Nuclear Theory·nucl-th

Monday·December 10, 2018

8 papers—6 primary·2 cross-listed

01
[Submitted on 6 Dec 2018]
Initial transverse-momentum broadening of Breit-Wheeler process in relativistic heavy-ion collisions
Wangmei Zha🇨🇳 · James Daniel Brandenburg🇨🇳 · Zebo Tang🇨🇳 · Zhangbu Xu🇨🇳
We calculate the cross section and transverse-momentum ( $P_{⊥}$ ) distribution of the Breit-Wheeler process in relativistic heavy-ion collisions and their dependence on collision impact parameter ( $b$ ). To accomplish this, the Equivalent Photon Approximation (EPA) was generalized in a more differential way compared to the approach traditionally used for inclusive collisions. In addition, a lowest-order QED calculation with straightline assumption was performed as a standard baseline for comparison. The cross section as a function of $b$ is consistent with previous calculations using the equivalent one-photon distribution function. Most importantly, the $P_{⊥}$ shape from this model is strongly dependent on impact parameter and can quantitatively explain the $P_{⊥}$ broadening observed recently by RHIC and LHC experiments. This broadening effect from the initial QED field strength should be considered in studying possible trapped magnetic field and multiple scattering in a Quark-Gluon Plasma (QGP). The impact-parameter sensitive observable also provides a controllable tool for studying extreme electromagnetic fields.
Comments:
3 figures, major update: 1. adding 2 more calculations with QED lowest-order Feynman diagrams, and gEPA1, and their equations; 2. adding more detailed explanations about the additional phase angle in gEPA2; 3. remove azimuthal angular calculation; 4. adding discussion about possible final-state effect
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1812.02820 [pdf]
PLB(2020)·99 citations
02
[Submitted on 7 Dec 2018]
Description of the critical point symmetry in 124Te by IBM-2
Dali Zhang🇨🇳 · Chengfu Mu🇨🇳
Based on the neutron and proton degrees of freedom, the low-lying energy levels, the $E 2$ , $M 1$ and $E 0$ transition strengths of nucleus $^{124}$ Te have been calculated by the neutron-proton interacting boson model. The calculated results are quite consistent with the experimental data. By comparing the key observables of states at the critical point of $U_{π ν} (5)$ -- $O_{π ν} (6)$ transition with experimental data and calculated results, we show that the $^{124}$ Te is a possible nucleus at the critical point of the second order phase transition from vibration to unstable rotation and such a critical point contains somewhat triaxial rotation. The 0 $_{2}^{+}$ state of $^{124}$ Te can be interpreted as the lowest state of the first excited family of intrinsic levels in the critical point symmetry.
Comments:
19 pages, 1 figure, 3 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1812.02908 [pdf]
CPC(2019)·1 citation
03
[Submitted on 7 Dec 2018]
Dependence of spin induced structural transitions on level density and Neutron emission spectra
Mamta Aggarwal🇮🇳
The impact of spin induced deformation and shape phase transitions on nuclear level density and consequently on neutron emission spectra of the decay of compound nuclear systems 112^Ru to 123^Cs (N = 68 isotones) is investigated in a microscopic framework of Statistical theory of superfluid nuclei. Our calculations are in good accord with experimental data for evaporation residue of 119^Sb^* and 185^Re^* and show a strong correlation between spin induced structural transitions and NLD. We find that the inverse level density parameter K increases with increasing spin for all the systems, but it decreases with a deformation or a shape change that results in the enhancement of level density and emission probability. A sharp shape phase transition from oblate to uncommon prolate non-collective in well deformed nuclei leads to band crossing and enhancement of level density which fades away while approaching sphericity at or near shell closure manifesting shell effects.
Comments:
6 pages, 8 figures. Accepted in Nuclear Physics A
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1812.02994 [pdf]
NPA(2019)·4 citations
04
[Submitted on 7 Dec 2018]
Covariant chiral nucleon-nucleon contact Lagrangian up to order $O (q^{4})$
Yang Xiao🇨🇳 · Li-Sheng Geng🇨🇳 · Xiu-Lei Ren🇩🇪
We adopt a covariant version of the naive dimensional analysis and construct the chiral two-nucleon contact Lagrangian constrained by Lorentz, parity, charge conjugation, hermitian conjugation, and chiral symmetries. We show that at $O (q^{0})$ , $O (q^{2})$ , $O (q^{4})$ , where $q$ denotes a generic small quantity, there are 4, 13, and 23 terms, respectively. We find that by performing $1/ m_{N}$ expansions, the covariant Lagrangian reduces to the conventional non-relativistic one, which includes 2, 7, and 15 terms at each corresponding order.
Comments:
9 pages
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1812.03005 [pdf]
