Nuclear Theory·nucl-th

Wednesday·August 8, 2018

9 papers—4 primary·5 cross-listed

05
[Submitted on 6 Aug 2018] (cross-list from hep-lat)
Gluon Quasi-PDF From Lattice QCD
Zhou-You Fan🇺🇸 · Yi-Bo Yang🇺🇸 · Adam Anthony🇺🇸 · Huey-Wen Lin🇺🇸 · Keh-Fei Liu🇺🇸
We present the first attempt to access the $x$ -dependence of the gluon unpolarized parton distribution function (PDF), based on lattice simulations using the large-momentum effective theory (LaMET) approach. The lattice calculation is carried out with pion masses of 340 and 678 MeV on a 2+1-flavor DWF configuration with lattice spacing $a = 0.111$ ~fm, for the gluon quasi-PDF matrix element with the nucleon momentum up to 0.93 GeV. Taking the normalization from similar matrix elements in the rest frame of the nucleon and pion, our results for these matrix elements are consistent with the Fourier transform of the global fit CT14 and PDF4LHC15 NNLO of the gluon PDF, within statistical uncertainty and the systematic one up to power corrections, perturbative $O (α_{s})$ matching and the mixing from the quark PDFs.
Comments:
5 pages, 5 figures, the version accepted by PRL
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.02077 [pdf]
PRL(2018)·107 citations
06
[Submitted on 6 Aug 2018] (cross-list from hep-ph)
Impact of unitarization on the $J / ψ$ -light meson cross section
L. M. Abreu🇧🇷 · E. Cavalcanti🇧🇷 · A. P. C. Malbouisson🇧🇷
Hidden charm mesons continue playing an essential role as relevant probes to understand the evolution of partonic matter. It is expected that the charmonia that survived the quark-gluon plasma phase suffer collisions with other particles composing the hadronic matter. In this work, we intend to contribute on this subject by presenting an updated study about the interactions of $J / ψ$ with surrounding hadronic medium. The meson-meson interactions are described with a $S U (4)$ effective Lagrangian, and within the framework of unitarized coupled channel amplitudes projected onto s-wave. The symmetry is explicitly broken to $S U (3)$ by suppression of the interactions driven by charmed mesons. We calculate the cross sections for $J / ψ$ scattering by light pseudoscalar mesons ( $π, K, η$ ) and vector mesons ( $ρ, K^{*}, ω$ ), as well as their inverse processes. Keeping the validity of this present approach in the low CM energy range, the most relevant channels are evaluated and a comparison of the findings with existing literature is performed.
Comments:
21 pages, 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.02115 [pdf]
NPA(2018)·3 citations
07
[Submitted on 7 Aug 2018] (cross-list from nucl-ex)
Studies of the Giant Dipole Resonance in $^{27}$ Al, $^{40}$ Ca, $^{56}$ Fe, $^{58}$ Ni and $^{208}$ Pb with high energy-resolution inelastic proton scattering under 0 $^{\circ}$
M. Jingo (1,2) · E.Z. Buthelezi (3) · J. Carter (1) · G.R.J. Cooper (4) · R.W. Fearick (5) · S.V. Förtsch (3) · C.O. Kureba (1) · A.M. Krumbholz (6) · P. von Neumann-Cosel (6) · R. Neveling (3) · P. Papka (7) · I. Poltoratska (6) and 7 other authors
A survey of the fine structure of the Isovector Giant Dipole Resonance (IVGDR) was performed, using the recently commissioned zero-degree facility of the K600 magnetic spectrometer at iThemba LABS. Inelastic proton scattering at an incident energy of 200 MeV was measured on $^{27}$ Al, $^{40}$ Ca, $^{56}$ Fe, $^{58}$ Ni and $^{208}$ Pb. A high energy resolution ( $Δ E ≃$ 40 keV FWHM) could be achieved after utilising faint-beam and dispersion-matching techniques. Considerable fine structure is observed in the energy region of the IVGDR and characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The comparison with Quasiparticle-Phonon Model (QPM) calculations provides insight into the relevance of different giant resonance decay mechanisms. Photoabsorption cross sections derived from the data assuming dominance of relativistic Coulomb excitation are in fair agreement with previous work using real photons.
Comments:
15 pages, 15 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1808.02282 [pdf]
EPJA(2018)·16 citations
08
[Submitted on 7 Aug 2018] (cross-list from astro-ph.HE)
Using Steady State Behavior to Assess Treatments of Nuclear Isomers in Astrophysical Environments
G. Wendell Misch🇨🇳 · Surja K. Ghorui🇨🇳 · Yang Sun🇨🇳
Differing reaction rates of long-lived nuclear states can force the level occupations out of thermal equilibrium, causing calculations of overall rates which rely on thermal equilibrium to be inaccurate. Therefore, nucleosynthesis calculations which include nuclei with isomers must use techniques that do not assume thermal equilibrium, and it is imperative that such techniques appropriately account for transitions between the ground and isomeric states via higher-lying levels. We develop a formalism to compute the steady state occupations of nuclear levels and apply it to the examples 26Al, 34Cl, and 85Kr. We show that this approach is useful both for assessing the required number of nuclear levels and for determining the temperature above which thermal equilibrium rates are appropriate.
Comments:
11 pages, 11 figures, 1 table
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1808.02304 [pdf]
2 citations
09
[Submitted on 6 Aug 2018] (cross-list from hep-ph)
Radial Flow and Differential Freeze-out in Proton-Proton Collisions at $s = 7$ TeV at the LHC
Arvind Khuntia🇮🇳 · Himanshu Sharma🇮🇳 · Swatantra Kumar Tiwari🇮🇳 · Raghunath Sahoo🇮🇳 · Jean Cleymans🇿🇦
We analyse the transverse momentum ( $p_{T}$ )-spectra as a function of charged-particle multiplicity at midrapidity ( $∣ y ∣ < 0.5$ ) for various identified particles such as $π^{\pm}$ , $K^{\pm}$ , $K_{S}^{0}$ , $p + p$ , $ϕ$ , $K^{* 0} + K^{* 0}$ , and $Λ$ + $Λ ˉ$ in proton-proton collisions at $s$ = 7 TeV using Boltzmann-Gibbs Blast Wave (BGBW) model and thermodynamically consistent Tsallis distribution function. We obtain the multiplicity dependent kinetic freeze-out temperature ( $T_{kin}$ ) and radial flow ( $β$ ) of various particles after fitting the $p_{T}$ -distribution with BGBW model. Here, $T_{kin}$ exhibits mild dependence on multiplicity class while $β$ shows almost independent behaviour. The information regarding Tsallis temperature and the non-extensivity parameter ( $q$ ) are drawn by fitting the $p_{T}$ -spectra with Tsallis distribution function. The extracted parameters of these particles are studied as a function of charged particle multiplicity density ( $d N_{c h} / d η$ ). In addition to this, we also study these parameters as a function of particle mass to observe any possible mass ordering. All the identified hadrons show a mass ordering in temperature, non-extensive parameter and also a strong dependence on multiplicity classes, except the lighter particles. It is observed that as the particle multiplicity increases, the $q$ -parameter approaches to Boltzmann-Gibbs value, hence a conclusion can be drawn that system tends to thermal equilibrium. The observations are consistent with a differential freeze-out scenario of the produced particles.
Comments:
Published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1808.02383 [pdf]
EPJA(2019)·48 citations

Affiliations

first authorsco-authorsvia INSPIRE

Gluon Quasi-PDF From Lattice QCD

Impact of unitarization on the J/ψ-light meson cross section

Studies of the Giant Dipole Resonance in 27Al, 40Ca, 56Fe, 58Ni and 208Pb with high energy-resolution inelastic proton scattering under 0∘

Using Steady State Behavior to Assess Treatments of Nuclear Isomers in Astrophysical Environments

Radial Flow and Differential Freeze-out in Proton-Proton Collisions at s​=7 TeV at the LHC

Affiliations

Impact of unitarization on the $J / ψ$ -light meson cross section

Studies of the Giant Dipole Resonance in $^{27}$ Al, $^{40}$ Ca, $^{56}$ Fe, $^{58}$ Ni and $^{208}$ Pb with high energy-resolution inelastic proton scattering under 0 $^{\circ}$

Radial Flow and Differential Freeze-out in Proton-Proton Collisions at $s = 7$ TeV at the LHC