Nuclear Theory·nucl-th

Monday·March 14, 2016

8 papers—4 primary·4 cross-listed

05
[Submitted on 10 Mar 2016] (cross-list from astro-ph.HE)
Spherical configuration of a super-dense hot compact object with particular EoS
E.P. Tito · V.I. Pavlov
The equation of state (EoS) $P = P (ρ, ...)$ -- pressure as a function of density and other thermodynamical quantities -- is what generates particularities of mass--radius distribution $M (R)$ for super--dense compact stellar bodies, the remnants of cosmic cataclysms. In view of recent nuclear experiments, we propose one particular EoS, which admits the critical state characterized by density $ρ_{c}$ and temperature $T_{c}$ , and which under certain conditions permits a radial distribution of the super--dense matter in "liquid" phase. We establish such conditions and demonstrate that a stable configuration is indeed possible (only) for temperatures smaller than the critical one. Using Tolman--Oppenheimer--Volkoff equations for hydrostatic equilibrium, we derive the mass--radius relation for the super--dense compact objects with masses smaller than the Sun, $M ≪ M_{⊙}$ . The obtained results are within the constraints established by both heavy--ion collision experiments and theoretical studies of neutron--rich matter.
Comments:
11 pages, 21 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1603.03427 [pdf]
0 citations
06
[Submitted on 11 Mar 2016] (cross-list from nucl-ex)
Measurements of $d_{2}^{n}$ and $A_{1}^{n}$ : Probing the neutron spin structure
D. Flay · M. Posik · D. S. Parno · K. Allada · W. Armstrong · T. Averett · F. Benmokhtar · W. Bertozzi · A. Camsonne · M. Canan · G. D. Cates · C. Chen and 79 other authors
We report on the results of the E06-014 experiment performed at Jefferson Lab in Hall A, where a precision measurement of the twist-3 matrix element $d_{2}$ of the neutron ( $d_{2}^{n}$ ) was conducted. This quantity represents the average color Lorentz force a struck quark experiences in a deep inelastic electron scattering event off a neutron due to its interaction with the hadronizing remnants. This color force was determined from a linear combination of the third moments of the spin structure functions $g_{1}$ and $g_{2}$ on $^{3}$ He after nuclear corrections had been applied to these moments. The kinematics included two average $Q^{2}$ bins of $3.2$ GeV $^{2}$ and $4.3$ GeV $^{2}$ , and Bjorken- $x$ $0.25 \leq x \leq 0.90$ covering the DIS and resonance regions. We found $d_{2}^{n}$ to be small and negative for $< Q^{2} >= 3.2$ GeV $^{2}$ , and smaller for $< Q^{2} >= 4.3$ GeV $^{2}$ , consistent with a lattice QCD calculation. The twist-4 matrix element $f_{2}^{n}$ was extracted by combining our $d_{2}^{n}$ with the world data on $Γ_{1}^{n} = \int_{0}^{1} g_{1}^{n} d x$ . We found $f_{2}^{n}$ to be roughly an order of magnitude larger than $d_{2}^{n}$ . Utilizing the extracted $d_{2}^{n}$ and $f_{2}^{n}$ data, we separated the color force into its electric and magnetic components, $F_{E}^{y, n}$ and $F_{B}^{y, n}$ , and found them to be equal and opposite in magnitude, in agreement with instanton model predictions but not with those from QCD sum rules. Additionally, we have extracted the neutron virtual photon-nucleon asymmetry $A_{1}^{n}$ , the structure function ratio $g_{1}^{n} / F_{1}^{n}$ , and the quark ratios $(Δ u + Δ u ˉ) / (u + u ˉ)$ and $(Δ d + Δ d ˉ) / (d + d ˉ)$ . These results were found to be consistent with DIS world data and with the prediction of the constituent quark model but at odds with those of perturbative QCD at large $x$ .
Comments:
55 Pages, 45 figures, 48 tables. 15 supplemental files. Grammatical and typo fixes. Revised some model descriptions and updated analyses for f_2^n and color forces
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1603.03612 [pdf]
PRD(2016)·64 citations
07
[Submitted on 11 Mar 2016] (cross-list from hep-ph)
Pion-nucleon scattering in covariant baryon chiral perturbation theory with explicit Delta resonances
De-Liang Yao🇩🇪 · D. Siemens🇩🇪 · V. Bernard🇫🇷 · E. Epelbaum🇩🇪 · A. M. Gasparyan🇩🇪 · J. Gegelia🇩🇪 · H. Krebs🇩🇪 · Ulf-G. Meißner🇩🇪
We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the $S$ - and $P$ -partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the $D$ and $F$ waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in order to determine the strangeness content of the nucleon, we calculate the octet baryon masses in the presence of decuplet resonances up to next-to-next-to-leading order in SU(3) baryon chiral perturbation theory. The octet baryon sigma terms are predicted as a byproduct of this calculation.
Comments:
41 pages, 12 figures, 7 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.03638 [pdf]
JHEP(2016)·125 citations
08
[Submitted on 11 Mar 2016] (cross-list from hep-ph)
Properties of single cluster structure of $d^{*} (2380)$ in chiral SU(3) quark model
Qi-Fang Lü🇨🇳 · Fei Huang🇨🇳 · Yu-Bing Dong🇨🇳 · Peng-Nian Shen🇨🇳 · Zong-Ye Zhang🇨🇳
The structure of $d^{*} (2380)$ is re-studied with the single cluster structure in the chiral SU(3) quark model which has successfully been employed to explain the scattering and binding behaviors of baryonic systems. The mass and width are explicitly calculated with two types of trial wave functions. The result shows that the $(0 s)^{6} [6]_{or b}$ configuration is easy to convert to the configuration with the same $[6]_{or b}$ symmetry but $2ℏ ω$ excitation back and forth, however, it is seldom to turn into a two-cluster configuration with a (1s) relative motion in between. The resultant mass and width are about $2394$ MeV and $25$ MeV, respectively, and the stable size is about $0.75 f m$ , which are consistent with both the results in the two-cluster configuration calculation and the data measured by the COSY collaboration. It seems that the observed $d^{*}$ is a six-quark dominated exotic state with a spherical shape and breath mode in the coordinate space. Moreover, if $d^{*}$ does have $2ℏ ω$ excitation, the $d^{*} \to n p π π π$ decay mode might be a good place to distinguish the real structure of the observed phenomenon by COSY. The masses of various isospin-spin states of six-light-quark systems are also computed. It is shown that by considering the coupling with the configurations with $2ℏ ω$ excitations, only the mirror state with $I S$ = $30$ will be lower down to the place where whose mass is slightly higher than the value of the $ΔΔ$ threshold.
Comments:
This paper has been withdrawn by the author as the further investigation is needed
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.03673 [pdf]
Phys. Rev. D 96, 014036 (2017)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Spherical configuration of a super-dense hot compact object with particular EoS

Measurements of d2n​ and A1n​: Probing the neutron spin structure

Pion-nucleon scattering in covariant baryon chiral perturbation theory with explicit Delta resonances

Properties of single cluster structure of d∗(2380) in chiral SU(3) quark model

Affiliations

Measurements of $d_{2}^{n}$ and $A_{1}^{n}$ : Probing the neutron spin structure

Properties of single cluster structure of $d^{*} (2380)$ in chiral SU(3) quark model