Nuclear Theory·nucl-th

Friday·September 23, 2016

8 papers—2 primary·6 cross-listed

01
[Submitted on 22 Sept 2016]
Two-dimensional collective Hamiltonian for chiral and wobbling modes
Q. B. Chen · S. Q. Zhang · P. W. Zhao · R. V. Jolos · J. Meng
A two-dimensional collective Hamiltonian (2DCH) on both azimuth and polar motions in triaxial nuclei is proposed to investigate the chiral and wobbling modes. In the 2DCH, the collective potential and the mass parameters are determined from three-dimensional tilted axis cranking (TAC) calculations. The broken chiral and signature symmetries in the TAC solutions are restored by the 2DCH. The validity of the 2DCH is illustrated with a triaxial rotor ( $γ = - 3 0^{\circ}$ ) coupling to one $h_{11/2}$ proton particle and one $h_{11/2}$ neutron hole. By diagonalizing the 2DCH, the angular momenta and energy spectra are obtained. These results agree with the exact solutions of the particle rotor model (PRM) at high rotational frequencies. However, at low frequencies, the energies given by the 2DCH are larger than those by the PRM due to the underestimation of the mass parameters. In addition, with increasing angular momentum, the transitions from the chiral vibration to chiral rotation and further to longitudinal wobbling motion have been presented in the 2DCH.
Comments:
30 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.06967 [pdf]
PRC(2016)·45 citations
02
[Submitted on 22 Sept 2016]
Partial restoration of chiral symmetry in hot and dense neutron matter
Jeremy W. Holt🇺🇸 · Keighley E. Rockcliffe🇺🇸
We review efforts to describe the approach to chiral symmetry restoration in neutron matter from the low-energy realization of QCD, chiral effective field theory.
Comments:
Contribution to the Gerry Brown 90th birthday memorial book published by World Scientific. v2 updated references
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.07109 [pdf]
IJMPE(2017)·2 citations
03
[Submitted on 21 Sept 2016] (cross-list from hep-ph)
On the pi pi continuum in the nucleon form factors and the proton radius puzzle
M. Hoferichter🇺🇸 · B. Kubis🇩🇪 · J. Ruiz de Elvira🇩🇪 · H.-W. Hammer🇩🇪 · U.-G. Meißner🇩🇪
We present an improved determination of the $π π$ continuum contribution to the isovector spectral functions of the nucleon electromagnetic form factors. Our analysis includes the most up-to-date results for the $π π \to N ˉ N$ partial waves extracted from Roy-Steiner equations, consistent input for the pion vector form factor, and a thorough discussion of isospin-violating effects and uncertainty estimates. As an application, we consider the $π π$ contribution to the isovector electric and magnetic radii by means of sum rules, which, in combination with the accurately known neutron electric radius, are found to slightly prefer a small proton charge radius.
Comments:
10 pages, 3 figures, spectral functions included as supplementary material; journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
1609.06722 [pdf]
EPJA(2016)·107 citations
04
[Submitted on 21 Sept 2016] (cross-list from astro-ph.HE)
Neutrino Astrophysics
Cristina Volpe🇫🇷
We summarize the progress in neutrino astrophysics and emphasize open issues in our understanding of neutrino flavor conversion in media. We discuss solar neutrinos, core-collapse supernova neutrinos and conclude with ultra-high energy neutrinos.
Comments:
Lectures presented at "52th Winter School of Theoretical Physics", Ladek Zdroj, 14-21 February 2016. arXiv admin note: text overlap with arXiv:1503.01355, arXiv:1411.6533
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:
1609.06747 [pdf]
Acta Phys.Polon.Supp.(2016)·11 citations
05
[Submitted on 22 Sept 2016] (cross-list from hep-ph)
The Validity of the Weizsacker-Williams Approximation and the Analysis of Beam Dump Experiments: Production of a New Scalar Boson
Yu-Sheng Liu🇺🇸 · David McKeen🇺🇸 · Gerald A. Miller🇺🇸
Beam dump experiments have been used to search for new particles with null results interpreted in terms of limits on masses $m_{ϕ}$ and coupling constants $ϵ$ . However these limits have been obtained by using approximations [including the Weizsäcker-Williams (WW) approximation] or Monte-Carlo simulations. We display methods, using a new scalar boson as an example, to obtain the cross section and the resulting particle production numbers without using approximations or Monte-Carlo simulations. We show that the approximations cannot be used to obtain accurate values of cross sections. The corresponding exclusion plots differ by substantial amounts when seen on a linear scale. In the event of a discovery, we generate pseudodata (assuming given values of $m_{ϕ}$ and $ϵ$ ) in the currently allowed regions of parameter space. The use of approximations to analyze the pseudodata for the future experiments is shown to lead to considerable errors in determining the parameters. Furthermore, a new region of parameter space can be explored without using one of the common approximations, $m_{ϕ} ≫ m_{e}$ . Our method can be used as a consistency check for Monte-Carlo simulations.
Comments:
21 pages, 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1609.06781 [pdf]
PRD(2017)·73 citations
06
[Submitted on 22 Sept 2016] (cross-list from hep-ph)
Doubly heavy baryon spectra guided by lattice QCD
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸
This paper provides results for the ground state and excited spectra of three-flavored doubly heavy baryons, $b c n$ and $b cs$ . We take advantage of the spin-independent interaction recently obtained to reconcile the lattice SU(3) QCD static potential and the results of nonperturbative lattice QCD for the triply heavy baryon spectra. We show that the spin-dependent potential might be constrained on the basis of nonperturbative lattice QCD results for the spin splittings of three-flavored doubly heavy baryons. Our results may also represent a challenge for future lattice QCD work, because a smaller lattice error could help in distinguishing between different prescriptions for the spin-dependent part of the interaction. Thus, by comparing with the reported baryon spectra obtained with parameters estimated from lattice QCD, one can challenge the precision of lattice calculations. The present work supports a coherent description of singly, doubly and triply heavy baryons with the same Cornell-like interacting potential. The possible experimental measurement of these states at LHCb is an incentive for this study.
Comments:
17 pages, 3 figures. To be published in Phys. Rev. D. Two references have been added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.06886 [pdf]
PRD(2016)·17 citations
07
[Submitted on 21 Sept 2016] (cross-list from astro-ph.HE)
A G2-QCD neutron star
Ouraman Hajizadeh🇦🇹 · Axel Maas🇦🇹
The determination of the properties of neutron stars from the underlying theory, QCD, is still an unsolved problem. This is mainly due to the difficulty to obtain reliable results for the equation of state for cold, dense QCD. As an alternative route to obtain qualitative insights, we determine the structure of a neutron star for a modified version of QCD: By replacing the gauge group SU(3) with the exceptional Lie group G2, it is possible to perform lattice simulations at finite density, while still retaining neutrons. Here, results of these lattice simulations are used to determine the mass-radius relation of a neutron star for this theory. The results show that phase changes express themselves in this relation. Also, the radius of the most massive neutron stars is found to vary very little, which would make radius determinations much simpler if this would also be true in QCD.
Comments:
7 pages, 4 figures. poster presented at the "XXXIV International Symposium on Lattice Field Theory", July 2016, Southampton, UK
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.06979 [pdf]
PoS(2016)·4 citations
08
[Submitted on 22 Sept 2016] (cross-list from hep-ph)
Chiral-scale effective theory including a dilatonic meson
Yan-Ling Li🇨🇳 · Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷
A scale-invariant chiral effective Lagrangian is constructed for octet pions and a dilaton figuring as Nambu-Goldstone bosons with vector mesons incorporated as hidden gauge fields. The Lagrangian is built to the next-to-leading order in chiral-scale counting without baryon fields and then to leading order including baryons. The resulting theory is hidden scale-symmetric and local symmetric. We also discuss some possible applications of the present Lagrangian.
Comments:
12 page, changes to match the published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.07014 [pdf]
PRD(2017)·56 citations

Affiliations

first authorsco-authorsvia INSPIRE