39485818
Nucleus-nucleus potential from fusion and elastic scattering.
An analytical expression for the calculation of the nucleus-nucleus potential has been derived from an empirical formula which describes the fusion excitation function. The nucleus-nucleus potentials calculated for the projectiles /sup 6/Li, /sup 9/Be, and /sup 12/C in the interaction region --3--6.5 fm by the above procedure agree remarkably well with the real part of the respective optical potentials determined from the analysis of elastic scattering data which exhibit the ''rainbow'' phenomenon.
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.
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.
121323084
Microscopic nucleon optical model potential at low energies
Nuclear optical model potentials at low energies have been computed utilizing the two (Micro I and Micro II) versions of the microscopic optical model of Jeukenne et al. A comparison has been made of the experimental nucleon-nucleus interaction data for E<10 MeV with the theoretical predictions obtained using the microscopic optical model.
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.
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.
28852253
Dealing with truncation in Monte Carlo renormalization-group calculations.
On utilise le modele d'Ising d=2 comme exemple concret pour montrer que la troncature de la matrice T derivee au sous-espace S des interactions a courte portee n'a pas besoin de justification
10011120
Bc spectroscopy in a quantum-chromodynamic potential model.
We have investigated {ital B}{sub {ital c}} spectroscopy with the use of a quantum-chromodynamic potential model which was recently used by us for the light-heavy quarkonia. We give our predictions for the energy levels and the {ital E}1 transition widths. We also find, rather surprisingly, that although {ital B}{sub {ital c}} is not a light-heavy system, the heavy quark effective theory with the inclusion of the {ital m}{sub {ital b}}{sup -}{sup 1} and {ital m}{sub {ital b}}{sup -}{sup 1}ln{ital m}{sub {ital b}} corrections is as successful for {ital B}{sub {ital c}} as it is for {ital B} and {ital B}{sub {ital s}}. {copyright} {ital 1995 The American Physical Society.}
6552264
Nonsingular potential model for heavy quarkonia.
A nonsingular potential model for heavy quarkonia is described which does not require recourse to an illegitimate perturbative treatment for the investigation of quarkonium spectra. Our overall results for the energy levels, the leptonic widths, and the E1 transition widths are in very good agreement with the experimental data for bb-bar and they are reasonably good for cc-bar. We also find that the confining part of the quarkonium potential is scalar-vector exchange rather than the currently favored scalar exchange.
43411058
Semirelativistic potential model for heavy quarkonia.
The c-italicc-bar, b-italicb-bar, and t-italic t-italic-bar spectra are investigated with the use of a semirelativistic potential model described in an earlier paper. Results for the energy levels, leptonic widths, and E-italic1 transition widths are compared with the experimental data for c-italicc-bar and b-italicb-bar and predicted for t-italic t-italic-bar. We also find that the quark-antiquark interaction can best be described by a quasistatic rather than a momentum-dependent potential, and propose a theoretical justification for this surprising conclusion.
1626866
Gauge-boson scattering signals at the CERN LHC.
We have extended our earlier treatment of the gauge-boson scattering with radiative corrections in the standard model at supercollider energies, and computed the rates for gauge-boson scattering modes in {ital pp} collisions leading to the final states {ital W}{sup +}{ital W}{sup {minus}}, {ital ZZ}(4{ital l}), {ital ZZ}(2{ital l}2{nu}), {ital W}{sup {plus_minus}}{ital Z}, and {ital W}{sup {plus_minus}}{ital W}{sup {plus_minus}}. Our results at the CERN LHC energy of {radical}{ital s}=14 TeV for {ital m}{sub {ital H}}=1000 GeV are compared with those recently obtained by Bagger {ital et} {ital al}. These results will be useful in the search for the Higgs bosons at supercollider energies as well as for experimentally distinguishing the standard model from nonminimal Higgs models. {copyright} {ital 1996 The American Physical Society.}