Nuclear Theory·nucl-th

Tuesday·February 18, 2020

14 papers—8 primary·6 cross-listed

01
GW170817 constraints analyzed with Gogny forces and momentum-dependent interactions
O. Lourenço · M. Bhuyan · C. H. Lenzi · M. Dutra · C. Gonzalez-Boquera · M. Centelles · X. Viñas
A set of equations of state obtained from finite-range Gogny forces and momentum-dependent interactions is used to investigate the recent observation of gravitational waves from the binary neutron star merger GW170817 event. For this set of interactions, we have calculated the neutron star tidal deformabilities (related to the second Love number), the mass-radius diagram, and the moment of inertia~( $I$ ). The $I$ -Love relation has been verified. We also have found strong correlations among the tidal deformability of the canonical neutron star, its radius, and the derivatives of the nuclear symmetry energy at the saturation density. Most of the obtained results are located within the constraints of the tidal deformabilities extracted from the GW170817 detection.
nucl-thPLB(2020)·21 citations
02
On the light-front wave functions of quarkonia
Pieter Maris🇺🇸 · Shaoyang Jia🇺🇸 · Meijian Li🇺🇸 · Yang Li🇺🇸 · Shuo Tang🇺🇸 · James P. Vary🇺🇸
The light-front wave functions of hadrons allow us to calculate a wide range of physical observables; however, the wave functions themselves cannot be measured. We discuss recent results for quarkonia obtained in basis light-front quantization using an effective Hamiltonian with a confining model in both the transverse and longitudinal directions and with explicit one-gluon exchange. In particular, we focus on the numerical convergence of the basis expansion, as well as the asymptotic behavior of the light-front wave functions. We also illustrate that, for mesons with unequal quark masses, the maxima of the light-front wave functions depend in a non-trivial way on the valence quark-mass difference.
nucl-thhep-phPoS(2020)·4 citations
03
$_{ΛΛ}^{5}$ H and $_{ΛΛ}^{5}$ He Hypernuclei reexamined in Halo/Cluster Effective Theory
Ghanashyam Meher🇮🇳 · Udit Raha🇮🇳
The J=1/2 iso-doublet double- $Λ$ -hypernuclei, namely, $_{ΛΛ}^{5}$ H and $_{ΛΛ}^{5}$ He, are examined as the three-body cluster states, $ΛΛ t$ ( $t \equiv^{3}$ H or triton) and $ΛΛ h$ ( $h \equiv^{3}$ He or helion), respectively, in a model independent framework utilizing pionless halo effective theory. Both singlet and triplet states of the constituent $Λ T$ ( $T \equiv t, h$ ) sub-system are used in the elastic channel for the study of $_{Λ}^{4}$ H $- Λ$ and $_{Λ}^{4}$ He $- Λ$ scattering processes. A prototypical leading order investigation using a sharp momentum cut-off regulator, irrespective of the type of the elastic channel chosen, yields almost identical cut-off dependence of the three-body binding energy or the double- $Λ$ -separation energy ( $B_{ΛΛ}$ ) is obtained for the mirror partners, evidently suggesting good isospin symmetry in these three-body systems. Subsequently, upon normalization of our solutions to the integral equation with respect to a single pair of input data from an {\it ab initio} potential model analysis for each mirror hypernuclei, yields $B_{ΛΛ}$ which agrees fairly well with various erstwhile regulator independent potential models for our choice of the cut-off regulator, $\sim 200$ MeV. This is either consistent with pionless effective theory or with its slightly augmented version with a hard scale around $2 m_{π}$ , where low-energy $Λ$ - $Λ$ interactions dominated by $π π$ or $σ$ -meson exchange. Finally, to demonstrate the predictability of our effective theory, we present preliminary estimates of the S-wave $ΛΛ T$ three-body scattering lengths and the $Λ$ -separation energies.
nucl-thPRC(2021)·4 citations
04
Neutron star matter equation of state including $d^{*}$ -hexaquark degrees of freedom
A. Mantziris🇬🇧 · A. Pastore🇬🇧 · I. Vidaña🇮🇹 · D. P. Watts🇬🇧 · M. Bashkanov🇬🇧 · A. M. Romero🇬🇧
We present an extension of a previous work where, assuming a simple free bosonic gas supplemented with a relativistic meand field model to describe the pure nucleonic part of the EoS, we studied the consequences that the first non-trivial hexaquark $d^{*}$ (2380) could have on the properties of neutron stars. Compared to that exploratory work we employ a standard non-linear Walecka model including additional terms that describe the interaction of the $d^{*} (2380)$ di-baryon with the other particles of the system through the exchange of $σ$ - and $ω$ -meson fields. Our results have show that the presence of the $d^{*} (2380)$ leads to maximum masses compatible with the recent observations of $\sim 2$ M $_{⊙}$ millisecond pulsars if the interaction of the $d^{*} (2380)$ is slightly repulsive or the $d^{*} (2380)$ does not interacts at all. An attractive interaction makes the equation of state too soft to be able to support a $2$ M $_{⊙}$ neutron star whereas an extremely repulsive one induces the collapse of the neutron star into a black hole as soon as the $d^{*} (2380)$ appears.
nucl-thnucl-exAstron.Astrophys.(2020)·10 citations
05
Multi-stage evolution of heavy quarks in the quark-gluon plasma
G. Vujanovic🇺🇸 · A. Angerami · S. A. Bass · S. Cao · Y. Chen · J. Coleman · L. Cunqueiro · T. Dai · L. Du · R. Ehlers · H. Elfner · D. Everett and 38 other authors
The interaction of heavy flavor with the quark-gluon plasma (QGP) in relativistic heavy-ion collisions is studied using JETSCAPE, a publicly available software package containing a framework for Monte Carlo event generators. Multi-stage (and multi-model) evolution of heavy quarks within JETSCAPE provides a cohesive description of heavy flavor quenching inside the QGP. As the parton shower develops, a model becomes active as soon as its kinematic region of validity is reached. Two combinations of heavy-flavor energy-loss models are explored within a realistic QGP medium, using parameters which were tuned to describe {\it light-flavor} partonic energy-loss.
nucl-thhep-phNPA(2021)·8 citations
06
Description of the reactions 36S + 238U and 64Ni + 238U within the two-stage fusion-fission model
V.L. Litnevsky · F.A. Ivanyuk · G.I. Kosenko · S. Chiba
We describe the capture, fusion, fission and evaporation residue formation cross sections of superheavy nuclei within the proposed earlier two stages dynamical model. The approaching of the projectile nucleus to the target nucleus is described in the first stage of the model. On the second stage, the evolution of the system formed after the touching of the projectile and target nuclei is considered. The evolution of the system on both stages is described by Langevin equations. The transport coefficients of these equations are calculated within the microscopic linear response theory. The mutual orientation of the colliding ions, the tunneling through the Coulomb barrier in the entrance channel and the shell effects in the potential energy on both stages of the calculations are taking into account. The obtained results are compared with the available experimental data and other theoretical predictions.
nucl-thPRC(2020)·13 citations
07
Effects of initial state fluctuations on the mean transverse momentum
Fernando G. Gardim🇧🇷 · Giuliano Giacalone🇫🇷 · Matthew Luzum🇧🇷 · Jean-Yves Ollitrault🇫🇷
We show that in ideal hydrodynamic simulations of heavy-ion collisions, initial state fluctuations result in an increase of the mean transverse momentum of outgoing hadrons, $⟨ p_{t} ⟩$ . Specifically, $⟨ p_{t} ⟩$ is larger by a few percent if realistic fluctuations are implemented than with smooth initial conditions, the multiplicity and impact parameter being kept fixed. We show that result can be traced back to the fact that for a given total entropy, the initial energy contained in the fluid is larger if the density profile is bumpy. We discuss the implication of these results for the extraction of the equation of state of QCD from experimental data.
nucl-thhep-phnucl-exNPA(2021)·26 citations
08
Jet quenching in a multi-stage Monte Carlo approach
A. Kumar🇺🇸 · A. Angerami · S. A. Bass · S. Cao · Y. Chen · J. Coleman · L. Cunqueiro · T. Dai · L. Du · R. Ehlers · H. Elfner · D. Everett and 38 other authors
We present a jet quenching model within a unified multi-stage framework and demonstrate for the first time a simultaneous description of leading hadrons, inclusive jets, and elliptic flow observables which spans multiple centralities and collision energies. This highlights one of the major successes of the JETSCAPE framework in providing a tool for setting up an effective parton evolution that includes a high-virtuality radiation dominated energy loss phase (MATTER), followed by a low-virtuality scattering dominated (LBT) energy loss phase. Measurements of jet and charged-hadron $R_{AA}$ set strong constraints on the jet quenching model. Jet-medium response is also included through a weakly-coupled transport description.
nucl-thhep-phnucl-exNPA(2021)·11 citations
09
The gluon condensation effect in the cosmic hadron spectra
W. Zhu🇨🇳 · P. Liu🇨🇳 · J.H. Ruan🇨🇳 · R.Q. Wang🇨🇳 · F. Wang🇨🇳
Hardening of cosmic proton- and nuclei-spectra is explained by using the gluon condensation (GC) model, which states that a large amount of gluons in proton may condense near the high energy threshold. The results present the GC-effect as common origin of a series of anomalous astrophysical phenomena including the broken power-law in gamma-ray spectra, the excess in positron- and electron-spectra and hardening of proton- and nuclei-spectra.
↳ astro-ph.HEhep-phnucl-thJCAP(2020)·5 citations
10
Interplaying mechanisms behind inclusive jet $R_{AA}$ and extraction of jet energy loss distributions
Y. He (1)🇨🇳 · S. Cao (2)🇺🇸 · W. Chen (1)🇨🇳 · T. Luo (1)🇨🇳 · L.-G. Pang (3 and 4)🇺🇸 · X.-N. Wang (1, 3 and 4) ((1) Central China Normal University, (2) Wayne State University, (3) University of California, Berkeley, (4) Lawrence Berkeley National Laboratory)🇨🇳
The observed inclusive jet suppression in heavy-ion collisions at LHC has a very weak $p_{T}$ dependence over a large range of $p_{T}$ = 50-1000 GeV and is almost independent of the colliding energy, though the initial energy density of the bulk medium has increased from $s$ = 2.76 to 5.02 TeV by about 20%. This interesting phenomenon is investigated in the linear Boltzmann transport (LBT) model for jet propagation in an event-by-event 3+1D hydro background. We show that the $p_{T}$ dependence of jet $R_{AA}$ is determined by the initial spectrum in $p + p$ collisions and $p_{T}$ dependence of jet energy loss. Furthermore, jet energy loss distributions for inclusive jet and $γ -$ jet at both LHC energies are extracted directly from experimental data through the state-of-art Bayesian analysis. The averaged jet energy loss has a weak $p_{T}$ dependence and the scaled jet energy loss distributions have a large width, both of which are consistent with the LBT simulations and indicate that jet quenching is caused by only a few out-of-cone jet medium scatterings.
↳ hep-phnucl-thNPA(2021)·1 citation
11
Constraints on the muon fraction and density profile in neutron stars
Nai-Bo Zhang🇨🇳 · Bao-An Li🇺🇸
Muons in neutron stars (NSs) play especially important roles in addressing several interesting new physics questions associated with detecting as well as understanding interactions and astrophysical effects of muonphilic dark matter particles. The key model inputs for studying the latter are the total muon mass $M_{μ}$ , the muon mass fraction $M_{μ} / M_{NS}$ over the NS mass $M_{NS}$ and the muon radial density profile $ρ_{μ} (r)$ in NSs of varying masses. We investigate these quantities within a minimum model for the core of NSs consisting of neutrons, protons, electrons, and muons using an explicitly isospin-dependent parametric Equation of State (EOS) constrained by available nuclear laboratory experiments and the latest astrophysical observations of NS masses, radii and tidal deformabilities. We found that the absolutely maximum muon mass $M_{μ}$ and its mass fraction $M_{μ} / M_{NS}$ in the most massive NSs allowed by causality are about 0.025 $M_{⊙}$ and 1.1\%, respectively. For the most massive NS of mass 2.14 $M_{⊙}$ observed so far, they reduce to about 0.020 $M_{⊙}$ and 0.9\%, respectively. We also study respective effects of individual parameters describing the EOS of high-density neutron-rich nucleonic matter on the muon contents in NSs with varying masses. We found that the most important but uncertain nuclear physics ingredient for determining the muon contents in NSs is the high-density nuclear symmetry energy.
↳ astro-ph.HEnucl-exnucl-thApJ(2020)·38 citations
12
Jet quenching parameters in strongly coupled anisotropic plasmas in the presence of magnetic fields
Romulo Rougemont (Rio de Janeiro State U.)🇧🇷
I use the holographic gauge/gravity duality to systematically calculate the jet quenching parameters in strongly coupled anisotropic plasmas in the presence of external magnetic fields. The magnetic field breaks down spatial rotation symmetry from $S O (3)$ to $S O (2)$ , leading to the presence of multiple anisotropic jet quenching parameters, which are evaluated here in two quite different holographic settings. One of them corresponds to a top-down deformation of the strongly coupled $N = 4$ Super Yang-Mills plasma triggered by an external magnetic field, while the other one is a bottom-up Einstein-Maxwell-Dilaton model of phenomenological relevance for high energy peripheral heavy ion collisions, since it is able to provide a quantitative description of $(2 + 1)$ -flavors lattice QCD thermodynamics with physical quark masses at zero and nonzero magnetic fields. I find for both models an overall enhancement of all the anisotropic jet quenching parameters with increasing magnetic fields. Moreover, I also conclude that for both models transverse momentum broadening is larger in transverse directions than in the direction of the magnetic field. Since these conclusions are shown to hold for two rather different holographic setups at finite temperature and magnetic fields, they are suggested as fairly robust features of strongly coupled anisotropic magnetized plasmas.
↳ hep-phhep-thnucl-thPRD(2020)·19 citations
13
Non-perturbative definition of the QCD energy-momentum tensor on the lattice
Mattia Dalla Brida🇮🇹 · Leonardo Giusti🇮🇹 · Michele Pepe🇮🇹
We present a strategy to define non-perturbatively the energy-momentum tensor in Quantum Chromodynamics (QCD) which satisfies the appropriate Ward identities and has the right trace anomaly. The tensor is defined by regularizing the theory on a lattice, and by fixing its renormalization constants non-perturbatively by suitable Ward identities associated to the Poincare' invariance of the continuum theory. The latter are derived in thermal QCD with a non-zero imaginary chemical potential formulated in a moving reference frame. A renormalization group analysis leads to simple renormalization-group-invariant definitions of the gluonic and fermionic contributions to either the singlet or the non-singlet components of the tensor, and therefore of their form factors among physical states. The lattice discussion focuses on the Wilson discretization of quark fields but the strategy is general. Specific to that case, we also carry out the analysis for the on-shell O(a)-improvement of the energy-momentum tensor. The renormalization and improvement programs profit from the fact that, as shown here, the thermal theory enjoys de-facto automatic O(a)-improvement at finite temperature. The validity of the proposal is scrutinized analytically by a study to 1-loop order in lattice perturbation theory with shifted and twisted (for quarks only) boundary conditions. The latter provides also additional useful insight for a precise non-perturbative calculation of the renormalization constants. The strategy proposed here is accessible to Monte Carlo computations, and in this sense it provides a practical way to define non-perturbatively the energy-momentum tensor in QCD.
↳ hep-lathep-phhep-thnucl-thJHEP(2020)·37 citations
14
Model-independent determination of the nucleon charge radius from lattice QCD
Constantia Alexandrou🇨🇾 · Kyriakos Hadjiyiannakou🇨🇾 · Giannis Koutsou🇨🇾 · Konstantin Ottnad🇩🇪 · Marcus Petschlies🇩🇪
Lattice QCD calculations of nucleon form factors are restricted to discrete values of the Euclidean four-momentum transfer. Therefore, the extraction of radii typically relies on parametrizing and fitting the lattice QCD data to obtain its slope close to zero momentum transfer. We investigate a new method, which allows to compute the nucleon radius directly from existing lattice QCD data, without assuming a functional form for the momentum dependence of the underlying form factor. The method is illustrated for the case of the isovector mean square charge radius of the nucleon $⟨ r_{isov}^{2} ⟩$ and the quark-connected contributions to $⟨ r_{p}^{2} ⟩$ and $⟨ r_{n}^{2} ⟩$ for the proton and neutron, respectively. Computations are performed using a single gauge ensemble with $N_{f} = 2 + 1 + 1$ maximally twisted mass clover-improved fermions at physical quark mass and a lattice spacing of $a = 0.08 fm$ .
↳ hep-lathep-phnucl-exnucl-thPRD(2020)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE