121879312
Isobaric analog impurity from total and differential neutron scattering cross sections of silicon
Resonance parameters for sour resonances in Si have been obtained by analyzing measured differential neutron scattering cross sections combined with the total neutron cross section in the neutron energy range 1.05--1.40 MeV and applying R-matrix single channel multilevel theory. The resonance at 1254 krB has been identified as the s-wave analog resonance in /sup 29/Si. The identification also takes into account experimental radiative neutron capture data and shell model calculations for the radiative width. Estimates of the isospin mixing matrix elements are given.
30676639
Ultrahigh-energy pulsed emission from Hercules X-1 with anomalous air-shower muon production.
A search for bursts of air-shower events from Hercules X-1 at energies above 50 TeV during the calendar period 2 April 1986 to 5 July 1987 yielded two significant bursts, both occurring on UT 24 July 1986. The events during these bursts were pulsed with a period of 1.235 68 s, significantly different from estimates of the contemporaneous x-ray period. The probability that this represents random statistical fluctuations of the background is estimated to be 2 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}5}$. The muon content of the burst events is anomalous when compared with expectations from $\ensuremath{\gamma}$-ray showers.
21268625
Search for signals from Cygnus X-3 at energies above 50 TeV.
Upper limits for the time-averaged flux of air showers from the direction of Cygnus X-3 during the calendar period 2 April 1986 to 3 May 1987 are found to be 1.5 x 10/sup -13/ cm/sup -2/ sec/sup -1/ for all events, and 7.6 x 10/sup -14/ cm/sup -2/ sec/sup -1/ for events with no observed muons in a 44-m/sup 2/ muon detector. These are integral fluxes above 50 TeV on the assumption of an E/sup -1/ primary spectrum. A possible observation of a short-term signal from Cygnus X-3, with an anomalous muon content, phase correlated with the 4.8-h orbital period, with an integral flux above 50 TeV of (8.2 +- 2.0) x 10/sup -13/ cm/sup -2/ sec/sup -1/ is also reported.
124703371
FEL ACTIVITIES IN INDIA
We are building a Compact Ultrafast TErahertz FreeElectron Laser (CUTE-FEL), designed to lase from 50 – 100 μm. The FEL will be driven by a 10-15 MeV electron beam from a Plane-Wave Transformer (PWT) linac. The undulator is a 5 cm period, 2.5 m long PPM planar undulator. We present details of the FEL design and the present status of activities. We also present very preliminary plans for a short-wavelength SASE FEL in India.
13571448
Apparent and Actual Shifts in Mass and Width of ϕ Mesons Produced in Heavy-Ion Collisions
We present a method of analyzing invariant-mass spectra of kaon pairs resulting from decay of ϕ mesons produced in high-energy heavy-ion collisions. It can be used to extract the shifts in the mass and the width (ΔM and ΔΓ) of the ϕ mesons when they are inside the dense matter formed in these collisions. We illustrate our method with the help of available preliminary data. Extracted values of ΔM and ΔΓ are significantly larger than those obtained with an earlier method. Our results are consistent with the experimentally observed pT dependence of the mass shift. Finally, we present a phenomenological relation between ΔM and ΔΓ. It provides a useful constraint on theories which predict the values of these two quantities.
331919
Monte Carlo code G3sim for simulation of plastic scintillator detectors with wavelength shifter fiber readout.
A detailed description of a compact Monte Carlo simulation code "G3sim" for studying the performance of a plastic scintillator detector with wavelength shifter (WLS) fiber readout is presented. G3sim was developed for optimizing the design of new scintillator detectors used in the GRAPES-3 extensive air shower experiment. Propagation of the blue photons produced by the passage of relativistic charged particles in the scintillator is treated by incorporating the absorption, total internal, and diffuse reflections. Capture of blue photons by the WLS fibers and subsequent re-emission of longer wavelength green photons is appropriately treated. The trapping and propagation of green photons inside the WLS fiber is treated using the laws of optics for meridional and skew rays. Propagation time of each photon is taken into account for the generation of the electrical signal at the photomultiplier. A comparison of the results from G3sim with the performance of a prototype scintillator detector showed an excellent agreement between the simulated and measured properties. The simulation results can be parametrized in terms of exponential functions providing a deeper insight into the functioning of these versatile detectors. G3sim can be used to aid the design and optimize the performance of scintillator detectors prior to actual fabrication that may result in a considerable saving of time, labor, and money spent.
121297767
High-energy graviton bremsstrahlung
118691839
Model for hypernucleus production in heavy ion collisions
We estimate the production cross sections of hypernuclei in projectile-like fragments (PLFs) in heavy ion collisions. The discussed scenario for the formation cross section of a LAMBDA hypernucleus is (a) LAMBDA particles are produced in the participant region but have a considerable rapidity spread and (b) LAMBDA with rapidity close to that of the PLF and total momentum (in the rest system of the PLF) up to Fermi motion can then be trapped and produce hypernuclei. Process (a) is considered here within the heavy ion jet interaction generator (HIJING/BB) model, and process (b) in the canonical thermodynamic model (CTM). We estimate the production cross sections for a hypernucleus {sub L}AMBDA{sup A}{sub F}Z where Z=1, 2, 3, and 4 for C + C at total nucleon-nucleon center of mass (c.m.) energy sq root(s{sub NN})=3.7 GeV, and for Ne + Ne and Ar + Ar collisions at sq root(s{sub NN})=5.0 GeV. By taking into account explicitly the impact parameter dependence of the colliding systems, it is found that the cross section is different from that predicted by the coalescence model, and large discrepancy is obtained for {sub L}AMBDA{sup 6}He and {sub L}AMBDA{sup 9}Be hypernuclei.
2463622
Towards continuum limit of screening lengths with chiral Fermions
We investigate mesonic screening correlators at T=2T_c using the overlap Fermions in the quenched approximation, where T_c is the QCD phase transition temperature. Using lattices with temporal extent up to 8, we found that both pseudoscalar and vector correlators exhibit a nice $cosh$ behaviour, leading to a plateau behaviour in the local screening masses as a function of distance. The rho and pi masses so determined show very little variation with the lattice spacing a. This augurs well for the use of chiral Fermions, and further suggests the small deviations of these masses from the ideal gas values are genuine effects of interactions.
119297909
High Scale Mixing Unification for Dirac Neutrinos
Starting with high scale mixing unification hypothesis, we investigate the renormalization group evolution of mixing parameters and masses for Dirac type neutrinos. Following this hypothesis, the PMNS mixing angles and phase are taken to be identical to the CKM ones at a unifying high scale. Then, they are evolved to a low scale using renormalization-group equations. The notable feature of this hypothesis is that renormalization group evolution with quasi-degenerate mass pattern can explain largeness of leptonic mixing angles even for Dirac neutrinos. The renormalization group evolution "naturally" results in a non-zero and small value of leptonic mixing angle $\theta_{13}$. One of the important predictions of this work is that the mixing angle $\theta_{23}$ is non-maximal and lies only in the second octant. We also derive constraints on the allowed parameter range for the SUSY breaking and unification scales for which this hypothesis works. The results are novel and can be tested by present and future experiments.
121068931
The thermodynamic model for relativistic heavy ion collisions
Abstract The collision between two heavy ions at high energies is discussed within the framework of a statistical model which is developed step by step so that it can be followed by a reader unfamiliar with this approach. As we hope to show, the statistical model forms a comprehensive framework for investigating various aspects of such collisions. When statistical thermodynamics is coupled with a one and two fireball model or a firestreak model, single particle and multiparticle inclusive cross sections can be evaluated. Specifically, single particle proton, deuteron, triton and pion cross sections are calculated and compared with experiment. Two particle correlations are discussed using the microcanonical ensemble. Multiplicity distributions are evaluated using the canonical ensemble and composite particle formation is simply obtained from the grand canonical ensemble. The power law behaviour of composite particle cross sections is studied. The thermodynamic model is justified by calculating various reaction rates. Many comparisons with experimental data are made.