Nuclear Theory·nucl-th

Tuesday·March 3, 2020

11 papers—5 primary·6 cross-listed

01
Connecting far-from-equilibrium hydrodynamics to resummed transport coefficients and attractors
Gabriel S. Denicol (Niteroi, Fluminense U.)🇧🇷 · Jorge Noronha (Illinois U., Urbana)🇺🇸
We investigate whether hydrodynamic attractors are present in simulations of the quark-gluon plasma formed in heavy-ion collisions. We argue that Lagrangian schemes to solve the relativistic viscous fluid equations can be particularly useful to characterize the properties of attractors in heavy ion collisions. Preliminary results are shown in Israel-Stewart theory to support such a claim. We also discuss how to perform the slow-roll expansion in Israel-Stewart theory undergoing a general flow, which naturally leads to the definition of a resummed shear viscosity coefficient that depends on the gradients of the hydrodynamic fields.
nucl-thNPA(2021)·19 citations
02
Neutron-rich matter in atomic nuclei and neutron stars
Claudia Gonzalez-Boquera🇪🇸
The proper understanding of the equation of state (EoS) of highly asymmetric nuclear matter is essential when studying systems such as neutron stars (NSs). Using zero-range Skyrme interactions and finite-range interactions such as Gogny forces, momentum-dependent interactions (MDI) and simple effective interactions (SEI), we analyze the properties of the EoS and the influence they may have on the calculations for NSs. We study the convergence properties of the Taylor series expansion of the EoS in powers of the isospin asymmetry and the accuracy of the results for $β$ -stable nuclear matter when it is computed using the Taylor expansion of the EoS. The NS mass-radius relation for Skyrme and finite-range interactions is also analyzed. As none of the existing parametrizations of the standard Gogny D1 interaction are able to provide an NS inside the observational constraints, we propose a new parametrization, which we name D1M $^{*}$ , that is able to provide NSs of $2 M_{⊙}$ while still providing the same good description of finite nuclei as D1M. A parametrization D1M $^{**}$ is also presented, which is fitted similarly as D1M $^{*}$ and provides NSs up to $1.91 M_{⊙}$ . An accurate determination of the core-crust transition point is necessary for the modeling of NSs for astrophysical purposes. We estimate the core-crust transition in NSs by finding where the nuclear matter in the core is unstable against fluctuations of the density. To do that, we employ two methods, the thermodynamical method and the dynamical method for zero-range and finite-range interactions. To apply the dynamical method to finite-range forces, we have explicitly derived the expression of the energy curvature matrix in momentum space. Finally, the NS crustal properties, moment of inertia and tidal deformability are thoroughly analyzed using Skyrme and finite-range interactions.
nucl-th4 citations
03
The possibility to study in-medium modification of $J / ψ$ mesons from their photoproduction on nuclei near threshold in the case of presence of the LHCb pentaquark states $P_{c}^{+}$ in this photoproduction
E. Ya. Paryev🇷🇺
We study the $J / ψ$ photoproduction from nuclei in the near-threshold beam energy region of $E_{γ}$ =5--11 GeV within the nuclear spectral function approach by considering incoherent direct ( $γ N \to J / ψ N$ ) and two-step ( $γ p \to P_{c}^{+} (4312)$ , $P_{c}^{+} (4312) \to J / ψ p$ ; $γ p \to P_{c}^{+} (4440)$ , $P_{c}^{+} (4440) \to J / ψ p$ ; $γ p \to P_{c}^{+} (4457)$ , $P_{c}^{+} (4457) \to J / ψ p$ ) $J / ψ$ production processes. We calculate the absolute excitation functions for the non-resonant and resonant production of $J / ψ$ mesons off $^{12}$ C and $^{208}$ Pb target nuclei within the different scenarios for in-medium modification of the directly photoproduced $J / ψ$ mesons and for branching ratios of the decays $P_{c}^{+} (4312) \to J / ψ p$ , $P_{c}^{+} (4440) \to J / ψ p$ and $P_{c}^{+} (4457) \to J / ψ p$ . We show that the non-resonant subthreshold $J / ψ$ production in $γ A$ reactions reveals some sensitivity to employed in-medium modification scenarios for $J / ψ$ mesons, which is not masked by the resonantly produced $J / ψ$ mesons, only if above branching ratios are less than 5\%. We also demonstrate that if these branching ratios more than 5\% then the presence of the $P_{c}^{+} (4312)$ , $P_{c}^{+} (4440)$ and $P_{c}^{+} (4457)$ resonances in $J / ψ$ photoproduction on nuclei produces above threshold additional enhancements in the behavior of the total $J / ψ$ creation cross section on nuclei, which could be also studied in the future JLab experiments at the CEBAF facility to provide both further evidence for their existence and valuable information on their nature.
nucl-thnucl-exNPA(2020)·9 citations
04
The single-particle unit for alpha decay
Chong Qi · Roberto Liotta · Ramon Wyss
A salient feature of quantum mechanics is the inherent property of collective quantum motion, when apparent independent quasiparticles move in highly correlated trajectories, resulting in strongly enhanced transition probabilities. To assess the extend of a collective quantity requires an appropriate definition of the uncorrelated average motion, often expressed by single particle units. A well known example in nuclear physics is the Weisskopf unit for electromagnetic transitions which reveals different aspects of collective motion. In this paper we define the corresponding single particle unit for alpha decay following Weisskopf's derivations. We evaluate the alpha decay amplitude as induced by four uncorrelated/non-interacting protons and neutrons and compare it with the one extracted from observed decay rates. Our definition elucidates the collectivity in alpha decay and facilitates an unified description of all alpha decay processes along the nuclear chart. Our formalism is also applicable to other particle decay processes.
nucl-thnucl-exPLB(2021)·7 citations
05
Microscopic description of the self-conjugate $^{108}$ Xe and $^{104}$ Te $α$ -decay chain
F. Mercier🇫🇷 · J. Zhao🇨🇳 · R.-D Lasseri🇫🇷 · J.-P. Ebran🇫🇷 · E. Khan🇫🇷 · T. Niksic🇭🇷 · D. Vretenar🇭🇷
A microscopic calculation of half-lives for the recently observed $^{108}$ Xe $\to$ $^{104}$ Te $\to$ $^{100}$ Sn $α$ -decay chain is performed using a self-consistent framework based on energy density functionals. The relativistic density functional DD-PC1 and a separable pairing interaction of finite range are used to compute axially-symmetric deformation energy surfaces of $^{104}$ Te and $^{108}$ Xe as functions of quadrupole, octupole and hexadecupole collective coordinates. Dynamic least-action paths are determined that trace the $α$ -particle emission from the equilibrium deformation to the point of scission. The calculated half-lives: 197 ns for $^{104}$ Te and 50 $μ$ s for $^{108}$ Xe, are compared to recent experimental values of the half-lives of superallowed $α$ -decay of $^{104}$ Te: $< 18$ ns, and $^{108}$ Xe: 58 $_{- 23}^{+ 106}$ $μ$ s.
nucl-thPRC(2020)·15 citations
06
Hadron Physics at J-PARC
Hiroaki Ohnishi🇯🇵 · Fuminori Sakuma🇯🇵 · Toshiyuki Takahashi🇯🇵
The aim of the hadron physics research programs conducted at J-PARC is to explore the structure of hadronic matter using the world's highest-intensity meson beams. Since the first beam was extracted at the hadron experimental facility (HEF) in February 2009, a wide variety of physics experiments have been proposed and performed to address open questions regarding quantum chromodynamics (QCD) at low energy. The high-intensity $K^{-}$ and high-momentum beams available at J-PARC open a new era in hadron and nuclear physics, in which strange and charm quarks play an important role. We review the programs focused on addressing the hadron structure as strongly interacting composite particles, the origin of hadron mass, and interactions between hadrons under broken flavor SU(3) symmetry.
↳ nucl-exnucl-thPPNP(2020)·43 citations
07
Quantum Kinetic Equation for spin polarization of massive quarks from pQCD
Shiyong Li🇺🇸
We review the recent progress in formulating a quantum kinetic theory for the polarization of spin- $\frac{1}{2}$ massive quarks from the leading-log order of perturbative QCD.
↳ hep-phnucl-thNPA(2021)·2 citations
08
Superfluid-Normal Quantum Phase Transitions in an Imbalanced Fermi Gas
Heron Caldas🇧🇷
We investigate the superfluid-to-normal zero temperature quantum phase transitions of asymmetric two-component Fermi gases as a function of the chemical potential imbalance $h$ . The calculations are performed for homogeneous and trapped imbalanced systems. We concentrate at unitarity, characterized by a divergent interaction parameter $k_{F} a$ , where most of the current experiments are realized. For homogeneous systems, we determine the critical chemical potential imbalance $h_{c}$ at which possible phase transitions occur. In the case of trapped gases, we show how $h_{c}$ can be consistently determined from experimental observations.
↳ cond-mat.quant-gascond-mat.supr-conhep-thnucl-thJ.Phys.B(2020)·1 citation
09
Analysis of Bose-Einstein correlation at 7 TeV by LHCb collaboration based on stochastic approach
Takuya Mizoguchi🇯🇵 · Minoru Biyajima🇯🇵
The Bose-Einstein correlation (BEC) in forward region ( $2.0 < η < 4.8$ ) measured at 7 TeV in the Large Hadron Collider (LHC) by the LHCb collaboration is analyzed using two conventional formulas of different types named CF $_{I}$ and CF $_{II}$ . The first formula is well known and contains the degree of coherence ( $λ$ ) and the exchange function $E_{BE}^{2}$ from the BE statistics. The second formula is an extended formula (CF $_{II}$ ) that contains the second degree of coherence $λ_{2}$ and the second exchange function $E_{B E_{2}}^{2}$ in addition to CF $_{I}$ . To examine the physical meaning of the parameters estimated by CF $_{II}$ , we analyze the LHCb BEC data by using a stochastic approach of the three-negative binomial distribution and the three-generalized Glauber-Lachs formula. Our results reveal that the BEC at 7 TeV consisted of three activity intervals defined by the multiplicity $n$ ([8, 18], [19, 35], and [36, 96]) can be well explained by CF $_{II}$ .
↳ hep-phhep-exnucl-thInt.J.Mod.Phys.A(2020)·4 citations
10
Analytical determination of the structure and nuclear abundances of the outer crust of a cold nonaccreted neutron star
Nicolas Chamel
A very fast iterative method is presented to calculate the internal constitution of the outer crust of a cold nonaccreted neutron star, making use of very accurate analytical formulas for the transition pressures between adjacent crustal layers and their density. In addition to the composition of the different crustal layers, their depth and their baryonic mass content can be simultaneously estimated using an approximate solution of Einstein's general relativistic equations. The overall computing time is drastically reduced compared to the traditional approach, thus opening the door to large-scale statistical studies and sensitivity analyses.
↳ astro-ph.HEnucl-thPRC(2020)·23 citations
11
Constraints on charm-anticharm asymmetry in the nucleon from lattice QCD
Raza Sabbir Sufian🇺🇸 · Tianbo Liu🇺🇸 · Andrei Alexandru🇺🇸 · Stanley J. Brodsky🇺🇸 · Guy F. de Téramond🇨🇷 · Hans Günter Dosch🇩🇪 · Terrence Draper🇺🇸 · Keh-Fei Liu🇺🇸 · Yi-Bo Yang🇨🇳
We present the first lattice QCD calculation of the charm quark contribution to the nucleon electromagnetic form factors $G_{E, M}^{c} (Q^{2})$ in the momentum transfer range $0 \leq Q^{2} \leq 1.4$ $Ge V^{2}$ . The quark mass dependence, finite lattice spacing and volume corrections are taken into account simultaneously based on the calculation on three gauge ensembles including one at the physical pion mass. The nonzero value of the charm magnetic moment $μ_{M}^{c} = - 0.00127 (38)_{stat} (5)_{sys}$ , as well as the Pauli form factor, reflects a nontrivial role of the charm sea in the nucleon spin structure. The nonzero $G_{E}^{c} (Q^{2})$ indicates the existence of a nonvanishing asymmetric charm-anticharm sea in the nucleon. Performing a nonperturbative analysis based on holographic QCD and the generalized Veneziano model, we study the constraints on the $[c (x) - c ˉ (x)]$ distribution from the lattice QCD results presented here. Our results provide complementary information and motivation for more detailed studies of physical observables that are sensitive to intrinsic charm and for future global analyses of parton distributions including asymmetric charm-anticharm distribution.
↳ hep-lathep-exhep-phnucl-thPLB(2020)·52 citations

Affiliations

first authorsco-authorsvia INSPIRE