Nuclear Theory·nucl-th

Tuesday·March 21, 2017

11 papers—8 primary·3 cross-listed

01
[Submitted on 17 Mar 2017]
Dilepton radiation and bulk viscosity in heavy-ion collisions
Gojko Vujanovic🇺🇸 · Jean-François Paquet🇺🇸 · Chun Shen🇨🇦 · Gabriel S. Denicol🇧🇷 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦 · Ulrich Heinz🇺🇸
Starting from IP-Glasma initial conditions, we investigate the effects of bulk pressure on thermal dilepton production at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) energies. Though results of the thermal dilepton $v_{2}$ under the influence of both bulk and shear viscosity is presented for top RHIC energy, more emphasis is put on LHC energy where such a calculation is computed for the first time. The effects of the bulk pressure on thermal dilepton $v_{2}$ at the LHC are explored through bulk-induced modifications on the dilepton yield.
Comments:
Talk given at the 8th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (Hard Probes 2016), September 23-27 2016, Wuhan, China; 4 pages, LaTeX, 2 PDF figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1703.06164 [pdf]
Nucl.Part.Phys.Proc.(2017)·5 citations
02
[Submitted on 13 Mar 2017]
A dispersive approach to two-photon exchange in elastic electron-proton scattering
P. G. Blunden🇨🇦 · W. Melnitchouk🇺🇸
We examine the two-photon exchange corrections to elastic electron-proton scattering within a dispersive approach, including contributions from both Nucleon and Delta intermediate states. The dispersive analysis avoids off-shell uncertainties inherent in traditional approaches based on direct evaluation of loop diagrams, and guarantees the correct unitary behavior in the high energy limit. Using empirical information on the electromagnetic nucleon elastic and N-Delta transition form factors, we compute the two-photon exchange corrections both algebraically and numerically. Results are compared with recent measurements of e+p to e-p cross section ratios from the CLAS, VEPP-3 and OLYMPUS experiments, as well as with polarization transfer observables.
Comments:
48 pages, 32 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1703.06181 [pdf]
PRC(2017)·65 citations
03
[Submitted on 18 Mar 2017]
$β$ -decay properties of waiting point nuclei for astrophysical applications
Jameel-Un Nabi · Munir Ahmad · Gul Daraz
We report microscopic calculation of key $β$ -decay properties for some of the crucial waiting point species having neutron closed magic shells 50 and 82. Our calculation bear astrophysical significance vis-á-vis speeding of the $r$ -process. The $β$ -decay properties include half-lives, energy rates of $β$ -delayed neutrons and their emission probabilities, both under terrestrial and stellar conditions. We perform a pn-QRPA calculation with a separable multi-shell interaction and include both allowed and unique first-forbidden (U1F) transitions in our calculation. We compare our results with previous calculations and measured data. Our calculation is in good agreement with the experimental data. For certain cases, we noted a significant decrease in the half-life calculation with the contribution of U1F transitions. This is in contradiction to the shell model study where only for $N$ = 126 waiting-point nuclei, the forbidden transitions were reported to significantly reduce the calculated half-lives. Our model fulfills the Ikeda sum rule for even-even cases. For odd-A cases the rule is violated by up to 15 $%$ for $^{125}$ Tc.
Comments:
21 pages, 14 figures, 5 Tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1703.06281 [pdf]
Acta Phys.Polon.B(2019)·4 citations
04
[Submitted on 18 Mar 2017]
Can one determine the neutrino mass by electron capture?
Amand Faessler (Institute of Theoretical Physics, University of Tuebingen, Germany)🇩🇪
There are three different methods used to search the neutrino mass: - The electron antineutrino mass can probably best be determined by the Triton decay. - The neutrinoless Double Beta Decay yields information, if the neutrino is a Dirac or a Majorana particle. It can also determine the Majorana neutrino mass. - Electron capture of an atomic bound electron by a proton in a nucleus bound electron plus proton to neutron plus electron-neutrino can give the mass of the electron neutrino. This contribution summarizes our theoretical work on the possibility to determine the electron neutrino mass by electron capture. One expects the largest influence of the neutrino mass on this decay for a small Q = 2.8 keV for electron capture in Holmium. The energy of the Q value is distributed to the emitted neutrino and the excitation of the Dy atom. Thus the energy difference between the Q value and the upper end of the deexcitation spectrum is the electron neutrino mass. The excitation spectrum of Dy is calculate by one-, two- and three-electron hole excitations, and by the shake-off process. The electron wave functions are calculated selfconsistently by the Dirac-Hartree-Fock approach for the bound and the continuum states. To extract the neutrino mass from the spectrum one must adjust simultaneously the neutrino mass, the Q value, the position, the relative strength and the width of the highest resonance. This fit is only possible, if the background is reduced relative to the present situation. In case of a drastically reduced background a fit of the Q-value and the neutrino mass only seems also to be possible. The analysis presented here shows, that the determination of the electron neutrino mass by electron capture is difficult, but seems not to be impossible.
Comments:
Dedicated to the memory of Walter Greiner 1935 - 2016, five figures. arXiv admin note: substantial text overlap with arXiv:1611.00325
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1703.06318 [pdf]
0 citations
05
[Submitted on 20 Mar 2017]
Solution of the eta-4He problem with quasi-particle formalism
A. Fix🇷🇺 · O. Kolesnikov🇷🇺
The Alt-Grassberger-Sandhas equations for the five-body eta-4N problem are solved for the case of the driving eta N and NN potentials limited to s-waves. The quasi-particle (Schmidt) method is employed to convert the equations into the effective two-body form. Numerical results are presented for the eta-4He scattering length.
Comments:
8 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1703.06591 [pdf]
PLB(2017)·23 citations
06
[Submitted on 20 Mar 2017]
Influence of the hadronic phase on observables in ultrarelativistic heavy ion collisions
J. Steinheimer🇩🇪 · J. Aichelin🇩🇪 · M. Bleicher🇩🇪 · H. Stöcker🇩🇪
The hadronic phase in ultrarelativistic nuclear collisions has a large influence on final state observables like multiplicity, flow and $p_{t}$ spectra, as studied in the UrQMD approach. In this model one assumes that a non-equilibrium decoupling phase follows a fluid dynamical description of the high density phase. Hadrons are produced assuming local thermal equilibrium and dynamically decouple during the hadronic rescattering until the particles are registered in the detectors. This rescattering of hadrons modifies every hadronic bulk observable. The apparent multiplicity of resonances is suppressed as compared to a chemical equilibrium freeze-out model, because the decay products rescatter. Therefore the resonances, which decay in the early hadronic phase, cannot be identified anymore by the invariant mass method. Stable and unstable particles change their momentum distribution by more than 30 $%$ through rescattering and their multiplicity is modified by resonance production and annihilation on a similar magnitude. These findings show that it is all but trivial to conclude from the final state observables on the properties of the system at an earlier time where it may have been in local equilibrium.
Comments:
10 pages 17 figures, version accepted by PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1703.06638 [pdf]
PRC(2017)·52 citations
07
[Submitted on 20 Mar 2017]
Comparison of the pp -> pi+ pn and pp -> pi+ d production rates
G.Faeldt🇸🇪 · C.Wilkin🇬🇧
Fully constrained bubble chamber data on the pp -> pi+ pn and pp -> pi+ d reactions are used to investigate the ratio of the counting rates for the two processes at low pn excitation energies. Whereas the ratio is in tolerable agreement with that found in a high resolution spectrometer experiment, the angular distribution in the final pn rest frame shows that the deviation from the predictions of final state interaction theory must originate primarily from higher partial waves in the pn system. These considerations might also be significant for the determination of the S-wave Lambda:p scattering length from data on the pp -> K+ Lambda p reaction.
Comments:
3 pages plus 1 figure
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1703.06677 [pdf]
PLB(2017)·1 citation
08
[Submitted on 20 Mar 2017]
Correlations and Clustering in Dilute Matter
G. Röpke🇩🇪
Nuclear systems are treated within a quantum statistical approach. Correlations and cluster formation are relevant for the properties of warm dense matter, but the description is challenging and different approximations are discussed. The equation of state, the composition, Bose condensation of bound fermions, the disappearance of bound states at increasing density because of Pauli blocking are of relevance for different applications in astrophysics, heavy ion collisions, and nuclear structure.
Comments:
22 pages, 7 figures, contribution to the special-topics volume on nuclear correlations and cluster physics, edited by W. U. Schröder
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1703.06734 [pdf]
2 citations

Affiliations

first authorsco-authorsvia INSPIRE