122805550
Studies of the energy spectrum and composition of the primary cosmic rays at 100?1000 TeV from the GRAPES-3 experiment
The composition and energy spectrum of primary cosmic rays (PCRs) are the only observables at high energies to study the nature of sources accelerating PCRs to �1000 TeV. These observables have been directly measured up to ∼300 TeV with detectors aboard balloons and satellites. But measurements at >1000 TeV have to be obtained indirectly from ground-based observations of extensive air showers. However, their interpretation relies on an inadequate knowledge of hadronic interactions at �1000 TeV. The GRAPES-3 experiment is designed to operate at �30 TeV providing a sizable overlap in energy with direct measurements, enabling the selection of a suitable model of hadronic interactions at ∼1000 TeV. We present salient features of GRAPES-3 including details of muon multiplicity distributions observed with a 560 m 2 detector as a function of shower size from an analysis of data of 545 days. These distributions were compared with expectations from Monte Carlo simulations, using some of the hadronic interaction generators in CORSIKA, to deduce energy spectra of five nuclear groups in the 100–1000 TeV region. A comparison of GRAPES-3 results with direct measurements indicates that SIBYLL provides a good description of hadronic interactions for interpreting our data. These measurements extend energy spectra and composition of PCRs that is consistent with extrapolation of direct measurements. (Some figures may appear in colour only in the online journal)
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.
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.
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.
10726324
Electromagnetic signals and backgrounds in heavy-ion collisions
Aspects of the dilepton spectrum in heavy-ion collisions are discussed, with special emphasis on using lattice computations to guide the phenomenology of finite temperature hadronic matter. The background rates for continuum dileptons expected in forthcoming experiments are summarised. Properly augmented by data from ongoing measurements at HERA, these rates will serve as a calibrating background for QGP searches. Recent results on the temperature dependence of the hadronic spectrum obtained in lattice computations below the deconfinement transition are summarised. Light vector meson masses are strongly temperature dependent. Accurate measurements of a, resolved ρ-peak in dimuon spectra in present experiments are thus of fundamental importance.
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.
16765015
Microcanonical lattice gas model for nuclear disassembly
Microcanonical calculations are no more difficult to implement than canonical calculations in the lattice gas model. We report calculations for a few observables where we compare microcanonical model results with canonical model results.
119587269
Quantization of Einstein's Gravitational Field: General Treatment
The quantization of the complete gravitational field is carried out by extending the work of an earlier paper. The main obstacles in the quantization of Einstein's field are overcome by expressing the field quantities in the Riemannian space as expansions in the flat space, and then splitting the gravitational field into the linear and the non-linear parts. The linear part of the gravitational field is regarded as the free gravitational field, while the non-linearity is treated as a direct interaction between the gravitons. This treatment is quite general, but it suffers from the usual limitations of the perturbation method. The gravitational self-energies of the photon and the electron are also investigated by using the linear approximation of the gravitational field It is found that the photon self-energy vanishes unambiguously, while the electron self-energy is quadratically divergent.
119393927
Spin-Orbit Interaction in Two-Pion Exchange Nuclear Potential