PRC(2019)·41 citations
05
[Submitted on 7 Dec 2018]
Kaons and antikaons in strong magnetic fields
Amruta Mishra🇮🇳 · Anuj Kumar Singh🇮🇳 · Neeraj Singh Rawat🇮🇳 · Pratik Aman🇮🇳
The in-medium masses of the kaons and antikaons in strongly magnetized asymmetric nuclear matter are studied using a chiral SU(3) model. The medium modifications of the masses of these open strange pseudoscalar mesons arise due to their interactions with the nucleons and scalar mesons within the model. The proton, the charged nucleon, has effects from the Landau energy levels in the presence of the magnetic field. The anomalous magnetic moments (AMM) of the nucleons are taken into consideration in the present study and these are seen to be large at high magnetic fields and high densities. The isospin effects are appreciable at high densities. The density effects are observed to be the dominant medium effects, as compared to the effects from magnetic field and isospin asymmetry. ~
Comments:
22 pages, 4 figures, version to be published in Eur. Phys. Jour. A. arXiv admin note: text overlap with arXiv:1712.07997
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1812.03011 [pdf]
EPJA(2019)·18 citations
06
[Submitted on 7 Dec 2018]
Entanglement Suppression and Emergent Symmetries of Strong Interactions
Silas R. Beane🇺🇸 · David B. Kaplan🇺🇸 · Natalie Klco🇺🇸 · Martin J. Savage🇺🇸
Entanglement suppression in the strong interaction $S$ -matrix is shown to be correlated with approximate spin-flavor symmetries that are observed in low-energy baryon interactions, the Wigner $S U (4)$ symmetry for two flavors and an $S U (16)$ symmetry for three flavors. We conjecture that dynamical entanglement suppression is a property of the strong interactions in the infrared, giving rise to these emergent symmetries and providing powerful constraints on the nature of nuclear and hypernuclear forces in dense matter.
Comments:
6 pages, 5 pages supplemental, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Quantum Physics (quant-ph)
arXiv:
1812.03138 [pdf]
PRL(2019)·184 citations
07
[Submitted on 6 Dec 2018] (cross-list from hep-ph)
Analysing direct photon spectra and elliptic flow from heavy ion collision measurements at the top RHIC energy within the integrated hydrokinetic model
V. Yu. Naboka🇺🇦 · Yu. M. Sinyukov🇺🇦 · G. M. Zinovjev🇺🇦
The integrated HydroKinetic Model (iHKM) is applied to analyse the results of direct photon spectra and elliptic flow measurements in 200A GeV Au+Au collisions at RHIC for the three centrality bins. We detect the strong centrality dependence of photon elliptic flow as $v_{2} (p_{T})$ -coefficient increases towards peripheral collisions. The photon production in the model is accumulated from the different sources along with the process of relativistic heavy ion collision developing. Those include the primary hard photons from the parton collisions at very early stage of the process, the photons generated at the pre-thermal phase of matter evolution, then thermal photons at equilibrated quark-gluon stage together with radiation displaying a confinement and, finally, from the hadron gas phase. Along the way a hadronic medium evolution is treated in two distinct, in a sense opposite, approaches: chemically equilibrated and chemically frozen system expansion. We find that similar as it was found in iHKM for the LHC energies, a description of the direct photon spectra and elliptic flows is significantly improved if an additional portion of the photon radiation, that is associated with hadronization processes, is included into consideration.
Comments:
16 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1812.02763 [pdf]
0 citations
08
[Submitted on 12 Nov 2018] (cross-list from physics.gen-ph)
The criticality of multiplicative processes
Bernard Gaveau🇫🇷 · Marc-Thierry Jaekel🇫🇷 · Jacques Maillard · Jorge Silva🇫🇷
Keeping in view applications to numerical simulations of the evolution of a nuclear reactor core around criticality, we use a general mathematical framework for describing the evolutions of multiplicative processes (processes involving particle creation) both in particle generations and in time. This framework allows us to obtain, within a same formalism, two corresponding estimates of the multiplication factor which describes the growth of particle numbers at large times. We obtain the relative positions of both estimates with respect to each other and to criticality. These relations may show particularly useful when simulating in a realistic way the monitoring of nuclear cores in subcritical states, such as is the case for Accelerator Driven Systems (ADS). More generally, this study applies to various multiplicative processes which can be found in nature.
Comments:
21 pages
Subjects:
physics.gen-ph (physics.gen-ph); Nuclear Theory (nucl-th)
arXiv:
1812.03171 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE