch point. In the sound channel it is set by a pole-pole collision on a non-principal sheet of the Green's function. More generally, we examine the consequences of the Implicit Function Theorem in hydrodynamics and give a prescription to determine a set of points that necessarily includes all complex singularities of the dispersion relation. This may be used as a practical tool to assist in determining the radius of convergence of hydrodynamic dispersion relations.
↳ hep-thnucl-thphysics.flu-dynSciPost Phys.(2021)·51 citations
15
Studying the onset of deconfinement with multi-messenger astronomy of neutron stars
David Blaschke🇵🇱 · Mateusz Cierniak🇵🇱
With the first multi-messenger observation of a binary neutron star merger (GW170817) new constraints became available for masses and radii of neutron stars. We introduce a class of hybrid EoS that fulfils all these constraints and predicts a region in the mass-radius diagram that could be populated only by hybrid neutron stars with quark matter cores. A confirmation of this conjecture would be provided when the NICER radius measurement for the high-mass pulsar PSR J0740+6620 yields a radius less than 11 km. Would this radius measurement yield a result in excess of 12 km, this would allow for both, a purely hadronic and a hybrid nature of this star. In the latter case the maximum mass could reach $2.6 M_{⊙}$ so that the lighter object in the asymmetric binary merger GW190814 could have been a hybrid star. We demonstrate that this high mass can be compatible with an early onset of deconfinement at star masses below $1 M_{⊙}$ and the occurrence of low-mass twin stars. In such a case the remnant of GW170817 could be a long-lived hypermassive pulsar.
↳ astro-ph.HEhep-phnucl-thAstron.Nachr.(2021)·34 citations
16
Constraints on quasinormal modes and bounds for critical points from pole-skipping
Navid Abbasi🇨🇳 · Matthias Kaminski🇺🇸
We consider a holographic thermal state and perturb it by a scalar operator whose associated real-time Green's function has only gapped poles. These gapped poles correspond to the non-hydrodynamic quasinormal modes of a massive scalar perturbation around a Schwarzschild black brane. Relations between pole-skipping points, critical points and quasinormal modes in general emerge when the mass of the scalar and hence the dual operator dimension is varied. First, this novel analysis reveals a relation between the location of a mode in the infinite tower of quasinormal modes and the number of pole-skipping points constraining its dispersion relation at imaginary momenta. Second, for the first time, we consider the radii of convergence of the derivative expansions about the gapped quasinormal modes. These convergence radii turn out to be bounded from above by the set of all pole-skipping points. Furthermore, a transition between two distinct classes of critical points occurs at a particular value for the conformal dimension, implying close relations between critical points and pole-skipping points in one of those two classes. We show numerically that all of our results are also true for gapped modes of vector and tensor operators.
↳ hep-thcond-mat.mes-hallcond-mat.str-elhep-ph+1JHEP(2021)·44 citations

Affiliations

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