Nuclear Theory·nucl-th

Wednesday·April 25, 2018

9 papers—6 primary·3 cross-listed

01
[Submitted on 23 Apr 2018]
New charm resonances and $J / ψ$ interactions in a hadron gas
L. M. Abreu🇧🇷 · K. P. Khemchandani🇧🇷 · A. Martínez Torres🇧🇷 · F. S. Navarra🇧🇷 · M. Nielsen🇧🇷
In relativistic heavy ion collisions, after the quark gluon plasma (QGP) phase there is a hadron gas (HG) phase. In both phases $J / ψ$ may be formed and destroyed. In this note we study the $J / ψ$ interactions with other mesons in the hadron gas phase. Making use of effective field Lagrangians we obtain the cross sections for the production and absorption processes. With respect to the existing calculations, the improvements introduced here are the inclusion of $K$ and $K^{*}$ 's in the effective Lagrangian approach and the inclusion of processes involving the new exotic charmonium states $Z_{c} (3900)$ and $Z_{c} (4025)$ . We conclude that the interactions between $J / ψ$ and all the considered mesons reduce the original $J / ψ$ abundance ( determined at the end of the quark gluon plasma phase ) by 20 \% and 24 \% in RHIC and LHC collisions respectively. Consequently, any really significant change in the $J / ψ$ abundance comes from dissociation and regeneration processes in the QGP phase.
Comments:
4 pages, 2 figures. Contribution to the Proceedings of the XIV HADRON PHYSICS, 2018, MARCH 18-23, FLORIANOPOLIS, BRAZIL
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1804.08775 [pdf]
0 citations
02
[Submitted on 24 Apr 2018]
A comparative study of Compact Objects using 3 models: Walecka Model, PAL Model, and M.I.T. Bag Model
Fabio Kopp🇧🇷 · Alex Quadros🇧🇷 · Guilherme Volkmer🇧🇷 · Moises Razeira🇧🇷 · Magno Machado🇧🇷 · Dimiter Hadjimichef🇧🇷 · Cesar Augusto Zen Vasconcellos🇧🇷
Compact objects are the name used to classify the following objects: white dwarf, neutron star and black holes. In addition to them, some authors have suggested that in the core of a neutron star we may have the quarks u,d,s and c. In this work we investigate the structure of neutron star and strange star, described by the Tolman-Openheimer-Volkof equations. For the neutron star, we used the relativistic EoS from Walecka's model and the non-relativistic EoS PAL model. For the strange star, we used the M.I.T. bag model. We obtain results for the mass-radius relation and then we compared ours results with the actual pulsar data recently observed PSR J1614-2230 with a mass $1.97 \pm 0.04 M_{⊙}$ .
Comments:
Poster presented at the XIV International Workshop on Hadron Physics, Florianópolis, Brazil, March 2018
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1804.08785 [pdf]
0 citations
03
[Submitted on 24 Apr 2018]
Intertwined effects of pairing and deformation on neutron halos in magnesium isotopes
H. Nakada · K. Takayama
Matter radii of the $^{34 - 40}$ Mg nuclei are investigated by self-consistent Hartree-Fock-Bogolyubov calculations assuming the axial symmetry. With the semi-realistic M3Y-P6 interaction, the $N$ -dependence of the matter radii observed in the experiments is reproduced excellently. Both the pairing and the deformation play significant roles in an intertwined manner. The $^{35}$ Mg nucleus has a smaller radius than the neighboring even- $N$ nuclei, which is attributed to its smaller deformation. In contrast, a neutron halo is obtained in $^{37}$ Mg. We point out that, in contrast to the pairing anti-halo effect that may operate on the even- $N$ nuclei, the pair correlation enhances halos in odd- $N$ nuclei, owing to the new mechanism which we call \textit{unpaired-particle haloing}. The halo in $^{37}$ Mg is predicted to have peanut shape in its intrinsic state, reflecting $p$ -wave contribution, as in $^{40}$ Mg. The $N$ -dependence of the deformation is significant again, by which the single-particle level dominated by the $p$ -wave component comes down.
Comments:
5 pages including 2 figures, to be published in PRC (Rapid Communication)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1804.08852 [pdf]
PRC(2018)·37 citations
04
[Submitted on 24 Apr 2018]
Nuclear interactions and net-proton number fluctuations in heavy ion collisions at the SIS18 accelerator
Jan Steinheimer🇩🇪 · Yongjia Wang🇨🇳 · Ayon Mukherjee🇩🇪 · Yunxiao Ye🇨🇳 · Chenchen Guo🇨🇳 · Qingfeng Li🇨🇳 · Horst Stoecker🇩🇪
The effect of nuclear interactions on measurable net-proton number fluctuations in heavy ion collisions at the SIS18/GSI accelerator is investigated. The state of the art UrQMD model including interaction potentials is employed. It is found that the nuclear forces enhance the baryon number cumulants, as predicted from grand canonical thermodynamical models. The effect however is smeared out for proton number fluctuations due to iso-spin randomization and global baryon number conservation, which decreases the cumulant ratios. For a rapidity acceptance window larger than $Δ y > 0.4$ the effects of global baryon number conservation dominate and all cumulant ratios are significantly smaller than 1.
Comments:
6 pages 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1804.08936 [pdf]
PLB(2018)·13 citations
05
[Submitted on 24 Apr 2018]
Neutral-current neutrino-nucleus scattering off Xe isotopes
Pekka Pirinen🇫🇮 · Jouni Suhonen🇫🇮 · Emanuel Ydrefors🇧🇷
Large liquid xenon detectors aiming for dark matter direct detection will soon become viable tools also for investigating neutrino physics. Information on the effects of nuclear structure in neutrino-nucleus scattering can be important in distinguishing neutrino backgrounds in such detectors. We perform calculations for differential and total cross sections of neutral-current neutrino scattering off the most abundant xenon isotopes. The nuclear structure calculations are made in the nuclear shell model for elastic scattering, and also in the quasiparticle random-phase approximation (QRPA) and microscopic quasiparticle phonon model (MQPM) for both elastic and inelastic scattering. Using suitable neutrino energy distributions, we compute estimates of total averaged cross sections for 8B solar neutrinos and supernova neutrinos.
Comments:
17 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1804.08995 [pdf]
Adv.High Energy Phys.(2018)·21 citations
06
[Submitted on 24 Apr 2018]
Magnetic field effect on nuclear matter from skyrmion crystal model
Mamiya Kawaguchi🇯🇵 · Yong-Liang Ma🇨🇳 · Shinya Matsuzaki🇯🇵
We explore magnetic field effects on the nuclear matter based on the skrymion crystal approach for the first time. It is found that the magnetic effect plays the role of a catalyzer for the topological phase transition (topological deformation for the skyrmion crystal configuration from the skrymion phase to half-skyrmion phase). Furthermore, we observe that in the presence of the magnetic field, the inhomogeneous chiral condensate persists both in the skyrmion and half-skyrmion phases. Explicitly, as the strength of magnetic field gets larger, the inhomogeneous chiral condensate in the skyrmion phase tends to be drastically localized, while in the half-skyrmion phase the inhomogeneity configuration is hardly affected. It also turns out that a large magnetic effect in a low density region distorts the baryon shape to an elliptic form but the crystal structure is intact. However, in a high density region, the crystal structure is strongly effected by the strong magnetic field. A possible correlation between the chiral inhomogeneity and the deformation of the skrymion configuration is also addressed. The results obtained in this paper might be realized in the deep interior of compact stars.
Comments:
13 pages, 31 figures, minor corrections made, some revision made, references added
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1804.09015 [pdf]
PRC(2018)·3 citations
07
[Submitted on 24 Apr 2018] (cross-list from physics.atom-ph)
Shielding of an external oscillating electric field inside atoms
V.V. Flambaum🇦🇺
According to the Schiff theorem an external electric field vanishes at atomic nucleus in a neutral atom, i.e. it is completely shielded by electrons. This makes a nuclear electric dipole moment (EDM) unobservable. In this paper an extension of the Schiff theorem to an oscillating electric field is considered. Such field can reach the nucleus and interact with the nuclear EDM. The enhancement effect appears if the field is in resonance with atomic or molecular transition. The shielding by electrons strongly affects low-energy nuclear electric dipole transition amplitudes in different nuclear reactions including radiative transitions, radiative nucleon capture, photo or electro-excitation of nuclei and laser-induced or laser-enhanced nuclear reactions.
Subjects:
Atomic Physics (physics.atom-ph); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1804.08898 [pdf]
PRA(2018)·9 citations
08
[Submitted on 24 Apr 2018] (cross-list from astro-ph.HE)
On parametrised cold dense matter equation of state inference
Thomas E. Riley · Geert Raaijmakers · Anna L. Watts
Constraining the equation of state of cold dense matter in compact stars is a major science goal for observing programmes being conducted using X-ray, radio, and gravitational wave telescopes. We discuss Bayesian hierarchical inference of parametrised dense matter equations of state. In particular we generalise and examine two inference paradigms from the literature: (i) direct posterior equation of state parameter estimation, conditioned on observations of a set of rotating compact stars; and (ii) indirect parameter estimation, via transformation of an intermediary joint posterior distribution of exterior spacetime parameters (such as gravitational masses and coordinate equatorial radii). We conclude that the former paradigm is not only tractable for large-scale analyses, but is principled and flexible from a Bayesian perspective whilst the latter paradigm is not. The thematic problem of Bayesian prior definition emerges as the crux of the difference between these paradigms. The second paradigm should in general only be considered as an ill-defined approach to the problem of utilising archival posterior constraints on exterior spacetime parameters; we advocate for an alternative approach whereby such information is repurposed as an approximative likelihood function. We also discuss why conditioning on a piecewise-polytropic equation of state model - currently standard in the field of dense matter study - can easily violate conditions required for transformation of a probability density distribution between spaces of exterior (spacetime) and interior (source matter) parameters.
Comments:
Accepted for publication in MNRAS, 43 pages, 7 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1804.09085 [pdf]
MNRAS(2018)·48 citations
09
[Submitted on 24 Apr 2018] (cross-list from astro-ph.HE)
A pitfall of piecewise-polytropic equation of state inference
G. Raaijmakers · T. E. Riley · A. L. Watts
The only messenger radiation in the Universe which one can use to statistically probe the Equation of State (EOS) of cold dense matter is that originating from the near-field vicinities of compact stars. Constraining gravitational masses and equatorial radii of rotating compact stars is a major goal for current and future telescope missions, with a primary purpose of constraining the EOS. From a Bayesian perspective it is necessary to carefully discuss prior definition; in this context a complicating issue is that in practice there exist pathologies in the general relativistic mapping between spaces of local (interior source matter) and global (exterior spacetime) parameters. In a companion paper, these issues were raised on a theoretical basis. In this study we reproduce a probability transformation procedure from the literature in order to map a joint posterior distribution of Schwarzschild gravitational masses and radii into a joint posterior distribution of EOS parameters. We demonstrate computationally that EOS parameter inferences are sensitive to the choice to define a prior on a joint space of these masses and radii, instead of on a joint space interior source matter parameters. We focus on the piecewise-polytropic EOS model, which is currently standard in the field of astrophysical dense matter study. We discuss the implications of this issue for the field.
Comments:
16 pages, 9 figures. Accepted for publication in MNRAS
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1804.09087 [pdf]
MNRAS(2018)·37 citations

Affiliations

first authorsco-authorsvia INSPIRE