Lyapunov Exponent and Charged Myers Perry Spacetimes

We compute the proper time Lyapunov exponent for charged Myers Perry black hole spacetime and investigate the instability of the equatorial circular geodesics (both timelike and null) via this exponent. We also show that for more than four spacetime dimensions $(N \geq 3)$, there are \emph{no} Innermost Stable Circular Orbits (ISCOs) in charged Myers Perry black hole spacetime. We further show that among all possible circular orbits, timelike circular orbits have \emph{longer} orbital periods than null circular orbits (photon spheres) as measured by asymptotic observers. Thus, timelike circular orbits provide the \emph{slowest way} to orbit around the charged Myers Perry black hole.Comment: Accepted for publication in EPJC. arXiv admin note: substantial text overlap with arXiv:1212.5758, arXiv:1205.565

Ψ(2s)\Psi(2s) production in p+Ap+A collisions

We have analyzed the data on $\psi'$ production in proton-nucleus ($p+A$) collisions, available from the NA50 Collaboration in the SPS energy domain. The investigated data sets include the absolute production cross sections as well as $\psi'$-to-Drell Yan (DY) cross section ratios. An adapted version of two component QVZ model has been employed to calculate $\psi'$ production cross sections. For both $\psi'$ and DY production, nuclear modifications to the free nucleon structure functions are taken into account. For $\psi'$, final state interaction of the produced $c\bar{c}$ pairs with the nuclear medium is also taken into account, in accordance with the previously analyzed $J/\psi$ data. A satisfactory description of the data in $p+A$ collisions is obtained. Model calculations are extrapolated to low energy regime to predict the $\psi'$ suppression in proton induced collisions at near threshold energies.Comment: 6 pages, 14 figures. Extensively revised, new figures adde