115460487
Compositional variation of Fe-group nuclei in cosmic rays due to K-capture effect.
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.
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.
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.
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.
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.
121254838
Sporadic emission of ultra high energy gamma rays from Crab pulsar
In a further study of sporadic emission from pulsars we find evidence for short lived intense emission from the Crab pulsar.
121535698
Intermittency analysis of fragmenting nuclei with exact conservation laws
We show that the speculative charge bin size dependence of the scaled factorial moments for fragmenting nuclei in recent nuclear emulsion data may be attributed in part to simple conservation laws. Monte Carlo results from both the Thermodynamic Model and an Evaporation Model suggest that in such studies most or all of the effect is due to the fact that there exist constraints owing to conserved quantities.
120829139
Improved gravitational coupling of scalar fields
Some physical processes involving scalar particles and gravitons are reexamined with the use of the improved scalar-graviton coupling. The improvement term is found to affect the one-graviton-exchange scalar-scalar potential at short distances and the graviton bremsstrahlung cross section at high energies.
55020997
Measurement of the radial density gradient of cosmic ray in the heliosphere by the GRAPES-3 experiment
Abstract A radial anisotropy in the flux of cosmic rays in heliosphere was theoretically predicted by Parker and others within the framework of the diffusion–convection mechanism. The solar wind is responsible for sweeping out the galactic cosmic rays, creating a radial density gradient within the heliosphere. This gradient coupled with the interplanetary magnetic field induces a flow of charged particles perpendicular to the ecliptic plane which was measured and correctly explained by Swinson, and is hereafter referred as ‘Swinson flow’. The large area GRAPES-3 tracking muon telescope offers a powerful probe to measure the Swinson flow and the underlying radial density gradient of the galactic cosmic rays at a relatively high rigidity of ∼100 GV. The GRAPES-3 data collected over a period of six years (2000–2005) were analyzed and the amplitude of the Swinson flow was estimated to be (0.0644 ± 0.0008)% of cosmic ray flux which was an ∼80 σ effect. The phase of the maximum flow was at a sidereal time of (17.70 ± 0.05) h which was 18 min earlier than the expected value of 18 h. This small 18 min phase difference had a significance of ∼6 σ indicating the inherent precision of the GRAPES-3 measurement. The radial density gradient of the galactic cosmic rays at a median rigidity of 77 GV was found to be 0.65% AU −1 .
18664179
Parametrizing yields of nuclear multifragmentation
We consider a model where, for a finite disintegrating system, yields of composites can be calculated to arbitrary accuracy. An analytic answer for yields is also known in the thermodynamic limit. In the range of temperature and density considered in this work, the model has a phase transition. This phase transition is first order. The analytic expression for yields of composites, in the thermodynamic limit, does not conform to the expression $ =a^{-\tau}f(a^{\sigma} (T-T_c))$ where, the usual identification would be that $T_c$ is the critical temperature and $\tau,\sigma$ are critical exponents. Nonetheless, for finite systems, we try to fit the yields with the above expression. A minimisation procedure is adopted to get the parameters $T_c,\tau$ and $\sigma$. While deviations from the formula are not negligible, one might believe that the deviations are consistent with the corrections attributable to finite particle number effects and might then conclude that one has deduced at least approximately the values of critical parameters. This exercise thus points to difficulties of trying to extract critical parameters from data on nuclear disintegration. An interesting result is that the value of $T_c$ deduced from the ``best'' fit is very close to the temperature at which the first order phase transition occurs in the model. The yields calculated in this model can also be fitted quite well by a parametrisation derived from a droplet model.