Nuclear Theory·nucl-th

Tuesday·October 20, 2015

16 papers—10 primary·6 cross-listed

01
[Submitted on 17 Oct 2015]
Chiral phase transition and Schwinger mechanism in a pure electric field
Gaoqing Cao🇨🇳 · Xu-Guang Huang🇨🇳
We systematically study the chiral symmetry breaking and restoration in the presence of a pure electric field in the Nambu--Jona-Lasinio (NJL) model at finite temperature and baryon chemical potential. In addition, we also study the effect of the chiral phase transition on the charged pair production due to the Schwinger mechanism. For these purposes, a general formalism for parallel electric and magnetic fields is developed at finite temperature and chemical potential for the first time. In the pure electric field limit $B \to 0$ , we compute the order parameter, the transverse-to-longitudinal ratio of the Goldstone mode velocities, and the Schwinger pair production rate as functions of the electric field. The inverse catalysis effect of the electric field to chiral symmetry breaking is recovered. And the Goldstone mode is find to disperse anisotropically such that the transverse velocity is always smaller than the longitudinal one, especially at nonzero temperature and baryon chemical potential. As expected, the quark-pair production rate is greatly enhanced by the chiral symmetry restoration.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
1510.05125 [pdf]
PRD(2016)·30 citations
02
[Submitted on 17 Oct 2015]
Statistical theory of light nucleus reaction and application to $^{9}$ Be(p, xn) reaction
Xiaojun Sun🇨🇳 · Jingshang Zhang🇨🇳
A statistical theory of light nucleus reaction (STLN) is proposed to describe both neutron and light charged particle induced nuclear reactions with 1p-shell light nuclei involved. The dynamic of STLN is described by the unified Hauser-Feshbach and exciton model, of which the angular momentum and parity conservations are considered in equilibrium and pre-equilibrium processes. The Coulomb barriers of the incident and outgoing charged particles, which seriously influence the open reaction channels, could be reasonably considered in the incident channel and the different outgoing channels. In kinematics, the recoiling effects in various emission processes are taken strictly into account. Taking $^{9}$ Be(p, xn) reaction as an example, we calculate the double-differential cross sections of outgoing neutrons and charged particles using PUNF code in the frame of STLN. The calculated results agree very well with the existing experimental neutron double-differential cross sections at $E_{p} = 18$ MeV, and indicate that PUNF code is a powerful tool to set up file-6 in the reaction data library for the light charged particle induced nuclear reactions with 1p-shell light nuclei involved.
Comments:
30 pages, 5 figures, 44 references. arXiv admin note: text overlap with arXiv:1510.04580
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.05163 [pdf]
PRC(2016)·7 citations
03
[Submitted on 18 Oct 2015]
Anatomy of molecular structures in $^{20}$ Ne
E. F. Zhou🇨🇳 · J. M. Yao🇨🇳 · Z. P. Li🇨🇳 · J. Meng🇨🇳 · P. Ring🇨🇳
We present a beyond mean-field study of clusters and molecular structures in low-spin states of $^{20}$ Ne with a multireference relativistic energy density functional, where the dynamical correlation effects of symmetry restoration and quadrupole-octupole shapes fluctuation are taken into account with projections on parity, particle number and angular momentum in the framework of the generator coordinate method. Both the energy spectrum and the electric multipole transition strengths for low-lying parity-doublet bands are better reproduced after taking into account the dynamical octupole vibration effect. Consistent with the finding in previous studies, a rotation-induced dissolution of the $α +^{16}$ O molecular structure in $^{20}$ Ne is predicted.
Comments:
6 pages with 6 figures, version to be published in Phys. Lett. B
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1510.05232 [pdf]
PLB(2016)·59 citations
04
[Submitted on 19 Oct 2015]
Systematical shell-model calculation in the pairing-plus-multipole Hamiltonian with a monopole interaction for the pf5/2g9/2 shell
K. Kaneko🇯🇵 · T. Mizusaki🇯🇵 · Y. Sun🇨🇳 · S. Tazaki🇯🇵
The recently-proposed effective shell-model interaction, the pairing-plus-multipole Hamiltonian with the monopole interaction obtained by empirical fits starting from the monopole-based universal force (PMMU), is systematically applied to nuclei of the pf5/2g9/2 shell region. It is demonstrated that the calculation describes reasonably well a wide range of experimental data, including not only the low-lying and high-excitation spectra, E2 transitions, quadrupole moments, and magnetic moments, but also the binding energies, for Ni, Cu, Zn, Ga, Ge, As, and Se isotopes with A=64-80. In particular, a structure of the neutron-rich Ge and Se isotopes is discussed in detail.
Comments:
21 pages, 31 figures, accepted in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.05340 [pdf]
PRC(2015)·37 citations
05
[Submitted on 19 Oct 2015]
Global $α$ -decay study based on the mass table of the relativistic continuum Hartree-Bogoliubov theory
Linfeng Zhang🇨🇳 · Xuewei Xia🇨🇳
The $α$ -decay energies ( $Q_{α}$ ) are systematically investigated with the nuclear masses for $10 \leq Z \leq 120$ isotopes obtained by the relativistic continuum Hartree-Bogoliubov (RCHB) theory with the covariant density functional PC-PK1, and compared with available experimental values. It is found that the $α$ -decay energies deduced from the RCHB results present similar pattern as those from available experiments. Owing to the large predicted $Q_{α}$ values ( $\geq$ 4 MeV), many undiscovered heavy nuclei in the proton-rich side and super-heavy nuclei may have large possibilities for $α$ -decay. The influence of nuclear shell structure on $α$ -decay energies is also analysed.
Comments:
7 pages, 4 figures. arXiv admin note: text overlap with arXiv:1309.3987 by other authors
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.05375 [pdf]
CPC(2016)·12 citations
06
[Submitted on 19 Oct 2015]
Evolution of $N = 28$ shell closure in relativistic continuum Hartree-Bogoliubov theory
Xuewei Xia
The $N = 28$ shell gap in sulfur, argon, calcium and titanium isotopes is investigated in the framework of relativistic continuum Hartree-Bogoliubov (RCHB) theory. The evolutions of neutron shell gap, separation energy, single particle energy and pairing energy are analyzed, and it is found that $N = 28$ shell gap is quenched in sulfur isotopes but persists in argon, calcium and titanium isotopes. The evolution of $N = 28$ shell gap in $N = 28$ isotonic chain is discussed, and the erosion of $N = 28$ shell gap is understood with the evolution of potential with proton number.
Comments:
9 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.05381 [pdf]
CPC(2016)·3 citations
07
[Submitted on 7 Aug 2015]
Can Tsallis distribution fit all the particle spectra produced at RHIC and LHC?
H. Zheng🇮🇹 · Lilin Zhu🇨🇳
The Tsallis distribution has been tested to fit the all particle spectra at mid-rapidity from central events produced in d+Au, Cu+Cu, Au+Au collisions at RHIC and p+Pb, Pb+Pb collisions at LHC. Even though there are strong medium effects in Cu+Cu and Au+Au collisions, the results show that the Tsallis distribution can be used to fit most of particle spectra in the collisions studied except in Au+Au collisions where some deviations are seen for proton and $Λ$ at low $p_{T}$ . In addition, as the Tsallis distribution can only fit part of the particle spectra produced in Pb+Pb collisions where $p_{T}$ is up to 20 GeV/c, a new formula with one more fitting degree of freedom is proposed in order to reproduce the entire $p_{T}$ region.
Comments:
8 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1510.05449 [pdf]
Adv.High Energy Phys.(2015)·60 citations
08
[Submitted on 17 Sept 2015]
Green's Function Monte Carlo Calculations with Two- and Three-Nucleon Interactions from Chiral Effective Field Theory
J. E. Lynn🇺🇸
I discuss our recent work on Green's function Monte Carlo (GFMC) calculations of light nuclei using local nucleon-nucleon interactions derived from chiral effective field theory (EFT) up to next-to-next-to-leading order (N $^{2}$ LO). I present the natural extension of this work to include the consistent three-nucleon (3N) forces at the same order in the chiral expansion. I discuss our choice of observables to fit the two low-energy constants which enter in the 3N sector at N $^{2}$ LO and present some results for light nuclei.
Comments:
Contribution to the Proceedings of the 21st International Conference on Few-Body Problems in Physics. May 18-22, 2015. Chicago, Illinois, USA
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1510.05450 [pdf]
EPJ Web Conf.(2016)·1 citation
09
[Submitted on 19 Oct 2015]
Deformation-induced splitting of the monopole giant resonance in 24Mg
J. Kvasil · V.O. Nesterenko · A. Repko · P.-G. Reinhard · W. Kleinig
The strong deformation splitting of the isoscalar giant monopole resonance (ISGMR), recently observed in ( $α, α^{'}$ ) reaction in prolate $^{24}$ Mg, is analyzed in the framework of the Skyrme quasiparticle random-phase-approximation (QRPA) approach with the Skyrme forces SkM*, SVbas and SkP $^{δ}$ . The calculations with these forces give close results and confirm that the low-energy E0-peak is caused by the deformation-induced coupling of ISGMR with the K=0 branch of the isoscalar giant quadrupole resonance.
Comments:
3 pages, 1 figure, to be published in EPJ Web of Conferences (Proceedings of the International Conference NSRT15, Dubna, Russia, 2015)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.05499 [pdf]
EPJ Web Conf.(2016)·8 citations
10
[Submitted on 19 Oct 2015]
Net-proton number kurtosis and skewness in nuclear collisions: Influence of deuteron formation
Zuzana Feckova🇸🇰 · Jan Steinheimer🇩🇪 · Boris Tomasik🇸🇰 · Marcus Bleicher🇩🇪
We explore the influence of deuteron formation in the late stage of nucleus-nucleus reactions on the fluctuations observed in the final net-proton yields around midrapidity. At each investigated energy, the produced (anti-)proton yield at chemical freeze-out is assumed to fluctuate according to a Poisson distribution and in each event the probability for deuteron formation by coalescence is proportional to $(d N_{proton} / d y)^{2}$ . The protons that are then clustered in deuterons are usually not included in the experimental measurement of the net-proton fluctuations, therefore, we subtract these clustered protons from the final state proton number for the calculation of the net-proton fluctuations (the same is done in the anti-proton sector). Due to the non-linear deuteron formation probability the resulting distribution is not a Skellam distribution, but shows the interesting feature of a decrease in the kurtosis $κ σ^{2}$ and a local maximum in the skewness $S σ$ observables as the collision energy decreases.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1510.05519 [pdf]
PRC(2015)·24 citations
11
[Submitted on 16 Oct 2015] (cross-list from astro-ph.HE)
X-ray Burst Oscillations: From Flame Spreading to the Cooling Wake
Simin Mahmoodifar (NASA/GSFC) · Tod Strohmayer (NASA/GSFC)
Type I X-ray bursts are thermonuclear flashes observed from the surfaces of accreting neutron stars (NSs) in Low Mass X-ray Binaries. Oscillations have been observed during the rise and/or decay of some of these X-ray bursts. Those seen during the rise can be well explained by a spreading hot spot model, but large amplitude oscillations in the decay phase remain mysterious because of the absence of a clear-cut source of asymmetry. To date there have not been any quantitative studies that consistently track the oscillation amplitude both during the rise and decay (cooling tail) of bursts. Here we compute the light curves and amplitudes of oscillations in X-ray burst models that realistically account for both flame spreading and subsequent cooling. We present results for several such "cooling wake" models, a "canonical" cooling model where each patch on the NS surface heats and cools identically, or with a latitude-dependent cooling timescale set by the local effective gravity, and an "asymmetric" model where parts of the star cool at significantly different rates. We show that while the canonical cooling models can generate oscillations in the tails of bursts, they cannot easily produce the highest observed modulation amplitudes. Alternatively, a simple phenomenological model with asymmetric cooling can achieve higher amplitudes consistent with the observations.
Comments:
8 pages, 7 figures, Accepted for publication in ApJ, Additional calculations and discussion compared to v1
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1510.05005 [pdf]
ApJ(2016)·28 citations
12
[Submitted on 19 Oct 2015] (cross-list from hep-ph)
Schwinger mechanism revisited
Francois Gelis🇫🇷 · Naoto Tanji🇩🇪
In this article, we review recent theoretical works on the Schwingermechanism of particle production in external electrical fields. Although the non-perturbative Schwinger mechanism is at the center of this discussion, many of the approaches that we discuss can cope with general time and space dependent fields, and therefore also capture the perturbative contributions to particle production.
Comments:
Review for Progress in Particle and Nuclear Physics. 76 pages, 36 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1510.05451 [pdf]
PPNP(2016)·194 citations
13
[Submitted on 19 Oct 2015] (cross-list from hep-ph)
The calorimetric spectrum of the electron-capture decay of $^{163}$ Ho. A preliminary analysis of the preliminary data
A. De Rújula🇪🇸 · M. Lusignoli🇮🇹
It is in principle possible to measure directly the electron neutrino mass (or masses and mixing angles) in weak electron-capture decays. The optimal nuclide in this respect is $^{163}$ Ho. The favoured experimental technique, currently pursued in various experiments (ECHo, HOLMES and NuMECS) is "calorimetric". The calorimetric energy spectrum is a sum over the unstable vacant orbitals, or "holes", left by the electrons weakly captured by the nucleus. We discuss the current progress in this field and analize the preliminary data. Our conclusion is that, as pointed out by Robertson, the contribution of two-hole states is not negligible. But --in strong contradistinction with the tacit conclusion of previous comparisons of theory and observations-- we find a quite satisfactory agreement. A crucial point is that, in the creation of secondary holes, electron shakeoff and not only electron shakeup must be taken into account.
Comments:
6 pages, 5 figures. Section IV and Fig.3 added. Minor text modifications
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
1510.05462 [pdf]
14 citations
14
[Submitted on 19 Oct 2015] (cross-list from hep-ph)
The pion-cloud contribution to the electromagnetic nucleon structure
D. Kupelwieser🇦🇹 · W. Schweiger🇦🇹
The present contribution continues and extends foregoing work on the calculation of electroweak form factors of hadrons using the point-form of relativistic quantum mechanics. Here we are particularly interested in studying pionic effects on the electromagnetic structure of the nucleon. To this aim we employ a hybrid constituent-quark model that comprises, in addition to the $3 q$ valence component, also a $3 q$ + $π$ non-valence component. With a simple wave function for the $3 q$ component we get reasonable results for the nucleon form factors. In accordance with other authors we find that the pionic effect is significant only below $Q^{2} ≲ 0.5$ ~GeV $^{2}$ .
Comments:
Contribution presented by W. Schweiger at the Mini-Workshop Bled 2015: Exploring Hadron Resonances, Bled (Slovenia), July 5-11, 2015; 4 pages, 2 figures. arXiv admin note: substantial text overlap with arXiv:1508.03991
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1510.05521 [pdf]
Bled Workshops Phys.(2015)·0 citations
15
[Submitted on 19 Oct 2015] (cross-list from hep-ph)
Two, three, many body systems involving mesons. Multimeson condensates
E. Oset🇪🇸 · M. Bayar🇹🇷 · A. Dote🇯🇵 · T. Hyodo🇯🇵 · P. K. Khemchandani🇧🇷 · W. H. Liang🇨🇳 · A. Martinez Torres🇧🇷 · M. Oka🇯🇵 · L.Roca🇪🇸 · T. Uchino🇪🇸 · C.W. Xiao🇩🇪
In this talk we review results from studies with unconventional many hadron systems containing mesons: systems with two mesons and one baryon, three mesons, some novel systems with two baryons and one meson, and finally systems with many vector mesons, up to six, with their spins aligned forming states of increasing spin. We show that in many cases one has experimental counterparts for the states found, while in some other cases they remain as predictions, which we suggest to be searched in BESIII, Belle, LHCb, FAIR and other facilities.
Comments:
8 pages, 2 figures, Talk at the Jagiellonian Symposium on Fundamental and Applied Subatomic Physics, June 2015
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1510.05547 [pdf]
Acta Phys.Polon.B(2016)·3 citations
16
[Submitted on 19 Oct 2015] (cross-list from astro-ph.HE)
Quark deconfinement and the duration of short Gamma Ray Bursts
Alessandro Drago (1) · Andrea Lavagno (2) · Brian Metzger (3) · Giuseppe Pagliara (1) ((1) Ferrara U. & INFN, Ferrara, (2) Turin Polytechnic & INFN, Turin, (3) Columbia U., Astron. Astrophys.)
We propose a model for short duration gamma-ray bursts (sGRBs) based on the formation of a quark star after the merger of two neutron stars. We assume that the sGRB central engine is a proto-magnetar, which has been previously invoked to explain the plateau-like X-ray emission observed following both long and short GRBs. Here, we show that: i) a few milliseconds after the merger it is possible to form a stable and massive star made in part of quarks; ii) during the early cooling phase of the incompletely formed quark star, the flux of baryons ablated from the surface by neutrinos is large and it does not allow the outflow to achieve a bulk Lorentz factor high enough to produce a GRB; iii) after the quark burning front reaches the stellar surface, baryon ablation ceases and the jet becomes too baryon poor to produce a GRB; iv) however, between these two phases a GRB can be produced over the finite timescale required for the baryon pollution to cease; a characteristic timescale of the order of $\sim 0.1$ s naturally results from the time the conversion front needs to cover the distance between the rotational pole and the latitude of the last closed magnetic field line; v) we predict a correlation between the luminosity of the sGRB and its duration, consistent with the data; vi) our model also predicts a delay of the order of ten seconds between the time of the merger event and the sGRB, allowing for the possibility of precursor emission and implying that the jet will encounter the dense cocoon formed immediately after the merger.
Comments:
4 pages, 3 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1510.05581 [pdf]
PRD(2016)·34 citations

Affiliations

first authorsco-authorsvia INSPIRE