Nuclear Theory·nucl-th

Monday·September 26, 2016

8 papers—4 primary·4 cross-listed

01
[Submitted on 23 Sept 2016]
Electromagnetic transitions in multiple chiral doublet bands
Hui Jia · Bin Qi · Shou-Yu Wang · Shuo Wang · Chen Liu
Multiple chiral doublet bands (M $χ$ D) in the $80$ , 130 and $190$ mass regions are studied by the model of $γ$ =90 $^{\circ}$ triaxial rotor coupled with identical symmetric proton-neutron configurations. By selecting the suitable basis, the calculated wave functions are explicitly exhibited to be symmetric under the operator $A^$ , which is defined as rotation by $9 0^{\circ}$ about 3-axis with the exchange of valance proton and neutron. We found that both $M 1$ and $E 2$ transitions are allowed between the levels with different values of $A$ , while are forbidden between the levels with same values of $A$ . Such a selection rule holds true for M $χ$ D in different mass regions.
Comments:
16 pages, 3 figures in Chinese Physics C 2016
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.07260 [pdf]
CPC(2016)·9 citations
02
[Submitted on 23 Sept 2016]
Applicability of pion-nucleus Drell-Yan data in global analysis of nuclear parton distribution functions
Petja Paakkinen🇫🇮 · Kari J. Eskola🇫🇮 · Hannu Paukkunen🇫🇮
Despite the success of modern nuclear parton distribution functions (nPDFs) in describing nuclear hard-process data, they still suffer from large uncertainties. One of the poorly constrained features is the possible asymmetry in nuclear modifications of valence $u$ and $d$ quarks. We study the possibility of using pion-nucleus Drell-Yan dilepton data as a new constraint in the global analysis of nPDFs. We find that the nuclear cross-section ratios from the NA3, NA10 and E615 experiments can be used without imposing significant new theoretical uncertainties and, in particular, that these datasets may have some constraining power on the $u$ / $d$ -asymmetry in nuclei.
Comments:
6 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1609.07262 [pdf]
PLB(2017)·13 citations
03
[Submitted on 23 Sept 2016]
Sensitivity of (d,p) reactions to high n-p momenta and the consequences for nuclear spectroscopy studies
G.W. Bailey · N.K. Timofeyuk · J.A. Tostevin
Theoretical models of low-energy (d,p) single-neutron transfer reactions are a crucial link between experimentation, nuclear structure and nuclear astrophysical studies. Whereas reaction models that use local optical potentials are insensitive to short-range physics in the deuteron, we show that including the inherent nonlocality of the nucleon-target interactions and realistic deuteron wave functions generates significant sensitivity to high n-p relative momenta and to the underlying nucleon-nucleon interaction. We quantify this effect upon the deuteron channel distorting potentials within the framework of the adiabatic deuteron breakup model. The implications for calculated (d,p) cross sections and spectroscopic information deduced from experiments are discussed.
Comments:
5 pages, accepted for publication by Phys. Rev. Lett
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1609.07303 [pdf]
PRL(2016)·26 citations
04
[Submitted on 23 Sept 2016]
Shear viscosity of nuclear matter
A.G. Magner · M.I. Gorenstein · U.V. Grygoriev · V.A. Plujko
Shear viscosity $η$ is calculated for the nuclear matter described as a system of interacting nucleons with the van der Waals (VDW) equation of state. The Boltzmann-Vlasov kinetic equation is solved in terms of the plane waves of the collective overdamped motion. In the frequent-collision regime, the shear viscosity depends on the particle-number density $n$ through the mean-field parameter $a$ , which describes attractive forces in the VDW equation. In the temperature region $T = 15 - 40$ ~MeV, a ratio of the shear viscosity to the entropy density $s$ is smaller than 1 at the nucleon number density $n = (0.5 - 1.5) n_{0}$ , where $n_{0} = 0.16$ fm $^{- 3}$ is the particle density of equilibrium nuclear matter at zero temperature. A minimum of the $η / s$ ratio takes place somewhere in a vicinity of the critical point of the VDW system. Large values of $η / s ≫ 1$ are, however, found in both the low-density, $n ≪ n_{0}$ , and high-density, $n > 2 n_{0}$ , regions. This makes the ideal hydrodynamic approach inapplicable for these densities.
Comments:
12 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.07453 [pdf]
PRC(2016)·2 citations
05
[Submitted on 22 Sept 2016] (cross-list from hep-ph)
Initial energy density of $s =$ 7 and 8 TeV p+p collisions at the LHC
Mate Csanad🇭🇺 · Tamas Csorgo🇭🇺 · Ze-Fang Jiang🇨🇳 · Chun-Bin Yan🇭🇺
Results from the RHIC and LHC experiments show, that in relativistic heavy ion collisions, a new state of matter, a strongly interacting perfect fluid is created. Accelerating, exact and explicit solutions of relativistic hydrodynamics allow for a simple and natural description of this medium. A finite rapidity distribution arises from these solutions, leading to an advanced estimate of the initial energy density of high energy collisions. These solutions can be utilized to describe various aspects of proton-proton collisions, as originally suggested by Landau. We show that an advanced estimate based on hydrodynamics yields an initial energy density in $s = 7$ and 8 TeV p+p collisions at LHC on the same order as the critical energy density from lattice QCD, and a corresponding initial temperature around the critical temperature from QCD and the Hagedorn temperature. The multiplicity dependence of the estimated initial energy density suggests that in high multiplicity pp collisions at the LHC, there is large enough initial energy density to create a non-hadronic perfect fluid.
Comments:
18 pages, 4 figures. Accepted for publication in the Special Issue "Quark-Gluon Plasma in the Early Universe and in Ultra-Relativistic Heavy-Ion Collisions" of Universe (ISSN 2218-1997)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.07176 [pdf]
Universe(2017)·32 citations
06
[Submitted on 23 Sept 2016] (cross-list from hep-ph)
Holographic Photon Production in Heavy Ion Collisions
Ioannis Iatrakis🇳🇱 · Elias Kiritsis🇫🇷 · Chun Shen🇨🇦 · Di-Lun Yang🇯🇵
The thermal-photon emission from strongly coupled gauge theories at finite temperature is calculated using holographic models for QCD in the Veneziano limit (V-QCD). The emission rates are then embedded in hydrodynamic simulations combined with prompt photons from hard scattering and the thermal photons from hadron gas to analyze the spectra and anisotropic flow of direct photons at RHIC and LHC. The results from different sources responsible for the thermal photons in QGP including the weakly coupled QGP (wQGP) from perturbative calculations, strongly coupled $N = 4$ super Yang-Mills (SYM) plasma (as a benchmark for reference), and Gubser's phenomenological holographic model are then compared. It is found that the direct-photon spectra are enhanced in the strongly coupled scenario compared with the ones in the wQGP, especially at high momenta. Moreover, both the elliptic flow and triangular flow of direct photons are amplified at high momenta for V-QCD and the SYM plasma. The results are further compared with experimental observations.
Comments:
39 pages, 14 figures; spectra and flow updated with NLO pQCD rates; an appendix added, conclusions remained unchanged; typos corrected; journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1609.07208 [pdf]
JHEP(2017)·36 citations
07
[Submitted on 23 Sept 2016] (cross-list from hep-ph)
The effective cross section for double parton scattering within a holographic AdS/QCD approach
Marco Traini🇫🇷 · Matteo Rinaldi🇪🇸 · Sergio Scopetta🇮🇹 · Vicente Vento🇪🇸
A first attempt to apply the AdS/QCD framework for a bottom-up approach to the evaluation of the effective cross section for double parton scattering in proton-proton collisions is presented. The main goal is the analytic evaluation of the dependence of the effective cross section on the longitudinal momenta of the involved partons, obtained within the holographic Soft-Wall model. If measured in high-energy processes at hadron colliders, this momentum dependence could open a new window on 2-parton correlations in a proton.
Comments:
5 pages, 1 figure, revised version accepted for publication in Phys. Lett. B
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.07242 [pdf]
PLB(2017)·28 citations
08
[Submitted on 23 Sept 2016] (cross-list from hep-ph)
Heavy quark fragmentation functions at next-to-leading perturbative QCD
S. M. Moosavi Nejad🇮🇷 · P. Sartipi Yarahmadi🇮🇷
It is well-known that the dominant mechanism to produce hadronic bound states with large transverse momentum is fragmentation. This mechanism is described by the fragmentation functions (FFs) which are the universal and process-independent functions. Here, we review the perturbative FFs formalism as an appropriate tool for studying these hadronization processes and detail the extension of this formalism at next-to-leading order (NLO). Using the Suzuki's model, we calculate the perturbative QCD FF for a heavy quark to fragment into a S-wave heavy meson at NLO. As an example, we study the LO and NLO FFs for a charm quark to split into the S-wave $D$ -meson and compare our analytic results both with experimental data and well-known phenomenological models.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.07422 [pdf]
EPJA(2016)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE