Nuclear Theory·nucl-th

Monday·April 29, 2019

10 papers—4 primary·6 cross-listed

01
[Submitted on 25 Apr 2019]
Tetraneutron condensation in neutron rich matter
O. Ivanytskyi🇪🇸 · M. Ángeles Pérez-García🇪🇸 · C. Albertus🇪🇸
In this work we investigate the possible condensation of tetraneutron resonant states in the lower density neutron rich gas regions inside Neutron Stars (NSs). Using a relativistic density functional approach we characterize the system containing different hadronic species including, besides tetraneutrons, nucleons and a set of light clusters ( $^{3}$ He, $α$ particles, deuterium and tritium). $σ, ω$ and $ρ$ mesonic fields provide the interaction in the nuclear system. We study how the tetraneutron presence could significantly impact the nucleon pairing fractions and the distribution of baryonic charge among species. For this we assume that they can be thermodynamically produced in an equilibrated medium and scan a range of coupling strengths to the mesonic fields from prescriptions based on isospin symmetry arguments. We find that tetraneutrons may appear over a range of densities belonging to the outer NS crust carrying a sizable amount of baryonic charge thus depleting the nucleon pairing fractions.
Comments:
10 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1904.11512 [pdf]
EPJA(2019)·13 citations
02
[Submitted on 25 Apr 2019]
Exact isovector pairing in a shell-model framework: Role of proton-neutron correlations in isobaric analog states
M. E. Miora · K. D. Launey · D. Kekejian · F. Pan · J. P. Draayer
We utilize a nuclear shell model Hamiltonian with only two adjustable parameters to generate, for the first time, exact solutions for pairing correlations for light to medium-mass nuclei, including the challenging proton-neutron pairs, while also identifying the primary physics involved. In addition to single-particle energy and Coulomb potential terms, the shell model Hamiltonian consists of an isovector $T = 1$ pairing interaction and an average proton-neutron isoscalar $T = 0$ interaction, where the $T = 0$ term describes the average interaction between non-paired protons and neutrons. This Hamiltonian is exactly solvable, where, utilizing 3 to 7 single-particle energy levels, we reproduce experimental data for 0 $^{+}$ state energies for isotopes with mass $A = 10$ through $A = 62$ exceptionally well including isotopes from He to Ge. Additionally, we isolate effects due to like-particle and proton-neutron pairing, provide estimates for the total and proton-neutron pairing gaps, and reproduce $N$ (neutron) = $Z$ (proton) irregularity. These results provide a further understanding for the key role of proton-neutron pairing correlations in nuclei, which is especially important for waiting-point nuclei on the rp-path of nucleosynthesis.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.11555 [pdf]
PRC(2019)·8 citations
03
[Submitted on 26 Apr 2019]
The many-nucleon unified model and the dynamics of nuclear rotations
David J. Rowe
It is determined that a many-nucleon version of the Bohr-Mottelson unified model that contains the essential observables of that model and has irreducible representations that span the Hilbert space of fully anti-symmetric states of nuclei, is given uniquely by the symplectic model. This model is shown to provide a framework for an examination of the dynamics of nuclear rotations. A first discovery is that rotational energies are mixtures of potential and kinetic energies even in an adiabatic limit.
Comments:
3 pages, 1 figure, 28 references
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1904.11756 [pdf]
0 citations
04
[Submitted on 26 Apr 2019]
Landau and Eckart frames for relativistic fluids in nuclear collisions
Akihiko Monnai🇯🇵
The quark matter created in relativistic nuclear collisions is interpreted as a nearly-perfect fluid. The recent efforts to explore its finite-density properties in the beam energy scan programs motivate one to revisit the issue of the local rest frame fixing in off-equilibrium hydrodynamics. I first investigate full second-order relativistic hydrodynamics in the Landau and the Eckart frames. Then numerical hydrodynamic simulations are performed to elucidate the effect of frame choice on flow observables in relativistic nuclear collisions. The results indicate that the flow can differ in the Landau and the Eckart frames but charged particle and net baryon rapidity distributions are mostly frame independent when off-equilibrium kinetic freeze-out is considered.
Comments:
11 pages, 5 figures; minor revision, published in Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1904.11940 [pdf]
PRC(2019)·23 citations
05
[Submitted on 25 Apr 2019] (cross-list from hep-ex)
Neutrino event generators: foundation, status and future
Ulrich Mosel🇩🇪
Neutrino event generators are an essential tool needed for the extraction of neutrino mixing parameters, the mass hierarchy and a CP violating phase from long-baseline experiments. In this article I first describe the theoretical basis and the approximations needed to get to present-days generators. I also discuss the strengths and limitations of theoretical models used to describe semi-inclusive neutrino-nucleus reactions. I then confront present day's generators with this theoretical basis by detailed discussions of the various reaction processes. Finally, as examples I then show for various experiments results of the generator GiBUU for lepton semi-inclusive cross sections as well as particle spectra. I also discuss features of these cross sections in terms of the various reaction components, with predictions for DUNE. Finally, I argue for the need for a new neutrino generator that respects our present-day knowledge of both nuclear theory and nuclear reactions and is as much state-of-the-art as the experimental equipment. I outline some necessary requirements for such a new generator.
Comments:
Topical Review, accepted for publication in Journals of Physics G
Subjects:
High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.11506 [pdf]
J.Phys.G(2019)·75 citations
06
[Submitted on 25 Apr 2019] (cross-list from hep-th)
Correlations far from equilibrium in charged strongly coupled fluids subjected to a strong magnetic field
Casey Cartwright🇺🇸 · Matthias Kaminski🇺🇸
Within a holographic model, we calculate the time evolution of 2-point and 1-point correlation functions (of selected operators) within a charged strongly coupled system of many particles. That system is thermalizing from an anisotropic initial charged state far from equilibrium towards equilibrium while subjected to a constant external magnetic field. One main result is that thermalization times for 2-point functions are significantly (approximately three times) larger than those of 1-point functions. Magnetic field and charge amplify this difference, generally increasing thermalization times. However, there is also a competition of scales between charge density, magnetic field, and initial anisotropy, which leads to an array of qualitative changes on the 2- and 1-point functions. There appears to be a strong effect of the medium on 2-point functions at early times, but approximately none at later times. At strong magnetic fields, an apparently universal thermalization time emerges, at which all 2-point functions appear to thermalize regardless of any other scale in the system. Hence, this time scale is referred to as saturation time scale. As extremality is approached in the purely charged case, 2- and 1-point functions appear to equilibrate at infinitely late time. We also compute 2-point functions of charged operators. Our results can be taken to model thermalization in heavy ion collisions, or thermalization in selected condensed matter systems.
Comments:
v2: published version, minor changes, clarified relation to anisotropies in heavy ion collisions, added references; v1: 25 figures, 14 tables, 57 pages, comments welcome
Subjects:
High Energy Physics — Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.11507 [pdf]
JHEP(2019)·23 citations
07
[Submitted on 26 Apr 2019] (cross-list from hep-ph)
Possibility to study pentaquark states $P_{c} (4312), P_{c} (4440)$ , and $P_{c} (4457)$ in $γ p \to J / ψ p$ reaction
Xiao-Yun Wang🇨🇳 · Xu-Rong Chen🇨🇳 · Jun He🇨🇳
Inspired by the observation of the pentaquark states $P_{c} (4312), P_{c} (4440)$ and $P_{c} (4457)$ at LHCb, photoproduction of these three $P_{c}$ states via the interaction $γ p \to J / ψ p$ is investigated in an effective Lagrangian approach. The $t$ -channel Pomeron exchange diffractive process is considered as the main background for the $J / ψ$ photoproduction. The numerical results show that the theoretical cross section, which is calculated by assuming a branching ratio $B r [P_{c} \to J / ψ p] ≃ 3%$ , is consistent with the existing experimental data of the $γ p \to J / ψ p$ process. With such a branching ratio, if experimental precision reaches 0.1 nb within a bin of 100 MeV for photon energy, two peaks are expected to be obviously observed in the $J / ψ$ photoproduction. To observe the two-peak structure from $P_{c} (4440)$ and $P_{c} (4457)$ , higher precision, about 0.1nb/10 MeV, is required to distinguish two close pentaquarks. If the physical branching ratio is larger, the requirement of experimental precision will be reduced. The differential cross sections for reaction $γ p \to J / ψ p$ are also present. It is found that the $t$ -channel Pomeron exchange provides a sharp increase at extreme forward angles and gives a sizable contribution at most energy points, while the contributions from the $s$ -channel $P_{c}$ exchanges play important roles at threshold energies. The experimental measurement of the $γ p \to J / ψ p$ process in the near-threshold energy region around $E_{γ} ≃ 9.4 - 10.5$ GeV is suggested, and is accessible at CEBAF@JLab and COMPASS.
Comments:
7 pages, 7 figures, version to be published in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.11706 [pdf]
PRD(2019)·73 citations
08
[Submitted on 26 Apr 2019] (cross-list from hep-ph)
On the critical end point in a two-flavor linear sigma model coupled to quarks
Alejandro Ayala🇲🇽 · Luis A. Hernandez🇲🇽 · Marcelo Loewe🇿🇦 · J. C. Rojas🇨🇱 · Renato Zamora🇨🇱
We use the linear sigma model coupled to quarks to explore the location of the phase transition lines in the QCD phase diagram from the point of view of chiral symmetry restoration at high temperature and baryon chemical potential. We compute analytically the effective potential in the high- and low-temperature approximations up to sixth order, including the contribution of the ring diagrams to account for the plasma screening properties. We determine the model parameters, namely, the couplings and mass-parameter, from conditions valid at the first order phase transition at vanishing temperature and, using the Hagedorn limiting temperature concept applied to finite baryon density, for a critical baryochemical potential of order of the nucleon mass. We show that when using the set of parameters thus determined, the second order phase transition line (our proxy for the crossover transition) that starts at finite temperature and zero baryon chemical potential converges to the line of first order phase transitions that starts at zero temperature and finite baryon chemical potential to determine the critical end point to lie in the region $5.02 < μ_{B}^{\mbox C E P} / T_{c} < 5.18$ , $0.14 < T^{\mbox C E P} / T_{c} < 0.23$ , where $T_{c}$ is the critical transition temperature at zero baryon chemical potential.
Comments:
11 pages, 3 figures, discussion extended, explicit calculations included in appendices and version accepted for publication in EPJ A
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1904.11905 [pdf]
EPJA(2020)·22 citations
09
[Submitted on 26 Apr 2019] (cross-list from hep-ph)
Associated Quarkonium Hadroproduction at High-Energy Colliders
Nodoka Yamanaka🇫🇷 · Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇫🇷 · Yu-Jie Zhang🇨🇳
Quarkonium production in proton-proton collision is interesting in profiling the partons inside the nucleon. Recently, the impact of double parton scatterings (DPSs) was suggested by experimental data of associated quarkonium production (J/psi+Z, J/psi+W, and J/psi+J/psi) at the LHC and Tevatron, in addition to single parton scatterings (SPSs). In this proceedings contribution, we review the extraction of the effective parameter of the DPS through the evaluation of the SPS contributions under quark-hadron duality.
Comments:
4 pages, 3 figures, proceedings of the 8th International Conference on Quarks and Nuclear Physics (QNP2018), November 13-17, 2018
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.11928 [pdf]
JPS Conf.Proc.(2019)·0 citations
10
[Submitted on 26 Apr 2019] (cross-list from hep-ph)
Higgs boson production in photon-photon interactions with proton, light-ion, and heavy-ion beams at current and future colliders
David d'Enterria🇨🇭 · Daniel E. Martins🇧🇷 · Patricia Rebello Teles🇧🇷
The production of the Higgs boson in photon-photon interactions with proton and nucleus beams at three planned or proposed future CERN colliders --- the high-luminosity Large Hadron Collider (HL-LHC), the high-energy LHC (HE-LHC), and the Future Circular Collider (FCC) --- is studied. The cross sections for the process AA $γ γ$ (A)H(A), with the ions A surviving the interaction and the Higgs scalar exclusively produced, are computed with MadGraph 5 modified to include the corresponding elastic $γ$ fluxes, for Pb-Pb, Xe-Xe, Kr-Kr, Ar-Ar, O-O, p-Pb, and p-p over the nucleon-nucleon collision energy range $s \approx 3$ --100 TeV. Simulations of the $γ γ \to H \to b b ˉ$ decay mode --- including realistic (mis)tagging and reconstruction efficiencies for the final-state b-jets, as well as appropriate kinematical selection criteria to reduce the similarly computed $γ γ \to b b ˉ, c c ˉ, q q ˉ$ continuum backgrounds --- have been carried out. Taking into account the expected luminosities for all systems, the yields and significances for observing the Higgs boson in ultraperipheral collisions (UPCs) are estimated. At the HL-LHC and HE-LHC, the colliding systems with larger Higgs significance are Ar-Ar(6.3 TeV) and Kr-Kr(12.5 TeV) respectively, but $3 σ$ evidence for two-photon Higgs production would require 200 and 30 times larger integrated luminosities than those planned today at both machines. Factors of ten can be gained by running for a year, rather than the typical 1-month heavy-ion LHC operation, but the process will likely remain unobserved until a higher energy hadron collider, such as the FCC, is built. In the latter machine, the $5 σ$ observation of Higgs production in UPCs is feasible in just the first nominal run of Pb-Pb and p-Pb collisions at $s = 39$ and 63 TeV respectively.
Comments:
8 pages, 4 figures. Minor mods. to match final PRD version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.11936 [pdf]
PRD(2020)·21 citations

Affiliations

first authorsco-authorsvia INSPIRE