Nuclear Theory·nucl-th

Wednesday·December 23, 2015

17 papers—8 primary·9 cross-listed

09
[Submitted on 12 Dec 2015] (cross-list from hep-ph)
Gluonic Structure of the Constituent Quark
Nikolai Kochelev🇷🇺 · Hee-Jung Lee🇰🇷 · Baiyang Zhang🇨🇳 · Pengming Zhang🇨🇳
Based on both the constituent quark picture and the instanton model for QCD vacuum, we calculate the unpolarized and polarized gluon distributions in the constituent quark and in the nucleon. Our approach consists of the two main steps. At the first step, we calculate the gluon distributions inside the constituent quark generated by the perturbative quark-gluon interaction, the non-perturbative quark-gluon interaction, and the non-perturbative quark-gluon-pion anomalous chromomagnetic interaction. The non-perturbative interactions are related to the existence of the instantons, strong topological fluctuations of gluon fields, in the QCD vacuum. At the second step, the convolution model is applied to derive the gluon distributions in the nucleon. A very important role of the pion field in producing the unpolarized and the polarized gluon distributions in the hadrons is discovered. We discuss a possible solution of the proton spin problem.
Comments:
6 pages, 5 figures, references added, discussion extended
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1512.03863 [pdf]
PLB(2016)·11 citations
10
[Submitted on 18 Dec 2015] (cross-list from hep-ph)
Multipole decomposition of the nucleon transverse phase space
C. Lorcé (Ecole Polytechnique, CPHT)🇫🇷 · B. Pasquini (Pavia U. & INFN, Pavia)🇮🇹
We present a complete study of the leading-twist quark Wigner distributions in the nucleon, discussing both the $T$ -even and $T$ -odd sector, along with all the possible configurations of the quark and nucleon polarizations. We identify the basic multipole structures associated with each distribution in the transverse phase space, providing a transparent interpretation of the spin-spin and spin-orbit correlations of quarks and nucleon encoded in these functions. Projecting the multipole parametrization of the Wigner functions onto the transverse-position and the transverse-momentum spaces, we find a natural link with the corresponding multipole parametrizations for the generalized parton distributions and transverse-momentum dependent parton distributions, respectively. Finally, we show results for all the distributions in the transverse phase space, introducing a representation that allows one to visualize simultaneously the multipole structures in both the transverse-position and transverse-momentum spaces.
Comments:
22 pages, 12 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1512.06744 [pdf]
PRD(2016)·41 citations
11
[Submitted on 21 Dec 2015] (cross-list from hep-ph)
Jet fragmentation functions in proton-proton collisions using soft-collinear effective theory
Yang-Ting Chien🇺🇸 · Zhong-Bo Kang🇺🇸 · Felix Ringer🇺🇸 · Ivan Vitev🇺🇸 · Hongxi Xing🇺🇸
The jet fragmentation function describes the longitudinal momentum distribution of hadrons inside a reconstructed jet. We study the jet fragmentation function in proton-proton collisions in the framework of soft-collinear effective theory (SCET). We find that, up to power corrections, the jet fragmentation function can be expressed as the ratio of the fragmenting jet function and the unmeasured jet function. Using renormalization group techniques, we are able to resum large logarithms of jet radii R in the perturbative expansion of the cross section. We use our theoretical formalism to describe the jet fragmentation functions for light hadron and heavy meson production measured at the Large Hadron Collider (LHC). Our calculations agree very well with the experimental data for the light hadron production. On the other hand, although our calculations for the heavy meson production inside jets are consistent with the PYTHIA simulation, they fail to describe the LHC data. We find that the jet fragmentation function for heavy meson production is very sensitive to the gluon-to-heavy-meson fragmentation function.
Comments:
26 pages, 7 figures, published version at JHEP
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1512.06851 [pdf]
JHEP(2016)·75 citations
12
[Submitted on 21 Dec 2015] (cross-list from nucl-ex)
Precise measurement of alpha_K and alpha_T for the 150.8-keV E3 transition in 111Cd: Test of internal-conversion theory
N. Nica · J.C. Hardy · V.E. Iacob · T.A. Werke · C.M. Folden III · L. Pineda · M.B. Trzhaskovskaya
We have measured the K-shell and total internal conversion coefficients, alpha_K and alpha_T, for the 150.8-keV E3 transition in 111Cd to be 1.449(18) and 2.217(26) respectively. The alpha_K result agrees well with Dirac-Fock calculations in which the effect of the K-shell atomic vacancy is accounted for; it extends our precision tests of alpha_K calculations to Z = 48, the lowest Z yet measured. However, the result for alpha_T disagrees by about two standard deviations from the calculated alpha_T value, whether or not the atomic vacancy is included.
Comments:
7 pages, two figures. arXiv admin note: text overlap with arXiv:1312.3883
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1512.06898 [pdf]
PRC(2016)·8 citations
13
[Submitted on 21 Dec 2015] (cross-list from hep-ph)
The quark susceptibility in a generalized dynamical quasiparticle model
Hamza Berrehrah🇩🇪 · Wolfgang Cassing🇩🇪 · Elena Bratkovskaya🇩🇪 · Thorsten Steinert🇩🇪
The quark susceptibility $χ_{q}$ at zero and finite quark chemical potential provides a critical benchmark to determine the quark-gluon-plasma (QGP) degrees of freedom in relation to the results from lattice QCD (lQCD) in addition to the equation of state and transport coefficients. Here we extend the familiar dynamical-quasiparticle model (DQPM) to partonic propagators that explicitly depend on the three-momentum with respect to the partonic medium at rest in order to match perturbative QCD (pQCD) at high momenta. Within the extended dynamical-quasi-particle model (DQPM $^{*}$ ) we reproduce simultaneously the lQCD results for the quark number density and susceptibility and the QGP pressure at zero and finite (but small) chemical potential $μ_{q}$ . The shear viscosity $η$ and the electric conductivity $σ_{e}$ from the extended quasiparticle model (DQPM $^{*}$ ) also turn out in close agreement with lattice results for $μ_{q}$ =0. The DQPM $^{*}$ , furthermore, allows to evaluate the momentum $p$ , temperature $T$ and chemical potential $μ_{q}$ dependencies of the partonic degrees of freedom also for larger $μ_{q}$ which are mandatory for transport studies of heavy-ion collisions in the regime 5 GeV $< s_{N N} <$ 10 GeV.
Comments:
12 pages, 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1512.06909 [pdf]
PRC(2016)·28 citations
14
[Submitted on 22 Dec 2015] (cross-list from nucl-ex)
Statistical model analysis of hadron yields in proton-nucleus and heavy-ion collisions at SIS 18 energies
G. Agakishiev🇷🇺 · O. Arnold🇩🇪 · A. Balanda🇵🇱 · D. Belver🇪🇸 · A. Belyaev🇷🇺 · J. C. Berger-Chen🇩🇪 · A. Blanco🇵🇹 · M. Böhmer🇩🇪 · J. L. Boyard🇫🇷 · P. Cabanelas🇪🇸 · E. Castro🇪🇸 · S. Chernenko🇷🇺 and 98 other authors
The HADES data from p+Nb collisions at center of mass energy of $s_{N N}$ = 3.2 GeV are analyzed by employing a statistical model. Accounting for the identified hadrons $π^{0}$ , $η$ , $Λ$ , $K_{s}^{0}$ , $ω$ allows a surprisingly good description of their abundances with parameters $T_{c h e m} = (99 \pm 11)$ MeV and $μ_{b} = (619 \pm 34)$ MeV, which fits well in the chemical freeze-out systematics found in heavy-ion collisions. In supplement we reanalyze our previous HADES data from Ar+KCl collisions at $s_{N N}$ = 2.6 GeV with an updated version of the statistical model. We address equilibration in heavy-ion collisions by testing two aspects: the description of yields and the regularity of freeze-out parameters from a statistical model fit. Special emphasis is put on feed-down contributions from higher-lying resonance states which have been proposed to explain the experimentally observed $Ξ^{-}$ excess present in both data samples.
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1512.07070 [pdf]
EPJA(2016)·73 citations
15
[Submitted on 22 Dec 2015] (cross-list from hep-ph)
Sudakov Resummations in Mueller-Navelet Dijet Production
A. H. Mueller🇺🇸 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷 · Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸
In high energy hadron-hadron collisions, dijet production with large rapidity separation proposed by Mueller and Navelet, is one of the most interesting processes which can help us to directly access the well-known Balitsky-Fadin-Kuraev-Lipatov evolution dynamics. The objective of this work is to study the Sudakov resummation of Mueller-Navelet jets. Through the one-loop calculation, Sudakov type logarithms are obtained for this process when the produced dijets are almost back-to-back. These results could play an important role in the phenomenological study of dijet correlations with large rapidity separation at the LHC.
Comments:
20 pages, 5 figures; v2, refs added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1512.07127 [pdf]
JHEP(2016)·55 citations
16
[Submitted on 22 Dec 2015] (cross-list from hep-ph)
Initial state azimuthal anisotropies in small collision systems
T. Lappi🇫🇮
Strong multiparticle azimuthal correlations have recently been observed in high energy proton-nucleus collisions. While final state collective effects can be responsible for many of the observations, the domain structure in the classical color field of a high energy nucleus also naturally leads to such correlations. We describe recent calculations of the momentum space 2-particle cumulant azimuthal anisotropy coefficients v_n{2}, n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. We find significant differences between Wilson lines from the MV model and from JIMWLK evolution. We also discuss the relation of this calculation to earlier work on the ridge correlation obtained in the "glasma graph" approximation, and to the "color electric field domain model."
Comments:
4 pages, 1 figure. Talk at the Quark Matter 2015 conference, September 27 - October 3, 2015, Kobe, Japan
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1512.07209 [pdf]
NPA(2016)·3 citations
17
[Submitted on 22 Dec 2015] (cross-list from hep-lat)
Charge transport and vector meson dissociation across the thermal phase transition in lattice QCD with two light quark flavors
Bastian B. Brandt🇩🇪 · Anthony Francis🇨🇦 · Benjamin Jaeger🇬🇧 · Harvey B. Meyer🇩🇪
We compute and analyze correlation functions in the isovector vector channel at vanishing spatial momentum across the deconfinement phase transition in lattice QCD. The simulations are carried out at temperatures $T / T_{c} = 0.156, 0.8, 1.0, 1.25$ and $1.67$ with $T_{c} ≃ 203$ MeV for two flavors of Wilson-Clover fermions with a zero-temperature pion mass of $≃ 270$ MeV. Exploiting exact sum rules and applying a phenomenologically motivated ansatz allows us to determine the spectral function $ρ (ω, T)$ via a fit to the lattice correlation function data. From these results we estimate the electrical conductivity across the deconfinement phase transition via a Kubo formula and find evidence for the dissociation of the $ρ$ meson by resolving its spectral weight at the available temperatures. We also apply the Backus-Gilbert method as a model-independent approach to this problem. At any given frequency, it yields a local weighted average of the true spectral function. We use this method to compare kinetic theory predictions and previously published phenomenological spectral functions to our lattice study.
Comments:
28 pages, 6 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1512.07249 [pdf]
PRD(2016)·94 citations

Affiliations

first authorsco-authorsvia INSPIRE