Nuclear Theory·nucl-th

Friday·April 3, 2020

10 papers—3 primary·7 cross-listed

01
[Submitted on 1 Apr 2020]
Transverse momentum fluctuations and their correlation with elliptic flow in nuclear collision
Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Derek Teaney🇺🇸
We propose observables $v_{0}$ and $v_{0} (p_{T})$ which quantify the relative fluctuations in the total transverse momentum at fixed multiplicity. We first study the factorization of the fixed multiplicity momentum dependent two particle correlation function into a product of $v_{0} (p_{T}^{a})$ and $v_{0} (p_{T}^{b})$ within realistic hydrodynamic simulations. Then we present computations of $v_{0} (p_{T})$ for different particle types. We determine the relation between the integrated $v_{0}$ and previously measured observables, and compare results from a hybrid hydrodynamics based model to experimental data. The effects of bulk viscosity and an initial pre-equilibrium stage on the results are quantified. We find that $v_{0}$ is strongly correlated with the initial state entropy per elliptic area, $S / A$ . Using this result, we explain how the observed correlations between the elliptic flow and the transverse momentum (both in simulations and experiment) reflect the initial state correlations between $1/ A$ and ellipticity $ε_{2}$ at fixed multiplicity. We argue that the systematic experimental study of $v_{0}$ , with the same sophistication as used for the other $v_{n}$ , can contribute significantly to our understanding of quark gluon plasma properties.
Comments:
14 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2004.00690 [pdf]
PRC(2020)·131 citations
02
[Submitted on 2 Apr 2020]
$α$ Decay Half-life Estimation and Uncertainty Analysis
Boshuai Cai · Guangshang Chen · Jiongyu Xu · Cenxi Yuan · Chong Qi · Yuan Yao
The non-parametric bootstrap method is used to evaluate the uncertainties of two $α$ decay formulas, the universal decay law (UDL) and the new Geiger-Nuttall law (NGNL). Such a method can simultaneously obtain the uncertainty of each parameter, the correlation between each pair of parameters, and the total, statistical, and systematic uncertainties of each formula. Both even-even (ee) nuclei and odd-A (oA) nuclei are used in the analysis. The collected data are separated into three parts: ee nuclei, oA nuclei without spin or parity change (oA\_nc), and oA nuclei with spin and/or parity change (oA\_c). Based on the residues between observed data and corresponding calculations, the statistical and systematic uncertainties are decomposed from the total uncertainty, from which one can clarify the effects from the shell structure, pairing, and angular momentum change on describing $α$ decay half-life. If $N > 126$ and $N ⩽ 126$ nuclei are considered together, the systematic uncertainty of residues between observed and predicted half-lives are larger than if those groups are considered separately. Without shell correction term, a much larger systematic uncertainty is found if parameters obtained for $N ⩽ 126$ nuclei are used to describe the half-lives of $N > 126$ nuclei. A global hindrance on the $α$ decay process is found in oA\_nc (oA\_c) nuclei comparing with ee (oA\_nc) nuclei. If parameters obtained from ee (oA\_nc) nuclei are used, the half-lives of oA\_nc (oA\_c) nuclei are generally underestimated with large systematic uncertainties, which can be related to the contribution of pairing effect and angular momentum. The recently observed superallowed decay from $^{104}$ Te to $^{100}$ Sn is also discussed based on uncertainty analysis. (Abstract is not fully presented because of length limitation)
Comments:
To be published in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2004.00964 [pdf]
PRC(2020)·20 citations
03
[Submitted on 2 Apr 2020]
Masses and Decay widths of Charmonium states in presence of strong magnetic fields
Amruta Mishra🇮🇳 · S.P. Misra🇮🇳
The masses and decay widths of charmonium states are studied in the presence of strong magnetic fields. The mixing between the pseudoscalar and vector charmonium states at rest is observed to lead to appreciable negative (positive) shifts in the masses of the pseudoscalar (longitudinal component of the vector) charmonium states in vacuum/hadronic medium in the presence of high magnetic fields. The pseudoscalar and vector charmonium masses in the hadronic medium, calculated in an effective chiral model from the medium changes of a scalar dilaton field, have additional significant modifications due to the mixing effects. The masses of the $D$ and $D ˉ$ mesons in the magnetized hadronic matter are calculated within the chiral effective model. The partial decay widths of the vector charmonium state to $D D ˉ$ are computed using a field theoretical model for composite hadrons with quark/antiquark constituents, and are compared to the decay widths calculated using an effective hadronic Lagrangian. The effects of the mixing are observed to lead to significant contributions to the masses of the pseusoscalar and vector charmonium states, and an appreciable increase in the decay width $ψ (3770) \to D D ˉ$ at large values of the magnetic fields. These studies of the charmonium states in strong magnetic fields should have observable consequences on the dilepton spectra, as well as on the production of the open charm mesons and the charmonium states in ultra relativistic heavy ion collision experiments.
Comments:
31 pages, 5 figures,to be published in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2004.01007 [pdf]
PRC(2020)·33 citations
04
[Submitted on 1 Apr 2020] (cross-list from hep-ph)
Radiative decay of $Ξ_{b} (6227)$ in a hadronic molecule picture
HongQiang Zhu🇨🇳 · Yin Huang🇨🇳
The $Ξ_{b} (6227)$ baryon with the quantum number $J^{P} = 1/ 2^{-}$ is considered as a molecular state composed of a $Σ_{b}$ baryon and $K ˉ$ meson. The partial decay widths of the $Σ_{b} K ˉ$ molecular state into $Ξ_{b} γ$ and $Ξ_{b}^{^{'}} γ$ final states through hadronic loops are evaluated with the help of the effective Lagrangians. The partial widths for the $Ξ_{b} (6227) \to γ Ξ_{b}$ and $Ξ_{b} (6227) \to γ Ξ_{b}^{^{'}}$ are evaluated to be about 1.50-1.02 KeV and 17.56-24.91 KeV, respectively, which may be accessible for the LHCb. Based on our results we argue that an experimental determination of the radiative decay width of $Ξ_{b} (6227)$ is important for the understanding of its intrinsic properties.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.00728 [pdf]
CPC(2020)·12 citations
05
[Submitted on 2 Apr 2020] (cross-list from nucl-ex)
A Study of the Properties of the QCD Phase Diagram in High-Energy Nuclear Collisions
Xiaofeng Luo🇨🇳 · Shusu Shi🇨🇳 · Nu Xu🇨🇳 · Yifei Zhang🇨🇳
With the aim of understanding the phase structure of nuclear matter created in high-energy nuclear collisions at finite baryon density, a beam energy scan program has been carried out at Relativistic Heavy Ion Collider (RHIC). In this mini-review, most recent experimental results on collectivity, criticality and heavy flavor productions will be discussed. The goal here is to establish the connection between current available data and future heavy-ion collision experiments in a high baryon density region.
Comments:
Invited review, 30 pages, 18 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2004.00789 [pdf]
Particles(2020)·77 citations
06
[Submitted on 2 Apr 2020] (cross-list from astro-ph.HE)
Equation of state constraints from the threshold binary mass for prompt collapse of neutron star mergers
Andreas Bauswein🇩🇪 · Sebastian Blacker🇩🇪 · Vimal Vijayan🇩🇪 · Nikolaos Stergioulas🇬🇷 · Katerina Chatziioannou🇺🇸 · James A. Clark🇺🇸 · Niels-Uwe F. Bastian🇵🇱 · David B. Blaschke🇵🇱 · Mateusz Cierniak🇵🇱 · Tobias Fischer🇵🇱
Using hydrodynamical simulations for a large set of high-density matter equations of state (EoSs) we systematically determine the threshold mass M_thres for prompt black-hole formation in equal-mass and asymmetric neutron star (NS) mergers. We devise the so far most direct, general and accurate method to determine the unknown maximum mass of nonrotating NSs from merger observations revealing M_thres. Considering hybrid EoSs with hadron-quark phase transition, we identify a new, observable signature of quark matter in NS mergers. Furthermore, our findings have direct applications in gravitational wave searches, kilonova interpretations and multi-messenger constraints on NS properties.
Comments:
Accepted for publication in Phys. Rev. Lett.; 14 pages, 5 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.00846 [pdf]
PRL(2020)·144 citations
07
[Submitted on 31 Mar 2020] (cross-list from astro-ph.HE)
Crucial role of neutron diffusion in the crust of accreting neutron stars
Andrey Chugunov · Nikolay Shchechilin
Observed temperatures of transiently accreting neutron stars in the quiescent state are generally believed to be supported by deep crustal heating, associated with non-equilibrium exothermic reactions in the crust. Traditionally, these reactions are studied by considering nuclear evolution governed by compression of the accreted matter. Here we show that this approach has a basic weakness, that is that in some regions of the inner crust the conservative forces, applied for matter components (nuclei and neutrons), are not in mechanical equilibrium. In principle the force balance can be restored by dissipative forces, however the required diffusion fluxes are of the same order as total baryon flux at Eddington accretion. We argue that redistribution of neutrons in the inner crust should be involved in realistic model of accreted crust.
Comments:
Accepted for publication in MNRAS:Letters, 6 pages, 1 figure
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2004.00997 [pdf]
MNRAS(2020)·12 citations
08
[Submitted on 1 Apr 2020] (cross-list from hep-ph)
Quark model relations for b-baryon decay
Jerrold Franklin🇺🇸
Properties of b-baryon decay matrix elements (amplitudes) have been derived in a nonsymmetric quark model without any use of SU(6), SU(3), or SU(2) (isotopic spin) groups. Equalities between pairs of amplitudes are derived, and $Λ - Σ$ mixing is used to calculate the branching ratio for the transition $Λ_{b} \to Σ^{0}$ .
Comments:
The derivation has been simplified
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2004.01037 [pdf]
J.Phys.G(2020)·3 citations
09
[Submitted on 2 Apr 2020] (cross-list from nucl-ex)
New estimator for symmetry plane correlations in anisotropic flow analyses
Ante Bilandzic🇩🇪 · Marcel Lesch🇩🇪 · Seyed Farid Taghavi🇩🇪
Correlations of symmetry planes are important observables used to quantify anisotropic flow phenomenon and constrain independently the properties of strongly interacting nuclear matter produced in the collisions of heavy ions at the highest energies. In this paper, we point out current problems of measuring correlations between symmetry planes and elaborate on why the available analysis techniques have a large systematic bias. To overcome this problem, we introduce a new approach to approximate multi-harmonic flow fluctuations via a two-dimensional Gaussian distribution. Employing this approximation, we introduce a new estimator, dubbed Gaussian Estimator (GE), to extract pure correlation between symmetry planes. We validate GE by using the realistic event-generator iEBE-VISHNU and demonstrate that it outperforms all existing estimators. Based on event-shape engineering, we propose an experimental procedure to improve GE accuracy even further.
Comments:
14 pages, 4 figures. v2: minor revision, v2 submitted to journal
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.01066 [pdf]
PRC(2020)·17 citations
10
[Submitted on 2 Apr 2020] (cross-list from hep-ph)
QCD Phase Diagram at NICA energies: $K^{+} / π^{+}$ horn effect and light clusters in THESEUS
D. Blaschke🇷🇺 · A.V. Friesen🇷🇺 · Yu.B. Ivanov🇷🇺 · Yu.L. Kalinovsky🇷🇺 · M. Kozhevnikova🇷🇺 · S. Liebing🇷🇺 · A. Radzhabov🇷🇺 · G. Röpke🇷🇺
We discuss recent progress in the development of the three-fluid hydrodynamics-based program THESEUS towards an event generator suitable for applications to heavy-ion collisions at the intermediate energies of the planned NICA and FAIR experiments. We follow the strategy that modifications of particle distributions at the freeze-out surface in the QCD phase diagram may be mapped directly to the observable ones within a sudden freeze-out scheme. We report first results of these investigations for the production of light clusters (deuterons and tritons) which can be compared to experimental data from the HADES and the NA49 experiment and for the interpretation of the "horn" effect observed in the collision energy dependence of the $K^{+} / π^{+}$ ratio. Medium effects on light cluster production in the QCD phase diagram are negligible at the highest NICA energies but shall play a dominant role at the lowest energies. A sharp "horn"-type signal in the $K^{+} / π^{+}$ ratio can be obtained when the onset of Bose condensation modelled by a pion chemical potential results in an enhancement of pions at low momenta (which is seen at LHC energies) and would occur already in the NICA energy range.
Comments:
5 pages, 3 figures, 3 references added, contribution to the Proceedings of "III NICA Days-2019 and IV MPD Collaboration Meeting", Warsaw, 21.-25.10.2019
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.01159 [pdf]
Acta Phys.Polon.Supp.(2021)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE