Nuclear Theory·nucl-th

Wednesday·June 3, 2015

9 papers—5 primary·4 cross-listed

01
[Submitted on 2 Jun 2015]
Charged-current inclusive neutrino cross sections in the SuperScaling model including quasielastic, pion production and meson-exchange contributions
M.V. Ivanov🇧🇬 · G.D. Megias🇪🇸 · R. Gonzalez-Jimenez🇧🇪 · O. Moreno🇺🇸 · M.B. Barbaro🇮🇹 · J.A. Caballero🇪🇸 · T.W. Donnelly🇺🇸
Charged current inclusive neutrino-nucleus cross sections are evaluated using the superscaling model for quasielastic scattering and its extension to the pion production region. The contribution of two-particle-two-hole vector meson-exchange current excitations is also considered within a fully relativistic model tested against electron scattering data. The results are compared with the inclusive neutrino-nucleus data from the T2K and SciBooNE experiments. For experiments where $⟨ E_{ν} ⟩ \sim 0.8$ GeV, the three mechanisms considered in this work provide good agreement with the data. However, when the neutrino energy is larger, effects from beyond the $Δ$ also appear to be playing a role. The results show that processes induced by two-body currents play a minor role at the kinematics considered.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1506.00801 [pdf]
J.Phys.G(2016)·44 citations
02
[Submitted on 2 Jun 2015]
Structure of the two-neutrino double- $β$ decay matrix elements within perturbation theory
Dusan Stefanik🇸🇰 · Fedor Simkovic🇸🇰 · Amand Faessler🇩🇪
The two-neutrino double- $β$ Gamow-Teller and Fermi transitions are studied within an exactly solvable model, which allows a violation of both spin-isospin SU(4) and isospin SU(2) symmetries, and is expressed with generators of the SO(8) group. It is found that this model reproduces the main features of realistic calculation within the quasiparticle random-phase approximation with isospin symmetry restoration concerning the dependence of the two-neutrino double- $β$ decay matrix elements on isovector and isoscalar particle-particle interactions. By using perturbation theory an explicit dependence of the two-neutrino double- $β$ decay matrix elements on the like-nucleon pairing, particle-particle T=0 and T=1, and particle-hole proton-neutron interactions is obtained. It is found that double- $β$ decay matrix elements do not depend on the mean field part of Hamiltonian and that they are governed by a weak violation of both SU(2) and SU(4) symmetries by the particle-particle interaction of Hamiltonian. It is pointed out that there is a dominance of two-neutrino double- $β$ decay transition through a single state of intermediate nucleus. The energy position of this state relative to energies of initial and final ground states is given by a combination of strengths of residual interactions. Further, energy-weighted Fermi and Gamow-Teller sum rules connecting Delta Z = 2 nuclei are discussed. It is proposed that these sum rules can be used to study the residual interactions of the nuclear Hamiltonian, which are relevant for charge-changing nuclear transitions.
Comments:
12 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1506.00835 [pdf]
PRC(2015)·22 citations
03
[Submitted on 2 Jun 2015]
$η$ meson production of high-energy nuclear collisions at NLO
Wei Dai🇨🇳 · Xiao-Fang Chen🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
The transverse momentum spectrum of $η$ meson in relativistic heavy-ion collisions is studied at the next-to-leading-order (NLO) within the perturbative QCD, where the jet quenching effect in the QGP is incorporated with the effectively medium-modified $η$ fragmentation functions using the higher-twist approach. We show that the theoretical simulations could give nice descriptions of PHENIX data on $η$ meson in both $p + p$ and central $Au + Au$ collisions at the RHIC, and also provide numerical predictions of $η$ spectra in central $Pb + Pb$ collisions with $s_{N N} = 2.76$ ~TeV at the LHC. The ratios of $η / π^{0}$ in $p + p$ and in central $Au + Au$ collisions at $200$ ~GeV are found to overlap in a wide $p_{T}$ region, which matches well the measured ratio $η / π^{0}$ by PHENIX. We demonstrate that, at the asymptotic region when $p_{T} \to \infty$ the ratios of $η / π^{0}$ in both $Au + Au$ and $p + p$ are almost determined only by quark jets fragmentation and thus approach to the one in $e^{+} e^{-}$ scattering; in addition, the almost identical gluon (quark) contribution fractions to $η$ and to $π$ result in a rather moderate variation of $η / π^{0}$ distribution at intermediate and high $p_{T}$ region in $A + A$ relative to that in $p + p$ ; while a slightly higher $η / π^{0}$ at small $p_{T}$ in $Au + Au$ can be observed due to larger suppression of gluon contribution fraction to $π^{0}$ as compared to the one to $η$ . The theoretical prediction for $η / π^{0}$ at the LHC has also been presented.
Comments:
7 pages, 8 figures, 2 typos corrected, revision for publication
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1506.00838 [pdf]
PLB(2015)·30 citations
04
[Submitted on 2 Jun 2015]
Spin-orbit coupling rule in bound fermions systems
J.-P. Ebran🇫🇷 · E. Khan🇫🇷 · A. Mutschler🇫🇷 · D. Vretenar🇭🇷
Spin-orbit coupling characterizes quantum systems such as atoms, nuclei, hypernuclei, quarkonia, etc., and is essential for understanding their spectroscopic properties. Depending on the system, the effect of spin-orbit coupling on shell structure is large in nuclei, small in quarkonia, perturbative in atoms. In the standard non-relativistic reduction of the single-particle Dirac equation, we derive a universal rule for the relative magnitude of the spin-orbit effect that applies to very different quantum systems, regardless of whether the spin-orbit coupling originates from the strong or electromagnetic interaction. It is shown that in nuclei the near equality of the mass of the nucleon and the difference between the large repulsive and attractive potentials explains the fact that spin-orbit splittings are comparable to the energy spacing between major shells. For a specific ratio between the particle mass and the effective potential whose gradient determines the spin-orbit force, we predict the occurrence of giant spin-orbit energy splittings that dominate the single-particle excitation spectrum.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1506.00911 [pdf]
J.Phys.G(2016)·8 citations
05
[Submitted on 2 Jun 2015]
Hadron-Quark Crossover and Hot Neutron Stars at Birth
Kota Masuda🇯🇵 · Tetsuo Hatsuda🇯🇵 · Tatsuyuki Takatsuka🇯🇵
We construct a new isentropic equation of state (EOS) at finite temperature "CRover" on the basis of the hadron-quark crossover at high density. By using the new EOS, we study the structure of hot neutron stars at birth with the typical lepton fraction ( $Y_{l} = 0.3 - 0.4$ ) and the typical entropy per baryon ( $S = 1 - 2$ ). Due to the gradual appearance of quark degrees of freedom at high density, the temperature T and the baryon density at the center of the hot neutron stars with the hadron-quark crossover are found to be smaller than those without the crossover by a factor of 2 or more. Typical energy release due to the contraction of a hot neutron star to a cold neutron star with 1.4 solarmass is shown to be about 0.04 solarmass with the spin-up rate about 14%.
Comments:
10 pages and 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1506.00984 [pdf]
PTEP(2016)·21 citations

Affiliations

first authorsco-authorsvia INSPIRE

Charged-current inclusive neutrino cross sections in the SuperScaling model including quasielastic, pion production and meson-exchange contributions

Structure of the two-neutrino double-β decay matrix elements within perturbation theory

η meson production of high-energy nuclear collisions at NLO

Spin-orbit coupling rule in bound fermions systems

Hadron-Quark Crossover and Hot Neutron Stars at Birth

Affiliations

Structure of the two-neutrino double- $β$ decay matrix elements within perturbation theory

$η$ meson production of high-energy nuclear collisions at NLO