Nuclear Theory·nucl-th

Thursday·January 16, 2020

12 papers—5 primary·7 cross-listed

01
Heavy Quarks Embedded in Glasma
Margaret E. Carrington🇨🇦 · Alina Czajka🇵🇱 · Stanislaw Mrowczynski🇵🇱
Heavy quarks, which are produced at the earliest stage of relativistic heavy-ion collisions, probe the entire history of the quark-gluon plasma that is created in the collision. Initially the plasma is populated with chromodynamic fields which can be treated as classical. We study the transport of heavy quarks across such a system, which is called glasma, using a Fokker-Planck equation where the quarks interact with long wavelength chromodynamic fields. We compute field correlators which are used to calculate the collision terms of the transport equation. Finally, the energy loss and momentum broadening of heavy quarks in the glasma are studied. Both of these quantities are sizable and strongly directionally dependent.
nucl-thhep-phNPA(2020)·54 citations
02
Low-lying level structure of $Λ$ hypernuclei and spin dependence of $Λ N$ interaction with antisymmetrized molecular dynamics
Masahiro Isaka🇯🇵 · Yasuo Yamamoto🇯🇵 · Toshio Motoba🇯🇵
$Λ N$ spin-spin and spin-orbit splittings in low-lying excitation spectra are investigated for $p$ -shell $Λ$ hypernuclei on the basis of the microscopic structure calculation within the antisymmetrized molecular dynamics, where the $Λ N$ $G$ -matrix interaction derived from the baryon-baryon interaction model ESC (extended soft core) is used. It is found that the ground-state spin-parity is systematically reproduced in the $p$ -shell $Λ$ hypernuclei by tuning the $Λ N$ spin-spin and spin-orbit interactions so as to reproduce the experimental data of $_{Λ}^{4}$ H, $_{Λ}^{7}$ Li and $_{Λ}^{9}$ Be. Furthermore, we also focus on the excitation energies of the excited doublets as well as the energy shifts of them by the addition of a $Λ$ particle.
nucl-thPRC(2020)·16 citations
03
Precision Predictions
Ulf-G. Meißner🇩🇪
Precision predictions combined with precise measurements are a major tool in sharpening our understanding of the fundamental laws underlying microscopic as well as macroscopic systems. Here, I present a few remarkable examples covering the fields of nuclear, particle and astrophysics.
nucl-thgr-qchep-phNucl.Phys.News(2020)·0 citations
04
Impact of the underlying O(4) criticality on net-proton number fluctuations
Michał Szymański🇵🇱
We discuss the beam-energy dependence of ratios of the first four cumulants of the net-proton number, calculated using a phenomenologically motivated model in which critical mode fluctuations couple to protons and anti-protons. The model takes into account an impact of the underlying $O (4)$ criticality on the QCD phase diagram in the presence of a $Z (2)$ critical point. This allows us to capture qualitatively both the monotonic behavior of the lowest-order ratio and the non-monotonic behavior of higher-order ratios which are seen in the experimental data from the STAR Collaboration. We also discuss the dependence of our results on the coupling strength between the critical mode and the protons as well as the location of the critical point.
nucl-thhep-phActa Phys.Polon.Supp.(2020)·0 citations
05
Exploring the partonic phase at finite chemical potential in and out-of equilibrium
O. Soloveva🇩🇪 · P. Moreau🇩🇪 · L. Oliva🇩🇪 · V. Voronyuk🇷🇺 · V. Kireyeu🇷🇺 · T. Song🇩🇪 · E. Bratkovskaya🇩🇪
We study the influence of the baryon chemical potential $μ_{B}$ on the properties of the Quark-Gluon-Plasma (QGP) in and out-of equilibrium. The description of the QGP in equilibrium is based on the effective propagators and couplings from the Dynamical QuasiParticle Model (DQPM) that is matched to reproduce the equation-of-state of the partonic system above the deconfinement temperature $T_{c}$ from lattice QCD. We study the transport coefficients such as the ratio of shear viscosity $η$ and bulk viscosity $ζ$ over entropy density $s$ , i.e. $η / s$ and $ζ / s$ in the $(T, μ)$ plane and compare to other model results available at $μ_{B} = 0$ . The out-of equilibrium study of the QGP is performed within the Parton-Hadron-String Dynamics (PHSD) transport approach extended in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections based on the DQPM and the evaluated at actual temperature $T$ and baryon chemical potential $μ_{B}$ in each individual space-time cell where partonic scattering takes place. The traces of their $μ_{B}$ dependences are investigated in different observables for symmetric Au+Au and asymmetric Cu+Au collisions such as rapidity and $m_{T}$ - distributions and directed and elliptic flow coefficients $v_{1}, v_{2}$ in the energy range 7.7 GeV $\leq s_{N N} \leq 200$ GeV.
nucl-thhep-phParticles(2020)·12 citations
06
First glimpse of the $N = 82$ shell closure below $Z = 50$ from masses of neutron-rich cadmium isotopes and isomers
V. Manea🇨🇭 · J. Karthein🇨🇭 · D. Atanasov🇩🇪 · M. Bender🇫🇷 · K. Blaum🇩🇪 · T. E. Cocolios🇧🇪 · S. Eliseev🇩🇪 · A. Herlert🇩🇪 · J. D. Holt🇨🇦 · W. J. Huang🇫🇷 · Yu. A. Litvinov🇩🇪 · D. Lunney🇫🇷 and 9 other authors
We probe the $N = 82$ nuclear shell closure by mass measurements of neutron-rich cadmium isotopes with the ISOLTRAP spectrometer at ISOLDE-CERN. The new mass of $^{132}$ Cd offers the first value of the $N = 82$ , two-neutron shell gap below $Z = 50$ and confirms the phenomenon of mutually enhanced magicity at $^{132}$ Sn. Using the recently implemented phase-imaging ion-cyclotron-resonance method, the ordering of the low-lying isomers in $^{129}$ Cd and their energies are determined. The new experimental findings are used to test large-scale shell-model, mean-field and beyond-mean-field calculations, as well as the ab initio valence-space in-medium similarity renormalization group.
↳ nucl-exnucl-thPRL(2020)·49 citations
07
Scaling and higher twist in the nucleon Compton amplitude
A. Hannaford-Gunn🇦🇺 · R. Horsley🇬🇧 · Y. Nakamura🇯🇵 · H. Perlt🇩🇪 · P. E. L. Rakow🇬🇧 · G. Schierholz🇩🇪 · K. Somfleth🇦🇺 · H. Stüben🇩🇪 · R. D. Young🇦🇺 · J. M. Zanotti🇦🇺
The partonic structure of hadrons plays an important role in a vast array of high-energy and nuclear physics experiments. It also underpins the theoretical understanding of hadron structure. Recent developments in lattice QCD offer new opportunities for reliably studying partonic structure from first principles. Here we report on the use of the Feynman-Hellmann theorem to study the forward Compton amplitude in the unphysical region. We demonstrate how this amplitude provides direct constraint on hadronic inelastic structure functions. The use of external momentum transfer allows us to study the $Q^{2}$ evolution to explore the onset of asymptotic scaling and reveal higher-twist effects in partonic structure.
↳ hep-lathep-phnucl-thPoS(2020)·21 citations
08
Dirac Eigenvalue spectrum of $N_{f}$ =2+1 QCD towards the chiral limit using HISQ fermions
Heng-Tong Ding🇨🇳 · Olaf Kaczmarek🇨🇳 · Frithjof Karsch🇩🇪 · Sheng-Tai Li🇨🇳 · Swagato Mukherjee🇺🇸 · Akio Tomiya🇺🇸 · Yu Zhang🇨🇳
We utilize the eigenvalue filtering technique combined with the stochastic estimate of the mode number to determine the eigenvalue spectrum. Simulations of (2 + 1)-flavor QCD are performed using the Highly Improved Staggered Quarks (HISQ/tree) action on $N_{τ}$ = 8 lattices with aspect ratios $N_{σ} / N_{τ}$ ranging from 5 to 7. The strange quark mass is fixed to its physical value $m_{s}^{phy}$ , and the light quark masses $m_{l}$ are varied from $m_{s}^{phy} /40$ to $m_{s}^{phy} /160$ which correspond to pion mass $m_{π}$ ranging from 110 MeV to 55 MeV in the continuum limit. We compute the chiral condensate and $χ_{π} - χ_{δ}$ through the eigenvalue spectrum obtained from the the eigenvalue filtering method. We compare these results with those obtained from a direct calculation of the observables which involves inversions of the fermion matrix using the stochastic "noise vector" method. We find that these approaches yield consistent results. Furthermore, we also investigate the quark mass and temperature dependences of the Dirac eigenvalue density at zero eigenvalues to gain more insights about the $U_{A} (1)$ symmetry breaking in QCD.
↳ hep-lathep-thnucl-thPoS(2020)·11 citations
09
Spectrum and rearrangement decays of tetraquark states with four different flavors
Jian-Bo Cheng🇨🇳 · Shi-Yuan Li🇨🇳 · Yan-Rui Liu🇨🇳 · Yu-Nan Liu🇨🇳 · Zong-Guo Si🇨🇳 · Tao Yao🇨🇳
We have systematically investigated the mass spectrum and rearrangement decay properties of the exotic tetraquark states with four different flavors using a color-magnetic interaction model. Their masses are estimated by assuming that the $X (4140)$ is a $cs c ˉ s ˉ$ tetraquark state and their decay widths are obtained by assuming that the Hamiltonian for decay is a constant. According to the adopted method, we find that the most stable states are probably the isoscalar $b s u ˉ d ˉ$ and $cs u ˉ d ˉ$ with $J^{P} = 0^{+}$ and $1^{+}$ . The width for most unstable tetraquarks is about tens of MeVs, but that for unstable $c u s ˉ d ˉ$ and $cs u ˉ d ˉ$ can be around 100 MeV. For the $X (5568)$ , our method cannot give consistent mass and width if it is a $b u s ˉ d ˉ$ tetraquark state. For the $I (J^{P}) = 0 (0^{+}), 0 (1^{+})$ double-heavy $T_{b c} = b c u ˉ d ˉ$ states, their widths can be several MeVs.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2020)·54 citations
10
Meson masses in external magnetic fields with HISQ fermions
Heng-Tong Ding🇨🇳 · Sheng-Tai Li🇨🇳 · Swagato Mukherjee🇺🇸 · Akio Tomiya🇺🇸 · Xiao-Dan Wang🇨🇳
We studied the temporal correlation function of mesons in the pseudo-scalar channel in (2+1)-flavor QCD in the presence of external magnetic fields at zero temperature. The simulations were performed on $3 2^{3} \times 96$ lattices using the Highly Improved Staggered Quarks (HISQ) action with $m_{π} \approx$ 230 MeV. The strength of magnetic fields $∣ e B ∣$ ranges from 0 to around 3.3 GeV $^{2}$ ( $\sim 60 m_{π}^{2}$ ). We found that the masses of neutral pseudo-scalar particles, e.g. neutral pion and kaon, monotonouslly decrease as the magnetic field grows and then saturate at a nonzero value. It is observed that heavier neutral pseudo-scalars are less affected by magnetic fields. Moreover, we found a non-monotonous behavior of charged pion and kaon mass in magnetic field for the first time. In the case of small magnetic field (0 $\leq ∣ e B ∣ ≲$ 0.3 GeV $^{2} \sim 6 m_{π}^{2}$ ) the mass of charged pseudo-scalar grows with magnetic field and can be well described by the Lowest Landau Level approximation, while for $∣ e B ∣$ larger than 0.3 GeV $^{2}$ the mass starts to decrease. The possible connection between $∣ e B ∣$ dependences of neutral pion mass and the decreasing behavior of pseudo-critical temperature in magnetic field is discussed. Due to the nonzero value of neutral pion mass our simulation indicates that the superconducting phase of QCD does not exist in the current window of magnetic field.
↳ hep-lathep-phnucl-thPoS(2020)·33 citations
11
Precision calculation of the axion-nucleon coupling in chiral perturbation theory
Thomas Vonk🇩🇪 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇨🇳
We derive the axion-nucleon interaction Lagrangian in heavy baryon chiral perturbation theory up to next-to-next-to-leading order. The effective axion-nucleon coupling is calculated to a few percent accuracy.
↳ hep-phastro-ph.HEhep-latnucl-thJHEP(2020)·38 citations
12
Real-time Dynamics of Plasma Balls from Holography
Hans Bantilan🇬🇧 · Pau Figueras🇬🇧 · David Mateos🇪🇸
Plasma balls are droplets of deconfined plasma surrounded by a confining vacuum. We present the first holographic simulation of their real-time evolution via the dynamics of localized, finite-energy black holes in the five-dimensional anti-de Sitter (AdS) soliton background. The dual gauge theory is four-dimensional, N=4 super Yang-Mills compactified on a circle with supersymmetry-breaking boundary conditions. We consider horizonless initial data sourced by a massless scalar field. Prompt scalar field collapse then produces an excited black hole at the bottom of the geometry together with gravitational and scalar radiation. The radiation disperses to infinity in the noncompact directions and corresponds to particle production in the dual gauge theory. The black hole evolves toward the dual of an equilibrium plasma ball on a time scale longer than naively expected. This feature is a direct consequence of confinement and is caused by long-lived, periodic disturbances bouncing between the bottom of the AdS soliton and the AdS boundary.
↳ hep-thgr-qcnucl-thPRL(2020)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE