Nuclear Theory·nucl-th

Thursday·May 28, 2015

7 papers—5 primary·2 cross-listed

01
[Submitted on 27 May 2015]
Dilepton production spectrum above Tc with a lattice quark propagator
Taekwang Kim🇯🇵 · Masayuki Asakawa🇯🇵 · Masakiyo Kitazawa🇯🇵
The dilepton production rate from the deconfined medium is analyzed with the photon self-energies constructed from quark propagators obtained by lattice numerical simulation for two values of temperature $T = 1.5 T_{c}$ and $3 T_{c}$ above the critical temperature $T_{c}$ . The photon self-energy is calculated by the Schwinger-Dyson equation with the lattice quark propagtor and a vertex function determined so as to satisfy the Ward-Takahashi identity. The obtained dilepton production rate at zero momentum exhibits divergences reflecting van Hove singularity, and is significantly enhanced around $ω ≃ T$ compared with the rate obtained by the perturbative analysis.
Comments:
12 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1505.07195 [pdf]
PRD(2015)·11 citations
02
[Submitted on 27 May 2015]
Few-nucleon systems with state-of-the-art chiral nucleon-nucleon forces
S. Binder🇺🇸 · A. Calci🇨🇦 · E. Epelbaum🇩🇪 · R.J. Furnstahl🇺🇸 · J. Golak🇵🇱 · K. Hebeler🇩🇪 · H. Kamada🇯🇵 · H. Krebs🇩🇪 · J. Langhammer🇩🇪 · S. Liebig🇩🇪 · P. Maris🇺🇸 · U.-G. Meißner🇩🇪 and 8 other authors
We apply improved nucleon-nucleon potentials up to fifth order in chiral effective field theory, along with a new analysis of the theoretical truncation errors, to study nucleon-deuteron (Nd) scattering and selected low-energy observables in 3H, 4He, and 6Li. Calculations beyond second order differ from experiment well outside the range of quantified uncertainties, providing truly unambiguous evidence for missing three-nucleon forces within the employed framework. The sizes of the required three-nucleon force contributions agree well with expectations based on Weinberg's power counting. We identify the energy range in elastic Nd scattering best suited to study three-nucleon force effects and estimate the achievable accuracy of theoretical predictions for various observables.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.07218 [pdf]
PRC(2016)·188 citations
03
[Submitted on 27 May 2015]
Lambda Polarization in an Exact Rotating and Expanding fluid dynamical model for peripheral heavy ion reactions
Yilong Xie🇳🇴 · Robert C. Glastad🇳🇴 · Laszlo P. Csernai🇳🇴
We calculate the Lambda polarization in an exact analytical, rotating model based on parameters extracted from a high resolution (3+1)D Particle-in-Cell Relativistic hydrodynamics calculation. The polarization is attributed to effects from thermal vorticity and for the first time the effects of the radial and axial acceleration are also studied separately
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.07221 [pdf]
PRC(2015)·31 citations
04
[Submitted on 27 May 2015]
Outer crust of a cold non-accreting magnetar
D. Basilico · D. Peña Arteaga · X. Roca-Maza · G. Colò
The outer crust structure and composition of a cold, non-accreting magnetar is studied. We model the outer crust to be made of fully equilibrated matter where ionized nuclei form a Coulomb crystal embedded in an electron gas. The main effects of the strong magnetic field are those of quantizing the electron motion in Landau levels and of modifying the nuclear single particle levels producing, on average, an increased binding of nucleons in nuclei present in the Coulomb lattice. The effect of an homogeneous and constant magnetic field on nuclear masses has been predicted by using a covariant density functional, in which induced currents and axial deformation due to the presence of a magnetic field that breaks time-reversal symmetry have been included self-consistently in the nucleon and meson equations of motion. Although not yet observed, for $B ≳ 1 0^{16}$ G both effects contribute to produce different compositions and to enlarge the range of pressures typically present in common neutron stars. Specifically, in such a regime, the magnetic field effects on nuclei favor the appearance of heavier nuclei at low pressures. As $B$ increases, such heavier nuclei are also preferred up to larger pressures. In the most extreme case, the whole outer crust is almost made of $_{40}^{92}$ Zr $_{52}$ .
Comments:
Published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.07304 [pdf]
PRC(2015)·26 citations
05
[Submitted on 27 May 2015]
On the compactness of neutron stars
Wei-Chia Chen · J. Piekarewicz
Recent progress in the determination of both masses and radii of neutron stars are starting to place stringent constraints on the dense matter equation of state. In particular, new theoretical developments together with improved statistical tools seem to favor stellar radii that are significantly smaller than those predicted by models using purely nucleonic equations of state. Given that the underlying equation of state must also account for the observation of $2 M_{⊙}$ neutron stars, theoretical approaches to the study of the dense matter equation of state are facing serious challenges. In response to this challenge, we compute in a model-independent way the underlying equation of state associated with an assumed mass-radius template similar to the "common radius" assumption used in recent studies. Once such a mass-radius template is adopted, the equation of state follows directly from the implementation of Lindblom's algorithm; assumptions on the nature or composition of the dense stellar core are not required. By analyzing mass-radius profiles with a maximum mass consistent with observation and common radii in the 8 to 11 km range, a lower limit on the stellar radius of a $1.4 M_{⊙}$ neutron star of $R_{NS} ≳ 10.7$ km is obtained in order to prevent the equation of state from violating causality.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1505.07436 [pdf]
PRL(2015)·34 citations
06
[Submitted on 26 May 2015] (cross-list from quant-ph)
The decay widths, the decay constants, and the branching fractions of a resonant state
Rafael de la Madrid🇺🇸
We introduce the differential and the total decay widths of a resonant (Gamow) state decaying into a continuum of stable states. When the resonance has several decay modes, we introduce the corresponding partial decay widths and branching fractions. In the approximation that the resonance is sharp, the expressions for the differential, partial and total decay widths of a resonant state bear a close resemblance with the Golden Rule. In such approximation, the branching fractions of a resonant state are the same as the standard branching fractions obtained by way of the Golden Rule. We also introduce dimensionless decay constants along with their associated differential decay constants, and we express experimentally measurable quantities such as the branching fractions and the energy distributions of decay events in terms of those dimensionless decay constants.
Subjects:
Quantum Physics (quant-ph); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1505.07139 [pdf]
NPA(2015)·11 citations
07
[Submitted on 27 May 2015] (cross-list from hep-th)
Chiral drag force
Krishna Rajagopal🇺🇸 · Andrey V. Sadofyev🇺🇸
We provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks and in that they are proportional to the coefficient of the axial anomaly. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to the drag force felt by a heavy quark are analogous to the chiral magnetic effect on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a suitably chosen frame. In this frame, the heavy quark at rest sees counterpropagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport, something that has been predicted previously via consideration of symmetries. Along the way to our principal results, we provide a general calculation of the corrections to the drag force due to the presence of gradients in the flowing fluid in the presence of a nonzero chemical potential. We close with a consequence of our result that is at least in principle observable in heavy ion collisions, namely an anticorrelation between the direction of the CME current for light quarks in a given event and the direction of the kick given to the momentum of all the heavy quarks and antiquarks in that event.
Comments:
28 pages, small improvement to the discussion of gravitational anomaly, references added
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1505.07379 [pdf]
JHEP(2015)·71 citations

Affiliations

first authorsco-authorsvia INSPIRE

Dilepton production spectrum above Tc with a lattice quark propagator

Few-nucleon systems with state-of-the-art chiral nucleon-nucleon forces

Lambda Polarization in an Exact Rotating and Expanding fluid dynamical model for peripheral heavy ion reactions

Outer crust of a cold non-accreting magnetar

On the compactness of neutron stars

The decay widths, the decay constants, and the branching fractions of a resonant state

Chiral drag force

Affiliations