Nuclear Theory·nucl-th

Friday·July 17, 2015

12 papers—6 primary·6 cross-listed

01
[Submitted on 15 Jul 2015]
Polarized Lepton-Nucleon Elastic Scattering and a Search for a Light Scalar Boson
Yu-Sheng Liu🇺🇸 · Gerald A. Miller🇺🇸
Lepton-nucleon elastic scattering, using the one-photon and one-scalar-boson exchange mechanisms considering all possible polarizations, is used to study searches for a new scalar boson and suggest new measurements of the nucleon form factors. A new light scalar boson, which feebly couples to leptons and nucleons, may account for the proton radius and muon $g - 2$ puzzles. We show that the scalar boson produces relatively large effects in certain kinematic region when using sufficient control of lepton and nucleon spin polarization. We generalize current techniques to measure the ratio $G_{E} / G_{M}$ and present a new method to separately measure $G_{M}^{2}$ and $G_{E}^{2}$ using polarized incoming and outgoing muons.
Comments:
27 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1507.04399 [pdf]
PRC(2015)·12 citations
02
[Submitted on 16 Jul 2015]
Femto-cyclones and hyperon polarization in Heavy-Ion Collisions
M.I. Baznat🇷🇺 · K.K. Gudima🇷🇺 · A.S. Sorin🇷🇺 · O.V. Teryaev🇷🇺
We study the structure of vorticity and hydrodynamic helicity fields in peripheral heavy-ion collisions using the kinetic Quark-Gluon String Model. The angular momentum conservation within this model holds with a good accuracy. We observe the formation of specific toroidal structures of vorticity field (vortex sheets). Their existence is mirrored in the polarization of hyperons of the percent order.
Comments:
LaTeX, 12 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1507.04652 [pdf]
PRC(2016)·67 citations
03
[Submitted on 16 Jul 2015]
Isospin splitting of nucleon effective mass from giant resonances in $^{208}$ Pb
Zhen Zhang🇨🇳 · Lie-Wen Chen🇨🇳
Based on mean field calculations with Skyrme interactions, we extract a constraint on the isovector effective mass in nuclear matter at saturation density $ρ_{0}$ , i.e., $m_{v}^{*} (ρ_{0}) = (0.77 \pm 0.03) m$ by combining the experimental data of the centroid energy of the isovector giant dipole resonance (IVGDR) and the electric dipole polarizability $α_{D}$ in $^{208}$ Pb. Meanwhile, the isoscalar effective mass at $ρ_{0}$ is determined to be $m_{s}^{*} (ρ_{0}) = (0.91 \pm 0.05) m$ by analyzing the measured excitation energy of the isoscalar giant quadrupole resonance (ISGQR) in $^{208}$ Pb. From the constrained $m_{s}^{*} (ρ_{0})$ and $m_{v}^{*} (ρ_{0})$ , we obtain the isospin splitting of nucleon effective mass in asymmetric nuclear matter of isospin asymmetry $δ$ at $ρ_{0}$ as $[m_{n}^{*} (ρ_{0}, δ) - m_{p}^{*} (ρ_{0}, δ)] / m = Δ m_{1}^{*} (ρ_{0}) δ + O (δ^{3})$ with the linear isospin splitting coefficient $Δ m_{1}^{*} (ρ_{0}) = 0.33 \pm 0.16$ . We notice that using the recently corrected data on the $α_{D}$ in $^{208}$ Pb with the contribution of the quasideuteron effect subtracted slightly enhances the isovector effective mass to $m_{v}^{*} (ρ_{0}) = (0.80 \pm 0.03) m$ and reduces the linear isospin splitting coefficient to $Δ m_{1}^{*} (ρ_{0}) = 0.27 \pm 0.15$ . Furthermore, the constraints on $m_{v}^{*} (ρ)$ , $m_{s}^{*} (ρ)$ and $Δ m_{1}^{*} (ρ)$ at other densities are obtained from the similar analyses and we find that the $Δ m_{1}^{*} (ρ)$ increases with the density.
Comments:
7 pages, 3 figures. New results and discussions added. Accepted version to appear in PRC
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1507.04675 [pdf]
PRC(2016)·51 citations
04
[Submitted on 16 Jul 2015]
Theoretical study of triaxial shapes of neutron-rich Mo and Ru nuclei
Chunli Zhang · Gowhar Bhat · Witek Nazarewicz · Javid Sheikh · Yue Shi
Background: Recently, transition quadrupole moments in rotational bands of even-mass neutron-rich isotopes of molybdenum and ruthenium nuclei have been measured. The new data have provided a challenge for theoretical descriptions invoking stable triaxial deformations. Purpose: To understand experimental data on rotational bands in the neutron-rich Mo-Ru region, we carried out theoretical analysis of moments of inertia, shapes, and transition quadrupole moments of neutron-rich even-even nuclei around $^{110}$ Ru using self-consistent mean-field and shell model techniques. Methods: To describe yrast structures in Mo and Ru isotopes, we use nuclear Density Functional Theory (DFT) with the optimized energy density functional UNEDF0. We also apply Triaxial Projected Shell Model (TPSM) to describe yrast and positive-parity, near-yrast band structures. Results: Our self-consistent DFT calculations predict triaxial ground-state deformations in $^{106, 108}$ Mo and $^{108.110, 112}$ Ru and reproduce the observed low-frequency behavior of moments of inertia. As the rotational frequency increases, a negative- $γ$ structure, associated with the aligned $ν (h_{11/2})^{2}$ pair, becomes energetically favored. The computed transition quadrupole moments vary with angular momentum, which reflects deformation changes with rotation; those variations are consistent with experiment. The TPSM calculations explain the observed band structures assuming stable triaxial shapes. Conclusions: The structure of neutron-rich even-even nuclei around $^{110}$ Ru is consistent with triaxial shape deformations. Our DFT and TPSM frameworks provide a consistent and complementary description of experimental data.
Comments:
10 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.04686 [pdf]
PRC(2015)·47 citations
05
[Submitted on 16 Jul 2015]
Ab Initio No Core Shell Model - Recent Results and Further Prospects
James P. Vary · Pieter Maris · Hugh Potter · Mark A. Caprio · Robin Smith · Sven Binder · Angelo Calci · Sebastian Fischer · Joachim Langhammer · Robert Roth · Hasan Metin Aktulga · Esmond Ng and 5 other authors
There has been significant recent progress in solving the long-standing problems of how nuclear shell structure and collective motion emerge from underlying microscopic inter-nucleon interactions. We review a selection of recent significant results within the ab initio No Core Shell Model (NCSM) closely tied to three major factors enabling this progress: (1) improved nuclear interactions that accurately describe the experimental two-nucleon and three-nucleon interaction data; (2) advances in algorithms to simulate the quantum many-body problem with strong interactions; and (3) continued rapid development of high-performance computers now capable of performing $20 \times 1 0^{15}$ floating point operations per second. We also comment on prospects for further developments.
Comments:
Invited paper presented at NTSE-2014 and published online in the proceedings (see footnote on p.1)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.04693 [pdf]
4 citations
06
[Submitted on 15 Jul 2015]
Core-crust transition and crustal fraction of moment of inertia in neutron stars
Debasis Atta · Somnath Mukhopadhyay · D. N. Basu
The crustal fraction of moment of inertia in neutron stars is calculated using $β$ -equilibrated nuclear matter obtained from density dependent M3Y effective interaction. The transition density, pressure and proton fraction at the inner edge separating the liquid core from the solid crust of the neutron stars determined from the thermodynamic stability conditions are found to be $ρ_{t} =$ 0.0938 fm $^{- 3}$ , P $_{t} =$ 0.5006 MeV fm $^{- 3}$ and $x_{p (t)} =$ 0.0308, respectively. The crustal fraction of the moment of inertia can be extracted from studying pulsar glitches and is most sensitive to the pressure as well as density at the transition from the crust to the core. These results for pressure and density at core-crust transition together with the observed minimum crustal fraction of the total moment of inertia provide a new limit for the radius of the Vela pulsar: $R \geq 4.10 + 3.36 M / M_{⊙}$ kms.
Comments:
6 pages including 2 figures and 3 tables; Calculations are made more accurate by using very accurate values of Solar mass, erg to MeV conversion factor, pi and gravitational constant G. arXiv admin note: substantial text overlap with arXiv:1406.5302; text overlap with arXiv:hep-ph/0009357, arXiv:hep-ph/0011333, arXiv:hep-ph/0109135, arXiv:hep-ph/0102047 by other authors
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.04728 [pdf]
Indian J.Phys.(2017)·13 citations
07
[Submitted on 14 Jul 2015] (cross-list from hep-ph)
Identifying exotic hidden-charm pentaquarks
Rui Chen🇨🇳 · Xiang Liu🇨🇳 · Xue-Qian Li🇨🇳 · Shi-Lin Zhu🇨🇳
The LHCb Collaboration at the Large Hadron Collider at CERN discovered two pentaquark states $P_{c} (4380)$ and $P_{c} (4450)$ . These two hidden-charm states are interpreted as the loosely bound $Σ_{c} (2455) D^{*}$ and $Σ_{c}^{*} (2520) D^{*}$ molecular states in the boson exchange interaction model, which provides an explanation for why the experimental width of $P_{c} (4450)$ is much narrower than that of $P_{c} (4380)$ . The discovery of the new resonances $P_{c} (4380)$ and $P_{c} (4450)$ , indeed, opens a new page for hadron physics. The partners of $P_{c} (4380)$ and $P_{c} (4450)$ should be pursued in future experiments.
Comments:
5 pages, 2 tables and 1 figure. More discussions and references added. Accepted by Phys. Rev. Lett
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1507.03704 [pdf]
PRL(2015)·341 citations
08
[Submitted on 16 Jul 2015] (cross-list from nucl-ex)
Direct mass measurements of Cd isotopes show strong shell gap at N=82
R. Knöbel🇩🇪 · M. Diwisch🇩🇪 · F. Bosch🇩🇪 · D. Boutin🇩🇪 · L. Chen🇩🇪 · C. Dimopoulou🇩🇪 · A. Dolinskii🇩🇪 · B. Franczak🇩🇪 · B. Franzke🇩🇪 · H. Geissel🇩🇪 · M. Hausmann🇺🇸 · C. Kozhuharov🇩🇪 and 23 other authors
A $^{238}$ U projectile beam was used to create cadmium isotopes via abrasion-fission at 410 MeV/u in a beryllium target at the entrance of the in-flight separator FRS at GSI. The fission fragments were separated with the FRS and injected into the isochronous storage ring ESR for mass measurements. The Isochronous Mass Spectrometry (IMS) was performed under two different experimental conditions, with and without B $ρ$ -tagging at the dispersive central focal plane of the FRS. In the experiment with B $ρ$ -tagging the magnetic rigidity of the injected fragments was determined by an accuracy of $2 \times 1 0^{- 4}$ . A new method of data analysis, using a correlation matrix for the combined data set from both experiments, has provided mass values for 25 different isotopes for the first time. The high selectivity and sensitivity of the experiment and analysis has given access even to rare isotopes detected with a few atoms per week. In this letter we present for the $^{129, 130, 131}$ Cd isotopes mass values directly measured for the first time. The Cd results clearly show a very pronounced shell effect at $N = 82$ which is in agreement with the conclusion from $γ$ -ray spectroscopy of $^{130}$ Cd and confirms the assumptions of modern shell-model calculations.
Comments:
7 pages, 5 figures, 3 tables
Subjects:
Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1507.04470 [pdf]
0 citations
09
[Submitted on 16 Jul 2015] (cross-list from astro-ph.HE)
Rotation-induced deep crustal heating of millisecond pulsars
M.E. Gusakov · E.M. Kantor · A. Reisenegger
The spin-down of a neutron star, e.g. due to magneto-dipole losses, results in compression of the stellar matter and induces nuclear reactions at phase transitions between different nuclear species in the crust. We show that this mechanism is effective in heating recycled pulsars, in which the previous accretion process has already been compressing the crust, so it is not in nuclear equilibrium. We calculate the corresponding emissivity and confront it with available observations, showing that it might account for the likely thermal ultraviolet emission of PSR J0437-4715.
Comments:
5 pages, 3 figures, accepted for publication in MNRAS Letters
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1507.04586 [pdf]
MNRAS(2015)·28 citations
10
[Submitted on 16 Jul 2015] (cross-list from astro-ph.HE)
Proton gaps and cooling of neutron stars with a stiff hadronic EoS
Hovik Grigorian🇷🇺 · Dmitry N. Voskresensky🇷🇺 · David Blaschke🇷🇺
The recent measurements of the masses of the pulsar J00737-3039B and of the companion J1756-2251 and pulsars PSR J1614-2230, PSR J0348-0432 demonstrate the existence of compact stars with masses in a broad range from 1.2 to 2 $M_{⊙}$ . To fulfill the constraint $M_{max} > 2 M_{⊙}$ and to demonstrate the possibility of cooling scenarios for purely hadronic and further for hybrid stars we exploit the stiff DD2 hadronic equation of state producing a maximum neutron star mass $M ≃ 2.43 M_{⊙}$ . We show that the "nuclear medium cooling" scenario for neutron stars comfortably explains the whole set of cooling curves just by a variation of the star masses without the necessity for the occurrence of the direct Urca reaction. To describe the cooling data with the very stiff DD2 equation of state we select a proton gap profile from those exploited in the literature and allow for a variation of the effective pion gap controlling the efficiency of the medium modified Urca process. Fast cooling of young neutron stars like it is seen in the data for Cas A is explained with the DD2 equation of state when the following conditions are provided: the presence of an efficient medium modified Urca process, and a large proton gap at densities $n \leq 2 n_{0}$ vanishing for $n \geq (2.5 - 3) n_{0}$ , where $n_{0}$ is the saturation nuclear density.
Comments:
16 pages, 7 figures, Proceedings of the Conference "Compact Stars in the QCD Phase Diagram IV", September 26-30, 2014, Prerow, Germany
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1507.04656 [pdf]
1 citation
11
[Submitted on 16 Jul 2015] (cross-list from hep-ph)
Heavy baryons in the large Nc limit
C. Albertus🇪🇸 · E. Ruiz Arriola🇪🇸 · I. P. Fernando🇺🇸 · J. L. Goity🇺🇸
It is shown that in the large Nc limit heavy baryon masses can be estimated quantitatively in a 1/Nc expansion using the Hartree approximation. The results are compared with available lattice calculations for different values of the ratio between the square root of the string tension and the heavy quark mass tension independent of Nc. Using a potential adjusted to agree with the one obtained in lattice QCD, a variational analysis of the ground state spin averaged baryon mass is performed using Gaussian Hartree wave functions. Relativistic corrections through the quark kinetic energy are included. The results provide good estimates for the first sub-leading in 1/Nc corrections.
Comments:
7 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1507.04667 [pdf]
PLB(2015)·2 citations
12
[Submitted on 16 Jul 2015] (cross-list from hep-ph)
Elliptic flow difference of charged pions in heavy-ion collisions
Yoshitaka Hatta🇯🇵 · Akihiko Monnai🇺🇸 · Bo-Wen Xiao🇨🇳
Recently, the STAR collaboration at RHIC has presented experimental evidence for the correlation between the elliptic flow difference of charged pions and charge asymmetry as a possible signal of the chiral magnetic wave. We demonstrate that the STAR results can be understood within the standard viscous hydrodynamics.
Comments:
5 pages, 4 figures; v2: revised version to appear in Nuclear Physics A
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1507.04690 [pdf]
NPA(2016)·43 citations

Affiliations

first authorsco-authorsvia INSPIRE