Thu·Oct 29, 2015Thursday·October 29, 2015

1. 01*

   A Scaling Phenomenon in Shannon Information Uncertainty Difference of fragments in Heavy-ion Collisions

   Chun-Wang Ma🇨🇳 · Yi-Dan Song🇨🇳 · Chun-Yuan Qiao🇨🇳 · Shan-Shan Wang🇨🇳 · Hui-Ling Wei🇨🇳 · Yu-Gang Ma🇨🇳 · Xi-Guang Cao🇨🇳

   The Shannon information-entropy uncertainty (in brief as "information uncertainty") is used to analyze the fragments in the measured 140$A$ MeV ${}^{40,48}$Ca + ${}^9$Be and ${}^{58,64}$Ni + ${}^9$Be reactions. A scaling phenomenon is found in the information-uncertainty difference of fragments between the reactions. The scaling phenomenon is explained in a manner of canonical ensemble theory, and is reproduced in the simulated reactions by the antisymmetric molecular dynamics (AMD) and AMD + GEMINI models. The probes based on information uncertainty, requiring no equilibrium state of reaction, can be used in the non-equilibrium system, and bridge the results of the static thermodynamics models and the evolving dynamical transport models.

   nucl-exnucl-thJ.Phys.G(2016)·17 citations
2. 02*

   Isobaric yield ratio difference between the 140 $A$ MeV ${}^{58,64}$Ni + ${}^9$Be reactions studied by antisymmetric molecular dynamics model

   C. Y. Qiao🇨🇳 · H. L. Wei🇨🇳 · C. W. Ma🇨🇳 · Y. L. Zhang🇨🇳 · S. S. Wang🇨🇳

   \item[Background] The isobaric yield ratio difference (IBD) method is found to be sensitive to the density difference of neutron-rich nucleus induced reaction around the Fermi energy. \item[Purpose] An investigation is performed to study the IBD results in the transport model. \item[Methods] The antisymmetric molecular dynamics (AMD) model plus the sequential decay model GEMINI are adopted to simulate the 140$A$ MeV ${}^{58,64}$Ni + ${}^9$Be reactions. A relative small coalescence radius R${}_c=$ 2.5 fm is used for the phase space at $t=$ 500 fm/c to form the hot fragment. Two limitations on the impact parameter ($b1=0-2$ fm and $b2=0-9$ fm) are used to study the effect of central collisions in IBD. \item[Results] The isobaric yield ratios (IYRs) for the large--$A$ fragments are found to be suppressed in the symmetric reaction. The IBD results for fragments with neutron-excess $I=$ 0 and 1 are obtained. A small difference is found in the IBDs with the $b1$ and $b2$ limitations in the AMD simulated reactions. The IBD with $b1$ and $b2$ are quite similar in the AMD + GEMINI simulated reactions. \item[Conclusions] The IBDs for the $I=$ 0 and 1 chains are mainly determined by the central collisions, which reflects the nuclear density in the core region of the reaction system. The increasing part of the IBD distribution is found due to the difference between the densities in the peripheral collisions of the reactions. The sequential decay process influences the IBD results. The AMD + GEMINI simulation can better reproduce the experimental IBDs than the AMD simulation.

   nucl-exnucl-thPRC(2015)·12 citations
3. 03*

   Recent results from NA61/SHINE on spectra and correlations in p+p and Be+Be interactions at the CERN SPS

   Andrzej Wilczek (for the NA61/SHINE Collaboration)🇵🇱

   The problem of pinning down the critical point of strongly interacting matter still puzzles the community. One of the answers suspected to emerge in the near future will surely come from NA61/SHINE - a fixed-target experiment aiming to discover the critical point as well as to study the properties of the onset of deconfinement. This goal will be pursued by obtaining precise data on hadron production in proton-proton, proton-nucleus and nucleus-nucleus interactions in a wide range of system size and collision energy. This contribution presents new results on inclusive spectra of identified hadrons and on fluctuations in inelastic p+p and Be+Be interactions at the SPS energies. These are compared with the world data, in particular with the corresponding measurements of NA49 for central Pb+Pb collisions as well as with some model predictions.

   nucl-exhep-exPoS(2017)·2 citations
4. 04*

   Measurement of an excess in the yield of J/$\psi$ at very low-$p_{\mathrm{T}}$ in Pb--Pb collisions with the ALICE detector

   Laure Massacrier (for the ALICE Collaboration)🇫🇷

   We report on the measurement of J/$\psi$ production at very low transverse momentum ($p_{\mathrm{T}}<$ 300 MeV/$c$) in Pb--Pb collisions performed with the ALICE detector at the LHC. We find an excess in the yield of J/$\psi$ with respect to expectations from hadronic production. Coherent photo-production of J/$\psi$ is proposed as a plausible origin of this excess. We show the nuclear modification factor of very low-$p_{\mathrm{T}}$ J/$\psi$ as a function of centrality. Then we measure the J/$\psi$ coherent photoproduction cross section in peripheral events assuming that it is the mechanism at the origin of the measured excess. It's worth noting that the observation of J/$\psi$ coherent photoproduction in Pb--Pb collisions at impact parameters smaller than twice the nuclear radius has never been observed so far and would open new theoretical challenges.

   nucl-exhep-exActa Phys.Polon.Supp.(2015)·2 citations
5. 05*

   Fluctuations of flow harmonics in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$~TeV from the Glauber model

   Maciej Rybczynski🇵🇱 · Wojciech Broniowski🇵🇱

   In the framework of the Glauber model as implemented in GLISSANDO 2, we study the fluctuations of flow harmonics in Pb+Pb collisions at the LHC centre-of-mass energy of 2.76 TeV. The model with wounded nucleons and the admixture of binary collisions leads to reasonable agreement for the ellipticity and triangularity fluctuations with the experimental data from the ATLAS, ALICE, and CMS collaborations, verifying the assumption that the initial eccentricity is approximately proportional to the harmonic flow of charged particles. While the agreement, in particular at the level of event-by-event distributions of eccentricities/flow coefficients in not perfect, it leads to a fair (at the level of a few percent for all centralities except the most peripheral collisions) description of the scaled standard deviation and the F measure which involve the four-particle cumulants. We also discuss the case of quadrangular flow. Computer scripts that generate our results from the GLISSANDO 2 simulations are provided.

   ↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2016)·10 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.