Nuclear Theory·nucl-th

Thursday·December 31, 2015

16 papers—7 primary·9 cross-listed

01
[Submitted on 29 Dec 2015]
Possible chiral symmetry in $^{138}$ Nd
A. A. Raduta · Al. H. Raduta · C. M. Petrache
The pheomenological Generalized Coherent State Model Hamiltonian is amended with a many body term describing a set of nucleons moving in a shell model mean-field and interacting among themselves with paring, as well as with a particle-core interaction involving a quadrupole-quadrupole and a hexadecapole-hexdecapole force and a spin-spin interaction. The model Hamiltonian is treated in a restricted space consisting of the core projected states associated to the bands ground, $β, γ, γ, 1^{+}$ and $1^{+}$ and two proton aligned quasiparticles coupled to the states of the ground band. The chirally transformed particle-core states are also included. The Hamiltonian contains two terms which are not invariant to the chiral transformations relating the right handed trihedral $(J_{F}, J_{p}, J_{n})$ and the left handed ones $(- J_{F}, J_{p}, J_{n})$ , $(J_{F}, - J_{p}, J_{n})$ , $(J_{F}, J_{p}, - J_{n})$ where $J_{F}, J_{p}, J_{n}$ are the angular momenta carried by fermions, proton and neutron bosons, respectively. The energies defined with the particle-core states form four chiral bands, two of them being degenerate. Electromagnetic properties of the chiral bands are investigated. Results are compared with the experimental data on $^{138}$ Nd.
Comments:
22 pages, 15 figures. arXiv admin note: text overlap with arXiv:1407.5059, arXiv:1505.00910
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.08656 [pdf]
0 citations
02
[Submitted on 29 Dec 2015]
Thermal Dileptons from Coarse-Grained Transport as Fireball Probes at SIS Energies
Tetyana Galatyuk🇩🇪 · Paul M. Hohler🇺🇸 · Ralf Rapp🇺🇸 · Florian Seck🇩🇪 · Joachim Stroth🇺🇸
Utilizing a coarse-graining method to convert hadronic transport simulations of Au+Au collisions at SIS energies into local temperature, baryon and pion densities, we compute the pertinent radiation of thermal dileptons based on an in-medium $ρ$ spectral function that describes available spectra at ultrarelativistic collision energies. In particular, we analyze how far the resulting yields and slopes of the invariant-mass spectra can probe the lifetime and temperatures of the fireball. We find that dilepton radiation sets in after the initial overlap phase of the colliding nuclei of about 7 fm/c, and lasts for about 13 fm/c. This duration closely coincides with the development of the transverse collectivity of the baryons, thus establishing a direct correlation between hadronic collective effects and thermal EM radiation, and supporting a near local equilibration of the system. This fireball "lifetime" is substantially smaller than the typical 20-30 fm/c that naive considerations of the density evolution alone would suggest. We furthermore find that the total dilepton yield radiated into the invariant-mass window of $M = 0.3 - 0.7$ GeV/ $c^{2}$ , normalized to the number of charged pions, follows a relation to the lifetime found earlier in the (ultra-) relativistic regime of heavy-ion collisions, and thus corroborates the versatility of this tool. The spectral slopes of the invariant-mass spectra above the $ϕ$ mass provide a thermometer of the hottest phases of the collision, and agree well with the maximal temperatures extracted from the coarse-grained hadron spectra.
Comments:
9 pages, 6 figures; v2: extended discussion, matches the version accepted for publication
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.08688 [pdf]
EPJA(2016)·97 citations
03
[Submitted on 30 Dec 2015]
Anisotropic emission of direct photons from Au+Au collisions at $s_{NN} = 200 GeV$ with EPOS3 and IP-Glasma
Fu-Ming Liu🇨🇳 · Sheng-Xu Liu🇨🇳 · Klaus Werner🇫🇷
The observed large elliptic flow ( $v_{2}$ ) of direct photons in relativistic heavy ion collisions challenges us to explain. In this paper we consider only two sources of direct photons, prompt photons and thermal photons. Prompt photons are calculated with QCD to next leading order, which fits well the spectra at high transverse momentum ( $p_{t}$ ) region. Thermal photons are calculated with AMY rate in a 3+1D viscous hydrodynamical evolution of the collision systems. Two types of initial conditions, EPOS3 and IP-Glasma, are employed. Our results with IP-Glasma initial condition agree with results in published work in most cases, and the difference tells the regions effected by the absence of viscous correction in photon emission rate. Because both models are well constrained with hadron data, the hydrodynamic evolution of collision systems in the two models have many common. However, the transverse velocity of the collective motion are quite different. This makes a big difference in the anisotropic emission of direct photon emission. The observed large elliptic flow of direct photons is reproduced with EPOS3 hydrodynamic evolution.
Comments:
10 pages 8 figs
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1512.08833 [pdf]
7 citations
04
[Submitted on 30 Dec 2015]
Octet baryon masses and sigma terms in covariant baryon chiral perturbation theory
Xiu-Lei Ren (Beihang U. and IPN Orsay)🇫🇷 · Li-Sheng Geng (Beihang U.)🇨🇳 · Jie Meng (Peking U., SKLNPT and Beihang U. and Stellenbosch U.)🇨🇳
We report on a recent study of the ground-state octet baryon masses and sigma terms in covariant baryon chiral perturbation theory with the extended-on-mass-shell scheme up to next-to-next-to-next-to-leading order. To take into account lattice QCD artifacts, the finite-volume corrections and finite lattice spacing discretization effects are carefully examined. We performed a simultaneous fit of all the $n_{f} = 2 + 1$ lattice octet baryon masses and found that the various lattice simulations are consistent with each other. Although the finite lattice spacing discretization effects up to $O (a^{2})$ can be safely ignored, but the finite volume corrections cannot even for configurations with $M_{ϕ} L > 4$ . As an application, we predicted the octet baryon sigma terms using the Feynman-Hellmann theorem. In particular, the pion- and strangeness-nucleon sigma terms are found to be $σ_{π N} = 55 (1) (4)$ MeV and $σ_{s N} = 27 (27) (4)$ MeV, respectively.
Comments:
8 pages, 3 figures; presented by Xiu-Lei Ren at The 8th International Workshop on Chiral Dynamics (CD2015), 29 June 2015 - 03 July 2015, Pisa, Italy. Final published version. Latest results of sigma terms are shown in Fig.3. arXiv admin note: text overlap with arXiv:1405.4990
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1512.08841 [pdf]
PoS(2016)·1 citation
05
[Submitted on 30 Dec 2015]
The R_AA and v_2 of muons from heavy-quark decays in Pb+Pb collisions at sqrt(s_NN)=2.76 TeV with the ATLAS detector
Alexander Milov (for the ATLAS Collaboration)🇮🇱
The ATLAS experiment measures the production of muons coming from the decays of heavy flavour particles in the kinematic interval 4<p_T<14 GeV and |eta|<1. The measurement is performed in sqrt(s) = 2.76 TeV pp collisions and over the centrality range of 0-60% in sqrt(s_NN) = 2.76 TeV Pb+Pb collisions. The heavy flavour muon differential cross-sections and per-event yields are measured in pp and Pb+Pb collisions, respectively. The nuclear modification factor measured in 0-10% most central collisions is observed to be approximately equal to 0.4 and independent of p_T within uncertainties, which indicates suppressed production of heavy flavour muons in Pb+Pb collisions. The muon yields are also measured as a function of the azimuthal angle with respect to the event plane. Fourier coefficients associated with the second harmonic modulation vary slowly with p_T and show a systematic variation with centrality that is characteristic of other elliptic anisotropy measurements.
Comments:
4 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1512.08877 [pdf]
NPA(2016)·2 citations
06
[Submitted on 30 Dec 2015]
New analytical forms of wave function in coordinate space and tensor polarization of deuteron
V. I. Zhaba
Numerically coefficients of the new analytical forms for deuteron wave function in coordinate space for NijmI, NijmII, Nijm93, Reid93 and Argonne v18 potentials are designed. The obtained wave functions do not contain superfluous knots. The designed parameters of a deuteron well agree with the experimental and theoretical data. The tensor polarization t20 designed on wave functions is proportionate to earlier published outcomes.
Comments:
9 pages, 4 figures, 6 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.08980 [pdf]
Mod.Phys.Lett.A(2016)·18 citations
07
[Submitted on 30 Dec 2015]
Acceptance dependence of fluctuation measures near the QCD critical point
Bo Ling🇺🇸 · Mikhail A. Stephanov🇺🇸
We argue that a crucial determinant of the acceptance dependence of fluctuation measures in heavy-ion collisions is the range of correlations in the momentum space, e.g., in rapidity, $Δ y_{corr}$ . The value of $Δ y_{corr} \sim 1$ for critical thermal fluctuations is determined by the thermal rapidity spread of the particles at freezeout, and has little to do with position space correlations, even near the critical point where the spatial correlation length $ξ$ becomes as large as $2 - 3$ fm (this is in contrast to the magnitudes of the cumulants, which are sensitive to $ξ$ ). When the acceptance window is large, $Δ y ≫ Δ y_{corr}$ , the cumulants of a given particle multiplicity, $κ_{k}$ , scale linearly with $Δ y$ , or mean multiplicity in acceptance, $⟨ N ⟩$ , and cumulant ratios are acceptance independent. While in the opposite regime, $Δ y ≪ Δ y_{corr}$ , the factorial cumulants, $κ^_{k}$ , scale as $(Δ y)^{k}$ , or $⟨ N ⟩^{k}$ . We demonstrate this general behavior quantitatively in a model for critical point fluctuations, which also shows that the dependence on transverse momentum acceptance is very significant. We conclude that extension of rapidity coverage proposed by STAR should significantly increase the magnitude of the critical point fluctuation signatures.
Comments:
9 pages, 4 figures, references added
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.09125 [pdf]
PRC(2016)·118 citations

Affiliations

first authorsco-authorsvia INSPIRE

Possible chiral symmetry in 138Nd

Thermal Dileptons from Coarse-Grained Transport as Fireball Probes at SIS Energies

Anisotropic emission of direct photons from Au+Au collisions at sNN​​=200 GeV with EPOS3 and IP-Glasma

Octet baryon masses and sigma terms in covariant baryon chiral perturbation theory

The R_AA and v_2 of muons from heavy-quark decays in Pb+Pb collisions at sqrt(s_NN)=2.76 TeV with the ATLAS detector

New analytical forms of wave function in coordinate space and tensor polarization of deuteron

Acceptance dependence of fluctuation measures near the QCD critical point

Affiliations

Possible chiral symmetry in $^{138}$ Nd

Anisotropic emission of direct photons from Au+Au collisions at $s_{NN} = 200 GeV$ with EPOS3 and IP-Glasma