Nuclear Theory·nucl-th

Tuesday·May 31, 2016

12 papers—5 primary·7 cross-listed

01
[Submitted on 28 May 2016]
Light Baryons Mass in a Non-Relativistic Quark Model within an Hypercentral Power Low Potential
Nasrin Salehi🇮🇷
In this work, we calculated the baryon mass within a non-relativistically quark model using an approach based on the Gürsey Radicati mass formula (GR). The average energy value of each SU(6) multiplet is described using the SU(6) invariant interaction given by a hypercentral potential. In our series studies we investigate different interactions and situations to gain the best possible model. This goal can be obtained by checking and studying various potentials in different situations. In this paper we present the solution of the Schrödinger equation with an hypercentral power low potential. The results of our model (the combination of our proposed hypercentral Potential and generalized GR mass formula to description of the spectrum) show that the strange and non-strange baryons spectra are in general fairly well reproduced. The overall good description of the mass which we obtain shows that our model can also be used to give a fair description of the energies of the excited multiplets up to three GeV and the position of the Roper resonances of the nucleon.
Comments:
arXiv admin note: substantial text overlap with arXiv:1511.01531; text overlap with arXiv:nucl-th/0506032 by other authors
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.08847 [pdf]
0 citations
02
[Submitted on 28 May 2016]
A combined model for pseudorapidity distributions in Cu-Cu collisions at BNL-RHIC energies
Zhjin Jiang🇨🇳 · Jie Wang🇨🇳 · Yan Huang🇨🇳
The charged particles produced in nucleus-nucleus collisions come from leading particles and those frozen out from the hot and dense matter created in collisions. The leading particles are conventionally supposed having Gaussian rapidity distributions normalized to the number of participants. The hot and dense matter is assumed to expand according to the unified hydrodynamics, a hydro model which unifies the features of Landau and Hwa-Bjorken model, and freeze out into charged particles from a space-like hypersurface with a proper time of Tau_FO . The rapidity distribution of this part of charged particles can be derived out analytically. The combined contribution from both leading particles and unified hydrodynamics is then compared against the experimental data performed by BNL-RHIC-PHOBOS Collaboration in different centrality Cu-Cu collisions at sqrt(s_NN)=200 and 62.4 GeV, respectively. The model predictions are in well consistent with experimental measurements.
Comments:
12 pages, 2 figures, 1 table, International Journal of Modern Physics E/2016. arXiv admin note: substantial text overlap with arXiv:1602.01394
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.08902 [pdf]
IJMPE(2016)·2 citations
03
[Submitted on 28 May 2016]
Alpha decay as a probe for the structure of neutron-deficient nuclei
Chong Qi
The advent of radioactive ion beam facilities and new detector technologies have opened up new possibilities to investigate the radioactive decays of highly unstable nuclei, in particular the proton emission, $α$ decay and heavy cluster decays from neutron-deficient (or proton-rich) nuclei around the proton drip line. It turns out that these decay measurements can serve as a unique probe for studying the structure of the nuclei involved. On the theoretical side, the development in nuclear many-body theories and supercomputing facilities have also made it possible to simulate the nuclear clusterization and decays from a microscopic and consistent perspective. In this article we would like to review the current status of these structure and decay studies in heavy nuclei, regarding both experimental and theoretical opportunities. We then discuss in detail the recent progress in our understanding of the nuclear $α$ formation probabilities in heavy nuclei and their indication on the underlying nuclear structure.
Comments:
15 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.08916 [pdf]
Rev.Phys.(2016)·46 citations
04
[Submitted on 28 May 2016]
Odd-even staggering in neutron drip line nuclei
S.A. Changizi · Chong Qi
We have done systematic Hartree-Fock-Bogoliubov calculations in coordinate space on the one-quasi-particle energies and binding energy odd-even staggering (OES) in semi-magic nuclei with the zero-range volume, mixed and surface pairing forces in order to explore the influence of their density dependence. The odd- $N$ isotopes are calculated within the blocking scheme. The strengths for the pairing forces are determined in two schemes by fitting locally to reproduce pairing gap in $^{120}$ Sn and globally to all available data on the OES of semi-magic nuclei with $Z \geq 8$ . In the former calculations, there is a noticeable difference between the neutron mean gaps in neutron-rich O, Ca, Ni and Sn isotopes calculated with the surface pairing and those with the mixed and volume pairing. The difference gets much smaller if the globally optimized pairing strengths are employed. The heavier Pb isotopes show the opposite trend. Moreover, large differences between the mean gap and the OES may be expected in both calculations when one goes towards the neutron drip line.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.08920 [pdf]
NPA(2016)·10 citations
05
[Submitted on 29 May 2016]
Solving the $R_{AA} \otimes v_{2}$ puzzle
Jacquelyn Noronha-Hostler🇺🇸
For the past ten years $R_{AA} (p_{T})$ , the nuclear modification factor that encodes the suppression of high $p_{T}$ particles due to energy loss within the medium was fairly well described by many theoretical models. However, the same models systematically under-predicted the high $p_{T}$ elliptic flow, $v_{2}$ , which is experimentally measured as the correlation between soft and hard hadrons. All previous calculations neglected the effect of event-by-event fluctuations of an expanding viscous hydrodynamical background as well as the soft-hard flow harmonic correlations in the experimentally measured $v_{2}$ . In this talk I show how event-by-event viscous hydrodynamics (computed using the v-USPhydro code) coupled to an energy loss model (BBMG) is able to simultaneously describe soft physics observables as well as the high- $p_{T}$ $R_{AA}$ and $v_{2}$ . Suggestions for future more differential calculations at the LHC run2 are made to explore soft-hard flow correlations.
Comments:
7 pages, 5 figures, proceedings for the Winter Workshop on Nuclear Dynamics 2016
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1605.09064 [pdf]
J.Phys.Conf.Ser.(2016)·2 citations
06
[Submitted on 1 Apr 2016] (cross-list from astro-ph.HE)
The influence of quantum vacuum friction on pulsars
Jaziel G. Coelho · Jonas P. Pereira · José C. N. de Araujo
We firstly revisit the energy loss mechanism known as quantum vacuum friction (QVF), clarifying some of its subtleties. Then we investigate the observables that could easily differentiate QVF from the classical magnetic dipole radiation for pulsars with braking indices (n) measured accurately. We show this is specially the case for the time evolution of a pulsar's magnetic dipole direction ( $ϕ ˙$ ) and surface magnetic field ( $B ˙_{0}$ ). As it is well known in the context of the classic magnetic dipole radiation, $n < 3$ would only be possible for positive $(B ˙_{0} / B_{0} + ϕ ˙ / tan ϕ)$ , which, for instance, leads to $B ˙_{0} > 0$ ( $ϕ ˙ > 0$ ) when $ϕ$ ( $B_{0}$ ) is constant. On the other hand, we show that QVF can result in very contrasting predictions with respect to the above ones. Finally, even in the case $B ˙_{0}$ in both aforesaid models for a pulsar has the same sign, for a given $ϕ$ , we show that they give rise to different associated timescales, which could be another way to falsify QVF.
Comments:
7 pages, 3 figures. Accepted for publication in ApJ
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1604.00430 [pdf]
ApJ(2016)·16 citations
07
[Submitted on 28 May 2016] (cross-list from hep-ph)
Bethe-Salpeter bound-state structure in Minkowski space
C. Gutierrez🇧🇷 · V. Gigante🇧🇷 · T. Frederico🇧🇷 · G. Salmè🇮🇹 · M. Viviani🇮🇹 · Lauro Tomio🇧🇷
The quantitative investigation of the scalar Bethe-Salpeter equation in Minkowski space, within the ladder-approximation framework, is extended to include the excited states. This study has been carried out for an interacting system composed by two massive bosons exchanging a massive scalar, by adopting (i) the Nakanishi integral representation of the Bethe-Salpeter amplitude, and (ii) the formally exact projection onto the null plane. Our analysis, on one hand, confirms the reliability of the method already applied to the ground state and, on the other one, extends the investigation from the valence distribution in momentum space to the corresponding quantity in the impact-parameter space, pointing out some relevant features, like (i) the equivalence between Minkowski and Euclidean transverse-momentum amplitudes, and (ii) the leading exponential fall-off of the valence wave function in the impact-parameter space.
Comments:
15 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1605.08837 [pdf]
PLB(2016)·32 citations
08
[Submitted on 28 May 2016] (cross-list from hep-ph)
Asymmetric vector mesons produced in nuclear collisions
I.M. Dremin🇷🇺 · V.A. Nechitailo🇷🇺
It is argued that the experimentally observed phenomenon of asymmetric shapes of vector mesons produced in nuclear media during high energy nucleus-nucleus collisions can be explained as Fano-Feshbach resonances. It has been observed that the mass distributions of lepton pairs created at meson decays decline from the traditional Breit-Wigner shape with some excess in the low-mass wing of the resonance. It is clear that the whole phenomenon is related to some interaction with the nuclear medium. Moreover, it can be further detalized in quantum mechanics as the interference of direct and continuum states in Fano-Feshbach effect. To reveal the nature of the interaction it is proposed to use a phenomenological model of the additional contribution due to Cherenkov gluons. They can be created because of the excess of the refractivity index over 1 just in the low-mass wing as required by the classical Cherenkov treatment. In quantum mechanics, this requirement is related to the positive real part of the interaction amplitude in this wing. The corresponding parameters are found from the comparison with $ρ$ -meson data and admit reasonable explanation.
Comments:
11 pages, 2 Figures. arXiv admin note: text overlap with arXiv:1505.06297
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1605.08850 [pdf]
EPJA(2016)·0 citations
09
[Submitted on 29 May 2016] (cross-list from hep-ph)
Right-Handed Neutrinos and T-Violating, P-Conserving Interactions
Basem Kamal El-Menoufi🇺🇸 · Michael J. Ramsey-Musolf🇺🇸 · Chien-Yeah Seng🇺🇸
We show that experimental probes of the P-conserving, T-violating triple correlation in polarized neutron or nuclear $β$ -decay provide a unique probe of possible T-violation at the TeV scale in the presence of right-handed neutrinos. In contrast to other possible sources of semileptonic T-violation involving only left-handed neutrinos, those involving right-handed neutrinos are relatively unconstrained by present limits on the permanent electric dipole moments of the electron, neutral atoms, and the neutron. On the other hand, LHC results for $pp \to e +$ missing transverse energy imply that an order of magnitude of improvement in $D$ -coefficient sensitivity would be needed for discovery. Finally, we discuss the interplay with the scale of neutrino mass and naturalness considerations.
Comments:
6 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1605.09060 [pdf]
PLB(2017)·10 citations
10
[Submitted on 30 May 2016] (cross-list from hep-th)
A semi-classical recipe for wobbly limp noodles in partonic soup
R. W. Moerman🇿🇦 · W. A. Horowitz🇿🇦
We compute the average squared distance, $s^{2} (t)$ , travelled by a light-flavour off-mass-shell coloured parton in a strongly-coupled $N = 4$ $S U (N_{c})$ super-symmetric Yang Mills plasma using the gauge/string duality. In fact, we derive a closed integral expression for $s^{2} (t; a)$ in $A d S_{3}$ -Schwarzschild, which interpolates between a heavy quark when $a = 0$ and a light quark when $a = 1$ , that we evaluate analytically for small virtualities - labelled $s_{small}^{2} (t; a)$ . For arbitrary virtualities, we show that for asymptotically early times the motion is ballistic, $s^{2} (t; a)_{t ≪ β} \sim t^{2}$ , while at asymptotically late times the motion is diffusive, $s^{2} (t; a)_{t ≫ β} = s_{small}^{2} (t; a) \sim 2 D (a) t$ , from which we are able to extract the diffusion coefficient $D (a)$ . Motivated by the apparent universality of the late time behaviour, we compute $s_{small}^{2} (t; a, d)$ and $D (a, d)$ for an arbitrary $A d S_{d}$ -Schwarzschild geometry. From $D (a, d)$ we then compute for the first time the dynamic, time-dependent transverse momentum squared per unit path length picked up by a high momentum light quark in a strongly-coupled plasma, the transport coefficient $q^(t)$ , which is critically important for phenomenology in heavy ion collisions.
Comments:
36 pages, 7 figures
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1605.09285 [pdf]
21 citations
11
[Submitted on 30 May 2016] (cross-list from cond-mat.mes-hall)
Renormalization group analysis of graphene with a supercritical Coulomb impurity
Yusuke Nishida
We develop a field-theoretic approach to massless Dirac fermions in a supercritical Coulomb potential. By introducing an Aharonov--Bohm solenoid at the potential center, the critical Coulomb charge can be made arbitrarily small for one partial-wave sector, where a perturbative renormalization group analysis becomes possible. We show that a scattering amplitude for reflection of particle at the potential center exhibits the renormalization group limit cycle, i.e., log-periodic revolutions as a function of the scattering energy, revealing the emergence of discrete scale invariance. This outcome is further incorporated in computing the induced charge and current densities, which turn out to have power-law tails with coefficients log-periodic with respect to the distance from the potential center. Our findings are consistent with the previous prediction obtained by directly solving the Dirac equation and can in principle be realized by graphene experiments with charged impurities.
Comments:
7 pages; published version
Subjects:
Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Nuclear Theory (nucl-th)
arXiv:
1605.09309 [pdf]
PRB(2016)·6 citations
12
[Submitted on 24 May 2016] (cross-list from cond-mat.stat-mech)
Non- Markovian Quantum Stochastic Equation For Two Coupled Oscillators
E.X. Alpomishev · Z. Kanokov
The system of nonlinear Langevin equations was obtained by using Hamiltonian's operator of two coupling quantum oscillators which are interacting with heat bath. By using the analytical solution of these equations, the analytical expressions for transport coefficients was found. Generalized Langevin equations and fluctuation-dissipation relations are derived for the case of a nonlinear non-Markovian noise. The explicit expressions for the time-dependent friction and diffusion coefficients are presented for the case of linear couplings in the coordinate between the collective two coupled harmonic oscillators and heat bath.
Comments:
17 pages. arXiv admin note: text overlap with arXiv:gr-qc/9403054 by other authors
Subjects:
Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
1605.09327 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE