Nuclear Theory·nucl-th

Friday·January 23, 2015

10 papers—5 primary·5 cross-listed

01
Forward Compton Scattering with weak neutral current: constraints from sum rules
Mikhail Gorchtein🇩🇪 · Xilin Zhang🇺🇸
We generalize forward real Compton amplitude to the case of the interference of the electromagnetic and weak neutral current, formulate a low-energy theorem, relate the new amplitudes to the interference structure functions and obtain a new set of sum rules. We address a possible new sum rule that relates the product of the axial charge and magnetic moment of the nucleon to the 0th moment of the structure function $g_{5} (ν, 0)$ . We apply the GDH and the finite energy sum rule for constraining the dispersive $γ Z$ -box correction to the proton's weak charge.
nucl-thhep-phnucl-exPLB(2015)·8 citations
02
Hyperons in neutron stars
Tetsuya Katayama🇯🇵 · Koichi Saito🇯🇵
Using the Dirac-Brueckner-Hartree-Fock approach, the properties of neutron-star matter including hyperons are investigated. In the calculation, we consider both time and space components of the vector self-energies of baryons as well as the scalar ones. Furthermore, the effect of negative-energy states of baryons is partly taken into account. We obtain the maximum neutron-star mass of $2.08 M_{⊙}$ , which is consistent with the recently observed, massive neutron stars. We discuss a universal, repulsive three-body force for hyperons in matter.
nucl-thastro-ph.SRhep-phPLB(2015)·69 citations
03
Elimination of influence of neutron-skin size difference of initial colliding nuclei in Pb+Pb collisions
Gao-Feng Wei🇨🇳
Within an isospin- and momentum-dependent transport model using as an input nucleon density profiles from Hartree-Fock calculations based on a modified Skyrme-like (MSL) model, we study how to eliminate the influence of neutron-skin size difference of initial colliding nuclei in probing the nuclear symmetry energy. Within the current experimental uncertainty range of neutron-skin size of $^{208}$ Pb, the Pb+Pb collisions are performed in semicentral and peripheral collisions with impact parameters of 5 and 9fm and at beam energies from 50 MeV/nucleon to 1000 MeV/nucleon, respectively. It is shown that combination of neutron and proton collective flows, i.e., neutron-proton differential elliptic flow, neutron-proton elliptic flow difference, neutron-proton differential transverse flow and neutron-proton transverse flow difference, can effectively eliminate the effects of neutron-skin size difference and thus can be as useful sensitive observables in probing nuclear matter symmetry energy in heavy-ion collisions. Moreover, the combined neutron-proton stopping power including the neutron-proton differential stopping power and neutron-proton stopping power difference can also eliminate the effects of neutron-skin size difference and shows some sensitivities to symmetry energy especially at the lower beam energy.
nucl-thnucl-exPRC(2015)·6 citations
04
Collective enhancement of nuclear state densities by the shell model Monte Carlo approach
C. Özen · Y. Alhassid · H. Nakada
The shell model Monte Carlo (SMMC) approach allows for the microscopic calculation of statistical and collective properties of heavy nuclei using the framework of the configuration-interaction shell model in very large model spaces. We present recent applications of the SMMC method to the calculation of state densities and their collective enhancement factors in rare-earth nuclei.
nucl-thJ.Phys.Conf.Ser.(2015)·0 citations
05
Proton Structure and PHENIX Experiment
Jian-Wei Qiu🇺🇸
We briefly summarize the important and critical roles that PHENIX Experiment has played in determining the proton's internal structure in terms of quarks and gluons, and their dynamics. Some pioneering measurements by PHENIX Experiment on the motion and polarization of quarks and gluons, as well as their correlations inside a fast moving proton are presented. Some future opportunities and potentials of PHENIX Experiment are also discussed.
nucl-thhep-phnucl-exPTEP(2015)·0 citations
06
Modern Studies of the Deuteron: from the Lab Frame to the Light Front
Werner Boeglin🇺🇸 · Misak Sargsian🇺🇸
We review the recent progress made in studies of deuteron structure at small internucleon distances. This progress is largely facilitated by the new generation of experiments in deuteron electrodisintegration carried out at unprecedentedly high momentum transfer. The theoretical analysis of these data confirms the onset of the high energy eikonal regime in the scattering process which allows one to separate long range nuclear effects from the effects genuinely related to the short distance structure of the deuteron. Our conclusion is that for the first time the deuteron is probed at relative momenta beyond 300 MeV/c without dominating long range effects. As a result, at these large nucleon momenta the cross section is sensitive to the nuclear dynamics at sub-fermi distances. Due to large internal momenta involved we are dealing with the relativistic bound state that is best described by the light-cone momentum distribution of nucleons in the deuteron. We present the first attempt of extracting the deuteron light-cone momentum distribution function from data and discuss the importance of this quantity for studies of QCD structure of the bound nucleon in deep inelastic scattering off the deuteron. We conclude the review giving an outlook of the next generation of high energy experiments which will extend our reach to much smaller distances in the deuteron.
↳ nucl-exhep-exhep-phnucl-thIJMPE(2015)·33 citations
07
Skyrmions with low binding energies
Mike Gillard🇬🇧 · Derek Harland🇬🇧 · Martin Speight🇬🇧
Nuclear binding energies are investigated in two variants of the Skyrme model: the first replaces the usual Skyrme term with a term that is sixth order in derivatives, and the second includes a potential that is quartic in the pion fields. Solitons in the first model are shown to deviate significantly from ansätze previously assumed in the literature. The binding energies obtained in both models are lower than those obtained from the standard Skyrme model, and those obtained in the second model are close to the experimental values.
↳ hep-thnucl-thNPB(2015)·95 citations
08
Azimuthal harmonics of color fields in a high energy nucleus
T. Lappi🇫🇮
Recent experimental results have revealed a surprisingly rich structure of multiparticle azimuthal correlations in high energy proton-nucleus collisions. Final state collective effects can be responsible for many of the observed effects, but it has recently been argued that a part of these correlations are present already in the wavefunctions of the colliding particles. We evaluate the momentum space 2-particle cumulant azimuthal anisotropy coefficients v_n{2}, n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. These would correspond to the flow coefficients in very forward proton nucleus scattering. We find significant differences beteen Wilson lines from the MV model and from JIMWLK evolution. The magnitude and transverse momentum dependence of the v_n{2} values suggest that the fluctuations present in the initial fields are a significant contribution to the observed anisotropies.
↳ hep-phnucl-thPLB(2015)·56 citations
09
Rotating Bose-Einstein condensates: Closing the gap between exact and mean-field solutions
J. C. Cremon · A. D. Jackson · E. Ö. Karabulut · G. M. Kavoulakis · B. R. Mottelson · S. M. Reimann
When a Bose-Einstein condensed cloud of atoms is given some angular momentum, it forms vortices arranged in structures with a discrete rotational symmetry. For these vortex states, the Hilbert space of the exact solution separates into a "primary" space related to the mean-field Gross-Pitaevskii solution and a "complementary" space including the corrections beyond mean-field. Considering a weakly-interacting Bose-Einstein condensate of harmonically-trapped atoms, we demonstrate how this separation can be used to close the conceptual gap between exact solutions for systems with only a few atoms and the thermodynamic limit for which the mean-field is the correct leading-order approximation. Although we illustrate this approach for the case of weak interactions, it is expected to be more generally valid.
↳ cond-mat.quant-gasnucl-thPRA(2015)·7 citations
10
Phase structure of mass- and spin-imbalanced unitary Fermi gases
Dietrich Roscher🇩🇪 · Jens Braun🇩🇪 · Joaquín E. Drut🇺🇸
We study the phase diagram of mass- and spin-imbalanced unitary Fermi gases, in search for the emergence of spatially inhomogeneous phases. To account for fluctuation effects beyond the mean-field approximation, we employ renormalization group techniques. We thus obtain estimates for critical values of the temperature, mass and spin imbalance, above which the system is in the normal phase. In the unpolarized, equal-mass limit, our result for the critical temperature is in accordance with state-of-the-art Monte Carlo calculations. In addition, we estimate the location of regions in the phase diagram where inhomogeneous phases are likely to exist. We show that an intriguing relation exists between the general structure of the many-body phase diagram and the binding energies of the underlying two-body bound-state problem, which further supports our findings. Our results suggest that inhomogeneous condensates form for mass ratios of the spin-down and spin-up fermions greater than three. The extent of the inhomogeneous phase in parameter space increases with increasing mass imbalance.
↳ cond-mat.quant-gashep-phnucl-thPRA(2015)·44 citations

Affiliations

first authorsco-authorsvia INSPIRE