Nuclear Theory·nucl-th

Monday·March 20, 2017

9 papers—4 primary·5 cross-listed

01
[Submitted on 16 Mar 2017]
Core-corona interplay in Pb-Pb collisions at $s_{N N}$ =2.76 TeV
M. Petrovici🇷🇴 · I. Berceanu🇷🇴 · A. Pop🇷🇴 · M. Târzilă🇷🇴 · C. Andrei🇷🇴
A simple approach based on the separation of wounded nucleons in an A-A collision in two categories, those suffering single collisions - corona and the rest - core, estimated within a Glauber Monte-Carlo approach, explains the centrality dependence of the light flavor hadrons production in Pb-Pb collisions at $s_{N N}$ =2.76 TeV. The core contribution does not include any dependence of any process on the fireball shape as a function of the impact parameter. Therefore, the ratios of the $p_{T}$ distributions to the one corresponding to the minimum bias pp collisions at the same energy, each of them normalised to the corresponding charged particle density, the $⟨ p_{T} ⟩$ and transverse energy per unit of rapidity are reproduced less accurate by such an approach. The results show that the corona contribution plays an important role also at LHC energies and it has to be considered in order to evidence the centrality dependence of different observables related to the core properties and dynamics.
Comments:
4 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1703.05805 [pdf]
PRC(2017)·13 citations
02
[Submitted on 16 Mar 2017]
3+1d quasiparticle anisotropic hydrodynamics for ultrarelativistic heavy-ion collisions
Mubarak Alqahtani🇺🇸 · Mohammad Nopoush🇺🇸 · Radoslaw Ryblewski🇵🇱 · Michael Strickland🇺🇸
We present the first comparisons of experimental data with phenomenological results from 3+1d quasiparticle anisotropic hydrodynamics (aHydroQP). We compare charged-hadron multiplicity, identified-particle spectra, identified-particle average transverse momentum, charged-particle elliptic flow, and identified-particle elliptic flow produced in LHC 2.76 TeV Pb+Pb collisions. The dynamical equations used for the hydrodynamic stage utilize non-conformal aHydroQP. The resulting aHydroQP framework naturally includes both shear and bulk viscous effects in addition to higher-order non-linear transport coefficients. The 3+1d aHydroQP evolution obtained is self-consistently converted to hadrons using anisotropic Cooper-Frye freezeout performed on a fixed-energy-density hypersurface. The final production and decays of the primordial hadrons are modeled using a customized version of THERMINATOR 2. In this first study, we utilized smooth Glauber-type initial conditions and a single effective freeze-out temperature T_FO = 130 MeV with all hadronic species in full chemical equilibrium. With this rather simple setup, we find a very good description of many heavy-ion observables.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1703.05808 [pdf]
PRL(2017)·94 citations
03
[Submitted on 17 Mar 2017]
Role of the direct processes in low-energy deuteron interactions
M.Avrigeanu · V. Avrigeanu · C. Costache
An extended analysis of the key role of direct interactions, i.e., breakup, stripping and pick-up processes, has been carried out for deuteron-induced reactions. Particular comments concern the deuteron breakup which is the dominant mechanism involved in surrogate reactions on heavy nuclei, around the Coulomb barrier.
Comments:
5 pages, 3 figures. Contribution at Int. Conf. on Nucl. Data for Science and Technology (ND2016), 11-16.09.2016, Bruges, Belgium
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1703.05956 [pdf]
EPJ Web Conf.(2017)·4 citations
04
[Submitted on 17 Mar 2017]
Interplay of Reggeon and photon in pA collisions
Gokce Basar🇺🇸 · Dmitri Kharzeev🇺🇸 · Ho-Ung Yee🇺🇸 · Ismail Zahed🇺🇸
We discuss the effects of the electromagnetic interaction in high-energy proton collisions with nuclei of large Z at strong coupling $λ = g^{2} N_{c}$ . Using the holographic dual limit of large $N_{c} > λ ≫ 1$ , we describe the Reggeon exchange as a twisted surface and show that it gets essentially modified by the electromagnetic interaction.
Comments:
19 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
1703.06078 [pdf]
PRD(2017)·3 citations
05
[Submitted on 16 Mar 2017] (cross-list from hep-ph)
Small- $x$ Asymptotics of the Quark Helicity Distribution: Analytic Results
Yuri V. Kovchegov🇺🇸 · Daniel Pitonyak🇺🇸 · Matthew D. Sievert🇺🇸
In this Letter, we analytically solve the evolution equations for the small- $x$ asymptotic behavior of the (flavor singlet) quark helicity distribution in the large- $N_{c}$ limit. These evolution equations form a set of coupled integro-differential equations, which previously could only be solved numerically. This approximate numerical solution, however, revealed simplifying properties of the small- $x$ asymptotics, which we exploit here to obtain an analytic solution. We find that the small- $x$ power-law tail of the quark helicity distribution scales as $Δ q^{S} (x, Q^{2}) \sim (\frac{1}{x})^{α_{h}}$ with $α_{h} = \frac{4}{3} \frac{α _{s} N _{c}}{2 π}$ , in excellent agreement with the numerical estimate $α_{h} \approx 2.31 \frac{α _{s} N _{c}}{2 π}$ obtained previously. We then verify this solution by cross-checking the predicted scaling behavior of the auxiliary "neighbor dipole amplitude" against the numerics, again finding excellent agreement.
Comments:
5 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1703.05809 [pdf]
PLB(2017)·78 citations
06
[Submitted on 17 Mar 2017] (cross-list from hep-ph)
Yield ratios of identified hadrons in p+p, p+Pb, Pb+Pb collisions at the Large Hadron Collider
Feng-lan Shao🇨🇳 · Guo-jing Wang🇨🇳 · Rui-qin Wang🇨🇳 · Hai-hong Li🇨🇳 · Jun Song🇨🇳
Yield ratios of identified hadrons observed in high multiplicity p+p and p+Pb collisions at LHC show remarkable similarity with those in Pb+Pb collisions, indicating some important and universal underlying dynamics in hadron production for different quark gluon final states. We use the quark combination model to explain the data of yield ratios in these three collision systems. The observed $p / π$ and $Λ/ K_{s}^{0}$ can be reproduced simultaneously by quark combination, and these two ratios reflect the rate of baryon production at hadronization which is the same in light sector and strange sector and is roughly constant in p+p, p+Pb and Pb+Pb collision systems over three orders of magnitude in charged particle multiplicity.The data of $K_{s}^{0} / π$ , $Λ/ π$ , $Ξ/ π$ and $Ω/ π$ show a hierarchy behavior relating to the strangeness content, and are naturally explained by quark combination both in the saturate stage at high multiplicity and in the increase stage at moderate multiplicity. Our results suggest that the dynamical characteristic of quark combination is necessary in describing the production of hadrons in small systems created in p+p and p+Pb collisions.
Comments:
8 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1703.05862 [pdf]
PRC(2017)·18 citations
07
[Submitted on 17 Mar 2017] (cross-list from hep-lat)
A simple model for a scalar two-point correlator in the presence of a resonance
Peter C. Bruns🇩🇪
We present a simple toy model for a scalar-isoscalar two-point correlator, which can serve as a testing ground for the extraction of resonance parameters from Lattice QCD calculations. We discuss in detail how the model correlator behaves when it is restricted to a finite spatial volume, and how the finite-volume data can be used to reconstruct the spectral function of the correlator in the infinite volume, which allows to extract properties of the resonance from such data.
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1703.05940 [pdf]
1 citation
08
[Submitted on 17 Mar 2017] (cross-list from hep-ph)
Baryon number fluctuations in chiral effective models and their phenomenological implications
Gabor Almasi🇩🇪 · Bengt Friman🇩🇪 · Krzysztof Redlich🇩🇪
We study the critical properties of net-baryon-number fluctuations at the chiral restoration transition in a medium at finite temperature and net baryon density. The chiral dynamics of quantum chromodynamics (QCD) is modeled by the Polykov-loop extended Quark-Meson Lagrangian, that includes the coupling of quarks to vector meson and temporal gauge fields. The Functional Renormalization Group is employed to properly account for the $O (4)$ criticality at the phase boundary. We focus on the properties and systematics of ratios of the net-baryon-number cumulants $χ_{B}^{n}$ , for $1 \leq n \leq 6$ , near the phase boundary. The results are presented in the context of the recent experimental data of the STAR Collaboration on fluctuations of the net proton number in heavy ion collisions at RHIC. We show that the model results for the energy dependence of the cumulant ratios are in good overall agreement with the data, with one exception. At center-of-mass energies below $19.6 GeV$ , we find that the measured fourth-order cumulant deviates considerably from the model results, which incorporate the expected $O (4)$ and $Z (2)$ criticality. We assess the influence of model assumptions and in particular of repulsive vector-interactions, which are used to modify the location of the critical endpoint in the model, on the cumulants ratios. Finally, we discuss a possibility to test to what extent the fluctuations are affected by nonequilibrium dynamics by comparing certain ratios of cumulants.
Comments:
15 pages, 13 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1703.05947 [pdf]
PRD(2017)·63 citations
09
[Submitted on 17 Mar 2017] (cross-list from hep-lat)
The role of the Euclidean signature in lattice calculations of quasi-distributions and other non-local matrix elements
Raúl A. Briceño🇺🇸 · Maxwell T. Hansen🇩🇪 · Christopher J. Monahan🇺🇸
Lattice quantum chromodynamics (QCD) provides the only known systematic, nonperturbative method for first-principles calculations of nucleon structure. However, for quantities such as lightfront parton distribution functions (PDFs) and generalized parton distributions (GPDs), the restriction to Euclidean time prevents direct calculation of the desired observable. Recently, progress has been made in relating these quantities to matrix elements of spatially nonlocal, zero-time operators, referred to as quasidistributions. Even for these time-independent matrix elements, potential subtleties have been identified in the role of the Euclidean signature. In this work, we investigate the analytic behavior of spatially non-local correlation functions and demonstrate that the matrix elements obtained from Euclidean lattice QCD are identical to those obtained using the LSZ reduction formula in Minkowski space. After arguing the equivalence on general grounds, we also show that it holds in a perturbative calculation, where special care is needed to identify the lattice prediction. Finally we present a proof of the uniqueness of the matrix elements obtained from Minkowski and Euclidean correlation functions to all order in perturbation theory.
Comments:
14 pages, 5 figures. Version published in Phys. Rev. D
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1703.06072 [pdf]
PRD(2017)·61 citations

Affiliations

first authorsco-authorsvia INSPIRE