Nuclear Theory·nucl-th

Tuesday·October 25, 2016

17 papers—12 primary·5 cross-listed

01
Phonon-particle coupling effects in odd-even double mass differences of semi-magic nuclei
E.E. Saperstein · M. Baldo · S.S. Pankratov · S.V. Tolokonnikov
A method is developed to consider the particle-phonon coupling (PC) effects in the calculation of the odd-even double mass differences (DMD) in semi-magic nuclei starting from the free $N N$ -potential. The PC correction $δ Σ^{PC}$ to the mass operator $Σ$ is found in $g_{L}^{2}$ -approximation, $g_{L}$ being the vertex of creating the $L$ -phonon. The tadpole term of the operator $δ Σ^{PC}$ is taken into account. The method is based on a direct, without any use of the perturbation theory, solution of the Dyson equation with the mass operator $Σ (ϵ) = Σ_{0} + δ Σ^{PC} (ϵ)$ for finding the single-particle energies and $Z$ -factors. In its turn, they are used as an input for finding different PC corrections to the DMD values. Results for a chain of even semi-magic nuclei $^{200 - 206}$ Pb show that the inclusion of the PC corrections makes agreement with the experimental data significantly better.
nucl-thJETP Lett.(2016)·5 citations
02
A novel nuclear dependence of nucleon-nucleon short-range correlations
Hongkai Dai🇨🇳 · Rong Wang🇨🇳 · Yin Huang🇨🇳 · Xurong Chen🇨🇳
A linear correlation is found between the magnitude of nucleon-nucleon short-range correlations and the nuclear binding energy per nucleon with pairing energy removed. By using this relation, the strengths of nucleon-nucleon short-range correlations of some unmeasured nuclei are predicted. Discussions on nucleon-nucleon pairing energy and nucleon-nucleon short-range correlations are made. The found nuclear dependence of nucleon-nucleon short-range correlations may shed some lights on the short-range structure of nucleus.
nucl-thhep-phPLB(2017)·8 citations
03
Probing the Source of Proton Mass by"Unbreaking" Scale-Chiral Symmetry
Mannque Rho🇫🇷
I describe a possible scenario for the origin of proton mass in terms of Cheshire Cat, half-skyrmions, topology change and interplay between hidden chiral-scale symmetry and induced local symmetry. This differs from the standard constituent-quark scenario. As the baryonic matter density is increased toward the vector manifestation (VM) fixed-point at which the $ρ$ mass is to vanish, the effective in-medium mass ratio $m_{ρ}^{*} / m_{N}^{*}$ is to tend to zero proportionally to $g_{ρ}^{*}$ where $g_{ρ}^{*}$ is the in-medium hidden gauge coupling constant. I develop the thesis that the intricacy involved in the mass generation could be decoded from experiments at RIB accelerators and massive compact stars.
nucl-thhep-phNew Phys.Sae Mulli(2016)·6 citations
04
Higher moments of multiplicity fluctuations in a hadron-resonance gas with exact conservation laws
Jing-Hua Fu🇨🇳
Higher moments of multiplicity fluctuations of hadrons produced in central nucleus-nucleus collisions are studied within the hadron-resonance gas model in the canonical ensemble. Exact conservation of three charges, baryon number, electric charge, and strangeness, is enforced in the large volume limit. Moments up to the forth order of various particles are calculated at SPS, RHIC and LHC energies. The asymptotic fluctuations within a simplified model with only one conserved charge in the canonical ensemble are discussed where simple analytical expressions for moments of multiplicity distributions can be obtained. Moments products of net-proton, net-kaon, and net-charge distributions in Au + Au collisions at RHIC energies are calculated. The pseudo-rapidity coverage dependence of net-charge fluctuation is discussed.
nucl-thPRC(2017)·17 citations
05
Determining Transport Coefficients for a Microscopic Simulation of a Hadron Gas
Scott Pratt🇺🇸 · Alexander Baez🇺🇸 · Jane Kim🇺🇸
Quark-Gluon plasmas produced in relativistic heavy-ion collisions quickly expand and cool, entering a phase consisting of multiple interacting hadronic resonances just below the QCD deconfinement temperature, $T \sim 155$ MeV. Numerical microscopic simulations have emerged as the principal method for modeling the behavior of the hadronic stage of heavy-ion collisions, but the transport properties that characterize these simulations are not well understood. Methods are presented here for extracting the shear viscosity, and two transport parameters that emerge in Israel-Stewart hydrodynamics. The analysis is based on studying how the stress-energy tensor responds to velocity gradients. Results agree with expectations based on Kubo relations.
nucl-thPRC(2017)·11 citations
06
Non-perturbative production rate of photons with a lattice quark propagator: effect of vertex correction
Taekwang Kim🇯🇵 · Masayuki Asakawa🇯🇵 · Masakiyo Kitazawa🇯🇵
We analyze the production rate of photons from the thermal medium above the deconfinement temperature with a quark propagator obtained from a lattice QCD numerical simulation. The photon-quark vertex is determined gauge-invariantly, so as to satisfy the Ward-Takahashi identity. The obtained photon production rate shows a suppression compared to perturbative results.
nucl-thhep-phActa Phys.Polon.Supp.(2017)·0 citations
07
Scattering states of Dirac particle equation with position dependent mass under the cusp potential
M. Chabab · A. El Batoul · H. Hassanabadi · M. Oulne · S. Zare
We solved the one-dimensional position-dependent mass Dirac equation in the presence of the cusp potential and reported the solutions in terms of the Whittaker functions. We have derived the reflection and transmission coefficients by making use of the matching conditions on the wave functions. The effect of position dependent mass on the reflection and transmission coefficients of the system is duly investigated.
nucl-thEur.Phys.J.Plus(2016)·8 citations
08
The dynamic polarization potential and dynamical non-locality in nuclear potentials: Deuteron-nucleus potential
R.S. Mackintosh · N.Keeley
The consequences for direct reactions of the dynamical non-locality generated by the excitation of the target and projectile are much less studied than the effects of non-locality arising from exchange processes. Here we are concerned with the dynamical non-locality due to projectile excitation in deuteron induced reactions. The consequences of this non-locality can be studied by the comparison of deuteron induced direct reactions calculated with alternative representations of the elastic channel wave functions: (i) the elastic channel wave functions from coupled channel (CC) calculations involving specific reaction processes, and, (ii) elastic channel wave functions calculated from local potentials that exactly reproduce the elastic scattering $S$ -matrix from the same CC calculations. In this work we produce the local equivalent deuteron potentials required for the study of direct reactions involving deuterons. These will enable the study of the effects of dynamical non-locality following a method previously employed in an investigation of the effects of non-locality due to target excitation. In this work we consider only excitations due to deuteron breakup, and some new properties of the breakup dynamical polarization potential (DPP) emerge that reveal dynamical non-locality directly. In addition, we evaluate the TELP inversion method and find that it fails to reproduce some features of the DPP due to breakup.
nucl-thnucl-ex5 citations
09
Deuteron properties from muonic atom spectroscopy
N. G. Kelkar🇨🇴 · D. Bedoya Fierro🇨🇴
Leading order ( $α^{4}$ ) finite size corrections in muonic deuterium are evaluated within a few body formalism for the $μ^{-} p n$ system in muonic deuterium and found to be sensitive to the input of the deuteron wave function. We show that this sensitivity, taken along with the precise deuteron charge radius determined from muonic atom spectroscopy can be used to determine the elusive deuteron D-state probability, $P_{D}$ , for a given model of the nucleon-nucleon (NN) potential. The radius calculated with a $P_{D}$ of 4.3\% in the chiral NN models and about 5.7\% in the high precision NN potentials is favoured most by the $μ^{-} d$ data.
nucl-thhep-phPLB(2017)·6 citations
10
Scalable Nuclear Density Functional Theory with Sky3D
Md Afibuzzaman · Bastian Schuetrumpf · Hasan Metin Aktulga
In nuclear astrophysics, quantum simulations of large inhomogeneous dense systems as they appear in the crusts of neutron stars present big challenges. The number of particles in a simulation with periodic boundary conditions is strongly limited due to the immense computational cost of the quantum methods. In this paper, we describe techniques for an efficient and scalable parallel implementation of Sky3D, a nuclear density functional theory solver that operates on an equidistant grid. Presented techniques allow Sky3D to achieve good scaling and high performance on a large number of cores, as demonstrated through detailed performance analysis on a Cray XC40 supercomputer.
nucl-thphysics.comp-phComput.Phys.Commun.(2018)·6 citations
11
Model Selection for Pion Photoproduction
J. Landay🇺🇸 · M. Döring🇺🇸 · C. Fernández-Ramírez🇲🇽 · B. Hu🇺🇸 · R. Molina🇺🇸
Partial-wave analysis of meson and photon-induced reactions is needed to enable the comparison of many theoretical approaches to data. In both energy-dependent and independent parametrizations of partial waves, the selection of the model amplitude is crucial. Principles of the $S$ -matrix are implemented to different degree in different approaches, but a many times overlooked aspect concerns the selection of undetermined coefficients and functional forms for fitting, leading to a minimal yet sufficient parametrization. We present an analysis of low-energy neutral pion photoproduction using the Least Absolute Shrinkage and Selection Operator (LASSO) in combination with criteria from information theory and $K$ -fold cross validation. These methods are not yet widely known in the analysis of excited hadrons but will become relevant in the era of precision spectroscopy. The principle is first illustrated with synthetic data, then, its feasibility for real data is demonstrated by analyzing the latest available measurements of differential cross sections ( $d σ / d Ω$ ), photon-beam asymmetries ( $Σ$ ), and target asymmetry differential cross sections ( $d σ_{T} / d Ω$ ) in the low energy regime.
nucl-thhep-phnucl-exPRC(2017)·41 citations
12
Functional renormalization group studies of nuclear and neutron matter
Matthias Drews🇩🇪 · Wolfram Weise🇺🇸
Functional renormalization group (FRG) methods applied to calculations of isospin-symmetric and asymmetric nuclear matter as well as neutron matter are reviewed. The approach is based on a chiral Lagrangian expressed in terms of nucleon and meson degrees of freedom as appropriate for the hadronic phase of QCD with spontaneously broken chiral symmetry. Fluctuations beyond mean-field approximation are treated solving Wetterich's FRG flow equations. Nuclear thermodynamics and the nuclear liquid-gas phase transition are investigated in detail, both in symmetric matter and as a function of the proton fraction in asymmetric matter. The equations of state at zero temperature of symmetric nuclear matter and pure neutron matter are found to be in good agreement with advanced ab-initio many-body computations. Contacts with perturbative many-body approaches (in-medium chiral perturbation theory) are discussed. As an interesting test case, the density dependence of the pion mass in the medium is investigated. The question of chiral symmetry restoration in nuclear and neutron matter is addressed. A stabilization of the phase with spontaneously broken chiral symmetry is found to persist up to high baryon densities once fluctuations beyond mean-field are included. Neutron star matter including beta equilibrium is discussed under the aspect of the constraints imposed by the existence of two-solar-mass neutron stars.
nucl-thhep-phPPNP(2017)·79 citations
13
Sensitivity of stellar electron-capture rates to parent neutron number: A case study on a continuous chain of twenty Vanadium isotopes
G. W. Hitt · S. Gupta · R. G. T. Zegers · R. Titus · C. Sullivan · B. A. Brown · A. L. Cole · S. Shams
Gamow-Teller (GT) strength distributions (B(GT)) in electron-capture (EC) daughters stemming from the parent ground state are computed with the shell-model in the full pf-shell space, with quasi-particle random-phase approximation (QRPA) in the formalism of Krumlinde and Möller and with an Approximate Method (AM) for assigning an effective B(GT). These are compared to data available from decay and charge-exchange (CE) experiments across titanium isotopes in the pf-shell from A=43 to A=62, the largest set available for any chain of isotopes in the pf-shell. The present study is the first to examine B(GT) and the associated EC rates across a particular chain of isotopes with the purpose of examining rate sensitivities as neutron number increases. EC rates are also computed for a wide variety of stellar electron densities and temperatures providing concise estimates of the relative size of rate sensitivities for particular astrophysical scenarios. This work underscores the astrophysical motivation for CE experiments in inverse kinematics for nuclei away from stability at the luminosities of future Radioactive Ion Beam Facilities.
↳ nucl-exastro-ph.SRnucl-th1 citation
14
Production of charmed baryon $Λ_{c} (2940)$ by kaon-induced reaction on a proton target
Yin Huang · Jun He · Ju-Jun Xie · Xurong Chen · Hong-Fei Zhang
We investigate the possibility to study the charmed baryon $Λ_{c} (2940)$ by kaon-induced reaction on a proton target. By assuming the $Λ_{c} (2940)$ as a $p D^{* 0}$ molecular state with spin-parity $J^{p} = 1/ 2^{\pm}$ , an effective Lagrangian approach was adopted to calculate the cross section, the $D^{0} p$ invariant mass spectrum and Dalitz plot of the $Λ (2940)$ production. The total cross section of the $K^{-} p \to Λ_{c} (2940) D_{s}^{-}$ reaction is found at an order of magnitude about 10 $μ$ b. By considering the sub sequential decay $Λ_{c} (2940) \to D^{0} p$ with contributions from the $Λ_{c} (2286)$ and the $Σ_{c} (2455)$ as background, the $K^{-} p \to D_{s}^{-} D^{0} p$ reaction are studied. It is found that the $Λ_{c} (2940)$ is produced mainly at forward angles. The $Λ_{c} (2940)$ signal is predicted to be significant in the $D^{0} p$ invariant mass spectrum and the Dalitz plot of the $K^{-} p \to D_{s}^{-} D^{0} p$ reaction. The results suggest that it is promising to study the $Λ_{c} (2940)$ with high-energy kaon beam on a proton target in experiment.
↳ hep-phhep-exnucl-exnucl-thPRD(2019)·19 citations
15
Directed flow of $Λ$ , $Λ ˉ$ , $K^{\pm}$ , $K_{S}^{0}$ and $ϕ$ mesons from Beam Energy Scan Au+Au collisions using the STAR experiment
Subhash Singha (for the STAR collaboration)🇺🇸
We report the results of $v_{1}$ and $d v_{1} / d y$ near mid-rapidity for $Λ$ , $Λ ˉ$ , $K^{\pm}$ , $K_{s}^{0}$ and $ϕ$ in Au+Au collisions at $s_{NN}$ = 7.7, 11.5, 14.5, 19.6, 27 and 39~GeV using the STAR detector at RHIC. The $d v_{1} / d y$ of $Λ$ is found to be consistent with that of the proton and shows a change in sign near $s_{NN} = 11.5$ ~GeV. The $v_{1}$ slope for $Λ ˉ$ , $p ˉ$ and $ϕ$ shows a similar trend for $s_{NN}$ $>$ 14.5~GeV, while below 14.5~GeV, $ϕ$ $v_{1}$ is consistent with zero but with a large uncertainty. The $d v_{1} / d y$ for net protons and net kaons is similar for $s_{NN} >$ 14.5~GeV, but they deviate at lower beam energies.
↳ nucl-exhep-exnucl-thJ.Phys.Conf.Ser.(2017)·3 citations
16
Partial Wave Decomposition in Friedrichs Model With Self-interacting Continua
Zhiguang Xiao🇨🇳 · Zhi-Yong Zhou🇨🇳
We consider the nonrelativistic model of coupling bare discrete states with continuum states in which the continuum states can have interactions among themselves. By partial-wave decomposition and constraint to the conserved angular momentum eigenstates, the model can be reduced to Friedrichs-like model with additional interactions between the continua. If a kind of factorizable form factor is chosen, the model can be exactly solvable, that is, the generalized discrete eigenstates including bound states, virtual states, and resonances, can all be represented using the original bare states, and so do the in-state and out-state. The exact $S$ matrix is thus obtained. We then discuss the behaviors of the dynamically generated $S$ -wave and $P$ -wave discrete states as the coupling is varying when there is only one self-interacting bare continuum state. We find that even when the potential is repulsive there could also be resonances and virtual states. In the $P$ -wave cases with attractive interaction, we find that when there is a near-threshold bound state, there will always be an accompanying virtual state and we also give a more general argument of this effect.
↳ hep-phmath-phmath.MPnucl-th+1J.Math.Phys.(2017)·21 citations
17
Baryon-Strangeness Correlations in Au+Au Collisions at $s_{NN}$ =7.7-200 GeV from the UrQMD model
Zhenzhen Yang🇨🇳 · Xiaofeng Luo🇨🇳 · Bedangadas Mohanty🇮🇳
Fluctuations and correlations of conserved charges are sensitive observables for studying the QCD phase transition and critical point in high-energy heavy-ion collisions. We have studied the centrality and energy dependence of mixed-cumulants (up to fourth order) between net-baryon and net-strangeness in Au+Au collisions at $s_{N N}$ = 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV from UrQMD model. To compare with other theoretical calculations, we normalize these mixed-cumulants by various order cumulants of net-strangeness distributions. We found that the results obtained from UrQMD calculations are comparable with the results from Lattice QCD at low temperature and hadron resonance gas model. The ratios of mixed-cumulants ( $R_{11}^{B S}, R_{13}^{B S}, R_{22}^{B S}$ ,~ $R_{31}^{B S}$ ) from UrQMD calculations show weak centrality dependence. However, the mixed-cumulant ratios $R_{11}^{B S}$ and $R_{31}^{B S}$ show strong increase at low energy, while the $R_{13}^{B S}$ snd $R_{22}^{B S}$ are similar at different energies. Furthermore, we have also studied the correlations between different hadron species and their contributions to the net-baryon and net-strangeness correlations. These models studies can provide baselines for searching for the signals of QCD phase transition and critical point in heavy-ion collisions.
↳ nucl-exhep-exhep-phnucl-thPRC(2017)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE