Nuclear Theory·nucl-th

Wednesday·February 4, 2015

7 papers—5 primary·2 cross-listed

01
Sign Structure of Susceptibilities of Conserved Charges in the (2+1) Polyakov Quark Meson Model
Sandeep Chatterjee🇮🇳 · Kirtimaan A. Mohan🇺🇸
The sign structure of correlations of conserved charges are investigated in a QCD like model: the (2+1) flavor Polyakov Quark Meson model. We compute all susceptibilities of the conserved charges on the $(μ_{B} - T)$ plane up to fourth order and a few at higher order as well. By varying the mass of the sigma meson, we are able to study and compare scenarios with as well as without a critical point. In the hadron-quark transition regime we identify certain correlations that turn negative unlike expectation from ideal hadron resonance gas calculations. The striking feature being that these remain negative deep into the hadronic side and thus could be measured in experiments. Measurement of such quantities in heavy ion collision experiments can elucidate the location of the QCD transition curve and possibly the critical point.
nucl-thhep-lathep-ph6 citations
02
Ab initio effective interactions for sd-shell valence nucleons
E. Dikmen · A. F. Lisetskiy · B. R. Barrett · P. Maris · A. M. Shirokov · J. P. Vary
We perform \textit{ab initio} no-core shell-model calculations for $A = 18$ and $19$ nuclei in a $4ℏΩ$ , or $N_{max} = 4$ , model space by using the effective JISP16 and chiral N3LO nucleon-nucleon potentials and transform the many-body effective Hamiltonians into the $0ℏΩ$ model space to construct the $A$ -body effective Hamiltonians in the $s d$ -shell. We separate the $A$ -body effective Hamiltonians with $A = 18$ and $A = 19$ into inert core, one-, and two-body components. Then, we use these core, one-, and two-body components to perform standard shell-model calculations for the $A = 18$ and $A = 19$ systems with valence nucleons restricted to the $s d$ shell. Finally, we compare the standard shell-model results in the $0ℏΩ$ model space with the exact no-core shell model results in the $4ℏΩ$ model space for the $A = 18$ and $A = 19$ systems and find good agreement.
nucl-thPRC(2015)·65 citations
03
Revisit of the neutron/proton ratio puzzle in intermediate-energy heavy-ion collisions
Hai-Yun Kong · Yin Xia · Jun Xu · Lie-Wen Chen · Bao-An Li · Yu-Gang Ma
Incorporating a newly improved isospin- and momentum-dependent interaction in the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model IBUU11, we have investigated relative effects of the density dependence of nuclear symmetry energy $E_{sy m} (ρ)$ and the neutron-proton effective mass splitting $m_{n}^{*} - m_{p}^{*}$ on the neutron/proton ratio of free nucleons and those in light clusters. It is found that the $m_{n}^{*} - m_{p}^{*}$ has a relatively stronger effect than the $E_{sy m} (ρ)$ and the assumption of $m_{n}^{*} \leq m_{p}^{*}$ leads to a higher neutron/proton ratio. Moreover, this finding is independent of the in-medium nucleon-nucleon cross sections used. However, results of our calculations using the $E_{sy m} (ρ)$ and $m_{n}^{*} - m_{p}^{*}$ both within their current uncertainty ranges are all too low compared to the recent NSCL/MSU double neutron/proton ratio data from central $^{124}$ Sn+ $^{124}$ Sn and $^{112}$ Sn+ $^{112}$ Sn collisions at 50 and 120 MeV/u, thus calling for new mechanisms to explain the puzzlingly high neutron/proton ratio observed in the experiments.
nucl-thnucl-exPRC(2015)·30 citations
04
On the near-threshold $p ˉ p$ invariant mass spectrum measured in $J / ψ$ and $ψ^{'}$ decays
Xian-Wei Kang🇩🇪 · J. Haidenbauer🇩🇪 · Ulf-G. Meißner🇩🇪
A systematic analysis of the near-threshold enhancement in the $p ˉ p$ invariant mass spectrum seen in the decay reactions $J / ψ \to x p ˉ p$ and $ψ (3686) \to x p ˉ p$ $(x = γ, ω, ρ, π, η)$ is presented. The enhancement is assumed to be due to the $N ˉ N$ final-state interaction (FSI) and the pertinent FSI effects are evaluated in an approach that is based on the distorted-wave Born approximation. For the $N ˉ N$ interaction a recent potential derived within chiral effective field theory and fitted to results of a partial-wave analysis of $p ˉ p$ scattering data is considered and, in addition, an older phenomenological model constructed by the Jülich group. It is shown that the near-threshold spectrum observed in various decay reactions can be reproduced simultaneously and consistently by our treatment of the $p ˉ p$ FSI. It turns out that the interaction in the isospin-1 $^{1} S_{0}$ channel required for the description of the $J / ψ \to γ p ˉ p$ decay predicts a $N ˉ N$ bound state.
nucl-thhep-phPRD(2015)·62 citations
05
Contribution of two particle-two hole final states to the nuclear response
Omar Benhar · Alessandro Lovato · Noemi Rocco
The excitation of two particle-two hole final states in neutrino-nucleus scattering has been advocated by many authors as the source of the excess cross section observed by the MiniBooNE Collaboration in the quasi elastic sector. We analyse the mechanisms leading to the appearance of these final states, and illustrate their significance through the results of accurate calculations of the nuclear electromagnetic response in the transverse channel. A novel approach, allowing for a consistent treatment of the amplitudes involving one- and two-nucleon currents in the kinematical region in which the non relativistic approximation breaks down, is outlined.
nucl-thPRC(2015)·68 citations
06
Pairing in Asymmetric Many-Fermion Systems: Functional Renormalisation Group Approach
Boris Krippa🇬🇧
Functional renormalisation group approach is applied to a imbalanced many- fermion system with a short-range attractive force. Composite boson field is introduced to describe the pairing between different flavour fermions. A set of approximate flow equations for the effective couplings is derived and solved. We identify the critical values of mass and particle number density mismatch when the system undergoes a phase transition to a normal state and determine the phase diagram both at unitary regime and nearby.
↳ cond-mat.quant-gascond-mat.supr-connucl-thPLB(2015)·10 citations
07
Thermodynamics and fluctuations of conserved charges in Hadron Resonance Gas model in finite volume
Abhijit Bhattacharyya🇮🇳 · Rajarshi Ray🇮🇳 · Subhasis Samanta🇮🇳 · Subrata Sur
The thermodynamics of hot and dense matter created in heavy-ion collision experiments are usually studied as a system of infinite volume. Here we report on possible effects for considering a finite system size for such matter in the framework of the Hadron Resonance Gas model. The bulk thermodynamic variables as well as the fluctuations of conserved charges are considered. We find that the finite size effects are insignificant once the observables are scaled with the respective volumes. The only substantial effect is found in the fluctuations of electric charge which may therefore be used to extract information about the volume of fireball created in heavy-ion collision experiments.
↳ hep-phnucl-thPRC(2015)·68 citations

Affiliations

first authorsco-authorsvia INSPIRE

Sign Structure of Susceptibilities of Conserved Charges in the (2+1) Polyakov Quark Meson Model

Ab initio effective interactions for sd-shell valence nucleons

Revisit of the neutron/proton ratio puzzle in intermediate-energy heavy-ion collisions

On the near-threshold pˉ​p invariant mass spectrum measured in J/ψ and ψ′ decays

Contribution of two particle-two hole final states to the nuclear response

Pairing in Asymmetric Many-Fermion Systems: Functional Renormalisation Group Approach

Thermodynamics and fluctuations of conserved charges in Hadron Resonance Gas model in finite volume

Affiliations

On the near-threshold $p ˉ p$ invariant mass spectrum measured in $J / ψ$ and $ψ^{'}$ decays