Nuclear Theory·nucl-th

Thursday·January 21, 2016

12 papers—7 primary·5 cross-listed

01
[Submitted on 19 Jan 2016]
Superfluid fission dynamics with microscopic approaches
C. Simenel · G. Scamps🇫🇷 · D. Lacroix🇫🇷 · A. S. Umar
Recent progresses in the description of the latter stage of nuclear fission are reported. Dynamical effects during the descent of the potential towards scission and in the formation of the fission fragments are studied with the time-dependent Hartree-Fock approach with dynamical pairing correlations at the BCS level. In particular, this approach is used to compute the final kinetic energy of the fission fragments. Comparison with experimental data on the fission of 258Fm are made.
Comments:
Proceeding of the "International Conference on Nuclear Structure and Related Topics" (NSRT15)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.05122 [pdf]
EPJ Web Conf.(2016)·4 citations
02
[Submitted on 20 Jan 2016]
Beyond Wigner's isobaric multiplet mass equation: Effect of charge-symmetry-breaking interaction and Coulomb polarization
J. M. Dong · J. Z. Gu · Y. H. Zhang · W. Zuo · L. J. Wang · Yu. A. Litvinov · Y. Sun
The quadratic form of the isobaric multiplet mass equation (IMME), which was originally suggested by Wigner and has been generally regarded as valid, is seriously questioned by recent high-precision nuclear mass measurements. The usual resolution to this problem is to add empirically the cubic and quartic $T_{z}$ -terms to characterize the deviations from the IMME, but finding the origin of these terms remains an unsolved difficulty. Based on a strategy beyond the Wigner's first-order perturbation, we derive explicitly the cubic and quartic $T_{z}$ -terms. These terms are shown to be generated by the effective charge-symmetry breaking and charge-independent breaking interactions in nuclear medium combined with the Coulomb polarization effect. Calculations for the $s d$ - and lower $f p$ -shells explore a systematical emergence of the cubic $T_{z}$ -term, suggesting a general deviation from the original IMME. Intriguingly, the magnitude of the deviation exhibits an oscillation-like behavior with mass number, modulated by the shell effect.
Comments:
13 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.05167 [pdf]
PRC(2019)·16 citations
03
[Submitted on 20 Jan 2016]
Time-dependent Hartree-Fock Study of Octupole Vibrations in doubly magic nuclei
C. Simenel · J. Buete · K. Vo-Phuoc
Octupole vibrations are studied in some doubly magic nuclei using the time-dependent Hartree-Fock (TDHF) theory with a Skyrme energy density functional. Through the use of the linear response theory, the energies and transition amplitudes of the low-lying vibrational modes for each of the nuclei were determined. Energies were found to be close to experimental results. However, transition amplitudes, quantified by the deformation parameter $β_{3}$ , are underestimated by TDHF. A comparison with single-particle excitations on the Hartree-Fock ground-state shows that the collective octupole vibrations have their energy lowered due to attractive RPA residual interaction.
Comments:
Proceeding of the Heavy-Ions Accelerator Symposium 2015
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.05185 [pdf]
EPJ Web Conf.(2016)·1 citation
04
[Submitted on 20 Jan 2016]
A theoretical analysis of mid-mass neutron halos. What changes going from few- to many-body systems regarding neutron halos?
T. Duguet
The present contribution summarizes the content and slightly updates the discussion of a recently proposed theoretical analysis of the halo phenomenon in many-fermion systems. We focus here on applications to potential neutron halos in mid-mass nuclei.
Comments:
17 pages, 19 figures. arXiv admin note: substantial text overlap with arXiv:nucl-th/0702050
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1601.05267 [pdf]
Few Body Syst.(2016)·1 citation
05
[Submitted on 20 Jan 2016]
Search for scaling onset in exclusive reactions with the lightest nuclei
Yu.N. Uzikov🇷🇺
The dimensional scaling of the differential cross sections of binary reactions $d σ / d t \sim s^{- (n - 2)}$ , where $n$ is given by constituent quark counting rules, was predicted for asymptotically high energies $s ≫ m_{i}$ and transferred momenta $- t ≫ m_{i}^{2}$ at $t / s = co n s t$ (here $s$ and $t$ are the Mandelstam variables and $m_{i}$ denotes a hadron mass), but manifested itself at surprisingly moderate energies of few GeV at large fixed cms angles $θ_{c m} \sim 9 0^{\circ}$ . This behaviour is observed not only in reactions with free hadrons, but with the deuteron and $^{3} H e$ too both for electromagnetic and pure hadronic interactions. One may suppose that observed scaling points out to effective restoration of near-conformal and, probably, chiral symmetry in these processes. A systematical experimental study of the scaling behaviour of the reactions with the deuteron, $^{3} H$ , $^{3} H e$ , and $^{4} H e$ nuclei is still absent. We consider a possibility to carry out this study in $dd$ collisions at the JINR Nuclotron.
Comments:
5 pages, 3 eps-figures, accepted by the European Physical Journal A
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.05280 [pdf]
EPJA(2016)·3 citations
06
[Submitted on 19 Jan 2016]
The Hyperon Puzzle in Neutron Stars
Ignazio Bombaci🇮🇹
The so called "hyperon puzzle", i.e. the difficulty to reconcile the measured masses of neutron stars (NSs) with the presence of hyperons in their interiors, is one of the hot topics in astrophysics which is stimulating copious experimental and theoretical research in hypernuclear physics. After illustrating the origin of the hyperon puzzle, I discuss some of its possible solutions, and particularly those related to the role of hyperonic two- and three-body interactions on the equation of state of dense matter. Afterward, I discuss a possibility to circumvent the hyperon puzzle allowing for the presence of strangeness in NSs in the form of deconfined strange quark matter, and thus considering the so called quark stars, i.e. hybrid stars or strange stars. Finally I discuss the astrophysical consequences of the possible conversion process of an hadronic star to a quark star.
Comments:
Invited keynote talk at the Topical Session "Hyperon puzzle in Neutron Stars" at the 12th International Conference on Hypernuclear and Strange Particle Physics (HYP2015), September 7-12, 2015, Sendai, Japan. arXiv admin note: text overlap with arXiv:1601.04559
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1601.05339 [pdf]
JPS Conf.Proc.(2017)·81 citations
07
[Submitted on 20 Jan 2016]
Origin of the mass splitting of elliptic anisotropy in a multiphase transport model
Hanlin Li🇨🇳 · Liang He🇺🇸 · Zi-Wei Lin🇺🇸 · Denes Molnar🇺🇸 · Fuqiang Wang🇺🇸 · Wei Xie🇺🇸
The mass splitting of elliptic anisotropy ( $v_{2}$ ) at low transverse momentum is considered as a hallmark of hydrodynamic collective flow. We investigate a multiphase transport (AMPT) model where the $v_{2}$ is mainly generated by an anisotropic escape mechanism, not of the hydrodynamic flow nature, and where mass splitting is also observed. We demonstrate that the $v_{2}$ mass splitting in AMPT is small right after hadronization (especially when resonance decays are included); the mass splitting mainly comes from hadronic rescatterings, even though their contribution to the overall charged hadron $v_{2}$ is small. These findings are qualitatively the same as those from hybrid models that combine hydrodynamics with a hadron cascade. We further show that there is no qualitative difference between heavy ion collisions and small system collisions. Our results indicate that the $v_{2}$ mass splitting is not a unique signature of hydrodynamic collective flow and thus cannot distinguish whether the elliptic flow is generated mainly from hydrodynamics or the anisotropic parton escape.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1601.05390 [pdf]
PRC(2016)·22 citations
08
[Submitted on 19 Jan 2016] (cross-list from hep-ph)
Factorization and Resummation for Generic Hierarchies between Jets
Piotr Pietrulewicz🇩🇪 · Frank J. Tackmann🇩🇪 · Wouter J. Waalewijn🇳🇱
Jets are an important probe to identify the hard interaction of interest at the LHC. They are routinely used in Standard Model precision measurements as well as in searches for new heavy particles, including jet substructure methods. In processes with several jets, one typically encounters hierarchies in the jet transverse momenta and/or dijet invariant masses. Large logarithms of the ratios of these kinematic jet scales in the cross section are at present primarily described by parton showers. We present a general factorization framework called SCET $_{+}$ , which is an extension of Soft-Collinear Effective Theory (SCET) and allows for a systematic higher-order resummation of such kinematic logarithms for generic jet hierarchies. In SCET $_{+}$ additional intermediate soft/collinear modes are used to resolve jets arising from additional soft and/or collinear QCD emissions. The resulting factorized cross sections utilize collinear splitting amplitudes and soft gluon currents and fully capture spin and color correlations. We discuss how to systematically combine the different kinematic regimes to obtain a complete description of the jet phase space. To present its application in a simple context, we use the case of $e^{+} e^{-} \to$ 3 jets. We then discuss in detail the application to N-jet processes at hadron colliders, considering representative classes of hierarchies from which the general case can be built. This includes in particular multiple hierarchies that are either strongly ordered in angle or energy or not.
Comments:
63 pages, 6 figures, v2: minor typos fixed, Ref. added, v3: journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1601.05088 [pdf]
JHEP(2016)·49 citations
09
[Submitted on 19 Jan 2016] (cross-list from hep-ph)
Bottomonium spectrum revisited
Jorge Segovia🇩🇪 · Pablo G. Ortega🇨🇭 · David R. Entem🇪🇸 · Francisco Fernández🇪🇸
We revisit the bottomonium spectrum motivated by the recently exciting experimental progress in the observation of new bottomonium states, both conventional and unconventional. Our framework is a nonrelativistic constituent quark model which has been applied to a wide range of hadronic observables from the light to the heavy quark sector and thus the model parameters are completely constrained. Beyond the spectrum, we provide a large number of electromagnetic, strong and hadronic decays in order to discuss the quark content of the bottomonium states and give more insights about the better way to determine their properties experimentally.
Comments:
23 pages, 17 tables, 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1601.05093 [pdf]
PRD(2016)·151 citations
10
[Submitted on 20 Jan 2016] (cross-list from hep-ph)
Glueball dynamics in the hot plasma
Nikolai Kochelev🇷🇺
We discuss the glueball contribution to the equation of state (EoS) of hot gluon matter below and above $T_{c}$ . It is shown that the strong changing of masses of scalar and pseudoscalar glueballs near $T_{c}$ plays very important role in the thermodynamics of $S U (3)$ gauge theory. In particular, we give the arguments that these glueballs become massless at $T_{G} \approx 1.1 T_{c}$ and this phenomenon is crucial in understanding of the mystery in the behavior of trace anomaly founded in the lattice calculation.
Comments:
5 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1601.05145 [pdf]
EPJA(2016)·1 citation
11
[Submitted on 20 Jan 2016] (cross-list from hep-ph)
Indication of a Differential Freeze-out in Proton-Proton and Heavy-Ion Collisions at RHIC and LHC energies
Dhananjaya Thakur🇮🇳 · Sushanta Tripathy🇮🇳 · Prakhar Garg🇮🇳 · Raghunath Sahoo🇮🇳 · Jean Cleymans🇿🇦
The experimental data from the RHIC and LHC experiments of invariant pT spectra in A+A and p + p collisions are analysed with Tsallis distributions in different approaches. The information about the freeze-out surface in terms of freeze-out volume, temperature, chemical potential and radial flow velocity for different particle species are obtained. Further, these parameters are studied as a function of the mass of the secondary particles. A mass-dependent differential freeze-out is observed which does not seem to distinguish between particles and their antiparticles. Further a mass-hierarchy in the radial flow is observed, meaning heavier particles suffer lower radial flow. Tsallis distribution function at finite chemical potential is used to study the mass dependence of chemical potential. The peripheral heavy-ion and proton-proton collisions at the same energies seem to be equivalent in terms of the extracted thermodynamic parameters.
Comments:
Version equivalent to that published in Adv. in High. Eng. Physics
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1601.05223 [pdf]
Adv.High Energy Phys.(2016)·75 citations
12
[Submitted on 20 Jan 2016] (cross-list from astro-ph.HE)
Rotating neutron stars with exotic cores: masses, radii, stability
P. Haensel🇵🇱 · M. Bejger🇵🇱 · M. Fortin🇵🇱 · J.L. Zdunik🇵🇱
A set of theoretical mass-radius relations for rigidly rotating neutron stars with exotic cores, obtained in various theories of dense matter, is reviewed. Two basic observational constraints are used: the largest measured rotation frequency (716 Hz) and the maximum measured mass ( $2 M_{⊙}$ ). Present status of measuring the radii of neutron stars is described. The theory of rigidly rotating stars in general relativity is reviewed and limitations of the slow rotation approximation are pointed out. Mass-radius relations for rotating neutron stars with hyperon and quark cores are illustrated using several models. Problems related to the non-uniqueness of the crust-core matching are mentioned. Limits on rigid rotation resulting from the mass-shedding instability and the instability with respect to the axisymmetric perturbations are summarized. The problem of instabilities and of the back-bending phenomenon are discussed in detail. Metastability and instability of a neutron star core in the case of a first-order phase transition, both between pure phases, and into a mixed-phase state, are reviewed. The case of two disjoint families (branches) of rotating neutron stars is discussed and generic features of neutron-star families and of core-quakes triggered by the instabilities are considered.
Comments:
Matches published version. Minor modifications and reference added
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1601.05368 [pdf]
EPJA(2016)·53 citations

Affiliations

first authorsco-authorsvia INSPIRE