Nuclear Theory·nucl-th

Monday·June 13, 2016

10 papers—5 primary·5 cross-listed

01
[Submitted on 9 Jun 2016]
Dependence of two-proton radioactivity on nuclear pairing models
Tomohiro Oishi · Markus Kortelainen · Alessandro Pastore
Sensitivity of two-proton emitting decay to nuclear pairing correlation is discussed within a time-dependent three-body model. We focus on the $^{6}$ Be nucleus assuming $α + p + p$ configuration, and its decay process is described as a time-evolution of the three-body resonance state. For a proton-proton subsystem, a schematic density-dependent contact (SDDC) pairing model is employed. From the time-dependent calculation, we observed the exponential decay rule of a two-proton emission. It is shown that the density dependence does not play a major role in determining the decay width, which can be controlled only by the asymptotic strength of the pairing interaction. This asymptotic pairing sensitivity can be understood in terms of the dynamics of the wave function driven by the three-body Hamiltonian, by monitoring the time-dependent density distribution. With this simple SDDC pairing model, there remains an impossible trinity problem: it cannot simultaneously reproduce the empirical $Q$ value, decay width, and the nucleon-nucleon scattering length. This problem suggests that a further sophistication of the theoretical pairing model is necessary, utilizing the two-proton radioactivity data as the reference quantities.
Comments:
Result and conclusion have been majorly revised from the previous version. 11 pages, 10 figures, 2 table
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1606.03111 [pdf]
PRC(2017)·29 citations
02
[Submitted on 10 Jun 2016]
Quark-Meson Coupling model based upon the Nambu-Jona Lasinio model
D. L. Whittenbury🇦🇺 · M. E. Carrillo-Serrano🇦🇺 · A. W. Thomas🇦🇺
The NJL model for the octet baryons, using proper time regularization to simulate some of the features of confinement, is solved self-consistently in nuclear matter. This provides an alternative framework to the MIT bag model which has been used in the quark-meson coupling model. After fitting the parameters of the model to the saturation properties of symmetric nuclear matter the model is used to explore the equation of state of pure neutron matter as well as nuclear matter at densities relevant to heavy ion collisions. With a view to future studies of high mass neutron stars, the binding of hyperons is also explored.
Comments:
7 pages and 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.03158 [pdf]
PLB(2016)·5 citations
03
[Submitted on 10 Jun 2016]
Solutions of random-phase approximation equation for positive-semidefinite stability matrix
H. Nakada
It is mathematically proven that, if the stability matrix $S$ is positive-semidefinite, solutions of the random-phase approximation (RPA) equation are all physical or belong to Nambu-Goldstone (NG) modes, and the NG-mode solutions may form Jordan blocks of $N S$ ( $N$ is the norm matrix) but their dimension is not more than two. This guarantees that the NG modes in the RPA can be separated out via canonically conjugate variables.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.03167 [pdf]
1 citation
04
[Submitted on 10 Jun 2016]
Can realistic interaction be useful for nuclear mean-field approaches?
H. Nakada🇯🇵 · K. Sugiura🇯🇵 · T. Inakura🇯🇵 · J. Margueron🇫🇷
Recent applications of the M3Y-type semi-realistic interaction to the nuclear mean-field approaches are presented: (i) Prediction of magic numbers and (ii) isotope shifts of nuclei with magic proton numbers. The results exemplify that realistic interaction, which is derived from the base $2 N$ and $3 N$ interaction, furnish a new theoretical instrument for advancing nuclear mean-field approaches.
Comments:
9 pages including 6 figures, published in EPJA 52, 185 (2016)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.03169 [pdf]
EPJA(2016)·1 citation
05
[Submitted on 10 Jun 2016]
Radii in the $s d$ shell and the $s_{1/2}$ "halo" orbit: A game changer
J. Bonnard🇮🇹 · A. P. Zuker🇮🇹
Proton radii of nuclei in the $s d$ shell depart appreciably from the asymptotic law, $ρ_{π} = ρ_{0} A^{1/3}$ . The departure exhibits systematic trends fairly well described by a single phenomenological term in the Duflo-Zuker formulation, which also happens to explain the sudden increase in slope in the isotope shifts of several chains at neutron number $N = 28$ . It was recently shown that this term is associated with the abnormally large size of the $s_{1/2}$ and $p$ orbits in the $s d$ and $p f$ shells respectively. Further to explore the problem, we propose to calculate microscopically radii in the former. Since the (square) radius is basically a one body operator, its evolution is dictated by single particle occupancies determined by shell model calculations. Assuming that the departure from the asymptotic form is entirely due to the $s_{1/2}$ orbit, the expectation value $⟨ s_{1/2} ∣ r^{2} ∣ s_{1/2} ⟩$ is determined by demanding that its evolution be such as to describe well nuclear radii. It does, for an orbit that remains very large (about 1.6 fm bigger than its $d$ counterparts) up to $N, Z = 14$ then drops abruptly but remains some 0.6 fm larger than the $d$ orbits. An unexpected behavior bound to challenge our understanding of shell formation.
Comments:
4 pages 6(7) figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.03345 [pdf]
J.Phys.Conf.Ser.(2018)·12 citations
06
[Submitted on 10 Jun 2016] (cross-list from hep-ph)
Theoretical estimate on tensor-polarization asymmetry in proton-deuteron Drell-Yan process
S. Kumano🇯🇵 · Qin-Tao Song🇯🇵
Tensor-polarized parton distribution functions are new quantities in spin-one hadrons such as the deuteron, and they could probe new quark-gluon dynamics in hadron and nuclear physics. In charged-lepton deep inelastic scattering (DIS), they are studied by the twist-two structure functions $b_{1}$ and $b_{2}$ . The HERMES collaboration found unexpectedly large $b_{1}$ values than a naive theoretical expectation based on the standard deuteron model. The situation should be significantly improved in the near future by an approved experiment to measure $b_{1}$ at JLab (Thomas Jefferson National Accelerator Facility). There is also an interesting indication in the HERMES result that finite antiquark tensor polarization exists. It could play an important role in solving a mechanism on tensor structure in the quark-gluon level. The tensor-polarized antiquark distributions are not easily determined from the charged-lepton DIS; however, they can be measured in a proton-deuteron Drell-Yan process with a tensor-polarized deuteron target. In this article, we estimate the tensor-polarization asymmetry for a possible Fermilab Main-Injector experiment by using optimum tensor-polarized PDFs to explain the HERMES measurement. We find that the asymmetry is typically a few percent. If it is measured, it could probe new hadron physics, and such studies could create an interesting field of high-energy spin physics. In addition, we find that a significant tensor-polarized gluon distribution should exist due to $Q^{2}$ evolution, even if it were zero at a low $Q^{2}$ scale. The tensor-polarized gluon distribution has never been observed, so that it is an interesting future project.
Comments:
10 pages, 9 eps figures, 4 style files, Phys. Rev. D in press
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1606.03149 [pdf]
PRD(2016)·30 citations
07
[Submitted on 10 Jun 2016] (cross-list from hep-ph)
Quarkonium Contribution to Meson Molecules
E. Cincioglu🇹🇷 · J. Nieves🇪🇸 · A. Ozpineci🇹🇷 · A. U. Yilmazer🇹🇷
Starting from a molecular picture for the X(3872) resonance, this state and its J^{PC}=2++ HQSS partner [X2(4012)] are analyzed within a model which incorporates possible mixings with 2P charmonium states. Since it is reasonable to expect the bare chi_{c1}(2P) to be located above the D\bar D* threshold, but relatively close to it, the presence of the charmonium state provides an effective attraction that will contribute to bind the X(3872), but it will not appear in the 2++ sector. Indeed in this latter sector, the chi_{c2}(2P) should provide an effective small repulsion, because it is placed well below the D*\bar D* threshold. We show how the 1++ and 2++ bare charmonium poles are modified due to the D(*)\bar D(*) loop effects, and the first one is moved to the complex plane. The meson loops produce, besides some shifts in the masses of the charmonia, a finite width for the 1++ dressed charmonium state. On the other hand, the X(3872) and X2(4012) start developing some charmonium content, which is estimated by means of the compositeness Weinberg sum-rule. We also show that for X(3872) molecular probabilities of around 70-90 %, the X2 resonance destabilizes and disappears from the spectrum, becoming either a virtual state or being located deep into the complex plane, with decreasing influence in the D* \bar D* scattering line.
Comments:
46 pages, 5 figures; Accepted in EPJC
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.03239 [pdf]
EPJC(2016)·85 citations
08
[Submitted on 10 Jun 2016] (cross-list from hep-ph)
HYDRO + JETS (HYDJET++) event generator for Pb+Pb collisions at LHC
L. Bravina🇳🇴 · B.H. Brusheim Johansson🇳🇴 · J. Crkovská🇫🇷 · G. Eyyubova🇷🇺 · V. Korotkikh🇷🇺 · I. Lokhtin🇷🇺 · L. Malinina🇷🇺 · E. Nazarova🇷🇺 · S. Petrushanko🇷🇺 · A. Snigirev🇷🇺 · E. Zabrodin🇳🇴
The Monte Carlo event generator HYDJET++ is one of the few generators, designed for the calculations of heavy-ion collisions at ultrarelativistic energies, which combine treatment of soft hydro-like processes with the description of jets traversing the hot and dense partonic medium. The model is employed to study the azimuthal anisotropy phenomena, dihadron angular correlations and event-by-event (EbyE) fluctuations of the anisotropic flow in Pb+Pb collisions at $s_{N N} = 2.76$ TeV. The interplay of soft and hard processes describes the violation of the mass hierarchy of meson and baryon elliptic and triangular flows at p_T > 2 GeV/c, the fall-off of the flow harmonics at intermediate transverse momenta, and the worsening of the number-of-constituent-quark (NCQ) scaling of elliptic/triangular flow at LHC compared to RHIC energies. The cross-talk of v_2 and v_3 leads to emergence of higher order harmonics in the model and to appearance of the ridge structure in dihadron angular correlations in a broad pseudorapidity range. HYDJET++ possesses also the dynamical EbyE fluctuations of the anisotropic flow. The model results agree well with the experimental data.
Comments:
8 pages, 6 figures, contribution to Proceedings of the Winter Workshop on Nuclear Dynamics 2016
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1606.03250 [pdf]
J.Phys.Conf.Ser.(2016)·4 citations
09
[Submitted on 10 Jun 2016] (cross-list from hep-ph)
Collinearly improved JIMWLK evolution in Langevin form
Yoshitaka Hatta🇯🇵 · Edmond Iancu🇫🇷
The high-energy evolution of Wilson line operators, which at leading order is described by the Balitsky-JIMWLK equations, receives large radiative corrections enhanced by single and double collinear logarithms at next-to-leading order and beyond. We propose a method for resumming such logarithmic corrections to all orders, at the level of the Langevin formulation of the JIMWLK equation. The ensuing, collinearly-improved Langevin equation features generalized Wilson line operators, which depend not only upon rapidity (the logarithm of the longitudinal momentum), but also upon the transverse size of the color neutral projectile to which the Wilson lines belong. This additional scale dependence is built up during the evolution, via the condition that the successive emissions of soft gluons be ordered in time. The presence of this transverse scale in the Langevin equation furthermore allows for the resummation of the one-loop running coupling corrections.
Comments:
24 pages, 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.03269 [pdf]
JHEP(2016)·35 citations
10
[Submitted on 10 Jun 2016] (cross-list from hep-ph)
Chiral Relaxation Time at the Crossover of Quantum Chromodynamics
M. Ruggieri🇨🇳 · G. X. Peng🇨🇳 · M. Chernodub🇷🇺
We study microscopic processes responsible for chirality flips in the thermal bath of Quantum Chromodynamics at finite temperature and zero baryon chemical potential. We focus on the temperature range where the crossover from chirally broken phase to quark-gluon plasma takes place, namely $T ≃ (150, 200)$ MeV. The processes we consider are quark-quark scatterings mediated by collective excitations with the quantum number of pions and $σ$ -meson, hence we refer to these processes simply as \sugg{to} one-pion (one- $σ$ ) exchange\sugg{s}. We use a Nambu-Jona-Lasinio model to compute equilibrium properties of the thermal bath, as well as the relevant scattering kernel to be used in the collision integral to estimate the chiral relaxation time $τ$ . We find $τ ≃ 0.1 \div 1$ fm/c around the chiral crossover.
Comments:
16 pages, 8 figures. One figure (lower panel of Fig. 6) added in comparison with V1. New version to appear on Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1606.03287 [pdf]
PRD(2016)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE