Nuclear Theory·nucl-th

Thursday·December 14, 2017

9 papers—6 primary·3 cross-listed

01
[Submitted on 12 Dec 2017]
Light-meson masses in an unquenched quark model
Xiaoyun Chen🇨🇳 · Jialun Ping🇨🇳 · Craig D. Roberts🇺🇸 · Jorge Segovia🇪🇸
We perform a coupled-channels calculation of the masses of light mesons with the quantum numbers $I J^{P = -}$ , $(I, J) = 0, 1$ , by including $q q ˉ$ and $(q q ˉ)^{2}$ components in a nonrelativistic chiral quark model. The coupling between two- and four-quark configurations is realized through a $^{3} P_{0}$ quark-pair creation model. With the usual form of this operator, the mass shifts are large and negative, an outcome which raises serious issues of validity for the quenched quark model. Herein, therefore, we introduce some improvements of the $^{3} P_{0}$ operator in order to reduce the size of the mass shifts. By introducing two simple factors, physically well motivated, the coupling between $q q ˉ$ and $(q q ˉ)^{2}$ components is weakened, producing mass shifts that are around 10-20% of hadron bare masses.
Comments:
10 pages, 1 figure, 7 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1712.04457 [pdf]
PRD(2018)·31 citations
02
[Submitted on 12 Dec 2017]
Self-consistency in the phonon space of the particle-phonon coupling model
V. Tselyaev · N. Lyutorovich · J. Speth · P.-G. Reinhard
In the paper the non-linear generalization of the time blocking approximation (TBA) is presented. The TBA is one of the versions of the extended random-phase approximation (RPA) developed within the Green-function method and the particle-phonon coupling model. In the generalized version of the TBA the self-consistency principle is extended onto the phonon space of the model. The numerical examples show that this non-linear version of the TBA leads to the convergence of the results with respect to enlarging the phonon space of the model.
Comments:
12 pages, 10 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.04494 [pdf]
PRC(2018)·28 citations
03
[Submitted on 12 Dec 2017]
The role of strangeness and isospin in low density expansions of hadronic matter
Thamirys de Oliveira🇧🇷 · Débora P. Menezes🇧🇷 · Marcus B. Pinto🇧🇷 · Francesca Gulminelli🇫🇷
We compare relativistic mean field models with their low density expansion counterparts used to mimic non-relativistic models by consistently expanding the baryonic scalar density in powers of the baryonic number density up to $O (13/3)$ , which goes two orders beyond the order considered in previous works. We show that, due to the non-trivial density dependence of the Dirac mass, the convergence of the expansion is very slow, and the validity of the non-relativistic approximation {\bf is} questionable even at subsaturation densities. In order to analyze the roles played by strangeness and isospin we consider $n - Λ$ and $n - p$ matter separately. Our results indicate that these degrees of freedom play quite different roles in the expansion mechanism and $n - Λ$ matter can be better described by low density expansions than $n - p$ matter in general.
Comments:
35 pages, 26 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1712.04526 [pdf]
PRC(2018)·1 citation
04
[Submitted on 13 Dec 2017]
Probing proton transition momentum in neutron-rich matter
Gao-Chan Yong
Around the nuclear Fermi momentum, there is a transition of nucleon momentum distribution n(k) in nuclear matter, i.e., from a constant to the $1/ k^{4}$ nucleon momentum distribution. While nowadays the transition momentum of minority in asymmetric matter is rarely studied and thus undetermined. In the framework of the IBUU transport model, proton transition momentum in nuclei is first studied. It is found that the transition momentum of proton is sensitive to the $π^{-} / π^{+}$ ratio as well as the energetic photon production in neutron-rich nuclear reaction. This result may push the study of how the proton momentum is distributed in neutron-rich matter forward and help us to better understand the dynamics of both neutron-rich nuclear reactions and neutron stars.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1712.04574 [pdf]
PLB(2018)·22 citations
05
[Submitted on 13 Dec 2017]
A flow paradigm in heavy-ion collisions
Li Yan🇨🇦
The success of hydrodynamics in high energy heavy-ion collisions leads to a flow paradigm, to understand the observed features of harmonic flow in terms of the medium collective expansion regarding initial state geometrical properties. In this review, we present some essential ingredients in the flow paradigm, including the hydrodynamic modeling, the characterization of initial state geometry and the medium response relations. The extension of the flow paradigm to small colliding systems is also discussed.
Comments:
Typo corrected, new references added. Published version for Chinese Physics C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1712.04580 [pdf]
CPC(2018)·42 citations
06
[Submitted on 13 Dec 2017]
Production of light hypernuclei with light-ion beams and targets
Y.L. Sun🇫🇷 · A.S. Botvina🇩🇪 · A. Obertelli🇫🇷 · A. Corsi🇫🇷 · M. Bleicher🇩🇪
Ion-ion collisions at relativistic energies have been shown recently to be a promising technique for the production of hypernuclei. In this article, we further investigate the production of light $Λ$ hypernuclei by use of a hybrid dynamical model, cascade-coalescence followed by Fermi breakup. The predictions are then compared with the available experimental data. The dependence of the production cross section upon the beam energy, beam mass number as well as different projectile-target combinations is investigated. In particular, we evaluate the yields and signal-over-background ratio in the invariant-mass spectrum for carbon projectiles impinging on hydrogen and carbon targets and various coincidence conditions in the experiment using the theoretical calculation as an input. It is found that comparing with carbon target, hydrogen target also leads to sizable hypernuclear yields, even for exotic species, and the hydrogen target could improve significantly signal-over-background ratio in some hypernuclear invariant mass studies.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1712.04658 [pdf]
PRC(2018)·16 citations
07
[Submitted on 12 Dec 2017] (cross-list from hep-ph)
Incoherent diffractive photoproduction of $J / ψ$ and $Υ$ on heavy nuclei in the color dipole approach
Agnieszka Łuszczak🇩🇪 · Wolfgang Schäfer🇵🇱
We calculate cross sections and transverse momentum distributions for the incoherent diffractive production of vector mesons $J / ψ$ and $Υ$ on heavy nuclei. In distinction to coherent diffraction, the nucleus is allowed to break up, but except for the vector meson no new particles are produced in the reaction. Within the color dipole approach, we derive the multiple scattering expansion of the incoherent diffractive cross section as an expansion over quasielastic scatterings of the color dipole. We also compare our results to the measurement of the ALICE collaboration for incoherent $J / ψ$ production at $s_{NN} = 2.76 TeV$ and show predictions at $s_{NN} = 5.02 TeV$ . We also briefly discuss a possible contribution to $J / ψ$ production in peripheral collisions in the $70 \div 90%$ centrality class.
Comments:
18 pages, 8 figs
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.04502 [pdf]
PRC(2018)·21 citations
08
[Submitted on 13 Dec 2017] (cross-list from hep-ph)
Revisiting the axial anomaly for light mesons and baryons
Francesco Giacosa🇩🇪
The axial anomaly is responsible for the masses and mixing of the mesons $η$ and $η^{'}$ . An open question is if (and to what extent) it affects also other hadrons. We show that anomalous terms can be important to understand the spectroscopy of the pseudotensor mesons $η_{2} (1645)$ and $η_{2} (1870)$ . In fact, pseudotensor mesons belong to a so-called heterochiral multiplet, for which a quadratic mixing term between nonstrange and strange isoscalar members arises. On the contrary, for so-called homochiral multiplets, such as the ground-state (axial-)vector and tensor mesons, this mixing is not possible, hence one can easily understand why the isoscalar members of these multiplets are almost purely nonstrange and strange, respectively. Moreover, the axial anomaly can be also coupled to baryons (within the mirror assignment), and thus it helps to explain the large decay width $N^{*} (1535) \to N η$ and to clarify which baryons are chiral partners.
Comments:
6 pages. Prepared for the proceedings of the XVII International Conference on Hadron Spectroscopy and Structure - Hadron2017, 25-29 September, 2017, University of Salamanca, Salamanca, Spain
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.04664 [pdf]
PoS(2018)·3 citations
09
[Submitted on 13 Dec 2017] (cross-list from hep-ph)
Lepton-rich cold QCD matter in protoneutron stars
J. C. Jiménez🇧🇷 · E. S. Fraga🇧🇷
We investigate protoneutron star matter using the state-of-the-art perturbative equation of state for cold and dense QCD in the presence of a fixed lepton fraction in which both electrons and neutrinos are included. Besides computing the modifications in the equation of state due to the presence of trapped neutrinos, we show that stable strange quark matter has a more restricted parameter space. We also study the possibility of nucleation of unpaired quark matter in the core of protoneutron stars by matching the lepton-rich QCD pressure onto a hadronic equation of state, namely TM1 with trapped neutrinos. Using the inherent dependence of perturbative QCD on the renormalization scale parameter, we provide a measure of the uncertainty in the observables we compute.
Comments:
9 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1712.04773 [pdf]
PRD(2018)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE