The PHENIX experiment at RHIC has measured transverse energy and charged particle multiplicity at mid-rapidity in Au + Au collisions at √ s N N = 19.6, 130 and 200 GeV as a function of centrality. The presented results are compared to measurements from other RHIC experiments, and experiments at lower energies. The √ s N N dependence of dET /dη and dN ch /dη per pair of participants is consistent with logarithmic scaling for the most central events. The centrality dependence of dET /dη and dN ch /dη is similar at all measured incident energies. At RHIC energies the ratio of transverse energy per charged particle was found independent of centrality and growing slowly with √ s N N . A survey of comparisons between the data and available theoretical models is also presented.

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We present here a robust analytical model based on nuclear reaction theory for non-resonant fusion cross sections near Coulomb barrier. The astrophysical S-factors involving stable and neutron rich isotopes of C, O, Ne, Mg and Si for fusion reactions have been calculated in the centre of mass energy range of 2-30 MeV. The model is based on the tunneling through barrier arising out of nuclear, Coulomb and centrifugal potentials. Our formalism predicts precisely the suppression of S-factor at sub-barrier energies which are of astrophysical interest. The cross sections can be convoluted with Maxwell-Boltzmann distribution of energies to obtain thermo-or pycno-nuclear reaction rates relevant to nucleosynthesis at high density environments and stellar burning at high temperatures as well as for 34 Ne + 34 Ne fusion occurring in the inner crust of accreting neutron stars.

The hindrance in fusion of heavy-ion reactions crops up in the region of extreme sub-barrier energies. This phenomenon can be effectively analyzed using a simple diffused barrier formula derived assuming a Gaussian distribution of fusion barrier heights. Folding the Gaussian barrier distribution with the classical expression for the fusion cross section for a fixed barrier, the fusion cross section is obtained. The energy dependence of the fusion cross section provides good description to the existing data on sub-barrier heavy-ion fusion for lighter systems of astrophysical interest. Using this simple formula, an analysis has been presented from 16 O + 18 O to 12 C + 198 Pt, all of which were measured down to < 10 µb. The agreement of the present analysis with the measured values is better than those calculated even from the sophisticated coupled channels calculations. The relatively smooth variation of the three parameters of this formula implies that it may be exploited to estimate the excitation function or to extrapolate cross sections for pairs of interacting nuclei which are yet to be measured. Possible extensions of the present methodology and its limitations have also been discussed.

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The PeV cosmogenic neutrino is still an interesting argument. Since cosmogenic neutrinos interact weakly with matter, the detection of their direction will precisely point out the source in the space. In this paper, we show the results of the simulation of tau lepton air showers induced by highenergy neutrinos detected by an array of stations designed to use the Earth Skimming method improved by the "mountain chain screen" strategy. Both track time stamp and position information of the stations on the array are used to reconstruct the shower to estimate the direction and the number of events. The studied array consists of 640 stations (40 × 16) spread over an area of 0.6 km 2 starting from 1500 m above the sea level (a.s.l.) on a 30 • inclined plane of the mountain. When we extrapolate to 3 years and 10 km 2 , we estimate 13 tau lepton events in an energy interval of 10 PeV to 1000 PeV detected using the present upper limits of tau neutrino flux.