Nuclear Theory·nucl-th

Thursday·May 21, 2015

9 papers—4 primary·5 cross-listed

01
[Submitted on 20 May 2015]
Nuclear dynamics induced by antiprotons
Zhao-Qing Feng🇨🇳
Reaction dynamics in collisions of antiprotons on nuclei is investigated within the Lanzhou quantum molecular dynamics model. The reaction channels of elastic scattering, annihilation, charge exchange and inelastic collisions of antiprotons on nucleons have been included in the model. Dynamics on particle production, in particular pions, kaons, antikaons and hyperons, is investigated in collisions of $p$ on $^{12}$ C, $^{20}$ Ne, $^{40}$ Ca and $^{181}$ Ta from a low to high incident momenta. It is found that the annihilations of $p$ on nucleons are of importance on the dynamics of particle production in phase space. Hyperons are mainly produced via meson induced reactions on nucleons and strangeness exchange collisions, which lead to the delayed emission in antiproton-nucleus collisions.
Comments:
8 pages, 4 figures. arXiv admin note: substantial text overlap with arXiv:1405.1997
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.05260 [pdf]
Nucl.Sci.Tech.(2015)·6 citations
02
[Submitted on 20 May 2015]
Effects of chiral imbalance and magnetic field on pion superfluidity and color superconductivity
Gaoqing Cao🇨🇳 · Pengfei Zhuang🇨🇳
The effects of chiral imbalance and external magnetic field on pion superfluidity and color superconductivity are investigated in extended Nambu--Jona-Lasinio models. We take Schwinger approach to treat the interaction between charged pion condensate and magnetic field at finite isospin density and include simultaneously the chiral imbalance and magnetic field at finite baryon density. For the superfluidity, the chiral imbalance and magnetic field lead to catalysis and inverse catalysis effects, respectively. For the superconductivity, the chiral imbalance enhances the critical baryon density, and the magnetic field results in a de Haas--van Alphan oscillation on the phase transition line.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1505.05307 [pdf]
PRD(2015)·63 citations
03
[Submitted on 20 May 2015]
Understanding the structure of $d^{*} (2380)$ in chiral quark model
F. Huang🇨🇳 · P. N. Shen🇨🇳 · Y. B. Dong🇨🇳 · Z. Y. Zhang🇨🇳
The structure and decay properties of $d^{*}$ have been detailedly investigated in both the chiral SU(3) quark model and the extended chiral SU(3) quark model that describe the energies of baryon ground states and the nucleon-nucleon (NN) scattering data satisfactorily. By performing a dynamical coupled-channels study of the system of $ΔΔ$ and hidden-color channel (CC) with quantum numbers $I (J^{P}) = 0 (3^{+})$ in the framework of the resonating group method (RGM), we find that the $d^{*}$ has a mass of about $2.38 - 2.42$ GeV and a root-mean-square radius (RMS) of about $0.76 - 0.88$ fm. The channel wave function is extracted by a projection of the RGM wave function onto the physical basis, and the fraction of CC component in the $d^{*}$ is found to be about $66% - 68%$ , which indicates that the $d^{*}$ is a hexaquark-dominated exotic state. Based on this scenario the partial decay widths of $d^{*} \to d π^{0} π^{0}$ and $d^{*} \to d π^{+} π^{-}$ are further explicitly evaluated and the total width is then obtained by use of the branching ratios extracted from the measured cross sections of other possible decay channels. Both the mass and the decay width of $d^{*}$ calculated in this work are compatible with the data ( $M \approx 2380$ MeV, $Γ \approx 70$ MeV) reported by WASA-at-COSY Collaboration.
Comments:
9 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1505.05395 [pdf]
SCPMA(2016)·39 citations
04
[Submitted on 20 May 2015]
Scaling violation and relativistic effective mass from quasielastic electron scattering: implications for neutrino reactions
J.E. Amaro🇪🇸 · E. Ruiz Arriola🇪🇸 · I. Ruiz Simo🇪🇸
The experimental data from quasielastic electron scattering from $^{12}$ C are reanalyzed in terms of a new scaling variable suggested by the interacting relativistic Fermi gas with scalar and vector interactions, which is known to generate a relativistic effective mass for the interacting nucleons. By choosing a mean value of this relativistic effective mass $m_{N}^{*} = 0.8 m_{N}$ , we observe that most of the data fall inside a region around the inverse parabola-shaped universal scaling function of the relativistic Fermi gas. This suggests a method to select the subset of data that highlight the quasielastic region, about two thirds of the total 2,500 data. Regardless of the momentum and energy transfer, this method automatically excludes the data that are not dominated by the quasielastic process. The resulting band of data reflects deviations from the perfect universality, and can be used to characterize experimentally the quasielastic peak, despite the manifest scaling violation. Moreover we show that the spread of the data around the scaling function can be interpreted as genuine fluctuations of the effective mass $M^{*} \equiv m_{N}^{*} / m_{N} \sim 0.8 \pm 0.1$ . Applying the same procedure we transport the scaling quasielastic band into a theoretical prediction band for neutrino scattering cross section that is compatible with the recent measurements and slightly more accurate.
Comments:
5 pages, 3 figures. Updated version as accepted for publication. Small updates to text, corrected some errors in equations and figure labels
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1505.05415 [pdf]
PRC(2015)·21 citations
05
[Submitted on 26 Mar 2015] (cross-list from math-ph)
Bethe states for the two-site Bose-Hubbard model: a binomial approach
Gilberto Santos🇧🇷 · Changrim Ahn🇰🇷 · Angela Foerster🇧🇷 · Itzhak Roditi🇧🇷
We calculate explicitly the Bethe vectors states by the algebraic Bethe ansatz method with the $g l (2)$ -invariant $R$ -matrix for the two-site Bose-Hubbard model. Using a binomial expansion of the n-th power of a sum of two operators we get and solve a recursion equation. We calculate the scalar product and the norm of the Bethe vectors states. The form factors of the imbalance current operator are also computed.
Comments:
13 pages
Subjects:
Mathematical Physics (math-ph); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Theory (hep-th); math.MP (math.MP); nlin.SI (nlin.SI); Nuclear Theory (nucl-th)
arXiv:
1503.07885 [pdf]
PLB(2015)·11 citations
06
[Submitted on 19 May 2015] (cross-list from astro-ph.HE)
The Dense Matter Equation of State from Neutron Star Radius and Mass Measurements
Feryal Ozel · Dimitrios Psaltis · Tolga Guver · Gordon Baym · Craig Heinke · Sebastien Guillot
We present a comprehensive study of spectroscopic radius measurements of twelve neutron stars obtained during thermonuclear bursts or in quiescence. We incorporate, for the first time, a large number of systematic uncertainties in the measurement of the apparent angular sizes, Eddington fluxes, and distances, in the composition of the interstellar medium, and in the flux calibration of X-ray detectors. We also take into account the results of recent theoretical calculations of rotational effects on neutron star radii, of atmospheric effects on surface spectra, and of relativistic corrections to the Eddington critical flux. We employ Bayesian statistical frameworks to obtain neutron star radii from the spectroscopic measurements as well as to infer the equation of state from the radius measurements. Combining these with the results of experiments in the vicinity of nuclear saturation density and the observations of ~2 Msun neutron stars, we place strong and quantitative constraints on the properties of the equation of state between approximately 2-8 times the nuclear saturation density. We find that around M=1.5 Msun, the preferred equation of state predicts radii between 10.1 - 11.1 km. When interpreting the pressure constraints in the context of high density equations of state based on interacting nucleons, our results suggest a relatively weak contribution of the three-body interaction potential.
Comments:
ApJ, in press. Revised version includes more expanded analyses and discussions of comparison to previous results
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1505.05155 [pdf]
ApJ(2016)·366 citations
07
[Submitted on 19 May 2015] (cross-list from astro-ph.HE)
Statistics of Measuring Neutron Star Radii: Assessing A Frequentist and A Bayesian Approach
Feryal Ozel · Dimitrios Psaltis
Measuring neutron star radii with spectroscopic and timing techniques relies on the combination of multiple observables to break the degeneracies between the mass and radius introduced by general relativistic effects. Here, we explore a previously used frequentist and a newly proposed Bayesian framework to obtain the most likely value and the uncertainty in such a measurement. We find that, for the expected range of masses and radii and for realistic measurement errors, the frequentist approach suffers from biases that are larger than the accuracy in the radius measurement required to distinguish between the different equations of state. In contrast, in the Bayesian framework, the inferred uncertainties are larger, but the most likely values do not suffer from such biases. We also investigate ways of quantifying the degree of consistency between different spectroscopic measurements from a single source. We show that a careful assessment of the systematic uncertainties in the measurements eliminates the need for introducing ad hoc biases, which lead to artificially large inferred radii.
Comments:
ApJ, in press
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1505.05156 [pdf]
ApJ(2015)·24 citations
08
[Submitted on 19 May 2015] (cross-list from hep-ph)
Implementing the exact kinematical constraint in the saturation formalism
Kazuhiro Watanabe🇨🇳 · Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸 · David Zaslavsky🇨🇳
We revisit the issue of the large negative next-to-leading order (NLO) cross section for single inclusive hadron production in $p A$ collisions in the saturation formalism. By implementing the exact kinematical constraint in the modified dipole splitting functions, two additional positive NLO correction terms are obtained. In the asymptotic large $k_{⊥}$ limit, we analytically show that these two terms become as large as the negative NLO contributions found in our previous calculation. Furthermore, the numerical results demonstrate that the applicable regime of the saturation formalism can be extended to a larger $k_{⊥}$ window, where the exact matching between the saturation formalism (in the asymptotic $k_{⊥}$ regime) and the collinear factorization calculations will have to be performed separately. In addition, after significantly improving the numerical accuracy of the NLO correction, we obtain excellent agreement with the LHC and RHIC data for forward hadron productions.
Comments:
20 pages, 7 figures; v2 fixes some typos
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1505.05183 [pdf]
PRD(2015)·69 citations
09
[Submitted on 20 May 2015] (cross-list from hep-ph)
$Z_{c} (3900)$ as a resonance from the $D D ˉ^{*}$ interaction
Jun He🇨🇳
In this paper it is proposed that the charged charmonium-like state $Z_{c} (3900)$ is a resonance above the threshold from the $D D ˉ^{*}$ interaction. The $D D ˉ^{*}$ interaction is described by the one-boson exchange model with light meson exchanges plus a short-range $J / ψ$ exchange. The scattering amplitude is calculated within a Bethe-Salpeter equation approach and the poles near the $D D ˉ^{*}$ threshold are searched. In the isoscalar sector, two poles found under the $D D ˉ^{*}$ threshold, i.e., bound states, have the quantum numbers $I^{G} (J^{P C}) = 0^{-} (1^{+-})$ and $0^{+} (1^{++})$ . The latter can be related to the $X (3872)$ . In the isovector sector, a bound state with $I^{G} (J^{P}) = 1^{+} (1^{+})$ is found with a large cutoff at about 3 GeV. If a cutoff at about 2 GeV is adopted with which a pole carrying the quantum number of the $X (3872)$ is produced at an energy of about 3871 MeV, the pole for the bound state with $1^{+} (1^{+})$ runs across the threshold to a second Rienman sheet and becomes a resonance above the $D D ˉ^{*}$ threshold, which can be identified with the $Z_{c} (3900)$ . With such a cutoff, the $D D ˉ^{*}$ invariant mass spectrum is also investigated and the experimental results found by BESIII can be reproduced.
Comments:
7 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1505.05379 [pdf]
PRD(2015)·85 citations

Affiliations

first authorsco-authorsvia INSPIRE