Nuclear Theory·nucl-th

Wednesday·April 17, 2019

11 papers—4 primary·7 cross-listed

01
[Submitted on 16 Apr 2019]
Large-amplitude quadrupole shape mixing probed by the $(p, p^{'})$ reaction : a model analysis
Koichi Sato · Takenori Furumoto · Yuma Kikuchi · Kazuyuki Ogata · Yukinori Sakuragi
To discuss a possible observation of large-amplitude nuclear shape mixing by nuclear reaction, we employ a simple collective model and evaluate transition densities, with which the differential cross sections are obtained through the microscopic coupled-channel calculation. Assuming the spherical-to-prolate shape transition, we focus on large-amplitude shape mixing associated with the softness of the collective potential in the $β$ direction. We introduce a simple model based on the five-dimensional quadrupole collective Hamiltonian, which simulates a chain of isotopes that exhibit spherical-to-prolate shape phase transition. Taking $^{154}$ Sm as an example and controlling the model parameters, we study how the large-amplitude shape mixing affects the elastic and inelastic proton scatterings. The calculated results suggest that the inelastic cross section of the $2_{2}^{+}$ state tells us an important role of the quadrupole shape mixing.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.07398 [pdf]
PTEP(2019)·2 citations
02
[Submitted on 16 Apr 2019]
Systematic study of proton radioactivity of spherical proton emitters within various versions of proximity potential formalisms
Jun-Gang Deng · Xiao-Hua Li · Jiu-Long Chen · Jun-Hao Cheng · Xi-Jun Wu
In this work we present a systematic study of the proton radioactivity half-lives of spherical proton emitters within the Coulomb and proximity potential model. We investigate 28 different versions of the proximity potential formalisms developed for the description of proton radioactivity, $α$ decay and heavy particle radioactivity. It is found that 21 of them are not suitable to deal with the proton radioactivity, because the classical turning points $r_{in}$ cannot be obtained due to the fact that the depth of the total interaction potential between the emitted proton and the daughter nucleus is above the proton radioactivity energy. Among the other 7 versions of the proximity potential formalisms, it is Guo2013 which gives the lowest rms deviation in the description of the experimental half-lives of the known spherical proton emitters. We use this proximity potential formalism to predict the proton radioactivity half-lives of 13 spherical proton emitters, whose proton radioactivity is energetically allowed or observed but not yet quantified, within a factor of 3.71.
Comments:
10 pages, 5 figures. This paper has been accepted by The European Physical Journal A (in press 2019)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1904.07597 [pdf]
EPJA(2019)·27 citations
03
[Submitted on 16 Apr 2019]
Nonlocalized motion in two-dimensional container of $α$ particles in $3^{-}$ and $4^{-}$ states of $^{12}$ C
Bo Zhou🇯🇵 · Yasuro Funaki🇯🇵 · Hisashi Horiuchi🇯🇵 · Masaaki Kimura🇯🇵 · Zhongzhou Ren🇨🇳 · Gerd Röpke🇩🇪 · Peter Schuck🇫🇷 · Akihiro Tohsaki🇯🇵 · Chang Xu🇨🇳 · Taiichi Yamada🇯🇵
The first $3^{-}$ and $4^{-}$ states of $^{12}$ C are studied in the present container model, in which the shift parameter is introduced to break the parity symmetry for projecting out the negative-parity states. Taking the limit as the shift parameter approaches zero and by variational calculations for one-deformed size parameter, the local energy minima are obtained for the $3^{-}$ and $4^{-}$ states. It is found that the obtained single THSR (Tohsaki-Horiuchi-Schuck-Röpke) wave functions for $3^{-}$ and $4^{-}$ states are 96% and 92% equivalent to the corresponding GCM wave functions, respectively. The calculated intrinsic densities further show that these negative-parity states of three clusters, different with the traditional understanding of rigid triangle structure, are found to have nonlocalized clustering structure in the two-dimensional container picture.
Comments:
7 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.07751 [pdf]
PRC(2019)·14 citations
04
[Submitted on 16 Apr 2019]
Antisymmetrized, translationally invariant theory of the nucleon optical potential
R.C.Johnson
Earlier work showed how a nucleon optical model wave function could be defined as a projection of a many-nucleon scattering state within a translationally invariant second quantised many-body theory. In this paper an optical potential operator that generates this optical model wave function is defined through a particular off-shell extension of the elastic transition operator. The theory is express explicitly in terms of the many-nucleon Hamiltonian in a mixed representation in which localised target nucleus states feature. No reference to a mean-field concept is involved in the definition. It is shown that the resulting optical model operator satisfies the requirements of rotational and translational invariance and has standard behaviour under the time reversal transformation. The contributions to the optical potential from two different exchange mechanisms are expressed in terms of an effective Hamiltonian involving a nucleon-number conserving one-body interaction. In the weak-binding limit the method reduces to a a version of Feshbach's projection operator formulation of the optical potential with a truncated nucleon-nucleon potential including exchange terms and recoil corrections. Definitions of the nucleon single-particle Green's function and the corresponding Dyson self-energy modified by corrections for translational invariance are presented and different definitions of the optical potential operator are compared.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.07809 [pdf]
PRC(2019)·6 citations
05
[Submitted on 15 Apr 2019] (cross-list from hep-ph)
Improved Constraints on Sterile Neutrinos in the MeV to GeV Mass Range
D. A. Bryman🇨🇦 · R. Shrock🇺🇸
Improved upper bounds are presented on the coupling $∣ U_{e 4} ∣^{2}$ of an electron to a sterile neutrino $ν_{4}$ from analyses of data on nuclear and particle decays, including superallowed nuclear beta decays, the ratios $R_{e / μ}^{(π)} = B R (π^{+} \to e^{+} ν_{e}) / B R (π^{+} \to μ^{+} ν_{μ})$ , $R_{e / μ}^{(K)}$ , $R_{e / τ}^{(D_{s})}$ , and $B_{e 2}^{+}$ decay, covering the mass range from MeV to GeV.
Comments:
6 pages, latex, 1 eps file
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1904.06787 [pdf]
PRD(2019)·75 citations
06
[Submitted on 16 Apr 2019] (cross-list from astro-ph.HE)
Cooling of the Cassiopeia A neutron star and the effect of diffusive nuclear burning
Wynn C.G. Ho🇺🇸 · M.J.P. Wijngaarden🇬🇧 · Philip Chang🇺🇸 · Craig O. Heinke🇨🇦 · Dany Page🇲🇽 · Mikhail Beznogov🇲🇽 · Daniel J. Patnaude🇺🇸
The study of how neutron stars cool over time can provide invaluable insights into fundamental physics such as the nuclear equation of state and superconductivity and superfluidity. A critical relation in neutron star cooling is the one between observed surface temperature and interior temperature. This relation is determined by the composition of the neutron star envelope and can be influenced by the process of diffusive nuclear burning (DNB). We calculate models of envelopes that include DNB and find that DNB can lead to a rapidly changing envelope composition which can be relevant for understanding the long-term cooling behavior of neutron stars. We also report on analysis of the latest temperature measurements of the young neutron star in the Cassiopeia A supernova remnant. The 13 Chandra observations over 18 years show that the neutron star's temperature is decreasing at a rate of 2-3 percent per decade, and this rapid cooling can be explained by the presence of a proton superconductor and neutron superfluid in the core of the star.
Comments:
7 pages, 7 figures; to appear in the AIP Conference Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy (January 3-7, 2019, Xiamen, China)
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1904.07505 [pdf]
AIP Conf.Proc.(2019)·5 citations
07
[Submitted on 16 Apr 2019] (cross-list from nucl-ex)
Kaon Photoproduction and the $Λ$ Decay Parameter $α_{-}$
D. G. Ireland🇬🇧 · M. Döring🇺🇸 · D. I. Glazier🇬🇧 · J. Haidenbauer🇩🇪 · M. Mai🇺🇸 · R. Murray-Smith🇬🇧 · D. Rönchen🇩🇪
The weak decay parameter $α_{-}$ of the $Λ$ is an important quantity for the extraction of polarization observables in various experiments. Moreover, in combination with $α_{+}$ from $Λ ˉ$ decay it provides a measure for matter-antimatter asymmetry. The weak decay parameter also affects the decay parameters of the $Ξ$ and $Ω$ baryons and, in general, any quantity in which the polarization of the $Λ$ is relevant. The recently reported value by the BESIII collaboration of $0.750 (9) (4)$ is significantly larger than the previous PDG value of $0.642 (13)$ that had been accepted and used for over 40 years. In this work we make an independent estimate of $α_{-}$ , using an extensive set of polarization data measured in kaon photoproduction in the baryon resonance region and constraints set by spin algebra. The obtained value is 0.721(6)(5). The result is corroborated by multiple statistical tests as well as a modern phenomenological model, showing that our new value yields the best description of the data in question. Our analysis supports the new BESIII finding that $α_{-}$ is significantly larger than the previous PDG value. Any experimental quantity relying on the value of $α_{-}$ should therefore be re-considered.
Comments:
6 pages, 1 figure;
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.07616 [pdf]
PRL(2019)·57 citations
08
[Submitted on 16 Apr 2019] (cross-list from hep-ph)
Quark mass function from a OGE-type interaction in Minkowski space
Elmar P. Biernat🇵🇹 · Franz Gross🇺🇸 · M. T. Peña🇵🇹 · Alfred Stadler🇵🇹 · Sofia Leitão🇵🇹
We present results for the quark mass function in Minkowski space calculated from an interaction kernel that consists of an effective one-gluon-exchange and a constant interaction. We analyze the gauge dependence of our results and compare them in the spacelike region to the available lattice QCD data.
Comments:
6 pages, 1 figure, presented at Excited QCD 2019, Schladming, Austria
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1904.07711 [pdf]
Acta Phys.Polon.Supp.(2021)·0 citations
09
[Submitted on 16 Apr 2019] (cross-list from hep-ph)
The Mass Gap Approach to QCD
Gergely Gábor Barnaföldi🇭🇺 · Vakhtang Gogokhia🇭🇺
We convincingly argue that the true dynamical and gauge structures of the QCD ground state are much more complicated than its Lagrangian exact gauge symmetry supposes to be. The dynamical source of these complications has been identified with the tadpole/seagull term, which renormalized version called, {\sl the mass gap}. It is explicitly present in the full gluon self-energy. The true dynamical role of the mass gap was hidden in the QCD ground state. To disclose it the splintering between the transverse conditions for the full gluon self-energy and its subtracted counterpart has been derived. We have established the equation of motion for the full gluon propagator on account of the mass gap. It allows to fix the dynamical and gauge structures of the full gluon propagator with a newly-derived generalized gauge. It is uniquely given as a function of the gluon momentum. All this makes it possible to present novel non-perturbative analytical approach to QCD, which we call the mass gap approach. It extends the mass gap concept to be accounted for the QCD ground state as well. We have found the general non-perturbative solution for the full gluon propagator with exactly defined finite gluon pole mass, and it is different from the excitations with the effective gluon masses. Despite the exact gauge symmetry is broken in the ground state, the renormalizability of the theory is not affected due to the important role of the Slavnov-Taylor identity in the renormalization beyond the perturbation theory. For this the non-perturbative multiplicative renormalization program for the full massive gluon propagator has been formulated. Our approach does not allow the massive gluons to be the mass-shell objects, and thus prevents them to appear as physical states at large distances (confinement of massive gluons).
Comments:
28 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1904.07748 [pdf]
3 citations
10
[Submitted on 16 Apr 2019] (cross-list from hep-ph)
New Realization of the Conversion Calculation for Reactor Antineutrino Fluxes
Yu-Feng Li🇨🇳 · Di Zhang🇨🇳
Validation of the effective conversion method in the reactor antineutrino flux calculation is examined using the \textit{ab initio} calculation of the electron and antineutrino spectra from the state-of-the-art nuclear database. It turns out that neglecting the shape variation of beta decay branches between the allowed and forbidden transitions would induce significant bias in the total inverse-beta-decay yields and energy spectral distributions. We propose a new realization of the conversion method with both the allowed and forbidden virtual branches, and apply it to both the \textit{simulated} data from the nuclear database and \textit{real} data from the fission measurements at ILL by virtue of statistical properties of the allowed and forbidden decays in the database. Two kinds of dominant uncertainty sources are identified and it turns out that the new realization of the conversion calculation can largely reduce the rate and spectral bias and thus present a reliable prediction of the antineutrino fluxes if accurate beta decay information is available in the high endpoint energy range.
Comments:
23 pages, 9 figures, 2 tables, with new results on uncertainty study, and ILL beta spectrum conversion, to appear in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1904.07791 [pdf]
PRD(2019)·18 citations
11
[Submitted on 16 Apr 2019] (cross-list from astro-ph.CO)
QED corrections to the big-bang nucleosynthesis reaction rates
Cyril Pitrou🇫🇷 · Maxim Pospelov🇨🇦
We compute radiative corrections to nuclear reaction rates that determine the outcome of the Big-Bang Nucleosynthesis (BBN). Any nuclear reaction producing a photon with an energy above $2 m_{e}$ must be supplemented by the corresponding reaction where the final state photon is replaced by an electron-positron pair. We find that pair production brings a typical $0.2%$ enhancement to photon emission rates, resulting in a similar size corrections to elemental abundances. The exception is $^{4} He$ abundance, which is insensitive to the small changes in the nuclear reaction rates. We also investigate the effect of vacuum polarisation on the Coulomb barrier, which brings a small extra correction when reaction rates are extrapolated from the measured energies to the BBN Gamow peak energies.
Comments:
10 pages, 4 figures
Subjects:
Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1904.07795 [pdf]
PRC(2020)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE