44941537
Entrance-channel dependence of fission-fragment anisotropies: A direct experimental signature of fission before equilibration.
Fission-fragment angular distributions in reactions of {sup 10}B, {sup 12}C, {sup 16}O+{sup 232}Th and {sup 237}Np, and {sup 19}F+{sup 237}Np have been measured. While the measured anisotropies in B- and C-induced fission are found to be in agreement with the predictions of the standard Halpern-Strutinsky theory, they are anomalously large in the case of O- and F-induced fission. Such a discontinuous behavior in angular anisotropy with respect to the entrance-channel mass-to-charge asymmetry provides an experimental verification of the predictions of the preequilibrium fission model proposed earlier to explain the anomalous fragment angular distributions.
119558719
Assembly, testing and production of bakelite RPCs for the end-cap region of the Compact Muon Solenoid experiment at CERN
Abstract The production of ten large area Resistive Plate Chambers (RPCs) for the end-cap region of CMS, under India-CMS-RPC Collaboration—“Action Plan (Phase-I)”, is in progress at the Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai, in active collaboration with Delhi University and Panjab University. These detectors are being assembled with gas-gaps fabricated in KODEL-Korea, mechanics from China and the FEBs from Italy. After testing and validating the series for REi/2,3, these chambers would be sent to CMS at CERN. This paper reports various pre-assembly jobs, leak tests and leakage current measurements of the gas-gaps, mechanical assembly and progress of ten RPCs under production.
2366114
Pattern recognition of particle tracks using principal component analysis and artificial neural network
Abstract A new method is suggested for pattern recognition of particle tracks based on a combined approach of both artificial neural network (ANN) and principal component analysis (PCA). It is seen that in high multiplicity environment, neither the PCA nor the ANN method is satisfactory when used separately as a track classifier. Best performance is achieved when the data are preprocessed using PCA technique, before it is fed to the backpropagated neural network.
53467090
Adiabatic heavy-ion fusion potentials for fusion at deep sub-barrier energies
The recently reported unusual behaviour of fusion cross-sections at extreme sub-barrier energies has been examined. The adiabatic limit of fusion barriers has been determined from experimental data using the barrier penetration model. These adiabatic barriers are consistent with the adiabatic fusion barriers derived from the modified Wilzynska-Wilzynski prescription. The fusion barrier systematics has been obtained for a wide range of heavy-ion systems.
120756008
Supercooling in viscous hydrodynamics for QCD phase transition
First order quark hadron phase transition is considered in scaling hydrodynamics including the Csernai-Kapusta model of nucleation of hadronic bubbles leading to supercooling. The effect of viscosity on the entropy production is studied in ideal as well as in viscous hydrodynamics with and without supercooling. It is found that the excess entropy produced due to supercooling depends weakly on viscosity.
15159040
Dissipative phenomena in a chemically nonequilibrated quark gluon plasma
The dissipative corrections to the hydrodynamic equations describing the evolution of energy-momentum tensor and parton densities are derived in a simple way using the scaling approximation for the expanding quark gluon plasma at finite baryon density. This procedure has been extended to study the process of chemical equilibration using a set of rate equations appropriate for a viscous quark gluon plasma. It is found that in the presence of dissipation, the temperature of the plasma evolves slower, whereas the quark and gluon fugacities evolve faster than their counterparts in the ideal case without viscosity.
15147590
Particle physics bounds from the Hulse-Taylor binary.
The orbital period of the binary pulsar PSR 1913+16 has been observed to decrease at the rate of 2.40{times}10{sup {minus}12} s/s which agrees with the prediction of the quadropole formula for gravitational radiation to within one percent. The decrease in orbital period may also occur by radiation of other massless particles such as scalars and pseudoscalar Nambu-Goldstone bosons. Assuming that this energy loss is less than one percent of the gravitational radiation, we can establish bounds on couplings of these particles to nucleons. For a scalar nucleon coupling of the form {ital g}{sub {ital s}}{phi}{bar {psi}}{psi} we find that {ital g}{sub {ital s}}{lt}3{times}10{sup {minus}19}. From the radiation loss of massless Goldstone bosons we establish the upper bound {theta}{ital g}{sub {ital p}}{lt}10{sup {minus}16} on the QCD vacuum angle {theta} and the pseudoscalar nucleon coupling constant {ital g}{sub {ital p}}. {copyright} {ital 1996 The American Physical Society.}