Nuclear Theory·nucl-th

Friday·March 3, 2017

8 papers—5 primary·3 cross-listed

01
New estimation for neutron-neutron scattering length: charge symmetry and charge independence breaking revisited
E.S. Konobeevski · S.V. Zuyev · V.I. Kukulin · V.N. Pomerantsev
Recent experimental results for neutron-neutron scattering length are reanalyzed from the point of view of three-nucleon force contribution. We found that the limiting value of $a_{nn} = - 15.8 \pm 0.5$ ~fm must be free of any implicit three-body force contribution. We have also shown that the difference between the above experimental value of $a_{nn}$ and the well established value of neutron-proton scattering length $a_{n p}$ can be explained by differences in the one-pion exchange potentials.
nucl-thnucl-ex3 citations
02
Collective flow and hydrodynamics in large and small systems at the LHC
Huichao Song🇨🇳 · You Zhou🇩🇰 · Katarina Gajdosova🇩🇰
In this article, we briefly review the recent progress on collective flow and hydrodynamics in large and small systems at the Large Hadron Collider (LHC), which includes the following topics: extracting the QGP viscosity from the flow data, initial state fluctuations and final state correlations in 2.76 A TeV Pb--Pb collisions, correlations and collective flow in high energy p--Pb and p--p collisions.
nucl-thhep-phnucl-exNucl.Sci.Tech.(2017)·154 citations
03
Isovector and isoscalar pairing in odd-odd $N = Z$ nuclei within a quartet approach
D. Negrea · N. Sandulescu · D. Gambacurta
The quartet condensation model (QCM) is extended for the treatment of isovector and isoscalar pairing in odd-odd N=Z nuclei. In the extended QCM approach the lowest states of isospin T=1 and T=0 in odd-odd nuclei are described variationally by trial functions composed by a proton-neutron pair appended to a condensate of 4-body operators. The latter are taken as a linear superposition of an isovector quartet, built by two isovector pairs coupled to the total isospin T=0, and two collective isoscalar pairs. In all pairs the nucleons are distributed in time-reversed single-particle states of axial symmetry. The accuracy of the trial functions is tested for realistic pairing Hamiltonians and odd-odd N=Z nuclei with the valence nucleons moving above the cores $^{16}$ O, $^{40}$ Ca and $^{100}$ Sn. It is shown that the extended QCM approach is able to predict with high accuracy the energies of the lowest T=0 and T=1 states. The present calculations indicate that in these states the isovector and the isoscalar pairing correlations coexist together, with the former playing a dominant role.
nucl-thPTEP(2017)·6 citations
04
Heavy and light flavor jet quenching at RHIC and LHC energies
Shanshan Cao🇺🇸 · Tan Luo🇨🇳 · Guang-You Qin🇨🇳 · Xin-Nian Wang🇨🇳
The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark-gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. The dependence of the jet quenching parameter $q^$ on medium temperature and jet flavor is quantitatively extracted.
nucl-thhep-phnucl-exPLB(2018)·173 citations
05
Nuclear dipole polarizability from mean-field modeling constrained by chiral effective field theory
Zhen Zhang · Yeunhwan Lim · Jeremy W. Holt · Che Ming Ko
We construct a new Skyrme interaction Sk $χ$ m $^{*}$ by fitting the equation of state and nucleon effective masses in asymmetric nuclear matter from chiral two- and three-body forces as well as the binding energies of finite nuclei. Employing this interaction to study the electric dipole polarizabilities of $^{48}$ Ca, $^{68}$ Ni, $^{120}$ Sn, and $^{208}$ Pb in the random-phase approximation, we find that the theoretical predictions are in good agreement with experimentally measured values without additional fine tuning of the Skyrme interaction, thus confirming the usefulness of the new Skyrme interaction in studying the properties of nuclei. We further use this interaction to study the neutron skin thicknesses of $^{48}$ Ca and $^{208}$ Pb, and they are found to be consistent with the experimental data.
nucl-thPLB(2018)·35 citations
06
Missing-mass spectroscopy with the $^{6}$ Li( $π^{-}, K^{+}$ )X reaction to search for $_{Λ}^{6}$ H
R. Honda🇯🇵 · M. Agnello🇮🇹 · J. K. Ahn🇰🇷 · S. Ajimura🇯🇵 · Y. Akazawa🇯🇵 · N. Amano🇯🇵 · K. Aoki🇯🇵 · H. C. Bhang🇰🇷 · N. Chiga🇯🇵 · M. Endo🇯🇵 · P. Evtoukhovitch🇷🇺 · A. Feliciello🇮🇹 and 54 other authors
We searched for the bound state of the neutron-rich $Λ$ -hypernucleus $_{Λ}^{6}$ H, using the $^{6}$ Li( $π^{-}, K^{+}$ )X double charge-exchange reaction at a $π^{-}$ beam momentum of 1.2 GeV/c at J-PARC. A total of $1.4 \times 1 0^{12}$ $π^{-}$ was driven onto a $^{6}$ Li target of 3.5-g/ $c m^{2}$ thickness. No event was observed below the bound threshold, i.e., the mass of $_{Λ}^{4}$ H + 2n, in the missing-mass spectrum of the $^{6}$ Li( $π^{-}, K^{+}$ )X reaction in the $2^{\circ}$ < $θ_{π K}$ < $2 0^{\circ}$ angular range. Furthermore, no event was found up to 2.8 MeV/ $c^{2}$ above the bound threshold. We obtained the the double-differential cross section spectra of the $^{6}$ Li( $π^{-}, K^{+}$ )X reaction in the angular range of $2^{\circ}$ < $θ_{π K}$ < $1 4^{\circ}$ . An upper limit of 0.56 nb/sr (90% C.L.) was obtained for the production cross section of the $_{Λ}^{6}$ H hypernucleus bound state. In addition, not only the bound state region, but also the $Λ$ continuum region and part of the $Σ^{-}$ quasi-free production region of the $^{6}$ Li( $π^{-}, K^{+}$ )X reaction, were obtained with high statistics. The present missing-mass spectrum will facilitate the investigation of the $Σ^{-}$ -nucleus optical potential for $Σ^{-}$ - $^{5}$ He through spectrum shape analysis.
↳ nucl-exnucl-thPRC(2017)·16 citations
07
String dynamics and metastability of fully-heavy tetraquarks
Jean-Marc Richard (Lyon)🇫🇷 · Alfredo Valcarce (Salamanca)🇪🇸 · Javier Vijande (Valencia)🇪🇸
Multiquark states have been advocated to explain recent experimental data in the heavy-light sector, and there are already speculations about multiquarks containing only heavy quarks and antiquarks. With a rigorous treatment of the four-body problem in current quark models, full-charm $(cc c ˉ c ˉ)$ and full-beauty $(bb b ˉ b ˉ)$ tetraquarks are found to be unbound. Thus their stability should rely on more subtle effects that are not included in the simple picture of constituent quarks. The case of $(b c b ˉ c ˉ)$ might be more favorable if the naive color-additive model of confinement is replaced by a string-inspired interaction.
↳ hep-phhep-exnucl-thPRD(2017)·117 citations
08
Parallel tempering algorithm for integration over Lefschetz thimbles
Masafumi Fukuma🇯🇵 · Naoya Umeda🇯🇵
The algorithm based on integration over Lefschetz thimbles is a promising method to resolve the sign problem for complex actions. However, this algorithm often meets a difficulty in actual Monte Carlo calculations because the configuration space is not easily explored due to the infinitely high potential barriers between different thimbles. In this paper, we propose to use the flow time of the antiholomorphic gradient flow as an auxiliary variable for the highly multimodal distribution. To illustrate this, we implement the parallel tempering method by taking the flow time as a tempering parameter. In this algorithm, we can take the maximum flow time to be sufficiently large such that the sign problem disappears there, and two separate modes are connected through configurations at small flow times. To exemplify that this algorithm does work, we investigate the (0+1)-dimensional massive Thirring model at finite density and show that our algorithm correctly reproduces the analytic results for large flow times such as T=2.
↳ hep-latcond-mat.stat-mechhep-thnucl-thPTEP(2017)·80 citations

Affiliations

first authorsco-authorsvia INSPIRE