Nuclear Theory·nucl-th

Monday·April 13, 2015

14 papers—8 primary·6 cross-listed

09
[Submitted on 10 Apr 2015] (cross-list from cond-mat.mtrl-sci)
Nature of Radiation-Induced Defects in Quartz
Bu Wang · Yingtian Yu · Isabella Pignatelli · Gaurav N. Sant · Mathieu Bauchy
Although quartz ( $α$ -form) is a mineral used in numerous applications wherein radiation exposure is an issue, the nature of the atomistic defects formed during radiation-induced damage have not been fully clarified. Especially, the extent of oxygen vacancy formation is still debated, which is an issue of primary importance as optical techniques based on charged oxygen vacancies have been utilized to assess the level of radiation damage in quartz. In this paper, molecular dynamics (MD) simulations are applied to study the effects of ballistic impacts on the atomic network of quartz. We show that the defects that are formed mainly consist of over-coordinated Si and O, as well as Si--O connectivity defects, e.g., small Si--O rings and edge-sharing Si tetrahedra. Oxygen vacancies, on the contrary, are found in relatively low abundance, suggesting that characterizations based on $E^{'}$ centers do not adequately capture radiation-induced structural damage in quartz. Finally, we evaluate the dependence on the incident energy, of the amount of each type of the point defects formed, and quantify unambiguously the threshold displacement energies for both O and Si atoms. These results provide a comprehensive basis to assess the nature and extent of radiation damage in quartz.
Subjects:
cond-mat.mtrl-sci (cond-mat.mtrl-sci); Nuclear Theory (nucl-th)
arXiv:
1504.02537 [pdf]
J.Chem.Phys.(2015)·2 citations
10
[Submitted on 10 Apr 2015] (cross-list from hep-ph)
Coupled-channel analysis of $D^{+} \to K^{-} π^{+} π^{+}$ decay
Satoshi X. Nakamura (Osaka Univ.)🇯🇵
We perform a coupled-channel analysis of pseudodata for the D+-> K-pi+pi+ Dalitz plot. The pseudodata are generated from the isobar model of the E791 Collaboration, and are reasonably realistic. We demonstrate that it is feasible to analyze the high-quality data within a coupled-channel framework that describes the final state interaction of D+-> K-pi+pi+ as multiple rescatterings of three pseudoscalar mesons through two-pseudoscalar-meson interactions in accordance with the two-body and three-body unitarity. The two-pseudoscalar-meson interactions are designed to reproduce empirical pi pi and pi bar K scattering amplitudes. Furthermore, we also include mechanisms that are beyond simple iterations of the two-body interactions, i.e., a three-meson force, derived from the hidden local symmetry model. A picture of hadronic dynamics in D+-> K-pi+pi+ described by our coupled-channel model is found to be quite different from those of the previous isobar-type analyses. For example, we find that the D+-> K-pi+pi+ decay width can get almost triplicated when the rescattering mechanisms are turned on. Among the rescattering mechanisms, those associated with the rho(770) bar K0 channel, which contribute to D+-> K-pi+pi+ only through a channel coupling, give a large contribution, and significantly improve the quality of the fits. The K-pi+ s-wave amplitude from our analysis is reasonably consistent with those extracted from the E791 model independent partial-wave analysis; the hadronic rescattering and the coupling to the rho(770) bar K0 channel play a major role here. We also find that the dressed D+ decay vertices have phases, induced by the strong rescatterings, that strongly depend on the momenta of the final pseudoscalar mesons. Although the conventional isobar-type analyses have assumed the phases to be constant, this common assumption is not supported by our more microscopic viewpoint.
Comments:
39 pages, 16 figures, published version, substantial changes (essentially new analysis) have been made from v1
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1504.02557 [pdf]
PRD(2016)·44 citations
11
[Submitted on 10 Apr 2015] (cross-list from cond-mat.quant-gas)
Perfect-fluid behavior of a dilute Fermi gas near unitary
Gabriel Wlazłowski🇵🇱 · Wei Quan🇺🇸 · Aurel Bulgac🇺🇸
We present an ab initio calculation of the shear viscosity as a function of interaction strength in a two-component unpolarized Fermi gas near the unitary limit, within a finite temperature quantum Monte Carlo (QMC) framework and using the Kubo linear-response formalism. The shear viscosity decreases as we tune the interaction strength 1/ak_F from the Bardeen-Cooper-Schrieffer side of the Feshbach resonance towards Bose-Einstein condensation limit and it acquires the smallest value for 1/ak_F approx 0.4, with a minimum value of (eta/s)_min approx 0.2 hbar/k_B, which is about twice as small as the value reported for experiments in quark-gluon plasma (eta/s)_QGP lesssim 0.4 hbar/k_B. The Fermi gas near unitarity thus emerges as the most "perfect fluid" observed so far in nature. The clouds of dilute Fermi gas near unitarity exhibit the unusual attribute that, for the sizes realized so far in the laboratory or larger (less than 10^9 atoms), can sustain quantum turbulence below the critical temperature, but at the same time the classical turbulence is suppressed in the normal phase.
Subjects:
Quantum Gases (cond-mat.quant-gas); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1504.02560 [pdf]
PRA(2015)·17 citations
12
[Submitted on 10 Apr 2015] (cross-list from hep-ph)
Anomalous decay and scattering processes of the eta meson
Bastian Kubis🇩🇪 · Judith Plenter🇩🇪
We amend a recent dispersive analysis of the anomalous $η$ decay process $η \to π^{+} π^{-} γ$ by the effects of the $a_{2}$ tensor meson, the lowest-lying resonance that can contribute in the $π η$ system. While the net effects on the measured decay spectrum are small, they may be more pronounced for the analogous $η^{'}$ decay. There are nonnegligible consequences for the $η$ transition form factor, which is an important quantity for the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment. We predict total and differential cross sections, as well as a marked forward-backward asymmetry, for the crossed process $γ π^{-} \to π^{-} η$ that could be measured in Primakoff reactions in the future.
Comments:
12 pages, 11 figures; v2 matches version published in EPJC
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1504.02588 [pdf]
EPJC(2015)·110 citations
13
[Submitted on 10 Apr 2015] (cross-list from nucl-ex)
Fission barrier, damping of shell correction and neutron emission in the fission of A $\sim$ 200
K. Mahata · S. Kailas · S. S. Kapoor
Decay of $^{210}$ Po compound nucleus formed in light and heavy-ion induced fusion reactions has been analyzed simultaneously using a consistent prescription for fission barrier and nuclear level density incorporating shell correction and its damping with excitation energy. Good description of all the excitation functions have been achieved with a fission barrier of 21.9 $\pm$ 0.2 MeV. For this barrier height, the predicted statistical pre-fission neutrons in heavy-ion fusion-fission are much smaller than the experimental values, implying the presence of dynamical neutrons due to dissipation even at these low excitation energies ( $\sim$ 50~MeV) in the mass region A $\sim$ 200. When only heavy-ion induced fission excitation functions and the pre-fission neutron multiplicities are included in the fits, the deduced best fit fission barrier depends on the assumed fission delay time during which dynamical neutrons can be emitted. A fission delay of (0.8 $\pm$ 0.1 ) $\times 1 0^{- 19}$ s has been estimated corresponding to the above fission barrier height assuming that the entire excess neutrons over and above the statistical model predictions are due to the dynamics. The present observation has implication on the study of fission time scale/ nuclear viscosity using neutron emission as a probe.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1504.02599 [pdf]
PRC(2015)·31 citations
14
[Submitted on 10 Apr 2015] (cross-list from physics.atom-ph)
TaN molecule as a candidate to search for New physics
L.V. Skripnikov🇷🇺 · A.N. Petrov🇷🇺 · N.S. Mosyagin🇷🇺 · A.V. Titov🇷🇺 · V. V. Flambaum🇦🇺
It is demonstrated that the TaN molecule is the best candidate to search for T,P-violating nuclear magnetic quadrupole moment (MQM), it also looks promising to search for other T,P-odd effects. We report results of coupled-cluster calculations of T,P-odd effects in TaN produced by the Ta nucleus MQM, electron electric dipole moment (EDM), scalar $-$ pseudoscalar nucleus $-$ electron interactions, also of the molecule-axis hyperfine structure constant and dipole moment. Nuclear calculations of $^{181}$ Ta MQM are performed to express the T,P-odd effect in terms of the strength constants of T,P-odd nuclear forces, proton and neutron EDM, QCD parameter $θ$ and quark chromo-EDM.
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th); physics.chem-ph (physics.chem-ph)
arXiv:
1504.02674 [pdf]
PRA(2015)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nature of Radiation-Induced Defects in Quartz

Coupled-channel analysis of D+→K−π+π+ decay

Perfect-fluid behavior of a dilute Fermi gas near unitary

Anomalous decay and scattering processes of the eta meson

Fission barrier, damping of shell correction and neutron emission in the fission of A∼200

TaN molecule as a candidate to search for New physics

Affiliations

Coupled-channel analysis of $D^{+} \to K^{-} π^{+} π^{+}$ decay

Fission barrier, damping of shell correction and neutron emission in the fission of A $\sim$ 200