Nuclear Theory·nucl-th

Thursday·April 13, 2017

15 papers—9 primary·6 cross-listed

01
[Submitted on 11 Apr 2017]
Toward the description of fluid dynamical fluctuations in heavy-ion collisions
Marlene Nahrgang🇫🇷 · Marcus Bluhm🇵🇱 · Thomas Schäfer🇺🇸 · Steffen Bass🇺🇸
In this talk we present results obtained when fluid dynamical fluctuations are included in relativistic $3 + 1$ dimensional viscous fluid dynamics. We discuss effects of the interactions of fluctuations due to nonlinearities and the cutoff dependence.
Comments:
Presented by M.~Nahrgang at Critical Point and Onset of Deconfinement (CPOD) 2016
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.03553 [pdf]
Acta Phys.Polon.Supp.(2017)·23 citations
02
[Submitted on 11 Apr 2017]
Local and global $Λ$ polarization in a vortical fluid
Hui Li🇨🇳 · Hannah Petersen🇩🇪 · Long-Gang Pang🇺🇸 · Qun Wang🇨🇳 · Xiao-Liang Xia🇨🇳 · Xin-Nian Wang🇨🇳
We compute the fermion spin distribution in the vortical fluid created in off-central high-energy heavy-ion collisions. We employ the event-by-event (3+1)D viscous hydrodynamic model. The spin polarization density is proportional to the local fluid vorticity in quantum kinetic theory. As a result of strong collectivity, the spatial distribution of the local vorticity on the freeze-out hyper-surface strongly correlates to the rapidity and azimuthal angle distribution of fermion spins. We investigate the sensitivity of the local polarization to the initial fluid velocity in the hydrodynamic model and compute the global polarization of {\Lambda} hyperons by the AMPT model. The energy dependence of the global polarization agrees with the STAR data.
Comments:
4 pages, 4 figures, Quark Matter 2017 proceeding
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1704.03569 [pdf]
NPA(2017)·19 citations
03
[Submitted on 12 Apr 2017]
Two-photon exchange corrections to $γ^{*} N Δ$ form factors for $Q^{2} \leq 4$ (Gev/ $c$ ) $^{2}$
Hai-Qing Zhou🇨🇳 · Shin Nan Yang🇹🇼
We evaluate the corrections of the two-photon exchange (TPE) process on the $γ^{*} N Δ$ transition form factors. The contributions of the TPE process to the $e N \to e Δ (1232) \to e N π$ are calculated in a hadronic model with the inclusion of only the elastic nucleon intermediate states, to estimate its effects on the multipoles $M_{1^{+}}^{(3/2)}, E_{1^{+}}^{(3/2)}, S_{1^{+}}^{(3/2)}$ at the $Δ$ peak. We find that TPE effects on $G_{M}^{*}$ is very small. $G_{E}^{*},$ and $G_{C}^{*}$ are also little affected at small $Q^{2}$ . For $G_{E}^{*}$ , the TPE effects reach about $3 - 8%$ near $Q^{2} \sim 4$ GeV $^{2}$ , depending on the model, MAID or SAID, used to emulate the data. For $G_{C}^{*}$ , the TPE effects decrease rapidly with increasing $ϵ$ while growing with increasing $Q^{2}$ to reach $\sim 6 - 15%$ with $Q^{2} \sim 4$ GeV $^{2}$ at $ϵ = 0.2$ . Sizeable TPE corrections to $G_{E}^{*}$ and $G_{C}^{*}$ found here points to the need of including TPE effects in the multipole analysis in the region of high $Q^{2}$ and small $ϵ$ . The TPE corrections to $R_{E M}$ and $R_{S M}$ obtained in our hadronic calculation are compared with those obtained in a partonic calculation for moderate momentum transfer of $2 < Q^{2} < 4$ GeV $^{2}$ .
Comments:
4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1704.03605 [pdf]
PRC(2017)·13 citations
04
[Submitted on 12 Apr 2017]
Examination of $N^{*} (1535)$ as a probe to observe the partial restoration of chiral symmetry in nuclear matter
Daiki Suenaga🇯🇵
We investigate modifications of mass and decay width of $N^{*} (1535)$ in nuclear matter in a chiral symmetric way. The nucleon and $N^{*} (1535)$ are introduced by a parity doublet model, and nuclear matter is constructed by one-loop diagrams of the nucleon and $N^{*} (1535)$ . The decay width of $N^{*} (1535)$ is studied respecting chiral symmetry. Our calculations show that the partial width of $Γ_{N^{*} \to N π}$ is slightly broadened by a collisional broadening, and that of $Γ_{N^{*} \to N η}$ is drastically suppressed at density. As a result, the total decay width $Γ_{tot}$ gets small at density. These modifications, especially the drastic narrowing of partial width of $Γ_{N^{*} \to N η}$ , together with the dropping of mass of $N^{*} (1535)$ provide experiments for observing the partial restoration of chiral symmetry in nuclear matter by means of $N^{*} (1535)$ resonance with useful information.
Comments:
16 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1704.03630 [pdf]
PRC(2018)·32 citations
05
[Submitted on 12 Apr 2017]
Effects of jet-induced medium excitation in $γ$ -hadron correlation in A+A collisions
Wei Chen🇨🇳 · Shanshan Cao🇺🇸 · Tan Luo🇨🇳 · Long-Gang Pang🇺🇸 · Xin-Nian Wang🇨🇳
Coupled Linear Boltzmann Transport and hydrodynamics (CoLBT-hydro) is developed for co-current and event-by-event simulations of jet transport and jet-induced medium excitation (j.i.m.e.) in high-energy heavy-ion collisions. This is made possible by a GPU parallelized (3+1)D hydrodynamics that has a source term from the energy-momentum deposition by propagating jet shower partons and provides real time update of the bulk medium evolution for subsequent jet transport. Hadron spectra in $γ$ -jet events of A+A collisions at RHIC and LHC are calculated for the first time that include hadrons from both the modified jet and j.i.m.e.. CoLBT-hydro describes well experimental data at RHIC on the suppression of leading hadrons due to parton energy loss. It also predicts the enhancement of soft hadrons from j.i.m.e. The onset of soft hadron enhancement occurs at a constant transverse momentum due to the thermal nature of soft hadrons from j.i.m.e. which also have a significantly broadened azimuthal distribution relative to the jet direction. Soft hadrons in the $γ$ direction are, on the other hand, depleted due to a diffusion wake behind the jet.
Comments:
4 pages, 4 figures in LaTeX, final version published in PLB
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1704.03648 [pdf]
PLB(2018)·182 citations
06
[Submitted on 12 Apr 2017]
Low- $x$ Physics in $p A$ Collisions and at the EIC
Bo-Wen Xiao🇨🇳
In this proceeding, I review what we have learned, and what we will be able to learn, about low- $x$ physics from proton-nucleus ( $p A$ ) collisions at RHIC and the LHC, and how this complements future Electron-Ion Collider (EIC) measurements. EIC not only will provide us essential and complementary information about the gluon saturation to the knowledge that we have learned from $p A$ collisions at RHIC and the LHC, it will also allow us to visualize the internal structure of protons and nuclei in a multi-dimensional fashion with unprecedented precision.
Comments:
8 pages, 2 figures; To appear in the conference proceedings for Quark Matter 2017, February 5-11, Chicago, Illinois, USA; v2
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1704.03662 [pdf]
NPA(2017)·3 citations
07
[Submitted on 12 Apr 2017]
Continuum effects in neutron-drip-line oxygen isotopes
K. Fossez · J. Rotureau · N. Michel · W. Nazarewicz
The binding-energy pattern along the neutron-rich oxygen chain, governed by an interplay between shell effects and many-body correlations impacted by strong couplings to one- and two-neutron continuum, make these isotopes a unique testing ground for nuclear models. In this work, we investigate ground states and low-lying excited states of $^{23 - 28}$ O using the complex-energy Gamow Shell Model and Density Matrix Renormalization Group method with a finite-range two-body interaction optimized to the bound states and resonances of $^{23 - 26}$ O, assuming a core of $^{22}$ O. Our results suggest that the ground-state of $^{28}$ O has a threshold character, i.e., is very weakly bound or slightly unbound. We also predict narrow excited resonances in $^{25}$ O and $^{27}$ O. The inclusion of the large continuum space significantly impacts predicted binding energies of $^{26 - 28}$ O. This implies that the careful treatment of neutron continuum is necessary prior to assessing the spectroscopic quality of effective interactions in this region.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.03785 [pdf]
PRC(2017)·48 citations
08
[Submitted on 12 Apr 2017]
Semiclassical approximation to the Hartree-Fock method in finite nuclei
K. A. Gridnev · V. B. Soubbotin · X. Viñas · M. Centelles
In this paper we review the semiclassical extended Thomas-Fermi theory for describing the ground-state properties of nuclei. The binding energies calculated in this approach do not contain shell effects and, in this sense, they are analogous to those obtained from the mass formula. We discuss some techniques for incorporating the shell effects which are missing in the semiclassical calculation, such as the so-called expectation value method and the Kohn-Sham scheme. We present numerical applications for effective zero-range Skyrme forces and finite-range Gogny forces.
Comments:
Contribution to the book "Quantum Theory: in honour of Vladimir A. Fock" pt. 2, eds. Y. Novozhilov, V. Novozhilov, Publishing group of St. Petersburg University, 1998, p. 118
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.03858 [pdf]
4 citations
09
[Submitted on 12 Apr 2017]
Deformation properties with a finite range simple effective interaction
B. Behera · X. Viñas · T. R. Routray · L. M. Robledo · M. Centelles · S. P. Pattnaik
Deformed and spherical even-even nuclei are studied using a finite range simple effective interaction within the Hartree-Fock-Bogoliubov mean field approach. Different parameter sets of the interaction, corresponding to different incompressibility, are constructed by varying the exponent gamma of the density in the traditional density-dependent term. Ten of the twelve parameters of these interactions are determined from properties of asymmetric nuclear matter and spin polarized pure neutron matter. The two remaining parameters are fitted to reproduce the experimental binding energies known in 620 even-even nuclei using several variants of the rotational energy correction. The rms deviations for the binding energy depend on the value of gamma and the way the rotational energy correction is treated but they can be as low as 1.56 MeV, a value competitive with other renowned effective interactions of Skyrme and Gogny type. Charge radii are compared to the experimental values of 313 even-even nuclei and the rms deviation is again comparable and even superior to the one of popular Skyrme and Gogny forces. Emphasis is given to the deformation properties predicted with these interactions by analyzing the Potential Energy Surfaces for several well deformed nuclei and the fission barriers of some nuclei. Comparison of the results with the experimental information, where available, as well as with the results of the Gogny D1S force shows satisfactory agreement.
Comments:
20 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.03860 [pdf]
J.Phys.G(2016)·25 citations
10
[Submitted on 11 Apr 2017] (cross-list from hep-ph)
Effective field theories for van der Waals interactions
Nora Brambilla🇩🇪 · Vladyslav Shtabovenko🇩🇪 · Jaume Tarrús Castellà🇩🇪 · Antonio Vairo🇩🇪
Van der Waals interactions between two neutral but polarizable systems at a separation $R$ much larger than the typical size of the systems are at the core of a broad sweep of contemporary problems in settings ranging from atomic, molecular and condensed matter physics to strong interactions and gravity. We reexamine the dispersive van der Waals interactions between two hydrogen atoms. The novelty of the analysis resides in the usage of nonrelativistic EFTs of QED. In this framework, the van der Waals potential acquires the meaning of a matching coefficient in an EFT suited to describe the low energy dynamics of an atom pair. It may be computed systematically as a series in $R$ times some typical atomic scale and in the fine structure constant $α$ . The van der Waals potential gets short range contributions and radiative corrections, which we compute in dimensional regularization and renormalize here for the first time. Results are given in $d$ spacetime dimensions. One can distinguish among different regimes depending on the relative size between $1/ R$ and the typical atomic bound state energy $m α^{2}$ . Each regime is characterized by a specific hierarchy of scales and a corresponding tower of EFTs. The short distance regime is characterized by $1/ R ≫ m α^{2}$ and the LO van der Waals potential is the London potential. We compute also NNNLO corrections. In the long distance regime we have $1/ R ≪ m α^{2}$ . In this regime, the van der Waals potential contains contact terms, which are parametrically larger than the Casimir-Polder potential that describes the potential at large distances. In the EFT the Casimir-Polder potential counts as a NNNLO effect. In the intermediate distance regime, $1/ R \sim m α^{2}$ , a significantly more complex potential is obtained which we compare with the two previous limiting cases. We conclude commenting on the hadronic van der Waals case.
Comments:
Journal version. 27 pages, 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
1704.03476 [pdf]
PRD(2017)·21 citations
11
[Submitted on 12 Apr 2017] (cross-list from nucl-ex)
Collective flow from AA, pA to pp collisions - Toward a unified paradigm
Wei Li🇺🇸
I give an overview of the latest development in understanding collective phenomena in high-multiplicity hadronic final state from relativistic nucleus-nucleus, proton-nucleus and proton-proton collisions. Upon reviewing the experimental data and confronting them with theoretical models, a unified paradigm in describing the observed collectivity across all hadronic collision systems is emerging. Potential future paths toward addressing key open questions, especially on collectivity in small systems (pp, pA), are discussed.
Comments:
9 pages, 6 figures, plenary contribution to Quark Matter 2017, February 5-11 (2017), Chicago (IL), USA
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1704.03576 [pdf]
NPA(2017)·22 citations
12
[Submitted on 12 Apr 2017] (cross-list from nucl-ex)
Single-neutron knockout from $^{20} C$ and the structure of $^{19} C$
J.W. Hwang🇰🇷 · S. Kim🇰🇷 · Y. Satou🇰🇷 · N.A. Orr🇫🇷 · Y. Kondo🇯🇵 · T. Nakamura🇯🇵 · J. Gibelin🇫🇷 · N.L. Achouri🇫🇷 · T. Aumann🇩🇪 · H. Baba🇯🇵 · F. Delaunay🇫🇷 · P. Doornenbal🇯🇵 and 33 other authors
The low-lying unbound level structure of the halo nucleus $^{19} C$ has been investigated using single-neutron knockout from $^{20} C$ on a carbon target at 280 MeV/nucleon. The invariant mass spectrum, derived from the momenta of the forward going beam velocity $^{18} C$ fragment and neutrons, was found to be dominated by a very narrow near threshold ( $E_{rel}$ = 0.036(1) MeV) peak. Two less strongly populated resonance-like features were also observed at $E_{rel}$ = 0.84(4) and 2.31(3) MeV, both of which exhibit characteristics consistent with neutron $p$ -shell hole states. Comparisons of the energies, measured cross sections and parallel momentum distributions to the results of shell-model and eikonal reaction calculations lead to spin-parity assignments of $5/ 2_{1}^{+}$ and $1/ 2_{1}^{-}$ for the levels at $E_{x}$ = 0.62(9) and 2.89(10) MeV with $S_{n}$ = 0.58(9) MeV. Spectroscopic factors were also deduced and found to be in reasonable accord with shell-model calculations. The valence neutron configuration of the $^{20} C$ ground state is thus seen to include, in addition to the known $1 s_{1/2}^{2}$ component, a significant $0 d_{5/2}^{2}$ contribution. The level scheme of $^{19} C$ , including significantly the $1/ 2_{1}^{-}$ cross-shell state, is well accounted for by the YSOX shell-model interaction developed from the monopole-based universal interaction.
Comments:
Physics Letters B, in press
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1704.03601 [pdf]
PLB(2017)·21 citations
13
[Submitted on 12 Apr 2017] (cross-list from cond-mat.quant-gas)
Determination of the density and temperature dependence of the shear viscosity of a unitary Fermi gas based on hydrodynamic flow
Marcus Bluhm🇺🇸 · Jiaxun Hou🇺🇸 · Thomas Schaefer🇺🇸
We determine the shear viscosity of the ultracold Fermi gas at unitarity in the normal phase using hydrodynamic expansion data. The analysis is based on a generalized fluid dynamic framework which ensures a smooth transition between the fluid dynamic core of the cloud and the ballistic corona. We use expansion data taken by Joseph et al. and measurements of the equation of state by Ku et al. We find that the shear viscosity to particle density ratio just above the critical temperature is $η / n ∣_{T_{c}} = 0.41 \pm 0.11$ . We also obtain evidence that the shear viscosity to entropy density ratio has a minimum slightly above $T_{c}$ with $η / s ∣_{min} = 0.50 \pm 0.10$ .
Comments:
Version to appear in PRL
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
1704.03720 [pdf]
PRL(2017)·30 citations
14
[Submitted on 12 Apr 2017] (cross-list from hep-ph)
Quasi-distribution amplitudes for pion and kaon via the nonlocal chiral-quark model
Seung-il Nam🇰🇷
We investigate the pseudoscalar (PS) meson ( $π$ and $K$ ) quasi-distribution amplitude (QDA), which is supposed to be an asymptotic analog to the meson distribution amplitude (DA) $ϕ_{π, K} (x)$ in the limit of the large longitudinal PS-meson momentum, i.e. $p_{3} \to \infty$ , in the nonperturbative region. For this purpose, we employ the nonlocal chiral-quark model (NLChQM) in the light-front formalism with a minimal Fock-state for the mesons $\sim q q ˉ$ at the low-energy scale parameter of the model $Λ \sim 1$ GeV. As a trial, we extract the transverse-momentum distribution amplitude (TMDA) from the light-front wave function within the model, and convert it to QDA with help of the virtuality-distribution amplitude. By doing that, we derive an analytical expression for the nonperturbative QDA with the current-quark mass correction up to $O (Δ m_{q})$ . Numerically, we confirm that the obtained TMDA reproduces the experimental data for the photon-pion transition form factor $F_{γ γ^{*} π^{0}} (Q^{2})$ at the low- $Q^{2}$ qualitatively well. We also observe that the obtained QDA approaches to DA as $p_{3}$ increases, showing the symmetric and asymmetric curves with respect to $x$ for the pion and kaon, respectively, due to the current-quark mass difference $m_{u, d} ≪ m_{s}$ . Assigning $ξ \equiv 2 x - 1$ , the moments $⟨ ξ^{n} ⟩_{π, K}$ are computed, using the pion and kaon QDAs, and there appear only a few percent deviations in the moments for $p_{3} ≳ 30Λ$ in comparison to the values calculated directly from DAs. It turns out that the higher moments are more sensitive to the change of $p_{3}$ , whereas the lower ones depend less on it.
Comments:
12 pages, 8 figures, accepted for publication via Mod. Phys. Lett. A
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1704.03824 [pdf]
Mod.Phys.Lett.A(2017)·28 citations
15
[Submitted on 12 Apr 2017] (cross-list from nucl-ex)
Disentangling flow and signals of Chiral Magnetic Effect in U+U, Au+Au and p+Au collisions
Prithwish Tribedy (for the STAR Collaboration)🇺🇸
We present STAR measurements of the charge-dependent three-particle correlator $γ^{a, b} = ⟨ cos (ϕ_{1}^{a} + ϕ_{2}^{b} - 2 ϕ_{3})⟩ / v_{2} {2}$ and elliptic flow $v_{2} {2}$ in U+U, Au+Au and p+Au collisions at RHIC. The difference $Δ γ = γ (opposite - sign) - γ (same - sign)$ measures charge separation across the reaction plane, a predicted signal of the Chiral Magnetic Effect (CME). Although charge separation has been observed, it has been argued that the measured separation can also be explained by elliptic flow related backgrounds. In order to separate the two effects, we perform measurements of the $γ$ -correlator where background expectations differ from magnetic field driven effects. A differential measurement of $γ$ with the relative pseudorapidity ( $Δ η$ ) between the first and second particles indicate that $Δ γ$ in peripheral A+A and p+A collisions are dominated by short-range correlations in $Δ η$ . However, a relatively wider component of the correlation in $Δ η$ tends to vanish the same way as projected magnetic field as predicted by MC-Glauber simulations.
Comments:
4 pages, 2 figures, proceedings for Quark Matter 2017
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1704.03845 [pdf]
NPA(2017)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE