Nuclear Theory·nucl-th

Friday·August 28, 2015

9 papers—6 primary·3 cross-listed

01
[Submitted on 27 Aug 2015]
The excitation functions of 187Re(n,2n)186m,gRe Reactions
Xiao-Long Huang · Meng-Xiao Kang · Li-Le Liu · Ji-Min Wang · Li-Yang Jiang · Xiong-Jun Chen
A new value for the emission probability of 137.144keV g-ray of 186gRe decay are re-recommended to be 9.47+-0.03 (%). From this new g-ray emission probability, the measured cross sections for 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions around 14MeV are evaluated, and the total cross section for 187Re(n,2n)186m+gRe reaction at 14.8MeV is recommended to be 2213+-116 mb. The UNF code are adopted to calculate the total cross sections for 187Re(n,2n)186m+gRe reaction below 20 MeV fitting to the recommended value 2213+-116 mb at 14.8MeV using a set of optimum neutron optical potential parameters which obtained on the relevant experimental data of Re. Then the isomeric cross section ratios for 187Re(n,2n)186m,gRe reaction are calculated using the method of Monte Carlo calculations based on the nuclear statistical theory. Combining these two calculated results, the excitation functions for 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions are obtained. The obtained results are in good agreement with the available experimental data, which indicates that present method is useful to deduce the isomeric cross sections for (n,2n) reaction.
Comments:
14 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1508.06718 [pdf]
CPC(2016)·1 citation
02
[Submitted on 27 Aug 2015]
Nuclear forces and their impact on neutron-rich nuclei and neutron-rich matter
K. Hebeler🇩🇪 · J.D. Holt🇩🇪 · J. Menendez🇩🇪 · A. Schwenk🇩🇪
We review the impact of nuclear forces on matter at neutron-rich extremes. Recent results have shown that neutron-rich nuclei become increasingly sensitive to three-nucleon forces, which are at the forefront of theoretical developments based on effective field theories of quantum chromodynamics. This includes the formation of shell structure, the spectroscopy of exotic nuclei, and the location of the neutron dripline. Nuclear forces also constrain the properties of neutron-rich matter, including the neutron skin, the symmetry energy, and the structure of neutron stars. We first review our understanding of three-nucleon forces and show how chiral effective field theory makes unique predictions for many-body forces. Then, we survey results with three-nucleon forces in neutron-rich oxygen and calcium isotopes and neutron-rich matter, which have been explored with a range of many-body methods. Three-nucleon forces therefore provide an exciting link between theoretical, experimental and observational nuclear physics frontiers.
Comments:
28 pages, 13 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1508.06893 [pdf]
Ann.Rev.Nucl.Part.Sci.(2015)·259 citations
03
[Submitted on 27 Aug 2015]
SU(3) breaking in hyperon transition vector form factors
P.E. Shanahan🇦🇺 · A.N. Cooke🇬🇧 · R. Horsley🇬🇧 · Y. Nakamura🇯🇵 · P.E.L. Rakow🇬🇧 · G. Schierholz🇩🇪 · A.W. Thomas🇦🇺 · R.D. Young🇦🇺 · J.M. Zanotti🇦🇺
We present a calculation of the SU(3)-breaking corrections to the hyperon transition vector form factors to $O (p^{4})$ in heavy baryon chiral perturbation theory with finite-range regularisation. Both octet and decuplet degrees of freedom are included. We formulate a chiral expansion at the kinematic point $Q^{2} = - (M_{B_{1}} - M_{B_{2}})^{2}$ , which can be conveniently accessed in lattice QCD. The two unknown low-energy constants at this point are constrained by lattice QCD simulation results for the $Σ^{-} \to n$ and $Ξ^{0} \to Σ^{+}$ transition form factors. Hence we determine lattice-informed values of $f_{1}$ at the physical point. This work constitutes progress towards the precise determination of $∣ V_{u s} ∣$ from hyperon semileptonic decays.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th)
arXiv:
1508.06923 [pdf]
PRD(2015)·18 citations
04
[Submitted on 27 Aug 2015]
How well do we understand Beryllium-7 + proton -> Boron-8 + photon? An Effective Field Theory perspective
Xilin Zhang · Kenneth M. Nollett · D. R. Phillips
We have studied the 7Be(p,photon)8B reaction in the Halo effective field theory (EFT) framework. The leading order (LO) results were published in Phys.Rev.C89,051602(2014) after the isospin mirror process, 7Li(n,photon)8Li, was addressed in Phys.Rev.C89,024613(2014). In both calculations, one key step was using the final shallow bound state asymptotic normalization coefficients (ANCs) computed by ab initio methods to fix the EFT couplings. Recently we have developed the next-to-LO (NLO) formalism (to appear soon), which could reproduce other model results by no worse than 1% when the 7Be-p energy was between 0 and 0.5 MeV. In our recent report (arXiv:1507.07239), a different approach from that in Phys.Rev.C89,051602(2014) was used. We applied Bayesian analysis to constrain all the NLO-EFT parameters based on measured S-factors, and found tight constraints on the S-factor at solar energies. Our S(E=0 MeV)= 21.3 + - 0.7 eV b. The uncertainty is half of that previously recommended. In this proceeding, we provide extra details of the Bayesian analysis, including the computed EFT parameters' probability distribution functions (PDFs) and how the choice of input data impacts final results.
Comments:
Contribution to the 21st International Conference on Few-Body Problems in Physics (2015). 4 pages and 2 figures
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1508.06935 [pdf]
EPJ Web Conf.(2016)·7 citations
05
[Submitted on 27 Aug 2015]
The contribution of NLO and LPM corrections to thermal dilepton emission in heavy ion collisions
Yannis Burnier🇨🇭 · Chiara Gastaldi🇨🇭
Recently lots of efforts have been made to obtain the next to leading order and Landau-Pomeranchuk-Migdal corrections to the thermal dilepton emission rate in perturbative QCD. Here we apply these results to the plasma created in heavy ion collisions and see wether these corrections improve the comparison between theoretical calculations and experimental results for the invariant mass dependence of the dilepton emission rate. In particular, we simulate the quark-gluon plasma produced at RHIC and LHC using a 2+1-dimensional viscous hydro model. We compare our results to STAR experiment and comment on the need for a non-perturbative determination of the dilepton rate at low invariant mass.
Comments:
9 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1508.06978 [pdf]
PRC(2016)·12 citations
06
[Submitted on 27 Aug 2015]
Interplay between antimagnetic and collective rotation in Fe-58
J. Peng · P. W. Zhao · S. Q. Zhang · J. Meng
The self-consistent tilted axis cranking covariant density functional theory based on the point- coupling interaction PC-PK1 is applied to investigate the possible existence of antimagnetic ro- tation in the nucleus Fe-58. The observed data for Band 3 and Band 4 are reproduced well with two assigned configurations. It is found that both bands correspond to a rotation of antimagnetic character, but, due to the presence of considerable deformation, the interplay between antimag- netic rotation and collective motion plays an essential role. In particular for Band 4, collective rotation is dominant in the competition with antimagnetic rotation. Moreover, it is shown that the behavior of the ratios between the dynamic moments of inertia and the B(E2) values reflects the interplay between antimagnetic and collective rotation.
Comments:
15 pages, 6 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1508.06987 [pdf]
IJMPE(2017)·7 citations
07
[Submitted on 26 Aug 2015] (cross-list from hep-ph)
On the proton charge extensions
Jesse R. Stryker🇺🇸 · Gerald A. Miller🇺🇸
We examine how corrections to $S$ -state energy levels, $E_{n S}$ , in hydrogenic atoms due to the finite proton size are affected by moments of the proton charge distribution. The corrections to $E_{n S}$ are computed moment by moment. The results demonstrate that the next-to-leading order term in the expansion is of order $r_{p} / a_{B}$ times the size of the leading order $⟨ r_{p}^{2} ⟩$ term. Our analysis thus dispels any concern that the larger relative size of this term for muonic hydrogen versus electronic hydrogen might account for the current discrepancy of proton radius measurements extracted from the two systems. Furthermore, the next-to-leading order term in powers of $r_{p} / a_{B}$ that we derive from a dipole proton form factor is proportional to $⟨ r_{p}^{3} ⟩$ , rather than $⟨ r_{p}^{4} ⟩$ as would be expected from the scalar nature of the form factor. The dependence of the finite-size correction on $⟨ r_{p}^{3} ⟩$ and higher odd-power moments is shown to be a general result for any spherically symmetric proton charge distribution. A method for computing the moment expansion of the finite-size correction to arbitrary order is introduced and the results are tabulated for principal quantum numbers up to $n = 7$ .
Comments:
10 pages, no figures. Clarified discussion in Sec. II, revised notation, journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
1508.06680 [pdf]
PRA(2016)·4 citations
08
[Submitted on 27 Aug 2015] (cross-list from hep-th)
Dissipative Charged Fluid in a Magnetic Field
Navid Abbasi🇮🇷 · Ali Davody🇮🇷
We study the collective excitations in a dissipative charged fluid at zero chemical potential when an external magnetic field is present. While in the absence of magnetic field, four collective excitations appear in the fluid, we find five hydrodynamic modes in presence of magnetic field. This implies that the magnetic field splits the degeneracy between the transverse shear modes. Using linear response theory, we then compute the retarded response functions. In particular, it turns out that the correlation between charge and the energy fluctuations will no longer vanish, even at zero chemical potential. By use of the response functions, we also derive the relevant Kubo formulas for the transport coefficients.
Comments:
6 pages
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.06879 [pdf]
PLB(2016)·4 citations
09
[Submitted on 27 Aug 2015] (cross-list from hep-ph)
The electron in three-dimensional momentum space
Alessandro Bacchetta🇮🇹 · Luca Mantovani🇮🇹 · Barbara Pasquini (Pavia U. and INFN, Pavia)🇮🇹
We study the electron as a system composed by an electron and a photon, using lowest order perturbation theory. We derive the leading-twist transverse-momentum-dependent distribution functions for both the electron and photon in the dressed electron, thereby offering a three-dimensional description of the dressed electron in momentum space. To obtain the distribution functions, we apply both the formalism of light-front wave function overlap representation and the diagrammatic approach. We perform the calculations both in light-cone gauge and Feynman gauge, and we present a detailed discussion of the role of the Wilson lines to obtain gauge-independent results. We provide numerical results and plots for many of the computed distributions.
Comments:
25 pages, 14 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.06964 [pdf]
PRD(2016)·21 citations

Affiliations

first authorsco-authorsvia INSPIRE