Nuclear Theory·nucl-th

Tuesday·June 6, 2017

13 papers—9 primary·4 cross-listed

01
A Novel Approach For Event-By-Event Early Gluon Fields
Rainer J. Fries🇺🇸 · Steven Rose🇺🇸
We report on efforts to construct an event generator that calculates the classical gluon field generated at early times in high energy nuclear collisions. Existing approaches utilize numerical solutions of the Yang-Mills equations after the collision. In contrast we employ the analytically known recursion relation in the forward light cone. The few lowest orders are expected to lead to reliable results for times of up to the inverse saturation scale, tau_0 ~ 1/Q_s. In these proceedings we sketch some calculational details, and show some preliminary results.
nucl-thNucl.Part.Phys.Proc.(2017)·2 citations
02
$Ω$ and $ϕ$ in Au + Au ~collisions at \srt~= 200 and 11.5 GeV from a multiphase transport model
Y. J. Ye🇨🇳 · J. H. Chen🇨🇳 · Y. G. Ma🇨🇳 · S. Zhang🇨🇳 · C. Zhong🇨🇳
Within the framework of a multiphase transport model, we study the production and properties of $Ω$ and $ϕ$ in Au + Au collisions with a new set of parameters for $s_{N N}$ = 200 GeV and with the original set of parameters for $s_{N N}$ = 11.5 GeV, respectively. The AMPT model with the string melting version provides a reasonable description at $s_{N N}$ = 200 GeV and while the AMPT model with default version describes the data well at $s_{N N}$ = 11.5 GeV. It indicates that the system created at top RHIC energy is dominated by partonic interaction and while the hadronic interaction becomes important at lower beam energy, such as $s_{N N}$ = 11.5 GeV. The comparison of $N (Ω^{+} + Ω^{-}) / [2 N (ϕ)]$ ratio between data and calculations further supports the argument. Our calculations can generally describe the data of nuclear modification factor as well as elliptic flow.
nucl-thnucl-exCPC(2017)·17 citations
03
Giant dipole resonance in proton capture reactions using an extended quantum molecular dynamics model
K. Wang · Y. G. Ma · G. Q. Zhang · X. G. Cao · W. B. He · W. Q. Shen
Proton capture reaction is an important process concerning the astrophysical origin of the elements. In present work, we focus on giant dipole resonance (GDR) in proton capture reactions, such as $^{11}$ B $(p, γ)^{12}$ C, $^{27}$ Al $(p, γ)^{28}$ Si, $^{39}$ K $(p, γ)^{40}$ Ca, and $^{67}$ Co $(p, γ)^{68}$ Ni in a framework of an extended quantum molecular dynamics model. The systematic properties of GDR parameters including the peak energy, the strength and full width at half maximum (FWHM) have been studied. The dependence of FWHM on temperature has also been discussed. Some comparisons with experimental data have been presented.
nucl-thnucl-exPRC(2017)·10 citations
04
Simulating spin dynamics with spin-dependent cross sections in heavy-ion collisions
Yin Xia · Jun Xu · Bao-An Li · Wen-Qing Shen
We have incorporated the spin-dependent nucleon-nucleon cross sections into a Boltzmann-Uehling-Uhlenbeck transport model for the first time, using the spin-singlet and spin-triplet nucleon-nucleon elastic scattering cross sections extracted from the phase-shift analyses of nucleon-nucleon scatterings in free space. We found that the spin splitting of the collective flows is not affected by the spin-dependent cross sections, justifying it as a good probe of the in-medium nuclear spin-orbit interaction. With the in-medium nuclear spin-orbit mean-field potential that leads to local spin polarization, we found that the spin-averaged observables, such as elliptic flows of free nucleons and light clusters, becomes smaller with the spin-dependent differential nucleon-nucleon scattering cross sections.
nucl-thnucl-exPRC(2017)·9 citations
05
On the existence of Rydberg nuclear molecules
C. A. Bertulani · T. Frederico · M. S. Hussein
Present nuclear detection techniques prevents us from determining if the analogue of a Rydberg molecule exists for the nuclear case. But nothing in nature disallows their existence. As in the atomic case, Rydberg nuclear molecules would be a laboratory for new aspects and applications of nuclear physics. We propose that Rydberg nuclear molecules, which represent the exotic, halo nuclei version, such as 11Be + 11Be, of the well known quasimolecules observed in stable nuclei such as 12C + 12C, might be common structures that could manifest their existence along the dripline. A study of possible candidates and the expected structure of such exotic clustering of two halo nuclei: the Rydberg nuclear molecules, is made on the basis of three diferent methods. It is shown that such cluster structures might be stable and unexpectedly common.
nucl-thnucl-exPLB(2017)·4 citations
06
Superheavy Nuclei in the Quark-Meson-Coupling Model
Jirina Stone🇬🇧 · Pierre Guichon🇫🇷 · Anthony Thomas🇦🇺
We present a selection of the first results obtained in a comprehensive calculation of ground state properties of even-even superheavy nuclei in the region of 96 < Z < 136 and 118 < N < 320 from the Quark-Meson-Coupling model (QMC). Ground state binding energies, the neutron and proton number dependence of quadrupole deformations and Q $_{α}$ values are reported for even-even nuclei with 100 < Z < 136 and compared with available experimental data and predictions of macro-microscopic models. Predictions of properties of nuclei, including Q $_{α}$ values, relevant for planning future experiments are presented.
nucl-thEPJ Web Conf.(2017)·16 citations
07
Ground-state properties of some N=Z medium mass heavy nuclei
Serkan Akkoyun · Tuncay Bayram · Şevki Şentürk
The ground-state properties of 64Ge, 68Se, 72Kr and 76Sr (N=Z) nuclei have been investigated by using Hartree-Fock-Bogolibov (HFB)method with Sly4 Skyrme forces and Relativistic Mean Field (RMF) model with NL3 and recently proposed DEFNE interaction parameters sets. For determination of ground-state axially deformed shape and quadrupole moment constrained calculations have been employed in RMF model. The results of the present study have been compared with each other and available experimental data in the literature. The ground-state binding energies,neutron, proton and charge radii, quadrupole moment deformation parameters of these nuclei have been calculated. Furthermore, neutron skin thickness of considered nuclei as a function of deformation parameter have been obtained and discussed in detail.
nucl-th0 citations
08
Effect of the Constant Potential in the Bethe-Salpeter Equation for Proton-Neutron Elastic Scattering
Susumu Kinpara
Nucleon-nucleon potential is given in coordinate space starting from the Bethe-Salpeter equation appropriate to elastic scattering at the intermediate energy region. The next order in the potential is added to construct the scattering wave for $^{3} S_{1}$ state. The constant terms have an effect on the spin observables particularly at the center of mass angle $θ = 9 0^{\circ}$
nucl-th1 citation
09
Feasability of constraining the curvature parameter of the symmetry energy using elliptic flow data
M.D. Cozma🇷🇴
A QMD type transport model supplemented by a phase-space coalescence model fitted to FOPI experimental multiplicities of free nucleons and light clusters has been used to study the density dependence of the symmetry energy above the saturation point by a comparison with experimental elliptic flow ratios measured by the FOPI-LAND and ASYEOS collaborations in $^{197}$ Au+ $^{197}$ Au collisions at 400 MeV/nucleon impact energy. A previous calculation has proven that neutron-to-proton and neutron-to-charged particles elliptic flow ratios probe on average different densities allowing in principle the extraction of both the slope $L$ and curvature $K_{sy m}$ parameters of the symmetry energy. Consequently a Gogny interaction inspired potential has been modified to allow independent changes of $L$ and $K_{sy m}$ . Comparing theoretical predictions with experimental data for neutron-to-proton and neutron-to-charged particles elliptic flow ratios the following constraints have been extracted: $L$ =85 $\pm$ 22(exp) $\pm$ 20(th) $\pm$ 12(sys) MeV and $K_{sy m}$ =96 $\pm$ 315(exp) $\pm$ 170(th) $\pm$ 166(sys) MeV. Residual model dependence is accounted for in the magnitude of the quoted theoretical error. Systematical uncertainties are generated by the inability of the transport model to reproduce experimental light-cluster-to-proton multiplicity ratios. A value for $L$ , free of systematical theoretical uncertainties, can be extracted from the neutron-to-proton elliptic flow ratio alone: $L$ =84 $\pm$ 30(exp) $\pm$ 19(th) MeV. It has also been demonstrated that elliptic flow ratios reach a maximum sensitivity on the $K_{sy m}$ parameter in heavy-ion collisions of about 250 MeV/nucleon impact energy, allowing a reduction of the experimental component of uncertainty to about 150 MeV for this parameter.
nucl-thEPJA(2018)·60 citations
10
Point-Particle Effective Field Theory III: Relativistic Fermions and the Dirac Equation
C.P. Burgess🇨🇦 · Peter Hayman🇨🇦 · Markus Rummel🇨🇦 · Laszlo Zalavari🇨🇦
We formulate point-particle effective field theory (PPEFT) for relativistic spin-half fermions interacting with a massive, charged finite-sized source using a first-quantized effective field theory for the heavy compact object and a second-quantized language for the lighter fermion with which it interacts. This description shows how to determine the near-source boundary condition for the Dirac field in terms of the relevant physical properties of the source, and reduces to the standard choices in the limit of a point source. Using a first-quantized effective description is appropriate when the compact object is sufficiently heavy, and is simpler than (though equivalent to) the effective theory that treats the compact source in a second-quantized way. As an application we use the PPEFT to parameterize the leading energy shift for the bound energy levels due to finite-sized source effects in a model-independent way, allowing these effects to be fit in precision measurements. Besides capturing finite-source-size effects, the PPEFT treatment also efficiently captures how other short-distance source interactions can shift bound-state energy levels, such as due to vacuum polarization (through the Uehling potential) or strong interactions for Coulomb bound states of hadrons, or any hypothetical new short-range forces sourced by nuclei.
↳ hep-phhep-thnucl-thJHEP(2017)·16 citations
11
Nonlinear approach to the entrainment matrix of superfluid nucleon mixture at zero temperature
Lev B. Leinson
The superfluid drag effect, in hydrodynamics of pulsating neutron stars, is conventionally described with the aid of the entrainment matrix relating the mass currents with the velocities of superfluid flows in the system. Equations for the entrainment matrix of a superfluid mixture of neutrons and protons are derived with allowance for the strong dependence of the energy gaps on the velocities of superfluid flows. The calculations are carried out in the frame of the Fermi-liquid theory. The equations obtained are highly nonlinear. Numerical solutions to the equations for some typical cases demonstrate that the components of the entrainment matrix possess a highly nonlinear dependence on the velocities of the two superflows simultaneously. This effect, previously ignored, can greatly influence the dynamics of neutron stars.
↳ astro-ph.HEnucl-thMNRAS(2017)·10 citations
12
Parton Distribution Function with Non-perturbative Renormalization from Lattice QCD
Jiunn-Wei Chen🇹🇼 · Tomomi Ishikawa🇨🇳 · Luchang Jin🇺🇸 · Huey-Wen Lin🇺🇸 · Yi-Bo Yang🇺🇸 · Jian-Hui Zhang🇩🇪 · Yong Zhao🇺🇸
We present lattice results for the isovector unpolarized parton distribution with nonperturbative RI/MOM-scheme renormalization on the lattice. In the framework of large-momentum effective field theory (LaMET), the full Bjorken- $x$ dependence of a momentum-dependent quasi-distribution is calculated on the lattice and matched to the ordinary lightcone parton distribution at one-loop order, with power corrections included. The important step of RI/MOM renormalization that connects the lattice and continuum matrix elements is detailed in this paper. A few consequences of the results are also addressed here.
↳ hep-lathep-phnucl-thPRD(2018)·176 citations
13
Identity Method Revisited
Claude A. Pruneau🇺🇸
We discuss the impact of finite particle losses associated with instrumental effects in measurements of moments of produced multiplicities with the Identity Method towards the evaluation of fluctuation measures such as $ν_{d y n}$ . We show that the identity method remains applicable provided it is modified to determine factorial moments $⟨ N (N - 1)⟩$ , rather than moments $⟨ N^{2} ⟩$ . We further show that $ν_{d y n}$ remains robust if detection efficiencies are uniform across the measurement's acceptance. The robustness is lost, however, if detection efficiencies are momentum dependent, although the identity methods remains applicable provided detection efficiencies can be determined with sufficient accuracy.
↳ physics.data-annucl-thPRC(2017)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE