Nuclear Theory·nucl-th

Friday·January 13, 2017

8 papers—3 primary·5 cross-listed

01
Hyperon threshold and stellar radii
Luiz L. Lopes🇧🇷 · Debora P. Menezes🇧🇷
We study how the $Λ$ hyperon threshold influences the radius of the canonical $1.4 M_{⊙}$ neutron star in the light of the measurements found in the recent literature. We show that the onset of a new degree of freedom not only causes the well known reduction of the maximum mass, but also compacts the neutron stars with high central density. With the help of the strange mesons $ϕ$ and $σ^{*}$ , we show that it is possible to simulate very compact neutron stars keeping realistic hyperon potentials, $U_{Λ} (n_{0}) = - 28$ MeV and $U_{Λ}^{Λ} (n_{0} /5)$ in agreement with recents measurements. In the end we generalize these results showing that the onset of a yet not known dark matter particle with mass of 1.04 GeV is able to produce simultaneously a 2 $M_{⊙}$ neutron star and a canonical one with a radius of only 11.62 km.
nucl-thastro-ph.HEhep-phJCAP(2018)·22 citations
02
Missing resonance decays in thermal models
V.V. Begun🇵🇱 · V.Yu. Vovchenko🇩🇪 · M.I. Gorenstein🇺🇦
Detailed information on decay channel probabilities is absent for many high mass resonances, which are typically included in thermal models. In these cases, the sum over all known decay branching probabilities is smaller than 1. Due to this systematic uncertainty of the model, the exact charge conservation may appear to be violated. We estimate the corresponding number of missing charge states in the canonical ensemble formulation of the hadron resonance gas for p+p reactions at the SPS energy $E_{lab} = 158$ GeV: $Δ B ≃ 0.16$ for baryon charge, $Δ Q ≃ 0.12$ for electric charge, and $Δ S = - 0.01$ for strangeness. The value of the considered effect is 5-8%, which seems to be important enough to include it as a systematic error in the calculations within a hadron gas.
nucl-thhep-exhep-phnucl-ex1 citation
03
Dilepton and $ϕ$ meson production in elementary and nuclear collisions at the NICA fixed target experiment
Gy. Wolf \🇭🇺 · M. Zétényi🇭🇺
We argue that the NICA fixed target experiment will be able to provide very important new experimental data on dilepton and $ϕ$ meson production in the basically undiscovered energy domain between the SIS and SPS energies. Experimental information about elementary cross sections in this energy region is an essential ingredient of models of nuclear collisions in the same energy range.
nucl-thhep-exhep-phnucl-exEPJA(2016)·0 citations
04
Interference Between Light and Heavy Neutrinos for $0 ν β β$ Decay in the Left-Right Symmetric Model
Fahim Ahmed🇺🇸 · Andrei Neacsu🇺🇸 · Mihai Horoi🇺🇸
Neutrinoless double-beta decay is proposed as an important low energy phenomenon that could test beyond the Standard Model physics. There are several potentially competing beyond the Standard Model mechanisms that can induce the process. It thus becomes important to disentangle the different processes. In the present study we consider the interference effect between the light left-handed and heavy right-handed Majorana neutrino exchange mechanisms. The decay rate, and consequently, the phase-space factors for the interference term are derived, based on the left-right symmetric model. The numerical values for the interference phase-space factors for several nuclides are calculated, taking into consideration the relativistic Coulomb distortion of the electron wave function and finite-size of the nucleus. The variation of the interference effect with the Q-value of the process is studied.
↳ hep-phnucl-thPLB(2017)·15 citations
05
Search for a hidden strange baryon-meson bound state from $ϕ$ production in a nuclear medium
Haiyan Gao🇺🇸 · Hongxia Huang🇺🇸 · Tianbo Liu🇺🇸 · Jialun Ping🇨🇳 · Fan Wang🇨🇳 · Zhiwen Zhao🇺🇸
We investigate the hidden strange light baryon-meson system. With the resonating-group method, two bound states, $η^{'} - N$ and $ϕ - N$ , are found in the quark delocalization color screening model. Focusing on the $ϕ - N$ bound state around 1950\,MeV, we obtain the total decay width of about 4\,MeV by calculating the phase shifts in the resonance scattering processes. To study the feasibility of an experimental search for the $ϕ - N$ bound state, we perform a Monte Carlo simulation of the bound state production with an electron beam and a gold target. In the simulation, we use the CLAS12 detector with the Forward Tagger and the BONUS12 detector in Hall B at Jefferson Lab. Both the signal and the background channels are estimated. We demonstrate that the signal events can be separated from the background with some momentum cuts. Therefore it is feasible to experimentally search for the $ϕ - N$ bound state through the near threshold $ϕ$ meson production from heavy nuclei.
↳ hep-phhep-exnucl-exnucl-thPRC(2017)·42 citations
06
Transverse Energy per Charged Particle in Heavy-Ion Collisions: Role of Collective Flow
Swatantra Kumar Tiwari🇮🇳 · Raghunath Sahoo🇮🇳
The ratio of (pseudo)rapidity density of transverse energy and the (pseudo)rapidity density of charged particles, which is a measure of the mean transverse energy per particle, is an important observable in high energy heavy-ion collisions, which reveals about the mechanism of particle production and the freeze-out criteria. Its collision energy and centrality dependence is exactly like the chemical freeze-out temperature till top RHIC energy. The LHC measurement at $s_{N N}$ = 2.76 TeV brings up new challenges to rule out the mechanisms of gluon saturation or non-equilibrium phenomena being prevalent at high energies, which could contribute to the above observable. The Statistical Hadron Gas Model (SHGM) with a static fireball approximation has been successful in describing both the centrality and energy dependence till top RHIC energies. However, the SHGM predictions for higher energies are highly underestimated by the LHC data. In order to understand this, we have incorporated radial flow effect in an excluded volume SHGM. The hard-core radius of baryons at lower collision energies plays an important role in the description of a hadronic system. In view of this, in order to make a complete energy dependence study from FAIR to LHC energies, we have considered an excluded volume SHGM. Our studies suggest that the collective flow plays an important role in describing $E_{T} / N_{c h}$ and it could be one of the possible parameters to explain the jump observed in $E_{T} / N_{c h}$ from RHIC to LHC energies. Predictions for the LHC measurements at $s_{N N}$ = 5.02 TeV are given.
↳ hep-phhep-exhep-thnucl-ex+1EPJA(2018)·5 citations
07
Enhanced effect of CP-violating nuclear magnetic quadrupole moment in HfF $^{+}$ molecule
L.V. Skripnikov🇷🇺 · A.V. Titov🇷🇺 · V.V. Flambaum🇦🇺
HfF $^{+}$ cation is a very promising system to search for the electron electric dipole moment (EDM), and corresponding experiment is carried out by E. Cornell group. Here we theoretically investigate the cation to search for another T,P-odd effect -- the nuclear magnetic quadrpole moment (MQM) interaction with electrons. We report the first accurate ab initio relativistic electronic structure calculations of the molecular parameter $W_{M}$ =0.494 $\frac{1 0 ^{33} Hz}{e cm ^{2}}$ that is required to interpret the experimental data in terms of the MQM of Hf nucleus. For this we have implemented and applied the combined Dirac-Coulomb(-Gaunt) and relativistic effective core potential approaches to treat electron correlation effects from all of the electrons and to take into account high-order correlation effects using the coupled cluster method with single, double, triple and noniterative quadruple cluster amplitudes, CCSDT(Q). We discuss interpretation of the MQM effect in terms of the strength constants of T,P-odd nuclear forces, proton and neutron EDM, QCD parameter $θ$ and quark chromo-EDM.
↳ physics.atom-phhep-phnucl-thphysics.chem-phPRA(2017)·35 citations
08
The chiral anomaly, Berry's phase and chiral kinetic theory, from world-lines in quantum field theory
Niklas Mueller🇩🇪 · Raju Venugopalan🇺🇸
We outline a novel chiral kinetic theory framework for systematic computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. The real part of the fermion determinant in the QCD effective action is expressed as a supersymmetric world-line action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. Berry's phase is obtained in a consistent non-relativistic adiabatic limit. The chiral anomaly, in contrast, arises from the phase of the fermion determinant; its topological properties are therefore distinct from those of the Berry phase. We show that the imaginary contribution to the fermion determinant too can be expressed as a point particle world-line path integral and derive the corresponding anomalous axial vector current. Our results can be used to derive a covariant relativistic chiral kinetic theory including the effects of topological fluctuations that has overlap with classical-statistical simulations of the CME at early times and anomalous hydrodynamics at late times.
↳ hep-phhep-thnucl-thPRD(2018)·97 citations

Affiliations

first authorsco-authorsvia INSPIRE