Nuclear Theory·nucl-th

Monday·November 5, 2018

9 papers—5 primary·4 cross-listed

01
Evolution of higher moments of multiplicity distribution
Radka Sochorova🇨🇿 · Boris Tomasik🇸🇰
Evolution of a multiplicity distribution can be described with the help of master equation. We first look at 3rd and 4th factorial moments of multiplicity distributions and derive their equilibrium values. From them central moments and other ratios can be calculated. We study the master equation for a fixed temperature, because we want to know how fast different moments of the multiplicity distribution approach their equilibrium value. Then we investigate the situation in which the temperature of the system decreases. We find out that in the non-equilibrium state, higher factorial moments differ more from their equilibrium values than the lower moments and that the behaviour of a combination of the central moments depends on the combination we choose.
nucl-thhep-phnucl-exPoS(2019)·0 citations
02
Kurtosis of elliptic flow fluctuations
Rajeev S. Bhalerao🇮🇳 · Giuliano Giacalone🇫🇷 · Jean-Yves Ollitrault🇫🇷
Elliptic flow ( $v_{2}$ ) in ultrarelativistic nucleus-nucleus collisions fluctuates event to event, both in magnitude and in orientation with respect to the reaction plane. Even though the reaction plane is not known event to event in experiment, we show that the statistical properties of $v_{2}$ fluctuations in the reaction plane can be precisely extracted from experimental data. Previous studies have shown how to measure the mean, variance and skewness using the first three cumulants $v_{2} {2}$ , $v_{2} {4}$ and $v_{2} {6}$ . We complement these studies by providing a formula for the kurtosis, which requires an accurate determination of the next cumulant $v_{2} {8}$ . Using existing data, we show that the kurtosis is positive for most centralities, in contrast with the kurtosis of triangular flow fluctuations, which is negative. We argue that these features are robust predictions of fluid-dynamical models.
nucl-thhep-phnucl-exPRC(2019)·24 citations
03
Effect of a realistic three-body force on the spectra of medium-mass hypernuclei
Petr Vesely🇨🇿 · Giovanni De Gregorio🇨🇿 · Jan Pokorny🇨🇿
We adopt the Hartree-Fock (HF) method in the proton-neutron- $Λ$ (p-n- $Λ$ ) formalism and the nucleon- $Λ$ Tamm-Dancoff Approximation (N $Λ$ TDA) to study the energy spectra of medium-mass hypernuclei. The formalism is developed for a potential derived from effective field theories which includes explicitly the 3-body $N N N$ forces plus the $Y N$ LO potential. The energy spectra of selected medium-mass hypernuclei are presented and their properties discussed. The present calculation is the first step of a project devoted to {\it ab initio} studies of hypernuclei in medium and heavy mass regions. This may provide a guide for a better understanding of the $Y N$ interactions at momentum scales not accessible in few-body hypernuclei.
nucl-thPhys.Scripta(2019)·4 citations
04
Singularities in Twist-3 Quark Distributions
Fatma Aslan🇺🇸 · Matthias Burkardt🇺🇸
We find in one-loop calculations and spectator models that twist-3 GPDs exhibit discontinuities. In the forward limit these discontinuities grow into Dirac delta functions which are essential to satisfy the sum rules involving twist-3 PDFs. We calculate twist-3 quasi-PDFs as a function of longitudinal momentum and identify the Dirac delta function terms with momentum components in the nucleon state that do not scale as the nucleon is boosted to the infinite momentum frame.
nucl-thhep-phPRD(2020)·32 citations
05
Anti-bubble effect of temperature \& deformation: a systematic study for nuclei across all mass regions between A $=$ 20 $-$ 300
G. Saxena · M. Kumawat · Mamta Aggarwal
Temperature dependent relativistic mean-field (RMF) plus BCS approach has been used for the first time to investigate the anti-bubble effect of the temperature and deformation in the light, medium-heavy and superheavy nuclei. Influence of temperature is studied on density distribution, charge form-factor, single particle (s.p.) energies, occupancy, deformation and the depletion fraction (DF). At T $=$ 0, the quenching effect of deformation is predominant. DF is found usually less in oblate deformation than in prolate. DF decreases with increasing prolate deformation even though the 2s-orbit is empty which shows the role of deformation in central depletion apart from the unoccupancy in s-orbit as is usually believed. As T increases, the occupancy of s-orbit increases, shell structure melts, the deformation vanishes and the weakening of central depletion is solely due to the temperature. The bubble effect is eliminated at T $\approx$ 3 $-$ 5 MeV as indicated by DF and the charge form factor. The temperature effect is found less prominent in superheavy bubble nuclei where the role of shell effects is indicated.
nucl-thnucl-exPLB(2019)·19 citations
06
Determining the Nonperturbative Collins-Soper Kernel From Lattice QCD
Markus A. Ebert🇺🇸 · Iain W. Stewart🇺🇸 · Yong Zhao🇺🇸
At small transverse momentum $q_{T}$ , transverse-momentum dependent parton distribution functions (TMDPDFs) arise as genuinely nonperturbative objects that describe Drell-Yan like processes in hadron collisions as well as semi-inclusive deep-inelastic scattering. TMDPDFs naturally depend on the hadron momentum, and the associated evolution is determined by the Collins-Soper equation. For $q_{T} \sim Λ_{QCD}$ the corresponding evolution kernel (or anomalous dimension) is nonperturbative and must be determined as an independent ingredient in order to relate TMDPDFs at different scales. We propose a method to extract this kernel using lattice QCD and the Large-Momentum Effective Theory, where the physical TMD correlation involving light-like paths is approximated by a quasi TMDPDF, defined using equal-time correlation functions with a large-momentum hadron state. The kernel is determined from a ratio of quasi TMDPDFs extracted at different hadron momenta.
↳ hep-phhep-latnucl-thPRD(2019)·129 citations
07
Hyperonic stars and the symmetry energy
Constança Providência🇵🇹 · Morgan Fortin🇵🇱 · Helena Pais🇵🇹 · Aziz Rabhi🇺🇸
In the present study we analyse the effect of the density dependence of the symmetry energy on the hyperonic content of neutron stars within a relativistic mean field description of stellar matter. For the $Λ$ -hyperon, we consider parametrizations calibrated to $Λ$ -hypernuclei. For the $Σ$ and $Ξ$ -hyperons uncertainties that reflect the present lack of experimental information on $Σ$ and $Ξ$ -hypernuclei are taken into account. We perform our study considering nuclear equations of state that predict two solar mass stars, and satisfy other well settled nuclear matter properties. The effect of the presence of hyperons on the radius, the direct Urca processes, and the cooling of accreting neutron stars are discussed. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. The density dependence of the symmetry energy affects the order of appearance of the different hyperons, which may have direct implications on the neutron star cooling as different hyperonic neutrino processes processes may operate at the center of massive stars. For models which allow for the direct Urca process to operate, hyperonic and purely nucleonic ones are shown to have a similar luminosity when hyperons are included in agreement with modern experimental data. It is shown that for a density dependent hadronic model constrained by experimental, theoretical and observational data, the low-luminosity of SAX J $1808.4 - 3658$ can only be modelled for a hyperonic NS, suggesting that hyperons could be present in its core.
↳ astro-ph.HEnucl-thFront. Astron. Space Sci., 26 March 2019·62 citations
08
Constituent quark number scaling from strange hadron spectra in $pp$ collisions at $s =$ 13 TeV
Jian-wei Zhang🇨🇳 · Hai-hong Li🇨🇳 · Feng-lan Shao🇨🇳 · Jun Song🇨🇳
We show that the data of $p_{T}$ spectra of $Ω^{-}$ and $ϕ$ at midrapidity in inelastic events in $pp$ collisions at $s =$ 13 TeV exhibit a constituent quark number scaling property, which is a clear signal of quark combination mechanism at hadronization. We use a quark combination model under equal velocity combination approximation to systematically study the production of identified hadrons in $pp$ collisions at $s$ = 13 TeV. The midrapidity data of $p_{T}$ spectra of proton, $Λ$ , $Ξ^{-}$ , $Ω^{-}$ , $ϕ$ and $K^{*}$ in inelastic events are simultaneously well fitted by the model. The data of multiplicity dependency of yields of these hadrons are also well understood. The strong $p_{T}$ dependence for data of $p / ϕ$ ratio is well explained by the model, which further suggests that the production of two hadrons with similar masses is determined by their quark contents at hadronization. $p_{T}$ spectra of strange hadrons at midrapidity in different multiplicity classes in $pp$ collisions at $s =$ 13 TeV are predicted to further test the model in the future. The midrapidity $p_{T}$ spectra of soft ( $p_{T} < 2$ GeV/c) strange quark and up/down quark at hadronization in $pp$ collisions at $s =$ 13 TeV are extracted.
↳ hep-phnucl-thCPC(2020)·12 citations
09
Quark mass function from a one-gluon-exchange-type interaction in Minkowski space
Elmar P. Biernat🇵🇹 · Franz Gross🇺🇸 · M. T Peña🇵🇹 · Alfred Stadler🇵🇹 · Sofia Leitão🇵🇹
We present first results for the quark mass function in Minkowski space in both the spacelike and timelike regions calculated from the same quark-antiquark interaction kernel used in the latest meson calculations using the Gross equation. This kernel consists of a Lorentz vector effective one-gluon-exchange-type interaction, a vector constant, and a mixed scalar-pseudoscalar covariant linear confining interaction that does not contribute to the mass function. We analyze the gauge dependence of our results, prove the gauge independence of the constituent quark mass and mass gap equation, and identify the Yennie gauge as the appropriate gauge to be used in CST calculations. We compare our results in the spacelike region to lattice QCD data and find good agreement.
↳ hep-phnucl-thPRD(2018)·17 citations

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first authorsco-authorsvia INSPIRE