Nuclear Theory·nucl-th

Friday·December 15, 2017

12 papers—9 primary·3 cross-listed

01
[Submitted on 13 Dec 2017]
Tensor Fermi liquid parameters in nuclear matter from chiral effective field theory
J. W. Holt · N. Kaiser · T. R. Whitehead
We compute from chiral two- and three-body forces the complete quasiparticle interaction in symmetric nuclear matter up to twice nuclear matter saturation density. Second-order perturbative contributions that account for Pauli-blocking and medium polarization are included, allowing for an exploration of the full set of central and noncentral operator structures permitted by symmetries and the long-wavelength limit. At the Hartree-Fock level, the next-to-next-to-leading order three-nucleon force contributes to all noncentral interactions, and their strengths grow approximately linearly with the nucleon density up that of saturated nuclear matter. Three-body forces are shown to enhance the already strong proton-neutron effective tensor interaction, while the corresponding like-particle tensor force remains small. We also find a large isovector cross-vector interaction but small center-of-mass tensor interactions in the isoscalar and isovector channels. The convergence of the expansion of the noncentral quasiparticle interaction in Landau parameters and Legendre polynomials is studied in detail.
Comments:
15 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.05013 [pdf]
PRC(2018)·18 citations
02
[Submitted on 14 Dec 2017]
On the spreading width of the Isobaric Analog Resonances
G. V. Kolomiytsev · M. L. Gorelik · M. H. Urin
A description of the spreading width of the Isobaric Analog Resonances in medium-heavy mass spherical nuclei is proposed within a combined approach. This latter consists in incorporating the "Coulomb description" of isospin-forbidden processes into the newly developed particle-hole dispersive optical model. Within this approach, the observed spreading width of the resonances based on the 208,209Pb parent-nuclei ground state is quantitatively estimated without the use of specific adjustable parameters.
Comments:
10 pages, 2 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.05146 [pdf]
EPJA(2018)·12 citations
03
[Submitted on 14 Dec 2017]
Hydrodynamic description of ultrarelativistic heavy-ion collisions
Wojciech Florkowski🇵🇱
Recent theoretical developments of relativistic hydrodynamics applied to ultrarelativistic heavy-ion collisions are briefly reviewed. In particular, the concept of a formal gradient expansion is discussed, which is a tool to compare different hydrodynamic models with underlying microscopic theories.
Comments:
Written version of lectures presented at the 53rd Karpacz Winter School of Theoretical Physics, Feb. 26 - March 4, 2017, Karpacz, Poland, submitted to Springer Lecture Notes in Physics
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.05162 [pdf]
8 citations
04
[Submitted on 14 Dec 2017]
Search for time-reversal-invariance violation in double polarized antiproton-deuteron scattering
Yuriy Uzikov🇷🇺 · Johann Haidenbauer🇩🇪
Apart from the $p d$ reaction also the scattering of antiprotons with transversal polarization $p_{y}^{p}$ on deuterons with tensor polarization $P_{x z}$ provides a null-test signal for time-reversal-invariance violating but parity conserving effects. Assuming that the time-reversal-invariance violating $N ˉ N$ interaction contains the same operator structure as the $N N$ interaction, we discuss the energy dependence of the null-test signal in $p ˉ d$ scattering on the basis of a calculation within the spin-dependent Glauber theory at beam energies of 50-300 MeV.
Comments:
6 pages, one figure; prepared for the proceedings of the International Conference on Exotic Atoms and related topics - EXA2017 (September 11-15, Wien, Austria)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1712.05184 [pdf]
EPJ Web Conf.(2018)·0 citations
05
[Submitted on 14 Dec 2017]
Matter distribution and spin-orbit force in spherical nuclei
G. Co' · M. Anguiano · V. De Donno · A. M. Lallena
We investigate the possibility that some nuclei show density distributions with a depletion in the center, a semi-bubble structure, by using a Hartree-Fock plus Bardeen-Cooper-Schrieffer approach. We separately study the proton, neutron and matter distributions in 37 spherical nuclei mainly in the $s - d$ shell region. We found a relation between the semi-bubble structure and the energy splitting of spin-orbit partner single particle levels. The presence of semi-bubble structure reduces this splitting, and we study its consequences on the excitation spectrum of the nuclei under investigation by using a quasi-particle random-phase-approximation approach. The excitation energies of the low-lying $4^{+}$ states can be related to the presence of semi-bubble structure in nuclei.
Comments:
15 pages, 7 tables, 11 figures. Version accepted for publication in Phys. Rev. C; the number of nuclei analysed has been reduced; some figure have bee redrawn, and a new figure and some references have been added
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.05186 [pdf]
PRC(2018)·10 citations
06
[Submitted on 14 Dec 2017]
Recent developments in nuclear structure theory: an outlook on the muonic atom program
Oscar Javier Hernandez🇨🇦 · Sonia Bacca🇨🇦 · Kyle Andrew Wendt🇺🇸
The discovery of the proton-radius puzzle and the subsequent deuteron-radius puzzle is fueling an on-going debate on possible explanations for the difference in the observed radii obtained from muonic atoms and from electron-nucleus systems. Atomic nuclei have a complex internal structure that must be taken into account when analyzing experimental spectroscopic results. Ab initio nuclear structure theory provided the so far most precise estimates of important corrections to the Lamb shift in muonic atoms and is well poised to also investigate nuclear structure corrections to the hyperfine splitting in muonic atoms. Independently on whether the puzzle is due to beyond-the-standard-model physics or not, nuclear structure corrections are a necessary theoretical input to any experimental extraction of electric and magnetic radii from precise muonic atom measurements. Here, we review the status of the calculations performed by the TRIUMF-Hebrew University group, focusing on the deuteron, and discuss preliminary results on magnetic sum rules calculated with two-body currents at next-to-leading order. Two-body currents will be an important ingredient in future calculations of nuclear structure corrections to the hyperfine splitting in muonic atoms.
Comments:
10 pages, accepted proceedings of the "55th International Winter Meeting on Nuclear Physics", 23-27 January 2017, to appear on PoS
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.05187 [pdf]
PoS(2017)·1 citation
07
[Submitted on 14 Dec 2017]
Monte-Carlo statistical hadronization in relativistic heavy-ion collisions
Radoslaw Ryblewski🇵🇱
A brief introduction to the statistical hadronization approach to particle production in relativistic heavy-ion collisions is given. In the context of fluid dynamics modeling various aspects of hadron emission at the freeze-out are discussed. Practical applications of the presented concepts are presented within the THERMINATOR Monte-Carlo hadron generator.
Comments:
Lectures delivered at the 53rd Karpacz Winter School of Theoretical Physics, February 26th - March 4th, 2017, Karpacz, Poland ; Submitted to Lect. Notes Phys
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1712.05213 [pdf]
Lect.Notes Phys.(2022)·2 citations
08
[Submitted on 14 Dec 2017]
Three-body effects in the Hoyle-state decay
Jonas Refsgaard · Hans O. U. Fynbo · Oliver S. Kirsebom · Karsten Riisager
We use a sequential $R$ -matrix model to describe the breakup of the Hoyle state into three $α$ particles via the ground state of $^{8} Be$ . It is shown that even in a sequential picture, features resembling a direct breakup branch appear in the phase-space distribution of the $α$ particles. We construct a toy model to describe the Coulomb interaction in the three-body final state and its effects on the decay spectrum are investigated. The framework is also used to predict the phase-space distribution of the $α$ particles emitted in a direct breakup of the Hoyle state and the possibility of interference between a direct and sequential branch is discussed. Our numerical results are compared to the current upper limit on the direct decay branch determined in recent experiments.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.05251 [pdf]
PLB(2018)·15 citations
09
[Submitted on 14 Dec 2017]
Partial-wave analysis of proton Compton scattering data below the pion-production threshold
Nadiia Krupina🇩🇪 · Vadim Lensky🇩🇪 · Vladimir Pascalutsa🇩🇪
Low-energy Compton scattering off the proton is used for determination of the proton polarizabilities. However, the present empirical determinations rely heavily on the theoretical description(s) of the experimental cross sections in terms of polarizabilities. The most recent determinations are based on either the fixed- $t$ dispersion relations (DR) or chiral perturbation theory in the single-baryon sector ( $χ$ PT). The two approaches obtain rather different results for proton polarizabilities, most notably for $β_{M 1}$ (magnetic dipole polarizability). We attempt to resolve this discrepancy by performing a partial-wave analysis of the world data on proton Compton scattering below threshold. We find a large sensitivity of the extraction to a few "outliers", leading us to conclude that the difference between DR and $χ$ PT extraction is a problem of the experimental database rather than of "model-dependence". We have specific suggestions for new experiments needed for an efficient improvement of the database. With the present database, the difference of proton scalar polarizabilities is constrainedto a rather broad interval: $α_{E 1} - β_{M 1} = (6.8 \dots 10.9) \times 1 0^{- 4}$ fm $^{3}$ , with their sum fixed much more precisely [to $14.0 (2)$ ] by the Baldin sum rule.
Comments:
8 pages, 6 figures, revised version accepted for publication in Physics Letters B
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1712.05349 [pdf]
PLB(2018)·21 citations
10
[Submitted on 12 Dec 2017] (cross-list from hep-ph)
Thermal radiation and entanglement in proton-proton collisions at the LHC
O.K. Baker🇺🇸 · D.E. Kharzeev🇺🇸
The origin of the apparent thermalization in high-energy collisions is investigated using the data of the ATLAS and CMS Collaborations at the LHC. For this purpose, we analyze the transverse momentum distributions in the following proton-proton collision processes, all at $s = 13$ TeV: i) inclusive inelastic $pp$ collisions; ii) single- and double-diffractive Drell-Yan production $pp \to μ^{+} μ^{-} X$ ; and iii) Higgs boson production. We confirm the relation between the effective temperature and the hard scattering scale observed at lower energies, and find that it extends even to the Higgs boson production process. In addition we find that the thermal component disappears in diffractive events (even though many charged hadrons are still produced). We discuss the implications of our study for the mechanism of multi-particle production -- in particular, we test the hypothesis about the link between quantum entanglement and thermalization in high-energy collisions.
Comments:
20 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1712.04558 [pdf]
PRD(2018)·98 citations
11
[Submitted on 13 Dec 2017] (cross-list from nucl-ex)
Experimental signals for broken axial symmetry in excited heavy nuclei from the valley of stability
Eckart Grosse · Arnd R. Junghans
An increasing number of experimental data indicates the breaking of axial symmetry in many heavy nuclei already in the valley of stability: Multiple Coulomb excitation analysed in a rotation invariant way, gamma transition rates and energies in odd nuclei, mass predictions, the splitting of Giant Resonances (GR), the collective enhancement of nuclear level densities and Maxwellian averaged neutron capture cross sections. For the interpretation of these experimental observations the axial symmetry breaking shows up in nearly all heavy nuclei as predicted by Hartree-Fock-Bogoliubov (HFB) calculations [1] ; this indicates a nuclear Jahn-Teller effect. We show that nearly no parameters remain free to be adjusted by separate fitting to level density or giant resonance data, if advance information on nuclear deformations, radii etc. are taken from such calculations with the force parameters already fixed. The data analysis and interpretation have to include the quantum mechanical requirement of zero point oscillations and the distinction between static vs. dynamic symmetry breaking has to be regarded.
Comments:
12 pages, 4 figures, Presented at XXIV Kazimierz NPW 20-24 IX 2017, to appear in Acta Physica Polonica B
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1712.04999 [pdf]
Acta Phys.Polon.Supp.(2018)·0 citations
12
[Submitted on 14 Dec 2017] (cross-list from hep-ph)
Chiralspin symmetry and QCD at high temperature
L. Ya. Glozman🇦🇹
It has been found very recently on the lattice that at high temperature at vanishing chemical potential QCD is increasingly SU(2)_CS and SU(2N_F) symmetric. We demonstrate that the chemical potential term in the QCD Lagrangian has precisely the same symmetry. Consequently the QCD matter beyond the chiral restoration line on the T - \mu plane is at least approximately SU(2)_CS and SU(2N_F) symmetric.
Comments:
3 pages, final version to appear in EPJA
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1712.05168 [pdf]
EPJA(2018)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE