Nuclear Theory·nucl-th

Thursday·February 15, 2018

11 papers—5 primary·6 cross-listed

01
One-proton emission from the $_{Λ}^{6}$ Li hypernucleus
Tomohiro Oishi🇮🇹
One-proton (1p) radioactive emission under the influence of the $Λ^{0}$ -hyperon inclusion is discussed. I investigate the hyper-1p emitter, $_{Λ}^{6}$ Li, with a time-dependent three-body model. Two-body interactions for $α$ -proton and $α$ - $Λ^{0}$ subsystems are determined consistently to their resonant and bound energies, respectively. For a proton- $Λ^{0}$ subsystem, a contact interaction, which can be linked to the vacuum-scattering length of the proton- $Λ^{0}$ scattering, is employed. A noticeable sensitivity of the 1p-emission observables to the scattering length of the proton- $Λ^{0}$ interaction is shown. The $Λ^{0}$ -hyperon inclusion leads to a remarkable fall of the 1p-resonance energy and width from the hyperon-less $α$ -proton resonance. For some empirical values of the proton- $Λ^{0}$ scattering length, the 1p-resonance width is suggested to be of the order of $0.1 - 0.01$ MeV. Thus, the 1p emission from $_{Λ}^{6}$ Li may occur in the timescale of $1 0^{- 20} - 1 0^{- 21}$ seconds, which is sufficiently shorter than the self-decay lifetime of $Λ^{0}$ , $1 0^{- 10}$ seconds. By taking the spin-dependence of the proton- $Λ^{0}$ interaction into account, a remarkable split of the $J^{π} = 1^{-}$ and $2^{-}$ 1p-resonance states is predicted. It is also suggested that, if the spin-singlet proton- $Λ^{0}$ interaction is sufficiently attractive, the 1p emission from the $1^{-}$ ground state is forbidden. From these results, I conclude that the 1p emission can be a suitable phenomenon to investigate the basic properties of the hypernuclear interaction, for which a direct measurement is still difficult.
nucl-thnucl-exPRC(2018)·3 citations
02
Chemical freezeout parameters within generic nonextensive statistics
Abdel Nasser Tawfik (Egyptian Ctr. Theor. Phys., Cairo, WLCAPP, Cairo)🇪🇬 · Hayam Yassin🇪🇬 · Eman R. Abo Elyazeed (Ain Shams U., Cairo, WLCAPP, Cairo)🇪🇬
The particle production in relativistic heavy-ion collisions seems to be created in a dynamically disordered system which can be best described by an extended exponential entropy. In distinguishing between the applicability of this and Boltzmann-Gibbs (BG) in generating various particle-ratios, generic (non)extensive statistics (GNS) is introduced to the hadron resonance gas model. Accordingly, the degree of (non)extensivity is determined by the possible modifications in the phase space. Both BG extensivity and Tsallis nonextensivity are included as very special cases defined by specific values of the equivalence classes $(c, d)$ . We found that the particle ratios at energies ranging between $3.8$ and $2760$ GeV are best reproduced by nonextensive statistics, where $c$ and $d$ range between $\sim 0.9$ and $\sim 1$ . The present work aims at illustrating that the proposed approach is well capable to manifest the statistical nature of the system on interest. We don't aim at highlighting deeper physical insights. In other words, while the resulting nonextensivity is neither BG nor Tsallis, the freezeout parameters are found very compatible with BG and accordingly with the well-known freezeout phase-diagram, which is in an excellent agreement with recent lattice calculations. We conclude that the particle production is nonextensive but should not necessarily be accompanied by a radical change in the intensive or extensive thermodynamic quantities, such as internal energy and temperature. Only, the two critical exponents defining the equivalence classes $(c, d)$ are the physical parameters characterizing the (non)extensivity.
nucl-thhep-phhep-thIndian J.Phys.(2018)·12 citations
03
Axial Charge Fluctuation and Chiral Magnetic Effect from Stochastic Hydrodynamics
Shu Lin🇨🇳 · Li Yan🇨🇦 · Gui-Rong Liang🇨🇳
The amount of axial charge produced in heavy ion collisions is one of the key quantities in understanding chiral magnetic effect. Current phenomenological studies assume large axial charge chemical potential $μ_{5}$ produced in Glasma phase and assume the conservation of axial charge throughout the evolution, which is valid in the long relaxation time limit. Based on the solution of stochastic hydrodynamics with phenomenological parameters, our study suggests that the situation of heavy ion collisions may be close to the opposite limit, in which axial charge fluctuation approaches thermodynamic limit. Using $μ_{5}$ set by the thermodynamic limit for chiral magnetic effect and a background from parity-even $v_{1}$ , we obtain a reasonable description of the centrality dependence of charged particle correlation measured in experiment.
nucl-thhep-phnucl-exPRC(2018)·22 citations
04
Interacting hadron resonance gas model in K-matrix formalism
Ashutosh Dash🇮🇳 · Subhasis Samanta🇮🇳 · Bedangadas Mohanty🇮🇳
An extension of Hadron Resonance Gas (HRG) model is constructed to include interactions using relativistic virial expansion of partition function. The non-interacting part of the expansion contains all the stable baryons and mesons and the interacting part contains all the higher mass resonances which decay into two stable hadrons. The virial coefficients are related to the phase shifts which are calculated using K-matrix formalism in the present work. We have calculated various thermodynamics quantities like pressure, energy density, and entropy density of the system. A comparison of thermodynamic quantities with non interacting HRG model, calculated using the same number of hadrons, shows that the results of above formalism are larger. A good agreement between equation of state calculated in K-matrix formalism and lattice QCD simulations is observed. Specifically the lattice QCD calculated interaction measure is well described in our formalism. We have also calculated second order fluctuations and correlations of conserved charges in K-matrix formalism. We observe a good agreement of second order fluctuations and baryon-strangeness correlation with lattice data below the cross-over temperature.
nucl-thhep-phPRC(2018)·40 citations
05
Dynamical and statistical bimodality in nuclear fragmentation
S.Mallik🇮🇳 · G. Chaudhuri🇮🇳 · F. Gulminelli🇫🇷
The origin of bimodal behavior in the residue distribution experimentally measured in heavy ion reactions is reexamined using Boltzmann-Uehling-Uhlenbeck simulations. We suggest that, depending on the incident energy and impact parameter of the reaction, both entrance channel and exit channel effects can be at the origin of the observed behavior. Specifically, fluctuations in the reaction mechanism induced by fluctuations in the collision rate, as well as thermal bimodality directly linked to the nuclear liquid-gas phase transition are observed in our simulations. Both phenomenologies were previously proposed in the literature, but presented as incompatible and contradictory interpretations of the experimental measurements. These results indicate that heavy ion collisions at intermediate energies can be viewed as a powerful tool to study both bifurcations induced by out-of-equilibrium critical phenomena, as well as finite size precursors of thermal phase transitions.
nucl-thnucl-exPRC(2018)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE

One-proton emission from the Λ6​Li hypernucleus

Chemical freezeout parameters within generic nonextensive statistics

Axial Charge Fluctuation and Chiral Magnetic Effect from Stochastic Hydrodynamics

Interacting hadron resonance gas model in K-matrix formalism

Dynamical and statistical bimodality in nuclear fragmentation

Affiliations

One-proton emission from the $_{Λ}^{6}$ Li hypernucleus