Nuclear Theory·nucl-th

Thursday·October 27, 2016

11 papers—6 primary·5 cross-listed

01
[Submitted on 26 Oct 2016]
Departure from Equilibrium of the Quasi-Particle Distribution Functions in High Energy Nuclear Collisions
P. Chakraborty🇮🇳 · J. I. Kapusta🇺🇸
In simulations of high energy heavy ion collisions that employ viscous hydrodynamics, single particle distributions are distorted from their thermal equilibrium form due to gradients in the flow velocity. These are closely related to the formulas for the shear and bulk viscosities in the quasi-particle approximation. Distorted single particle distributions are now commonly used to calculate the emission of photons and dilepton pairs, and in the late stage to calculate the conversion of a continuous fluid to individual particles. We show how distortions of the single particle distribution functions due to both shear and bulk viscous effects can be done rigorously in the quasi-particle approximation and illustrate it with the linear $σ$ model at finite temperature.
Comments:
5 pages, 3 figures. This is the published version which takes into account comments from the referee
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.08144 [pdf]
PRC(2017)·9 citations
02
[Submitted on 26 Oct 2016]
Effects of the Lorentz invariance violation in Coulomb interaction in nuclei and atoms
V.V. Flambaum🇩🇪 · M.V. Romalis🇺🇸
Anisotropy in the speed of light that has been constrained by Michelson-Morley-type experiments also generates anisotropy in the Coulomb interactions. This anisotropy can manifest itself as an energy anisotropy in nuclear and atomic experiments. Here the experimental limits on Lorentz violation in 21Ne are used to improve the limits on the Lorentz symmetry in the photon sector, namely the anisotropy of the speed of light and the Coulomb interactions, by 7 orders of magnitude in comparison with previous experiments: the speed of light is isotropic to a part in E-28.
Comments:
Calculation of the effect of anisotropy in the Coulomb interactions in the electron sector has been added in v2
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Atomic Physics (physics.atom-ph)
arXiv:
1610.08188 [pdf]
PRL(2017)·28 citations
03
[Submitted on 26 Oct 2016]
A microscopic rotational cranking model and its connection to conventional cranking and other collective rotational models
P. Gulshani
A microscopic time-reversal invariant cranking model (MCRM) for nuclear collective rotation about a single axis and its coupling to intrinsic motion is derived. The MCRM is derived by transforming the stationary nuclear Schrodinger equation using a collective rotation-intrinsic product wavefunction, imposing no constraints on the wavefunction and the nucleon coordinates, and using no relative co-ordinates. The derivatives of the collective-rotation angle are defined in terms of a combination of rigid and irrotational collective flows of the nucleons. The collective wavefunction is chosen to be an eigenstate of the angular momentum, yielding a MCRM Schrodinger equation for the intrinsic wavefunction that contains a cranking Coriolis energy term that is linear in the angular momentum and shear operators, a collective centrifugal energy term, and a rotation-fluctuation energy term. In absence of the irrotational-flow component and fluctuation energy term, the MCRM equation reduces to that of the conventional cranking model (CCRM), but with a dynamic rigid-flow angular velocity and rigid-flow centrifugal-energy term. The expectation of the angular momentum operator, which is the sum of the collective rotation angular momentum and the expectation of the angular momentum in the intrinsic state, would reduce to that in the CCRM if the collective rotation angular momentum were small. However, it is shown that, even for the simple case of the anisotropic harmonic oscillator mean-field potential in , the collective rotation angular momentum is not small in the current version of the MCRM, and that this problem needs further study. It is also shown that the MCRM Schrodinger equation is reducible to the equations of the particle-plus-rotor, phenomenological and microscopic collective rotation-vibration, and two-fluid semi-classical collective models.
Comments:
23 pages, 6 figures, 58 references. Clarifying changes have been made to the article: 6 footnotes have been added; In Section 2, Eqs. (11), (13), (15), and (17) have been corrected, Sections 3, and 4 have been restructured to remove repetition, deleting the subsections; Figs 5 and 6 have been deleted; Some clarifying changes have been made to Sections 5 and 6
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.08337 [pdf]
2 citations
04
[Submitted on 25 Oct 2016]
Dynamics of Anti-Proton -- Protons and Anti-Proton -- Nucleus Reactions
A. Galoyan🇷🇺 · A. Ribon🇨🇭 · V. Uzhinsky🇷🇺
A short review of simulation results of anti-proton-proton and anti-proton-nucleus interactions within the framework of Geant4 FTF (Fritiof) model is presented. The model uses the main assumptions of the Quark-Gluon-String Model or Dual Parton Model. The model assumes production and fragmentation of quark-anti-quark and diquark-anti-diquark strings in the mentioned interactions. Key ingredients of the model are cross sections of string creation processes and an usage of the LUND string fragmentation algorithm. They allow one to satisfactory describe a large set of experimental data, especially, a strange particle production, Lambda hyperons and K mesons.
Comments:
7 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1610.08341 [pdf]
Nucl.Theor.(2016)·4 citations
05
[Submitted on 24 Oct 2016]
Charge conservation effects for high order fluctuations
Viktor Begun🇵🇱
The exact charge conservation significantly impacts multiplicity fluctuations. The result depends strongly on the part of the system charge carried by the particles of interest. Along with the expected suppression of fluctuations for large systems, charge conservation may lead to negative skewness or kurtosis for small systems.
Comments:
Presented at Critical Point and Onset of Deconfinement 2016 (CPOD2016)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1610.08344 [pdf]
Acta Phys.Polon.Supp.(2017)·1 citation
06
[Submitted on 26 Oct 2016]
Constraints on rapidity-dependent initial conditions from charged particle pseudorapidity densities and two-particle correlations
Weiyao Ke🇺🇸 · J. Scott Moreland🇺🇸 · Jonah E. Bernhard🇺🇸 · Steffen A. Bass🇺🇸
We study the initial three-dimensional spatial configuration of the quark-gluon plasma produced in relativistic heavy-ion collisions using centrality and rapidity-dependent measurements of charged particle pseudorapidity densities and two-particle correlations. A cumulant-generating function is used to parametrize the rapidity dependence of local entropy deposition and extend arbitrary boost-invariant initial conditions to nonzero beam rapidities. The model is compared to p+Pb and Pb+Pb single-particle distributions and systematically optimized using Bayesian parameter estimation to extract high-probability initial condition parameters. The optimized initial conditions are then compared to a number of experimental observables including two-particle rapidity correlations, the rapidity dependence of anisotropic flow, and event-plane decorrelations.
Comments:
This version contains major updates including improved Bayesian calibration and results discussion compared to the previous version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1610.08490 [pdf]
PRC(2017)·73 citations
07
[Submitted on 24 Oct 2016] (cross-list from cond-mat.str-el)
Consistent Chiral Kinetic Theory in Weyl Materials: Chiral Magnetic Plasmons
E. V. Gorbar🇺🇦 · V. A. Miransky🇨🇦 · I. A. Shovkovy🇺🇸 · P. O. Sukhachov🇨🇦
We argue that the correct definition of the electric current in the chiral kinetic theory for Weyl materials should include the Chern-Simons contribution that makes the theory consistent with the local conservation of the electric charge in electromagnetic and strain-induced pseudoelectromagnetic fields. By making use of such a kinetic theory, we study the plasma frequencies of collective modes in Weyl materials in constant magnetic and pseudomagnetic fields, taking into account the effects of dynamical electromagnetism. We show that the collective modes are chiral plasmons. While the plasma frequency of the longitudinal collective mode coincides with the Langmuir one, this mode is unusual because it is characterized not only by oscillations of the electric current density, but also by oscillations of the chiral current density. The latter are triggered by a dynamical version of the chiral electric separation effect. We also find that the plasma frequencies of the transverse modes split up in a magnetic field. This finding suggests an efficient means of extracting the chiral shift parameter from the measurement of the plasma frequencies in Weyl materials.
Comments:
6 pages, 2 figures; published version
Subjects:
Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1610.07625 [pdf]
PRL(2017)·81 citations
08
[Submitted on 25 Oct 2016] (cross-list from hep-ph)
Atomki anomaly and dark matter in a radiative seesaw model with gauged $B - L$ symmetry
Osamu Seto🇯🇵 · Takashi Shimomura🇯🇵
Motivated by recently reported anomalies in a decay of an excited state of beryllium by the Atomki collaboration, we study a radiative seesaw model with gauged $B - L$ symmetry and a $Z_{2}$ parity. Assuming that the anomalies originate from the decay of the $B - L$ gauge boson followed by the nuclear decay, the mass of the lightest right-handed neutrino or the dark matter candidate can be determined below $10$ GeV. We show that for this mass range, the model can explain the anomalies in the beryllium decay and the relic dark matter abundance consistent with neutrino masses. We also predict its spin-independent cross section in direct detection experiments for this mass range.
Comments:
16 pages, 3 figures; 1 figure added, final results updated, published version in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1610.08112 [pdf]
PRD(2017)·52 citations
09
[Submitted on 26 Oct 2016] (cross-list from hep-lat)
Confinement-Deconfinement transition in $S U (2) +$ Higgs Theory
Minati Biswal🇮🇳 · Mridupawan Deka🇷🇺 · Sanatan Digal🇮🇳 · P. S. Saumia🇮🇳
We study the confinement-deconfinement transition in $S U (2)$ gauge theory in the presence of massless bosons using lattice Monte Carlo simulations. The nature of this transition depends on the temporal extent ( $N_{τ}$ ) of the Euclidean lattice. We find that the transition is a cross-over for $N_{τ} = 2, 4$ and second order with $3 D$ Ising universality class for $N_{τ} = 8$ . Our results show that the second order transition is accompanied by realization of the $Z_{2}$ symmetry.
Comments:
13 pages, 9 figures (Accepted in PRD)
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1610.08265 [pdf]
PRD(2017)·7 citations
10
[Submitted on 26 Oct 2016] (cross-list from hep-ph)
Open charm physics with Heavy Ions: theoretical overview
Andrea Beraudo🇮🇹
The peculiar role of heavy-flavour observables in relativistic heavy-ion collisions is discussed. Produced in the early stage, $c$ and $b$ quarks cross the hot medium arising from the collision, interacting strongly with the latter, until they hadronize. Depending on the strength of the interaction heavy quarks may or not approach kinetic equilibrium with the plasma, tending in the first case to follow the collective flow of the expanding fireball. The presence of a hot deconfined medium may also affect heavy-quark hadronization, being possible for them to recombine with the surrounding light thermal partons, so that the final heavy-flavour hadrons inherit part of the flow of the medium. Here we show how it is possible to develop a complete transport setup allowing one to describe heavy-flavour production in high-energy nuclear collisions, displaying some major results one can obtain. Information coming from recent lattice-QCD simulations concerning both the heavy-flavour transport coefficients in the hot QCD plasma and the nature of the charmed degrees around the deconfinement transition is also presented. Finally, the possibility that the formation of a hot deconfined medium even in small systems (high-multiplicity p-Au and d-Au collisions, so far) may affect also heavy-flavour observables is investigated.
Comments:
Invited plenary talk at the conference CHARM 2016. arXiv admin note: substantial text overlap with arXiv:1609.06449
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1610.08269 [pdf]
PoS(2016)·1 citation
11
[Submitted on 26 Oct 2016] (cross-list from nucl-ex)
Overview of recent azimuthal correlation measurements from ALICE
You Zhou (for the ALICE Collaboration)🇩🇰
Azimuthal correlations are a powerful tool to probe the properties and the evolution of the collision system. In this proceedings, we will review the recent azimuthal correlation measurements from ALICE at the LHC. The comparison to other experimental measurements and various theoretical calculations will be discussed as well.
Comments:
12 pages, 9 figures, invited talk in 5th International Conference on New Frontiers in Physics (6-14 July 2016), Crete, Greece
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1610.08311 [pdf]
EPJ Web Conf.(2017)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE