Nuclear Theory·nucl-th

Thursday·October 22, 2020

11 papers—6 primary·5 cross-listed

01
Hadron-Quark Phase Transition at Finite Density in the Presence of a Magnetic Field: Anisotropic Approach
E. J. Ferrer🇺🇸 · A. Hackebill🇺🇸
We investigate the hadron-quark phase transition at finite density in the presence of a magnetic field taking into account the anisotropy created by a uniform magnetic field in the system's equations of state. We find a new anisotropic equilibrium condition that will drive the first-order phase transition along the boundary between the two phases. Fixing the magnetic field in the hadronic phase, the phase transition is realized by increasing the baryonic chemical potential at zero temperature. It is shown that the magnetic field is mildly boosted after the system transitions from the hadronic to the quark phase. The magnetic-field discontinuity between the two phases is supported by a surface density of magnetic monopoles, which accumulate at the boundary separating the two phases. The mechanism responsible for the monopole charge density generation is discussed. Each phase is found to be paramagnetic with higher magnetic susceptibility in the quark phase. The connection with the physics of neutron stars is highlighted through out the paper.
nucl-thastro-ph.HEhep-phInt.J.Mod.Phys.A(2022)·16 citations
02
Windowed multipole representation of R-matrix cross sections
Pablo Ducru · Vladimir Sobes · Abdulla Alhajri · Isaac Meyer · Benoit Forget · Colin Josey · Jingang Liang
Nuclear cross sections are basic inputs to any nuclear computation. Campaigns of experiments are fitted with the parametric R-matrix model of quantum nuclear interactions, and the resulting cross sections are documented - both point-wise and as resonance parameters (with uncertainties) - in standard evaluated nuclear data libraries (ENDF, JEFF, BROND, JENDL, CENDL, TENDL): these constitute our common knowledge of fundamental nuclear physics. In the past decade, a collaborative effort has been deployed to establish a new nuclear cross section library format - the Windowed Multipole Library - with the goal of considerably reducing the cost of cross section calculations in nuclear transport simulations. This article lays the theoretical foundations underpinning these efforts. From general R-matrix scattering theory, we derive the windowed multipole representation of nuclear cross sections. Though physically and mathematically equivalent, the windowed multipole representation is particularly well suited for subsequent temperature treatment of angle-integrated cross sections: we show that accurate Doppler broadening can be performed analytically up to the first reaction threshold; and we derive cross sections temperature derivatives to any order. Furthermore, we here establish a way of converting the R-matrix resonance parameters uncertainty (covariance matrices) into windowed multipole parameters uncertainty. We show that generating stochastic nuclear cross sections by sampling from the resulting windowed multipole covariance matrix can reproduce the cross section uncertainty in the original nuclear data file. Through this foundational article, we hope to make the Windowed Multipole Representation accessible, reproducible, and usable for the nuclear physics community, as well as provide the theoretical basis for future research on expanding its capabilities.
nucl-thPRC(2021)·6 citations
03
Properties of dibaryons in nuclear medium
M. Kakenov🇷🇺 · V.I. Kukulin🇷🇺 · V.N. Pomerantsev🇷🇺 · O. Bayakhmetov🇰🇿
Properties of six-quark dibaryons in nuclear medium are considered by example of $A = 6$ nuclei within the three-cluster $α + 2 N$ model. Dibaryon production in nuclei leads to the appearance of a three-body force between the dibaryon and nuclear core. This non-conventional scalar force is shown to provide an additional attractive contribution to the three-body binding energy. This three-body contribution improves noticeably agreement between theoretical results and experimental data for the majority of observables. The most serious difference between the traditional $N N$ -force models and the dibaryon-induced model is found for the nucleon momentum distribution, the latter model providing a strong enrichment of the high-momentum components both for $^{6}$ Li and $^{6}$ He cases.
nucl-thEPJA(2020)·3 citations
04
Euclidean formulation of relativistic quantum mechanics of N particles
Gohin Shaikh Samad🇺🇸 · W.N.Polyzou🇺🇸
A Euclidean formulation of relativistic quantum mechanics for systems of a finite number of degrees of freedom is discussed. Relativistic treatments of quantum theory are needed to study hadronic systems at sub-hadronic distance scales. While direct interaction approaches to relativistic quantum mechanics have proved to be useful, they have two disadvantages. One is that cluster properties are difficult to realize for systems of more than two particles. The second is that the relation to quantum field theories is indirect. Euclidean formulations of relativistic quantum mechanics provide an alternative representation that does not have these difficulties. More surprising, the theory can be formulated entirely in the Euclidean representation without the need for analytic continuation. In this work a Euclidean representation of a relativistic $N$ -particle system is discussed. Kernels for systems of N free particles of any spin are given and shown to be reflection positive. Explicit formulas for generators of the Poincaré group for any spin are constructed and shown to be self-adjoint on the Euclidean representation of the Hilbert space. The structure of correlations that preserve both the Euclidean covariance and reflection positivity is discussed.
nucl-thhep-thquant-phPRC(2021)·3 citations
05
SU(3) partial dynamical symmetry and nuclear shapes
A. Leviatan
We consider several variants of SU(3) partial dynamical symmetry in relation to quadrupole shapes in nuclei. Explicit construction of Hamiltonians with such property is presented in the framework of the interacting boson model (IBM), including higher order terms, and in its proton-neutron extension (IBM-2). The cases considered include a single prolate-deformed shape with solvable ground and $γ$ or $β$ bands, coexisting prolate-oblate shapes with solvable ground bands, and aligned axially-deformed proton-neutron shapes with solvable symmetric ground and $γ$ bands and mixed-symmetry scissors and $γ$ bands.
nucl-thEur.Phys.J.ST(2020)·3 citations
06
Dispersive evaluation of the Lamb shift in muonic deuterium from chiral effective field theory
Bijaya Acharya🇩🇪 · Vadim Lensky🇩🇪 · Sonia Bacca🇩🇪 · Mikhail Gorchtein🇩🇪 · Marc Vanderhaeghen🇩🇪
We merge the dispersive relation approach and the ab initio method to compute nuclear structure corrections to the Lamb shift in muonic deuterium. We calculate the deuteron response functions and corresponding uncertainties up to next-to-next-to-next-to-leading order in chiral effective field theory and compare our results to selected electromagnetic data to test the validity of the theory. We then feed response functions calculated over a wide range of kinematics to the dispersion-theory formalism and show that an improved accuracy is obtained compared to that with the use of available experimental data in the dispersive analysis. This opens up the possibility of applying this hybrid method to other light muonic atoms and supplementing experimental data with ab initio theory for kinematics where data are scarce or difficult to measure with the goal of reducing uncertainties in estimates of nuclear structure effects in atomic spectroscopy.
nucl-thnucl-exPRC(2021)·20 citations
07
Vector dominance, one flavored baryons, and QCD domain walls from the "hidden" Wess-Zumino term
Avner Karasik🇬🇧
We further explore a recent proposal that the vector mesons in QCD have a special role as Chern-Simons fields on various QCD objects such as domain walls and the one flavored baryons. We compute contributions to domain wall theories and to the baryon current coming from a generalized Wess-Zumino term including vector mesons. The conditions that lead to the expected Chern-Simons terms and the correct spectrum of baryons, coincide with the conditions for vector meson dominance. This observation provides a theoretical explanation to the phenomenological principle of vector dominance, as well as an experimental evidence for the identification of vector mesons as the Chern-Simons fields. By deriving the Chern-Simons theories directly from an action, we obtain new results about QCD domain walls. One conclusion is the existence of a first order phase transition between domain walls as a function of the quarks' masses. We also discuss applications of our results to Seiberg duality between gluons and vector mesons and provide new evidence supporting the duality.
↳ hep-thhep-phnucl-thSciPost Phys.(2021)·28 citations
08
Early-Stage Shear Viscosity far from Equilibrium via Holography
Michael F. Wondrak🇩🇪 · Matthias Kaminski🇺🇸 · Marcus Bleicher🇩🇪
Shear viscosity is a crucial property of QCD matter which determines the collective behavior of the the quark-gluon plasma (QGP) in ultrarelativistic heavy-ion collisions. Extending the near-equilibrium, high-precision investigations in theory and experiment, we take into account the fact that, in a collision, the QGP is generated far from equilibrium. We use the AdS/CFT correspondence to study a strongly coupled plasma and find a significant impact on the ratio of shear viscosity to entropy density, $η / s$ . In particular, we investigate the initial heating phase and find a decrease reaching down to below 60% followed by an overshoot to 110% of the near-equilibrium value. This finding might be highly relevant for the extraction of transport coefficients from anisotropic flow measurements at RHIC and LHC.
↳ hep-phhep-thnucl-thNPA(2021)·5 citations
09
Effects of hadronic repulsive interactions on the fluctuations of conserved charges
Somenath Pal🇮🇳 · Guruprasad Kadam🇮🇳 · Hiranmaya Mishra🇮🇳 · Abhijit Bhattacharyya🇮🇳
We investigate the effects of repulsive interaction between hadrons on the fluctuations of the conserved charges. We calculate the baryon,the electric charge and the strangeness susceptibilities within the ambit of hadron resonance gas model extended to include the short range repulsive interactions.The repulsive interactions are included through a mean-field approach where the single particle energy gets modified due to mean field interactions between hadrons proportional to the number density of hadrons.We assume different mean-field interactions for mesons and baryons. It is shown that the repulsive interactions play a very crucial role to describe hadronic matter near transition temperature. We also show that in order to consistently describe higher order conserved charge fluctuations mesonic repulsive interactions cannot be neglected. Further, we demonstrate that the repulsive interaction of baryons are essential to describe the lattice simulation results at finite baryonchemical potential for higher order fluctuations.
↳ hep-phnucl-thPRD(2021)·16 citations
10
Anisotropy in Dijet Production in Exclusive and Inclusive Processes
Yoshitaka Hatta🇺🇸 · Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸 · Jian Zhou🇨🇳
We investigate the effect of soft gluon radiations on the azimuthal angle correlation between the total and relative momenta of two jets in inclusive and exclusive dijet processes. We show that the final state effect induces a sizable $cos (2 ϕ)$ anisotropy due to gluon emissions near the jet cones. The phenomenological consequences of this observation are discussed for various collider experiments, including diffractive processes in ultraperipheral $p A$ and $AA$ collisions, inclusive and diffractive dijet production at the EIC, and inclusive dijet in $pp$ and $AA$ collisions at the LHC.
↳ hep-phhep-exnucl-exnucl-thPRL(2021)·85 citations
11
3-D structure of the Glasma initial state -- Breaking boost-invariance by collisions of extended shock waves in classical Yang-Mills theory
Soeren Schlichting🇩🇪 · Pragya Singh🇩🇪
We simulate the 3+1 D classical Yang-Mills dynamics of the collisions of longitudinally extended nuclei, described by eikonal color charges in the Color Glass Condensate framework. By varying the longitudinal thickness of the colliding nuclei, we discuss the violations of boost invariance and explore how the boost invariant high-energy limit is approached. Subsequently, we develop a more realistic model of the three dimensional color charge distributions that connects longitudinal and transverse fluctuations to the $x$ and $k_{⊥}$ dependence of transverse momentum dependent parton distributions, and explore the resulting rapidity profiles and their longitudinal fluctuations.
↳ hep-phnucl-thPRD(2021)·31 citations

Affiliations

first authorsco-authorsvia INSPIRE