Shell model description of Ge isotopes

A shell model study of the low energy region of the spectra in Ge isotopes for $38\leq N\leq 50$ is presented, analyzing the excitation energies, quadrupole moments, $B(E2)$ values and occupation numbers. The theoretical results have been compared with the available experimental data. The shell model calculations have been performed employing three different effective interactions and valence spaces.We have used two effective shell model interactions, JUN45 and jj44b, for the valence space $f_{5/2} \, p \,g_{9/2}$ without truncation. To include the proton subshell $f_{7/2}$ in valence space we have employed the $fpg$ effective interaction due to Sorlin {\it et al.}, with $^{48}$Ca as a core and a truncation in the number of excited particles.Comment: 10 pages, 10 figures, Proc. of the XXXV Nuclear Physics Symposium, January 3-6 2012, Cocoyoc, Morelos, Mexico. IOP Journal of Physics: Conference Series (in press

Numerical Study of the Lowest Energy Configurations for Global String-Antistring Pairs

We investigate the lowest energy configurations for string - antistring pairs at fixed separations by numerically minimizing the energy. We show that for separations smaller than a critical value, a region of false vacuum develops in the middle due to large gradient energy density. Consequently, well defined string - antistring pairs do not exist for such separations. We present an example of vortex - antivortex production by vacuum bubbles where this effect seems to play a dynamical role in the annihilation of the pair. We also study the dependence of the energy of an string-antistring pair on their separation and find deviations from a simple logarithmic dependence for small separations.Comment: 14 pages, in LATEX, 7 figures (not included

Enhancement of gluonic dissociation of J/ψJ/\psi in viscous QGP

We have investigated the effect of viscosity on the gluonic dissociation of $J/\psi$ in an equilibrating plasma. Suppression of $J/\psi$ due to gluonic dissociation depend on the temperature and also on the chemical equilibration rate. In an equilibrating plasma, viscosity affects the temperature evolution and also the chemical equilibration rate, requiring both of them to evolve slowly compared to their ideal counter part. For Au+Au collisions at RHIC and LHC energies, gluonic dissociation of $J/\psi$ increases for a viscous plasma. Low $P_T$ $J/\psi$'s are found to be more suppressed due to viscosity than the high $P_T$ ones. Also the effect is more at LHC energy than at RHIC energy.Comment: 3 pages, 1 figur

Energy Dependence of Short and Long-Range Multiplicity Correlations in Au+Au Collisions from STAR

A general overview of the measurement of long-range multiplicity correlations measured by the STAR experiment in Au+Au collisions at RHIC is presented. The presence of long-range correlations can provide insight into the early stages, and the type of matter produced in, these collisions. These measurements have been made in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 and 62.4 GeV. These results indicate a relatively large long-range correlation is produced in Au+Au collisions compared to a {\it pp} baseline at $\sqrt{s_{NN}}$ = 200 GeV. A weaker long-range correlation is seen as a function of incident energy. Further, comparison of the onset of the long-range correlation to the calculated percolation density parameter at $\sqrt{s_{NN}}$ = 200 GeV is presented.Comment: 8 pages, 6 figures, Conference Proceedings for the XI International Workshop on Correlation and Fluctuation in Multiparticle Production, Hangzhou, China, November 21-25, 200

Heat Transfer in Rarefied MHD Laminar Channel Flow

The problem of heat transfer for the steady axi-symmetrical laminar source flow of a slightly rarefied electrically conducting gas between two infinite parallel circular disks under transverse magnetic field is analytically investigated where both Joulean and viscous heating are considered. The flow parameters and the temperature are expanded in powers of 1/r. The quantity of heat transfer per unit time from a finite disk has been calculated. It is found that with the increase of magnetic field, the rate of heat transfer from the lower disk decrease and increases from the upper disk. The maximum temperature increase with the increase of the magnetic field. The rate of heat transfer from both the disks as well as the maximum temperature decreases with the increase of the rarefication of the gas

Hadronization in heavy ion collisions: Recombination and fragmentation of partons

We argue that the emission of hadrons with transverse momentum up to about 5 GeV/c in central relativistic heavy ion collisions is dominated by recombination, rather than fragmentation of partons. This mechanism provides a natural explanation for the observed constant baryon-to-meson ratio of about one and the apparent lack of a nuclear suppression of the baryon yield in this momentum range. Fragmentation becomes dominant at higher transverse momentum, but the transition point is delayed by the energy loss of fast partons in dense matter.Comment: 4 pages, 2 figures; v2: reference [8] added; v3: Eq.(2) corrected, two references added, version to appear in PR