Nuclear Theory·nucl-th

Wednesday·February 24, 2016

9 papers—6 primary·3 cross-listed

01
Half-quantized Non-Abelian Vortices in Neutron $^{3} P_{2}$ Superfluids inside Magnetars
Kota Masuda🇯🇵 · Muneto Nitta🇯🇵
We point out that half-quantized non-Abelian vortices exist as the minimum energy states in rotating neutron $^{3} P_{2}$ superfluids in the inner cores of magnetars with magnetic field greater than $3 \times 1 0^{15}$ Gauss, while they do not in ordinary neutron stars with smaller magnetic fields. One integer vortex is split into two half-quantized vortices. The number of vortices is about $1 0^{19}$ and they are separated at about $μ$ m in a vortex lattice for typical parameters, while the vortex core size is about 10-100 fm. They are non-Abelian vortices characterized by non-Abelian first homotopy group, and consequently when two vortices corresponding to non-commutative elements collide, a rung vortex must be created between them, implying the formation of an entangled vortex network inside the cores of magnetars. We find the spontaneous magnetization in the vortex core showing anti-ferromagnetism whose typical magnitude is about $1 0^{8 - 9}$ Gauss that is ten times larger than that of integer vortices, when external magnetic fields are present along the vortex line.
nucl-thastro-ph.HEcond-mat.otherhep-thPTEP(2020)·25 citations
02
$β$ -decay half-lives and nuclear structure of exotic proton-rich waiting point nuclei under $r p$ -process conditions
Jameel-Un Nabi · Mahmut Böyükata
We investigate even-even nuclei in the $A \sim 70$ mass region within the framework of the proton-neutron quasi-particle random phase approximation (\mbox{pn-QRPA}) and the interacting boson model-1 (\mbox{IBM-1}). Our work includes calculation of the energy spectra and the potential energy surfaces $V (β, γ)$ of Zn, Ge, Se, Kr and Sr nuclei with the same proton and neutron number, $N = Z$ . The parametrization of the \mbox{IBM-1} Hamiltonian was performed for the calculation of the energy levels in the ground state bands. Geometric shape of the nuclei was predicted by plotting the potential energy surfaces $V (β, γ)$ obtained from the \mbox{IBM-1} Hamiltonian in the classical limit. The \mbox{pn-QRPA} model was later used to compute half-lives of the neutron-deficient nuclei which were found to be in very good agreement with the measured ones. The \mbox{pn-QRPA} model was also used to calculate the Gamow-Teller strength distributions and was found to be in decent agreement with the measured data. We further calculate the electron capture and positron decay rates for these $N$ = $Z$ waiting point (WP) nuclei in the stellar environment employing the \mbox{pn-QRPA} model. For the $r p$ -process conditions, our total weak rates are within a factor two compared with the Skyrme HF+BCS+QRPA calculation. All calculated electron capture rates are comparable to the competing positron decay rates under $r p$ -process conditions. Our study confirms the finding that electron capture rates form an integral part of the weak rates under $r p$ -process conditions and should not be neglected in the nuclear network calculations.
nucl-thastro-ph.SRNPA(2016)·15 citations
03
Cumulants of multiplicity distributions in most-central heavy-ion collisions
Hao-jie Xu🇨🇳
I investigate the volume corrections on cumulants of total charge distributions and net proton distributions. The required volume information is generated by an optical Glauber model. I find that the corrected statistical expectations of multiplicity distributions mimic the negative binomial distributions at non-central collisions, and they tend to approach the Poisson ones at most-central collisions due to the "boundary effects," which suppress the volume corrections. However, net proton distributions and reference multiplicity distributions are sensitive to the external volume fluctuations at most-central collisions, which imply that one has to consider the details of volume distributions in event-by-event multiplicity fluctuation studies.
nucl-thhep-phnucl-exPRC(2016)·20 citations
04
Impact of momentum anisotropy and turbulent chromo-fields on thermal particle production in quark-gluon plasma medium
Vinod Chandra🇮🇳 · V. Sreekanth🇮🇳
Momentum anisotropy present during the hydrodynamic evolution of Quark-Gluon Plasma (QGP) in RHIC may lead to chromo-Weibel instability and turbulent chromo-fields.The dynamics of the quark and gluon momentum distributions in this case is governed by an effective diffusive Vlasov equation (linearized). The solution of this linearized transport equation for the modified momentum distribution functions lead to the mathematical form of non-equilibrium momentum distribution functions of quarks/antiquarks and gluons. The modification to these distributions encode the physics of turbulent color fields and momentum anisotropy. In the present manuscript, we employ these distribution functions to to estimate thermal dilepton production rate in the QGP medium. The production rate is seen to have appreciable sensitivity to the strength of the anisotropy.
nucl-thEPJC(2017)·16 citations
05
Phenomena at the QCD phase transition in nonequilibrium chiral fluid dynamics (N $χ$ FD)
Marlene Nahrgang🇺🇸 · Christoph Herold🇹🇭
Heavy-ion collisions performed in the beam energy range accessible by the NICA collider facility are expected to produce systems of extreme net-baryon densities and can thus reach yet unexplored regions of the QCD phase diagram. Here, one expects the phase transition between the plasma of deconfined quarks and gluons and the hadronic matter to be of first order. A discovery of the first-order phase transition would as well prove the existence of the QCD critical point, a landmark in the phase diagram. In order to understand possible signals of the first-order phase transition in heavy-ion collision experiments it is very important to develop dynamical models of the phase transition. Here, we discuss the opportunities of studying dynamical effects at the QCD first-order phase transition within our model of nonequilibrium chiral fluid dynamics.
nucl-thhep-phEPJA(2016)·9 citations
06
An Effective Field Theory Approach to the Stabilization of $^{8}$ Be in a QED Plasma
Xiaojun Yao🇺🇸 · Thomas Mehen🇺🇸 · Berndt Müller🇺🇸
We use effective field theory to study the $α$ - $α$ resonant scattering in a finite-temperature QED plasma. The static plasma screening effect causes the resonance state $^{8}$ Be to live longer and eventually leads to the formation of a bound state when $m_{D} ≳ 0.3$ MeV. We speculate that this effect may have implications on the rates of cosmologically and astrophysically relevant nuclear reactions involving $α$ particles.
nucl-thhep-phJ.Phys.G(2016)·3 citations
07
Inverse Magnetic Catalysis in Nambu--Jona-Lasinio Model beyond Mean Field
Shijun Mao🇨🇳
We study inverse magnetic catalysis in the Nambu--Jona-Lasinio model beyond mean field approximation. The feed-down from mesons to quarks is embedded in an effective coupling constant at finite temperature and magnetic field. While the magnetic catalysis is still the dominant effect at low temperature, the meson dressed quark mass drops down with increasing magnetic field at high temperature due to the dimension reduction of the Goldstone mode in the Pauli-Villars regularization scheme.
↳ hep-phhep-thPLB(2016)·98 citations
08
Understanding the nature of the heavy pentaquarks and searching for them in pion-induced reactions
Xiao-Hai Liu🇯🇵 · Makoto Oka🇯🇵
We investigate the reaction $π^{-} p \to π^{-} J / ψ p$ via the open-charm hadron rescattering diagrams. Due to the presence of the triangle singularity (TS) in the rescattering amplitudes, the TS peaks can simulate the pentaquark-like resonances arising in the $J / ψ p$ invariant mass distributions, which may bring ambiguities on our understanding of the nature of the exotic states. Searching for the heavy pentaquark in different processes may help us to clarify the ambiguities, because of the highly process-dependent characteristic of the TS mechanism.
↳ hep-phhep-exnucl-exnucl-thNPA(2016)·39 citations
09
Evolution of fusion hindrance for asymmetric systems at deep sub barrier energies
A. Shrivastavaa🇮🇳 · K. Mahata🇮🇳 · S.K. Pandit🇮🇳 · V. Nanal🇮🇳 · T. Ichikawa🇯🇵 · K. Hagino🇯🇵 · A. Navin🇫🇷 · C.S. Palshetkar🇮🇳 · V.V. Parkar🇮🇳 · K. Ramachandran🇮🇳 · P.C. Rout🇮🇳 · Abhinav Kumar🇮🇳 · A. Chatterjee🇮🇳 · S. Kailas🇮🇳
Measurements of fusion cross-sections of 7Li and 12C with 198Pt at deep sub-barrier energies are reported to unravel the role of the entrance channel in the occurrence of fusion hindrance. The onset of fusion hindrance has been clearly observed in 12C + 198Pt system but not in 7Li + 198Pt system, within the measured energy range. Emergence of the hindrance, moving from lighter (6,7Li) to heavier (12C,16O) projectiles is explained employing a model that considers a gradual transition from a sudden to adiabatic regime at low energies. The model calculation reveals a weak effect of the damping of coupling to collective motion for the present systems as compared to that obtained for systems with heavier projectiles.
↳ nucl-exnucl-thPLB(2016)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE