Nuclear Theory·nucl-th

Monday·February 5, 2018

5 papers—1 primary·4 cross-listed

01
[Submitted on 2 Feb 2018]
Application of Nilsson model for deformed nucleus in relativistic heavy ion collisions
S. K. Tripathy🇮🇳 · M. Younus🇮🇳 · P. K. Sahu🇮🇳 · Z. Naik🇮🇳
Electron scattering methods, involving nucleus which have little or no intrinsic deformation suggest nucleon distribution to be of Fermi type. This distribution is further parameterised as Wood Saxon (WS) distribution, where an uniform charge density with smoothed-out surface have been implemented. Incorporating shape modification in WS, earlier attempts were made to explain observables in deformed nuclear collisions, such as charged particle multiplicity. In this work, we use an alternate approach known as Nilsson model or Modified Harmonic Oscillator (MHO), to explain charged particle multiplicity in U+U collisions at top RHIC energy. We have implemented the formalism in HIJING model and we found that the model describes the experimental data to an extent.
Comments:
9 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1802.00639 [pdf]
0 citations
02
[Submitted on 14 Nov 2017] (cross-list from nucl-ex)
Photoproduction of $Λ$ and $Σ^{0}$ hyperons off protons with linearly polarized photons at $E_{γ} = 1.5 - 3.0$ GeV
S. H. Shiu · H. Kohri · W. C. Chang · D. S. Ahn · J. K. Ahn · J. Y. Chen · S. Date · H. Ejiri · H. Fujimura · M. Fujiwara · S. Fukui · W. Gohn and 33 other authors
We report the measurement of the $γ p \to K^{+} Λ$ and $γ p \to K^{+} Σ^{0}$ reactions at SPring-8. The differential cross sections and photon-beam asymmetries are measured at forward $K^{+}$ production angles using linearly polarized tagged-photon beams in the range of $E_{γ} = 1.5$ --3.0 GeV. With increasing photon energy, the cross sections for both $γ p \to K^{+} Λ$ and $γ p \to K^{+} Σ^{0}$ reactions decrease slowly. Distinct narrow structures in the production cross section have not been found at $E_{γ} = 1.5$ --3.0 GeV. The forward peaking in the angular distributions of cross sections, a characteristic feature of $t$ -channel exchange, is observed for the production of $Λ$ in the whole observed energy range. A lack of similar feature for $Σ^{0}$ production reflects a less dominant role of $t$ -channel contribution in this channel. The photon-beam asymmetries remain positive for both reactions, suggesting the dominance of $K^{*}$ exchange in the $t$ channel. These asymmetries increase gradually with the photon energy, and have a maximum value of +0.6 for both reactions. Comparison with theoretical predictions based on the Regge trajectory in the $t$ channel and the contributions of nucleon resonances indicates the major role of $t$ -channel contributions as well as non-negligible effects of nucleon resonances in accounting for the reaction mechanism of hyperon photoproduction in this photon energy regime.
Comments:
published version, two-column format, 10 pages, 8 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1711.04996 [pdf]
PRC(2018)·25 citations
03
[Submitted on 1 Feb 2018] (cross-list from hep-ph)
Exploring hyperon structure with electromagnetic transverse densities
Jose Manuel Alarcón · Astrid N. Hiller Blin · Manuel J. Vicente Vacas · Christian Weiss
We explore the structure of the spin-1/2 flavor-octet baryons (hyperons) through their electromagnetic transverse densities. The transverse densities describe the distribution of charge and magnetization at fixed light-front time and enable a spatial representation of the baryons as relativistic systems. At peripheral distances b~1/M_pi the transverse densities are computed using a new method that combines chiral effective field theory and dispersion analysis. The peripheral isovector densities arise from two-pion exchange, which includes the rho-meson resonance through elastic unitarity. The isoscalar densities are estimated from vector meson exchange (omega, phi). We find that the "pion cloud" in the charged Sigma hyperons is comparable to the nucleon, while in the Xi it is suppressed. The Lambda-Sigma^0 transition density is pure isovector and represents a clear manifestiation of peripheral two-pion dynamics.
Comments:
NSTAR 2017 conference proceedings
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1802.00479 [pdf]
Few Body Syst.(2018)·0 citations
04
[Submitted on 2 Feb 2018] (cross-list from hep-lat)
Bayesian study of relativistic open and hidden charm in anisotropic lattice QCD
Aoife Kelly🇮🇪 · Alexander Rothkopf🇩🇪 · Jon-Ivar Skullerud🇮🇪
We present the first combined study of correlators and spectral properties of charmonium and open-charm-mesons at finite temperature using a fully relativistic lattice QCD approach. The QCD medium is captured by second generation anisotropic 24^3xN_t lattices from the FASTSUM collaboration, including 2+1 flavors of clover discretized quarks with m_pi~380 MeV. Two Bayesian methods are deployed to reconstruct the spectral functions, the recent BR method as well as the Maximum Entropy Method with Fourier basis. We take particular care to disentangle genuine in-medium effects from method artifacts with the help of the reconstructed correlator. Consistent with the direct inspection of correlators, we observe no significant in-medium modification for J/Psi and eta_c around the crossover, while the chi_c states on the other hand show clear changes around the transition. At the highest temperature, T=352 MeV, J/Psi and eta_c also exhibit discernible changes compared to the vacuum. For D mesons around $T_{c}$ , no significant modifications are observed, but we find clear indications that no bound state survives at the highest temperature of T=352 MeV. Above T_c we discover a significant difference between D and D* mesons, the latter being much more strongly affected by the medium.
Comments:
17 pages, many pdf figures. Matches version published in PRD
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1802.00667 [pdf]
PRD(2018)·40 citations
05
[Submitted on 2 Feb 2018] (cross-list from hep-ph)
Photon or meson formation in $J / ψ$ decays into $p p$
J.-P. Dedonder🇫🇷 · B. Loiseau🇫🇷 · S. Wycech🇵🇱
The measurements of the $J / ψ \to γ p p$ decays by the BES Collaboration indicate an enhancement at the $p p$ threshold which, however, is not present in the J/ $ψ$ decays into $ω p p$ and into $π p p$ . Here, two processes for describing the decays $J / ψ \to B p p$ where $B = γ, ω$ are presented in some detail and the cases $B = ϕ, π$ are briefly touched on. The first one, applied not only to the radiative decay to reproduce the threshold peak but also to the $ω p p$ decay channel to improve the description of the spectrum, postulates a direct emission of the boson before the baryon pair is formed. The second process assumes that the boson $B$ is emitted from the baryon pair following the $J / ψ$ decay and includes for the decays into $γ p p$ a final state nucleon-antinucleon interaction based on the Paris $N N$ potential. The reproduction of the $p p$ distribution in the $J / ψ \to ω p p$ decays needs a final state interaction involving a $N (2050) 3/ 2^{-}$ resonance. The photon- and meson-emission rates are reproduced in a semi-quantitative way.
Comments:
37 pages, 5 tables and 10 figures. Extended discussions, one more figure and several references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1802.00763 [pdf]
PRC(2018)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE

Application of Nilsson model for deformed nucleus in relativistic heavy ion collisions

Photoproduction of Λ and Σ0 hyperons off protons with linearly polarized photons at Eγ​=1.5−3.0 GeV

Exploring hyperon structure with electromagnetic transverse densities

Bayesian study of relativistic open and hidden charm in anisotropic lattice QCD

Photon or meson formation in J/ψ decays into pp​

Affiliations

Photoproduction of $Λ$ and $Σ^{0}$ hyperons off protons with linearly polarized photons at $E_{γ} = 1.5 - 3.0$ GeV

Photon or meson formation in $J / ψ$ decays into $p p$