Nuclear Theory·nucl-th

Friday·August 7, 2020

10 papers—5 primary·5 cross-listed

06
[Submitted on 5 Aug 2020] (cross-list from astro-ph.HE)
Black Dwarf Supernova in the Far Future
M. E. Caplan
In the far future long after star formation has ceased the universe will be populated by sparse degenerate remnants, mostly white dwarfs, though their ultimate fate is an open question. These white dwarfs will cool and freeze solid into black dwarfs while pycnonuclear fusion will slowly process their composition to iron-56. However, due to the declining electron fraction the Chandrasekhar limit of these stars will be decreasing and will eventually be below that of the most massive black dwarfs. As such, isolated dwarf stars with masses greater than $\sim 1.2 M_{⊙}$ will collapse in the far future due to the slow accumulation of iron-56 in their cores. If proton decay does not occur then this is the ultimate fate of about $1 0^{21}$ stars, approximately one percent of all stars in the observable universe. We present calculations of the internal structure of black dwarfs with iron cores as a model for progenitors. From pycnonuclear fusion rates we estimate their lifetime and thus delay time to be $1 0^{1100}$ years. We speculate that high mass black dwarf supernovae resemble accretion induced collapse of O/Ne/Mg white dwarfs while later low mass transients will be similar to stripped-envelope core-collapse supernova, and may be the last interesting astrophysical transients to occur prior to heat death.
Comments:
6 pages, 1 figure, accepted for publication in MNRAS
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2008.02296 [pdf]
MNRAS(2020)·7 citations
07
[Submitted on 6 Aug 2020] (cross-list from hep-ph)
Centrality, transverse momentum and collision energy dependence of the Tsallis parameters in relativistic heavy-ion collisions
Rajendra Nath Patra🇺🇦 · Bedangadas Mohanty🇮🇳 · Tapan K. Nayak🇨🇭
The thermodynamic properties of matter created in high-energy heavy-ion collisions have been studied in the framework of the non-extensive Tsallis statistics. The transverse momentum ( $p_{T}$ )~spectra of identified charged particles (pions, kaons, protons) and all charged particles from the available experimental data of Au-Au collisions at the Relativistic Heavy Ion Collider (RHIC) energies and Pb-Pb collisions at the Large Hadron Collider (LHC) energies are fitted by the Tsallis distribution. The fit parameters, $q$ and $T$ measure the degree of deviation from an equilibrium state and the effective temperature of the thermalized system, respectively. The $p_{T}$ ~spectra are well described by the Tsallis distribution function from peripheral to central collisions for the wide range of collision energies, from $s_{NN}$ = 7.7 GeV to 5.02 TeV. The extracted Tsallis parameters are found to be dependent on the particle species, collision energy, centrality, and fitting ranges in $p_{T}$ . For central collisions, both $q$ and $T$ depend strongly on the fit ranges in $p_{T}$ . For most of the collision energies, $q$ remains almost constant as a function of centrality, whereas $T$ increases from peripheral to central collisions. For a given centrality, $q$ systematically increases as a function of collision energy whereas $T$ has a decreasing trend. A profile plot of $q$ and $T$ with respect to collision energy and centrality shows an anti-correlation between the two parameters.
Comments:
12 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2008.02559 [pdf]
Eur.Phys.J.Plus(2021)·25 citations
08
[Submitted on 6 Aug 2020] (cross-list from hep-ph)
Correlating $h \to μ^{+} μ^{-}$ to the Anomalous Magnetic Moment of the Muon via Leptoquarks
Andreas Crivellin🇨🇭 · Dario Mueller🇨🇭 · Francesco Saturnino🇨🇭
Recently, both ATLAS and CMS measured the decay $h \to μ^{+} μ^{-}$ , finding a signal strength with respect to the Standard Model expectation of $1.2 \pm 0.6$ and $1.19 + 0.41 + 0.17 - 0.39 - 0.16$ , respectively. This provides, for the first time, evidence that the Standard Model Higgs couples to second generation fermions. This measurement is particularly interesting in the context of the intriguing hints for lepton flavor universality violation, accumulated within recent years, as new physics explanations could also be tested in the $h \to μ^{+} μ^{-}$ decay mode. Leptoquarks are prime candidates to account for the flavor anomalies. In particular, they can provide the necessary chiral enhancement (by a factor $m_{t} / m_{μ}$ ) to address $a_{μ}$ with TeV scale new physics. In this letter we point out that such explanations of $a_{μ}$ also lead to enhanced effects in $h \to μ^{+} μ^{-}$ and we examine the correlations between $h \to μ^{+} μ^{-}$ and $a_{μ}$ within leptoquark models. We find that the effect in the branching ratio of $h \to μ^{+} μ^{-}$ ranges from several percent up to a factor three, if one aims at accounting for $a_{μ}$ at the $2 σ$ level. Hence, the new ATLAS and CMS measurements already provide important constraints on the parameter space, rule out specific $a_{μ}$ explanations and will be very important to test the flavor anomalies in the future.
Comments:
8 pages, 3 figures, g-2 updated, EFT discussion added, version accepted for publication in PRL
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2008.02643 [pdf]
PRL(2021)·83 citations
09
[Submitted on 6 Aug 2020] (cross-list from hep-ph)
Relativistic Friedrichs-Lee model and quark-pair creation model
Zhi-Yong Zhou🇨🇳 · Zhiguang Xiao🇨🇳
In this paper, we present how the Friedrichs-Lee model could be extended to the relativistic scenario and be combined with the relativistic quark pair creation model in a consistent way. This scheme could be applied to study the "unquenched" effect of the meson spectra. As an example, if the lowest $J^{P C} = 0^{++}$ $(u u ˉ + d d ˉ) / 2$ bound state in the potential model is coupled to the $π π$ continuum, two resonance poles could be found from the scattering amplitude for the continuum states. One of them could correspond to the $f_{0} (500) / σ$ and the other probably $f_{0} (1370)$ . This scheme might shed more light on why extra states could appear in the hadron spectrum other than the prediction of the quark potential model.
Comments:
v3, figure 3 added, some discussions added, published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2008.02684 [pdf]
EPJC(2020)·14 citations
10
[Submitted on 5 Aug 2020] (cross-list from hep-ph)
Neutron star structure with nuclear force mediated by hypothetical X17 boson
Vlasios Petousis🇨🇿 · Martin Veselsky🇨🇿 · Jozef Leja🇸🇰
A reported $17$ MeV boson, which has been proposed as an explanation to the $^{8}$ Be and $^{4}$ He anomaly, is investigated in the context of its possible influence to neutron stars structure. Implementing a $m_{X}$ =17 MeV to the nuclear equation of state using different incompressibility values K $_{0}$ =245 MeV and K $_{0}$ =260 MeV and solving Tolman-Oppenheimer-Volkoff equations, we estimate an upper limit of $M_{T O V} \approx 2.4 M ⊙$ for a non rotating neutron star with span in radius $R$ between $11.5$ km to $14$ km. Moving away from pure - NN with admixture of 10\% protons and simulating possible softening of equation of state due to hyperons, we see that our estimated limits fit quite well inside the newest reported studies, coming from neutron stars merger event, GW190814
Comments:
5 pages, 4 figures, To appear in the EPJ Web of Conferences
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2008.02733 [pdf]
EPJ Web Conf.(2021)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Black Dwarf Supernova in the Far Future

Centrality, transverse momentum and collision energy dependence of the Tsallis parameters in relativistic heavy-ion collisions

Correlating h→μ+μ− to the Anomalous Magnetic Moment of the Muon via Leptoquarks

Relativistic Friedrichs-Lee model and quark-pair creation model

Neutron star structure with nuclear force mediated by hypothetical X17 boson

Affiliations

Correlating $h \to μ^{+} μ^{-}$ to the Anomalous Magnetic Moment of the Muon via Leptoquarks