Nuclear Theory·nucl-th

Wednesday·December 21, 2016

18 papers—10 primary·8 cross-listed

01
[Submitted on 20 Dec 2016]
Effects of volume corrections and resonance decays on cumulants of net-charge distributions in a Monte Carlo hadron resonance gas model
Hao-jie Xu🇨🇳
The effects of volume corrections and resonance decays (the resulting correlations between positive charges and negative charges) on cumulants of net-proton distributions and net-charge distributions are investigated by using a Monte Carlo hadron resonance gas ({\tt MCHRG}) model. The required volume distributions are generated by a Monte Carlo Glauber ({\tt MC-Glb}) model. Except the variances of net-charge distributions, the {\tt MCHRG} model with more realistic simulations of volume corrections, resonance decays and acceptance cuts can reasonably explain the data of cumulants of net-proton distributions and net-charge distributions reported by the STAR collaboration. The {\tt MCHRG} calculations indicate that both the volume corrections and resonance decays make the cumulant products of net-charge distributions deviate from the Skellam expectations: the deviations of $S σ$ and $κ σ^{2}$ are dominated by the former effect while the deviations of $ω$ are dominated by the latter one.
Comments:
A Monte Carlo hadron resonance gas (MCHRG) model is proposed to study the cumulants of multiplicity distributions. 6 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1612.06485 [pdf]
PLB(2017)·25 citations
02
[Submitted on 20 Dec 2016]
Pion Production in Rare Isotope Collisions
M.B. Tsang · J. Estee · H. Setiawan · W.G. Lynch · J. Barney · M.B. Chen · G. Cerizza · P. Danielewicz · J. Hong · P. Morfouace · R. Shane · S. Tangwancharoen and 6 other authors
Pion energy spectra are presented for central collisions of neutron-rich 132Sn+124Sn and neutron-deficient 108Sn+112Sn systems using simulations with Boltzmann-Uehling-Uhlenbeck transport model. These calculations, which incorporate isospin-dependent mean field potentials for relevant baryons and mesons, display a sensitivity to the pion spectra that could allow significant constraints on the density dependence of the symmetry energy and its mean field potential at supra-saturation densities. The predicted sensitivity increases with the isospin asymmetry of the total system and decreases with incident energy.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.06561 [pdf]
PRC(2017)·42 citations
03
[Submitted on 20 Dec 2016]
Collinear cluster tri-partition: Kinematics constraints and stability of collinearity
Patric Holmvall🇸🇪 · Ulli Köster🇫🇷 · Andreas Heinz🇸🇪 · Thomas Nilsson🇸🇪
A new mode of nuclear fission has been proposed by the FOBOS collaboration, called Collinear Cluster Tri-partition (CCT), suggesting that three heavy fission fragments can be emitted perfectly collinearly in low-energy fission. It is surprising that CCT escaped observation for so long given the relatively high reported yield, of roughly 0.5% relative to binary fission. These claims call for an independent verification with a different experimental technique. Verification experiments based on direct observation of CCT fragments with fission fragment spectrometers require guidance with respect to the allowed kinetic energy range, which we present in this paper. We discuss corresponding model calculations which, if CCT is found in such verification experiments, could indicate how the breakups proceed. We also study the intrinsic stability of collinearity. Three different decay models are used, which span together the timescales of three-body fission. These models are used to calculate the possible kinetic energy ranges of CCT fragments in 235U(n,f) and 252Cf(sf). We use semi-classical trajectory calculations with a Monte-Carlo method to study the intrinsic stability of collinearity. CCT has a high net Q-value, but in a sequential decay, the intermediate steps are energetically and geometrically unfavorable or even forbidden. Moreover, perfect collinearity is extremely unstable, and broken by the slightest perturbation. According to our results, the central fragment would be very difficult to detect due to its low kinetic energy, raising the question of why previous experiments could not detect a missing-mass signature corresponding to CCT. We find that a realization of CCT would require an unphysical fine-tuning of the initial conditions. Our results enable independent experimental verification and encourage further critical theoretical studies of CCT.
Comments:
20 pages, 19 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.06583 [pdf]
PRC(2017)·11 citations
04
[Submitted on 20 Dec 2016]
Recent progress on dense nuclear matter in skyrmion approaches
Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷
The Skyrme model provides a novel unified approach to nuclear physics. In this approach, single baryon, baryonic matter and medium-modified hadron properties are treated on the same footing. Intrinsic density dependence (IDD) reflecting the change of vacuum by compressed baryonic matter figures naturally in the approach. In this article, we review the recent progress on accessing dense nuclear matter by putting baryons treated as solitons, namely, skyrmions, on crystal lattice with accents on the implications in compact stars.
Comments:
Published version. Typos are corrected
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.06600 [pdf]
SCPMA(2017)·32 citations
05
[Submitted on 20 Dec 2016]
Monopole transition strength function of $^{12}$ C in three- $α$ model
Souichi Ishikawa
The energy level structure of $^{12}$ C nucleus at a few MeV above the three- $α$ threshold is still unsatisfactory known. For instance, most microscopic calculations predicted that there exist one $0^{+}$ -state in this energy region besides the well known Hoyle state, while some experimental and theoretical studies show the existing of two $0^{+}$ -states. In this paper, I will take a three- $α$ -boson (3 $α$ ) model for bound and continuum states in $^{12}$ C, and study a transition process from the $^{12}$ C( $0_{1}^{+}$ ) ground state to 3 $α$ $0^{+}$ continuum states by the electric monopole ( $E 0$ ) operator. The strength distribution of the process will be calculated as a function of $3 α$ energy using the Faddeev three-body theory. The Hamiltonian for the $3 α$ system consists of two- and three- $α$ potentials, and some three- $α$ potentials with different range parameters will be examined. Results of the strength function show a double-peaked bump at low energy region, which can be considered as two $0^{+}$ -states. The peak at higher energy may originate from a 3 $α$ resonant state. However, it is unlikely that the peak at the lower energy is related to a resonant state, which suggests that it may be due to so called "ghost anomaly". Distributions of decaying particles are also calculated.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1612.06653 [pdf]
PRC(2016)·4 citations
06
[Submitted on 20 Dec 2016]
On the Implications of Energy and Momentum Conservation for Particle Emission in A+A Collisions at SPS Energies
Antoni Szczurek🇵🇱 · Mirosław Kiełbowicz🇵🇱 · Andrzej Rybicki🇵🇱
We construct a simple model of heavy ion collisions, local in the impact parameter plane, and appropriate for the SPS energy range. This model can be regarded as a new realization of the "fire-streak" approach, originally applied to studies of lower energy nucleus-nucleus reactions. Starting from local energy and momentum conservation, we nicely describe the broadening of the pion rapidity distribution when going from central to peripheral Pb+Pb collisions at $s_{N N}$ =17.3 GeV. The results of our calculations are compared with SPS experimental data. We discuss the resulting implications on the role of energy and momentum conservation for the dynamics of particle production in heavy ion collisions. A specific space-time picture emerges, where the longitudinal evolution of the system strongly depends on the position in the impact parameter ( $b_{x}$ , $b_{y}$ ) plane. This picture is consistent with our earlier findings on the longitudinal evolution of the system as deduced from electromagnetic effects on charged pion directed flow, and can provide an explanation for specific low- $p_{T}$ phenomena seen in the fragmentation region of Pb+Pb collisions.
Comments:
Corrected version, accepted for publication in Phys. Rev. C (13 pages, 9 figures)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.06694 [pdf]
PRC(2017)·16 citations
07
[Submitted on 20 Dec 2016]
Rapidity-dependent jet energy loss in small systems with finite-size effects and running coupling
Chanwook Park🇨🇦 · Chun Shen🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
Longitudinal dynamics of particle production and rapidity-dependent jet energy loss are investigated in small and asymmetric colliding systems. We utilize an improved version of \textsc{martini} in which two improvements are implemented to calculate the effect of the strongly coupled QGP droplet on jet energy loss. We show that those realistic prescriptions improve the results of nuclear modification factor calculations. We also observe visible energy loss of jets in a thermal background of high-multiplicity p-Pb collisions, and a clear correlation between the energy loss and elliptic flow coefficients for energetic particles. We conclude that systematic measurements of jet quenching in central collisions of small systems can support the formation of the QGP droplet.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1612.06754 [pdf]
Nucl.Part.Phys.Proc.(2017)·23 citations
08
[Submitted on 20 Dec 2016]
Extracting $q^$ from single inclusive data at RHIC and at the LHC for different centralities: a new puzzle?
Carlota Andres🇪🇸 · Nestor Amesto🇪🇸 · Matthew Luzum🇪🇸 · Carlos A. Salgado🇪🇸 · Pia Zurita🇪🇸
We present here an extraction of the jet transport coefficient, $q^$ , using RHIC and LHC single-inclusive high- $p_{T}$ data for different centralities. We fit a $K$ -factor that determines the deviation of this coefficient from an ideal estimate, $K \equiv q^/ (2 ϵ^{3/4})$ , where $ϵ$ is given by hydrodynamic simulations. As obtained already in previous studies, this $K$ -factor is found to be larger at RHIC than at the LHC. However it is, unexpectedly, basically no-dependent on the centrality of the collision. Taken at face value this result, the $K$ -factor would not depend on local properties of the QGP as temperature, but on global collision variables such as the center of mass energy.
Comments:
4 pages, 4 figures, proceedings for the 8th International Conference on Hard and Electromagnetic Probes of High-energy Nuclear Collisions (Hard Probes 2016)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1612.06781 [pdf]
Nucl.Part.Phys.Proc.(2017)·5 citations
09
[Submitted on 20 Dec 2016]
Search for $α$ -cluster states in even-even Cr isotopes
M. A. Souza🇧🇷 · H. Miyake🇧🇷
The $α + core$ structure is investigated in even-even Cr isotopes from the viewpoint of the local potential model. The comparison of $Q_{α} / A$ values for even-even Cr isotopes and even-even $A = 46, 54, 56, 58$ isobars indicates that $^{46}$ Cr and $^{54}$ Cr are the most favorable even-even Cr isotopes for $α$ -clustering. The ground state bands of the two Cr isotopes are calculated through a local $α + core$ potential with two variable parameters. The calculated spectra give a very good description of most experimental $^{46}$ Cr and $^{54}$ Cr levels. The reduced $α$ -widths, rms intercluster separations and $B (E 2)$ transition rates are determined for the ground state bands. The calculations reproduce the order of magnitude of the available experimental $B (E 2)$ values without using effective charges and indicate that the first members of the ground state bands present a stronger $α$ -cluster character. The volume integral per nucleon pair and rms radius obtained for the $α +^{50}$ Ti potential are consistent with those reported previously in the analysis of $α$ elastic scattering on $^{50}$ Ti.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.06805 [pdf]
EPJA(2017)·13 citations
10
[Submitted on 20 Dec 2016]
Neutron Moderation Theory Taking into Accout the Thermal Motion of Moderating Medium Nuclei
V.D. Rusov · V.A. Tarasov · S.A. Chernezhenko · A.A. Kakaev · V.P. Smolyar
In this paper we present the analytical expression for the neutron scattering law for an isotropic source of neutrons, obtained within the framework of the gas model with the temperature of the moderating medium as a parameter. The obtained scattering law is based on the solution of the kinematic problem of elastic scattering of neutrons on nuclei in the L-system in the general case. I.e. both the neutron and the nucleus possess the arbitrary velocity vectors in the L-system. For the new scattering law the flux densities and neutron moderation spectra depending on the temperature are obtained for the reactor fissile medium. The expressions for the moderating neutrons spectra allow reinterpreting the physical nature of the underlying processes in the thermal region.
Comments:
26 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.06838 [pdf]
EPJA(2017)·5 citations
11
[Submitted on 19 Dec 2016] (cross-list from astro-ph.HE)
Twin Stars within the SU(3) Chiral Quark-Meson Model
Andreas Zacchi🇩🇪 · Laura Tolos🇪🇸 · Jürgen Schaffner-Bielich🇩🇪
We present new stable solutions of the Tolman Oppenheimer Volkoff equations for quark stars using a quark matter equation of state based on the SU(3) Quark-Meson model that exhibits the onset of the chiral phase transition. These new solutions appear as two stable branches in the mass-radius relation allowing for so called twin stars, i.e. two stable quark star solutions with the same mass, but distinctly different radii. We find solutions which are compatible with causality, the stability conditions of dense matter, the astrophysical constraints of the rotation of the millisecond pulsar PSR J1748-2446ad and the 2 $M_{⊙}$ pulsar mass constraint.
Comments:
7 pages, 5 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.06167 [pdf]
PRD(2017)·41 citations
12
[Submitted on 19 Dec 2016] (cross-list from astro-ph.HE)
Probing Extreme-Density Matter with Gravitational Wave Observations of Binary Neutron Star Merger Remnants
David Radice🇺🇸 · Sebastiano Bernuzzi🇮🇹 · Walter Del Pozzo🇮🇹 · Luke F. Roberts🇺🇸 · Christian D. Ott🇺🇸
We present a proof-of-concept study, based on numerical-relativity simulations, of how gravitational waves (GWs) from neutron star merger remnants can probe the nature of matter at extreme densities. Phase transitions and extra degrees of freedom can emerge at densities beyond those reached during the inspiral, and typically result in a softening of the equation of state (EOS). We show that such physical effects change the qualitative dynamics of the remnant evolution, but they are not identifiable as a signature in the GW frequency, with the exception of possible black-hole formation effects. The EOS softening is, instead, encoded in the GW luminosity and phase and is in principle detectable up to distances of the order of several Mpcs with advanced detectors and up to hundreds of Mpcs with third generation detectors. Probing extreme-density matter will require going beyond the current paradigm and developing a more holistic strategy for modeling and analyzing postmerger GW signals.
Comments:
5 pages, 3 figures. Matches version accepted on ApJL
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1612.06429 [pdf]
ApJL(2017)·160 citations
13
[Submitted on 19 Dec 2016] (cross-list from hep-ph)
Equilibration and freeze-out of an expanding gas in a transport approach in a Friedmann-Robertson-Walker metric
J. Tindall🇬🇧 · J.M. Torres-Rincon🇩🇪 · J.B. Rose🇩🇪 · H. Petersen🇩🇪
Motivated by a recent finding of an exact solution of the relativistic Boltzmann equation in a Friedmann-Robertson-Walker spacetime, we implement this metric into the newly developed transport approach Simulating Many Accelerated Strongly-interacting Hadrons (SMASH). We study the numerical solution of the transport equation and compare it to this exact solution for massless particles. We also compare a different initial condition, for which the transport equation can be independently solved numerically. Very nice agreement is observed in both cases. Having passed these checks for the SMASH code, we study a gas of massive particles within the same spacetime, where the particle decoupling is forced by the Hubble expansion. In this simple scenario we present an analysis of the freeze-out times, as function of the masses and cross sections of the particles. The results might be of interest for their potential application to relativistic heavy-ion collisions, for the characterization of the freeze-out process in terms of hadron properties.
Comments:
v2: 9 pages, 7 figures. Added discussion on the numerical relation between the Hubble and scattering rates at the end of Sec. 3. Updated references. This version matches the accepted manuscript by Phys.Lett.B journal
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.06436 [pdf]
PLB(2017)·25 citations
14
[Submitted on 20 Dec 2016] (cross-list from hep-ph)
Amplitude analysis and the nature of the Zc(3900)
JPAC Collaboration: A. Pilloni🇺🇸 · C. Fernandez-Ramirez🇲🇽 · A. Jackura🇺🇸 · V. Mathieu🇺🇸 · M. Mikhasenko🇩🇪 · J. Nys🇧🇪 · A.P. Szczepaniak🇺🇸
The microscopic nature of the XYZ states remains an unsettled topic. We show how a thorough amplitude analysis of the data can help constraining models of these states. Specifically, we consider the case of the Zc(3900) peak and discuss possible scenarios of a QCD state, virtual state, or a kinematical enhancement. We conclude that current data are not precise enough to distinguish between these hypotheses, however, the method we propose, when applied to the forthcoming high-statistics measurements should shed light on the nature of these exotic enhancements.
Comments:
14 pages, 10 figures, 3 tables. Version accepted for publication on Phys.Lett.B
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.06490 [pdf]
PLB(2017)·102 citations
15
[Submitted on 20 Dec 2016] (cross-list from hep-ph)
Jet and heavy flavor production in heavy-ion collisions
Zhong-Bo Kang🇺🇸 · Felix Ringer🇺🇸 · Ivan Vitev🇺🇸
We review recent progress in the theoretical description of hard probes in heavy-ion collisions within the framework of Soft Collinear Effective Theory (SCET). Firstly, we consider the inclusive production of heavy flavor mesons and jets with a small radius parameter in proton-proton collisions. Secondly, we describe how in-medium effects can be incorporated consistently with the proton-proton baseline calculations. The in-medium interactions are described by Glauber gluon interactions. We present results for the nuclear modification factor $R_{AA}$ which is most commonly used to study the quenching of hadron or jet production yields in heavy-ion collisions and we compare to recent data from the LHC.
Comments:
Hard Probes 2016 proceedings contribution, Sep. 23-27, Wuhan, China. 4 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1612.06511 [pdf]
Nucl.Part.Phys.Proc.(2017)·0 citations
16
[Submitted on 20 Dec 2016] (cross-list from astro-ph.HE)
Magnetic fields in turbulent quark matter and magnetar bursts
Maxim Dvornikov (IZMIRAN, Tomsk State University)🇷🇺
We analyze the magnetic field evolution in dense quark matter with unbroken chiral symmetry, which can be found inside quark and hybrid stars. The magnetic field evolves owing to the chiral magnetic effect in the presence of the electroweak interaction between quarks. In our study, we also take into account the magnetohydrodynamic turbulence effects in dense quark matter. We derive the kinetic equations for the spectra of the magnetic helicity density and the magnetic energy density as well as for the chiral imbalances. On the basis of the numerical solution of these equations, we find that turbulence effects are important for the behavior of small scale magnetic fields. It is revealed that, under certain initial conditions, these magnetic fields behave similarly to the electromagnetic flashes of some magnetars. We suggest that fluctuations of magnetic fields, described in frames of our model, which are created in the central regions of a magnetized compact star, can initiate magnetar bursts.
Comments:
19 pages in LaTeX2e, 11 eps figures; paper is significantly extended, discussion of magnetic fields in strange stars is added, new Fig. 2 is included, many references are added; variant published in Int.J.Mod.Phys.D
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.06540 [pdf]
Int.J.Mod.Phys.D(2018)·11 citations
17
[Submitted on 20 Dec 2016] (cross-list from astro-ph.HE)
Exploring phases of dense QCD with compact stars
Armen Sedrakian🇩🇪
I review a number of recent developments in the physics of compact stars containing deconfined quark matter, including (a)~their cooling with possible phase transition from a fully gapped to a gapless phase of QCD at low temperatures and large isospin, (b)~the transport coefficients of the 2SC phase and the role played by the Aharonov-Bohm interactions between flux-tubes and unpaired fermions; (c)~rapidly rotating compact stars and spin-down and spin-up induced phase transition between hadronic and QCD matter as well as between different phases of QCD.
Comments:
11 pages, 6 figures, Proceedings of the 5th International Conference on New Frontiers in Physics (ICNFP2016), 6-14 July 2016, Kolymbari, Crete, Greece
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.06714 [pdf]
EPJ Web Conf.(2017)·5 citations
18
[Submitted on 20 Dec 2016] (cross-list from hep-ph)
Structure of the Energy-Momentum Tensor and Applications
Jonathan Hudson (UConn)🇺🇸 · Irina A. Perevalova (Irkutsk State U.)🇷🇺 · Maxim V. Polyakov (St. Petersburg, INP & Ruhr U., Bochum)🇷🇺 · Peter Schweitzer (UConn)🇺🇸
The probably most fundamental information about a particle is contained in the matrix elements of its energy momentum tensor (EMT) which are accessible from hard-exclusive reactions via generalized parton distribution functions. The spin decomposition of the nucleon and Ji sum rule are one example. Less prominent but equally important information is encoded in the stress tensor, related to the spatial components of the EMT, which shows in detail how the strong forces inside the nucleon balance to form a bound state. This provides not only unique insights on nucleon structure. It also leads to fascinating new applications to hadron spectroscopy which allow us to formulate new interpretations of the charmonium-nucleon pentaquarks discovered by LHCb. Recent progress is reviewed in this short overview article.
Comments:
10 pages, 6 figures, based on talk presented at "QCD Evolution 2016", 30 May to 3 June 2016, Amsterdam
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1612.06721 [pdf]
PoS(2017)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE