Nuclear Theory·nucl-th

Tuesday·May 17, 2016

8 papers—3 primary·5 cross-listed

01
Thermal fission rates with temperature dependent fission barriers
Yi Zhu🇨🇳 · Junchen Pei🇨🇳
The fission processes of thermal excited nuclei are conventionally studied by statistical models which rely on inputs of phenomenological level densities and potential barriers. Therefore the microscopic descriptions of spontaneous fission and induced fission are very desirable for a unified understanding of various fission processes. We propose to study the fission rates, at both low and high temperatures, with microscopically calculated temperature-dependent fission barriers and collective mass parameters. The fission barriers are calculated by the finite-temperature Skyrme-Hartree-Fock+BCS method. The mass parameters are calculated by the temperature-dependent cranking approximation. The thermal fission rates can be obtained by the imaginary free energy approach at all temperatures, in which fission barriers are naturally temperature dependent. The fission at low temperatures can be described mainly as a barrier-tunneling process. While the fission at high temperatures has to incorporate the reflection above barriers. Our results of spontaneous fission rates reasonably agree with other studies and experiments. The temperature dependencies of fission barrier heights and curvatures have been discussed. The temperature dependent behaviors of mass parameters have also been discussed. The thermal fission rates from low to high temperatures with a smooth connection have been given by different approaches. \item[Conclusions] Since the temperature dependencies of fission barrier heights and curvatures, and the mass parameters can vary rapidly for different nuclei, the microscopic descriptions of thermal fission rates are very valuable. Our studies without free parameters provide a consistent picture to study various fissions such as that in fast-neutron reactors, astrophysical environments and fusion reactions for superheavy nuclei.
nucl-thPRC(2016)·31 citations
02
Novel halos in light kaonic nuclei as an indicator of nuclear equation of state at supra-normal densities
Yang Rong-Yao · Jiang Wei-Zhou · Wei Si-Na · Zhang Dong-Rui
The sensitive correlations between the low-density halo structure and the high-density properties of the nuclear equation of state (EOS) are constructed in light kaonic nuclei with the relativistic mean-field theory. More specifically, the $1 p_{1/2}$ halo spreads out linearly with increasing the pressure and sound velocity square at supra-normal densities and quadratically with decreasing the incompressibility at saturation density. These results suggest that the novel halo in light kaonic nuclei can serve as a sensitive indicator of the nuclear EOS of symmetric matter at supra-normal densities.
nucl-thSci.Rep.(2017)·4 citations
03
Study of the Low-Energy Characteristics of Neutron-Neutron Scattering in the Effective-Range Approximation
V. A. Babenko · N. M. Petrov
The influence of the mass difference between the charged and neutral pions on the low-energy characteristics of nucleon-nucleon interaction in the $^{1} S_{0}$ spin-singlet state is studied within the framework of the effective-range approximation. By making use of the experimental singlet neutron-proton scattering parameters and the experimental value of neutron-neutron virtual-state energy, the following values were obtained for the neutron-neutron scattering length and effective range: $a_{nn} = - 16.59 (117)$ fm, $r_{nn} = 2.83 (11)$ fm. The calculated neutron-neutron scattering length $a_{nn}$ is in good agreement with one of the two well known and differing experimental values of this quantity, and the calculated effective range $r_{nn}$ is also in good agreement with present-day experimental results.
nucl-th7 citations
04
Hadronic resonances enhanced by thresholds
T.F. Caramés🇪🇸 · A. Valcarce🇪🇸
We present a neat example of a meson--baryon system where the vicinity of two different thresholds enhances the binding of a hadronic resonance, a pentaquark. As a consequence the pattern of states may change when moving among different flavor sectors, what poses a warning on naive extrapolations to heavy flavor sectors based on systematic expansions. For this purpose we simultaneously analyze the $N D ˉ$ and $N B$ two-hadron systems looking for possible bound states or resonances. When a resonance is controlled by a coupled-channel effect, going to a different flavor sector may enhance or diminish the binding. This effect may, for example, generate significant differences between the charmonium and bottomonium spectra above open-flavor thresholds or pentaquark states in the open-charm and open-bottom sectors.
↳ hep-phnucl-thPLB(2016)·6 citations
05
Heavy Quark Entropy shift: From the Hadron Resonance Gas to Power Corrections
E. Megias🇩🇪 · E. Ruiz Arriola🇪🇸 · L.L. Salcedo🇪🇸
A heavy quark placed in the medium modifies its specific heat. Using a renormalization group argument we show a low energy theorem in terms of the defect in the trace of the energy-momentum tensor which allows the unambiguous determination of the corresponding entropy shift after imposing the third principle of thermodynamics for degenerate states. We show how recent lattice QCD data can be understood in the confined phase in terms of a single-heavy hadronic spectrum and above the phase transition through power corrections which are analyzed by means of a dimension 2 gluon condensate of the dimensionally reduced theory.
↳ hep-phhep-lathep-thnucl-thActa Phys.Polon.Supp.(2016)·4 citations
06
Electrophobic Scalar Boson and Muonic Puzzles
Yu-Sheng Liu🇺🇸 · David McKeen🇺🇸 · Gerald A. Miller🇺🇸
A new scalar boson which couples to the muon and proton can simultaneously solve the proton radius puzzle and the muon anomalous magnetic moment discrepancy. Using a variety of measurements, we constrain the mass of this scalar and its couplings to the electron, muon, neutron, and proton. Making no assumptions about the underlying model, these constraints and the requirement that it solve both problems limit the mass of the scalar to between about 100 keV and 100 MeV. We identify two unexplored regions in the coupling constant-mass plane. Potential future experiments and their implications for theories with mass-weighted lepton couplings are discussed.
↳ hep-phhep-exnucl-exnucl-th+1PRL(2016)·75 citations
07
Two-flavor Simulations of the $ρ (770)$ and the Role of the $K K ˉ$ Channel
B. Hu🇺🇸 · R. Molina🇺🇸 · M. Döring🇺🇸 · A. Alexandru🇺🇸
The $ρ (770)$ meson is the most extensively studied resonance in lattice QCD simulations in two ( $N_{f} = 2$ ) and three ( $N_{f} = 2 + 1$ ) flavor formulations. We analyze $N_{f} = 2$ lattice scattering data using unitarized Chiral Perturbation Theory, allowing not only for the extrapolation in mass but also in flavor, $N_{f} = 2 \to N_{f} = 2 + 1$ . The flavor extrapolation requires information from a global fit to $π π$ and $π K$ phase shifts from experiment. While the chiral extrapolation of $N_{f} = 2$ lattice data leads to masses of the $ρ (770)$ meson far below the experimental one, we find that the missing $K K ˉ$ channel is able to explain this discrepancy.
↳ hep-latnucl-thPRL(2016)·63 citations
08
The physics of neutrino cross sections: theoretical studies
Luis Alvarez-Ruso🇪🇸
The present status of neutrino cross section physics is reviewed focusing on the recent theoretical developments in quasielastic scattering, multi-nucleon contributions to the inclusive scattering and pion production on nucleons and nuclei. A good understanding of these processes is crucial to meet the precision needs of neutrino oscillation experiments. Some of the challenges that arise in the consistent description of MiniBooNE and MINERvA recent data are discussed.
↳ hep-phhep-exnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE