Nuclear Theory·nucl-th

Thursday·July 7, 2016

11 papers—3 primary·8 cross-listed

01
Equation of state and hybrid star properties with the weakly interacting light U-boson in relativistic models
Dong-Rui Zhang🇨🇳 · Wei-Zhou Jiang🇨🇳 · Si-Na Wei🇨🇳 · Rong-Yao Yang🇨🇳 · Qian-Fei Xiang🇨🇳
It has been a puzzle whether quarks may exist in the interior of massive neutron stars, since the hadron-quark phase transition softens the equation of state (EOS) and reduce the neutron star (NS) maximum mass very significantly. In this work, we consider the light U-boson that increases the NS maximum mass appreciably through its weak coupling to fermions. The inclusion of the U-boson may thus allow the existence of the quark degrees of freedom in the interior of large mass neutron stars. Unlike the consequence of the U-boson in hadronic matter, the stiffening role of the U-boson in the hybrid EOS is not sensitive to the choice of the hadron phase models. In addition, we have also investigated the effect of the effective QCD correction on the hybrid EOS. This correction may reduce the coupling strength of the U-boson that is needed to satisfy NS maximum mass constraint. While the inclusion of the U-boson also increases the NS radius significantly, we find that appropriate in-medium effects of the U-boson may reduce the NS radii significantly, satisfying both the NS radius and mass constraints well.
nucl-thastro-ph.COEPJA(2016)·8 citations
02
Discrete Wave-Packet Representation in Nuclear Matter Calculations
H. Müther · O.A. Rubtsova · V.I. Kukulin · V.N. Pomerantsev
The Lippmann-Schwinger equation for the nucleon-nucleon $t$ -matrix as well as the corresponding Bethe-Goldstone equation to determine the Brueckner reaction matrix in nuclear matter are reformulated in terms of the resolvents for the total two-nucleon Hamiltonians defined in free space and in medium correspondingly. This allows to find solutions at many energies simultaneously by using the respective Hamiltonian matrix diagonalization in the stationary wave packet basis. Among other important advantages, this approach simplifies greatly the whole computation procedures both for coupled-channel $t$ -matrix and the Brueckner reaction matrix. Therefore this principally novel scheme is expected to be especially useful for self-consistent nuclear matter calculations because it allows to accelerate in a high degree single-particle potential iterations. Furthermore the method provides direct access to the properties of possible two-nucleon bound states in the nuclear medium. The comparison between reaction matrices found via the numerical solution of the Bethe-Goldstone integral equation and the straightforward Hamiltonian diagonalization shows a high accuracy of the method suggested. The proposed fully discrete approach opens a new way to an accurate treatment of two- and three-particle correlations in nuclear matter on the basis of three-particle Bethe-Faddeev equation by an effective Hamiltonian diagonalization procedure.
nucl-thPRC(2016)·12 citations
03
Hydrodynamic flow amplitude correlations in event-by-event fluctuating heavy-ion collisions
Jing Qian🇨🇳 · Ulrich Heinz🇺🇸
The effects of event-by-event fluctuations in the initial geometry of the colliding nuclei are important in the analysis of final flow observables in relativistic heavy-ion collisions. We use hydrodynamic simulations to study the amplitude correlations between different orders of event-by-event fluctuating anisotropic flow harmonics. While the general trends seen in the experimental data are qualitatively reproduced by the model, deviations in detail, in particular for peripheral collisions, point to the need for more elaborate future calculations with a hybrid approach that describes the late hadronic stage of the evolution microscopically. It is demonstrated explicitly that the observed anti-correlation between $v_{2}$ and $v_{3}$ is the consequence of approximately linear hydrodynamic response to a similar anti-correlation of the corresponding initial eccentricities $ϵ_{2}$ and $ϵ_{3}$ . For $n > 3$ , the hydrodynamic correlations between $v_{2, 3}$ and $v_{n}$ deviate from the rescaled correlations among the corresponding initial eccentricities, demonstrating nonlinear mode coupling effect in higher order flows.
nucl-thhep-phnucl-exPRC(2016)·39 citations
04
Direct photon production in Au+Au collisions at $s_{N N} = 200$ GeV at STAR
Chi Yang🇨🇳
We present the direct photon production for $1 < p_{T} < 10$ GeV/ $c$ derived from continuum in the dielectron invariant mass region $0.1 < M_{ee} < 0.3$ GeV/ $c^{2}$ from one billion $s_{N N} = 200$ GeV Au+Au events taken in year 2010 and 2011. A clear excess in the invariant yield compared to the number of binary collision scaled $p + p$ reference is observed in the \pt~range 1-4 GeV/ $c$ . Model calculations with contributions from thermal radiation and initial hard parton scattering are consistent within uncertainties with the direct photon invariant yield.
↳ hep-exhep-phnucl-exnucl-thNPA(2014)·7 citations
05
Direct virtual photon production in Au+Au collisions at $s_{N N}$ = 200 GeV
STAR Collaboration
We report the direct virtual photon invariant yields in the transverse momentum ranges $1 < p_{T} < 3$ GeV/ $c$ and $5 < p_{T} < 10$ GeV/ $c$ at mid-rapidity derived from the dielectron invariant mass continuum region $0.10 < M_{ee} < 0.28$ GeV/ $c^{2}$ for 0-80\% minimum-bias Au+Au collisions at $s_{N N} = 200$ GeV. A clear excess in the invariant yield compared to the number-of-binary-collisions ( $N_{bin}$ ) scaled $p + p$ reference is observed in the $p_{T}$ range $1 < p_{T} < 3$ GeV/ $c$ . For $p_{T} > 6$ GeV/ $c$ the production follows $N_{bin}$ scaling. Model calculations with contributions from thermal radiation and initial hard parton scattering are consistent within uncertainties with the direct virtual photon invariant yield.
↳ nucl-exhep-exhep-phnucl-thPLB(2017)·96 citations
06
Nuclear neutrino energy spectra in high temperature astrophysical environments
G. Wendell Misch🇨🇳 · George M. Fuller🇺🇸
Astrophysical environments that reach temperatures greater than $\sim$ 100 keV can have significant neutrino energy loss via both plasma processes and nuclear weak interactions. We find that nuclear processes likely produce the highest-energy neutrinos. Among the important weak nuclear interactions are both charged current channels (electron capture/emission and positron capture/emission) and neutral current channels (de-excitation of nuclei via neutrino pair emission). We show that in order to make a realistic prediction of the nuclear neutrino spectrum, one must take nuclear structure into account; in some cases, the most important transitions may involve excited states, possibly in both parent and daughter nuclei. We find that the standard technique of producing a neutrino energy spectrum by using a single transition with a Q-value and matrix element chosen to fit published neutrino production rates and energy losses will not accurately capture important spectral features.
↳ astro-ph.HEnucl-thPRC(2016)·15 citations
07
Axial form factor of the nucleon at large momentum transfers
I.V. Anikin🇩🇪 · V.M. Braun🇩🇪 · N. Offen🇩🇪
Motivated by the emerging possibilities to study threshold pion electroproduction at large momentum transfers at Jefferson Laboratory following the 12 GeV upgrade, we provide a short theory summary and an estimate of the nucleon axial form factor for large virtualities in the $Q^{2} = 1 - 10 GeV^{2}$ range using next-to-leading order light-cone sum rules.
↳ hep-phnucl-exnucl-thPRD(2016)·27 citations
08
Effective Field Theory for Few-Boson Systems
Betzalel Bazak🇫🇷 · Moti Eliyahu🇮🇱 · Ubirajara van Kolck🇫🇷
We study universal bosonic few-body systems within the framework of effective field theory at leading order (LO). We calculate binding energies of systems of up to six particles and the atom-dimer scattering length. Convergence to the limit of zero-range two- and three-body interactions is shown, indicating that no additional few-body interactions need to be introduced at LO. Generalizations of the Tjon line are constructed, showing correlations between few-body binding energies and the binding energy of the trimer, for a given dimer energy. As a specific example, we implement our theory for 4He atomic systems, and show that the results are in surprisingly good agreement with those of sophisticated 4He-4He potentials. Potential implications for the convergence of the EFT expansion are discussed.
↳ cond-mat.quant-gasnucl-thphysics.atom-phPRA(2016)·47 citations
09
Charge redistribution from anomalous magnetovorticity coupling
Koichi Hattori🇨🇳 · Yi Yin🇺🇸
We investigate novel transport phenomena in a chiral fluid originated from an interplay between a vorticity and strong magnetic field, which induces a redistribution of vector charges in the system and an axial current along the magnetic field. The corresponding transport coefficients are obtained from an energy-shift argument for the chiral fermions in the lowest Landau level (LLL) due to a spin-vorticity coupling and also from diagrammatic computations on the basis of the linear response theory. Based on consistent results from the both methods, we observe that the transport coefficients are proportional to the anomaly coefficient and are independent of temperature and chemical potential. We therefore speculate that these transport phenomena are connected to quantum anomaly.
↳ hep-thcond-mat.mes-hallhep-phnucl-thPRL(2016)·49 citations
10
Dynamical scheme for hadronization with first-order phase transition
Bohao Feng🇨🇳 · Zhe Xu🇨🇳 · Carsten Greiner🇩🇪
We present a dynamical scheme for hadronization with first-order confinement phase transition. The thermodynamical conditions of phase equilibrium, the fluid velocity profile, and the dissipative effect determine the macroscopic changes of the parton volume and the corresponding hadron volume during the phase transition. The macroscopic volume changes are the basis for building up a dynamical scheme by considering microscopic transition processes from partons to hadrons and backwards. The established scheme is proved by comparing the numerical results with the analytical solutions in the case of a one-dimensional expansion of a dissipative fluid with Bjorken boost invariance. The comparisons show almost perfect agreements, which demonstrate the applicability of the introduced scheme.
↳ hep-phnucl-thPRC(2017)·6 citations
11
Revealing proton shape fluctuations with incoherent diffraction at high energy
Heikki Mäntysaari🇺🇸 · Björn Schenke🇺🇸
The differential cross section of exclusive diffractive vector meson production in electron proton collisions carries important information on the geometric structure of the proton. More specifically, the coherent cross section as a function of the transferred transverse momentum is sensitive to the size of the proton, while the incoherent, or proton dissociative cross section is sensitive to fluctuations of the gluon distribution in coordinate space. We show that at high energies the experimentally measured coherent and incoherent cross sections for the production of $J /Ψ$ mesons are very well reproduced within the color glass condensate framework when strong geometric fluctuations of the gluon distribution in the proton are included. For $ρ$ meson production we also find reasonable agreement. We study in detail the dependence of our results on various model parameters, including the average proton shape, analyze the effect of saturation scale and color charge fluctuations and constrain the degree of geometric fluctuations.
↳ hep-phnucl-thPRD(2016)·159 citations

Affiliations

first authorsco-authorsvia INSPIRE