29516949
Measurement of the Abundance of Radioactive Be-10 and Other Light Isotopes in Cosmic Radiation Up to 2 GeV /Nucleon with the Balloon-Borne Instrument Isomax
The Isotope Magnet Experiment (ISOMAX), a balloon-borne superconducting magnet spectrometer, was designed to measure the isotopic composition of the light isotopes (3 ≤ Z ≤ 8) of cosmic radiation up to 4 GeV nucleon^(-1) with a mass resolution of better than 0.25 amu by using the velocity versus rigidity technique. To achieve this stringent mass resolution, ISOMAX was composed of three major detector systems: a magnetic rigidity spectrometer with a precision drift chamber tracker in conjunction with a three-layer time-of-flight system, and two silica-aerogel Cerenkov counters for velocity determination. A special emphasis of the ISOMAX program was the accurate measurement of radioactive ^(10)Be with respect to its stable neighbor isotope ^9Be, which provides important constraints on the age of cosmic rays in the Galaxy. ISOMAX had its first balloon flight on 1998 August 4–5 from Lynn Lake, Manitoba, Canada. Thirteen hours of data were recorded during this flight at a residual atmosphere of less than 5 g cm^(-2). The isotopic ratio at the top of the atmosphere for 10Be/9Be was measured to be 0:195 ± 0:036 (statistical) ± 0:039 (systematic) between 0.26 and 1.03 GeV nucleon^(-1) and 0:317 ± 0:109 (statistical) ± 0:042 (systematic) between 1.13 and 2.03 GeV nucleon^(-1). This is the first measurement of its kind above 1 GeV nucleon^(-1). ISOMAX results tend to be higher than predictions from current propagation models. In addition to the beryllium results, we report the isotopic ratios of neighboring lithium and boron in the energy range of the time-of-flight system (up to ~1 GeV nucleon^(-1)). The lithium and boron ratios agree well with existing data and model predictions at similar energies.
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.
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.
14702466
Right-Chiral Sneutrino LSP in mSUGRA: Event characteristics of NLSP at the LHC
We study a supersymmetric scenario where the lighter tau-sneutrino is the lightest supersymmetric particle, while the lighter stau-state is the next lightest. Such a scenario can be motivated within the framework of minimal supergravity, with just the addition of a right-chiral neutrino superfield. Such a spectrum leads to rather unusual signals of supersymmetry, showing stable tracks of the stau in the muon chambers. We study the event characteristics of the long-lived staus at the LHC and demonstrate that the stau tracks can be distinguished from the muonic ones through proper kinematic cuts which also enable one to remove all standard model backgrounds.
120205505
Quarkonium Spectra and Quantum Chromodynamics
119032709
Emission of Radiation at Energies > 1014 eV: Binary X-Ray Sources SCO X-1, CYG X-1, HER X-1 and Others
55962889
Solar diurnal anisotropy measured using muons in GRAPES-3 experiment in 2006
The GRAPES-3 experiment at Ooty contains a large-area (560 m2) tracking muon detector. This detector consists of 16 modules, each 35 m2 in area, that are grouped into four supermodules of 140 m2 each. The threshold energy of muons is sec(θ) GeV along a direction with zenith angle θ and the angular resolution of the muon detector is 6°. Typically, it records ~4×109 muons every day. The muon detector has been operating uninterruptedly since 2001, thus providing a high statistics record of the cosmic ray flux as a function of time over one decade. However, prior to using these data, the muon rate has to be corrected for two important atmospheric effects, namely, variations in atmospheric pressure and temperature. Because of the near equatorial location of Ooty (11.4°N), the seasonal variations in the atmospheric temperature are relatively small and shall be ignored here. Due to proximity to the equator, the pressure changes at Ooty display a dominant 12 h periodic behaviour in addition to other seasonal changes. Here, we discuss various aspects of a novel method for accurate pressure measurement and subsequent corrections applied to the GRAPES-3 muon data to correct these pressure-induced variations. The pressure-corrected muon data are used to measure the profile of the solar diurnal anisotropy during 2006. The data, when divided into four segments, display significant variation both in the amplitude (~45%) and phase (~42 m) of the solar diurnal anisotropy during 2006, which was a period of relatively low solar activity.
55518164
The current status of the GRAPES-3 extensive air shower experiment
The GRAPES-3 is a dense extensive air shower array operating with ∼400 scintillator detectors and it also contains a 560 m 2 tracking muon detector ( E μ > 1 GeV ), at Ooty in India. 25% of scintillator detectors are instrumented with two fast photomultiplier tubes (PMTs) for extending the dynamic range to ∼ 5 × 10 3 particles m − 2 . The scintillators, signal processing electronics and data recording systems were fabricated in-house to cut costs and optimize performance. The muon multiplicity distribution of the EAS is used to probe the composition of primary cosmic rays below the ‘knee’, with an overlap with direct measurements. Search for multi-TeV γ -rays from point sources is done with the aid of the muon detector. A good angular resolution of 0.7° at 30 TeV, is measured from the shadow of the Moon on the isotropic flux of cosmic rays. A sensitive limit on the diffuse flux of 100 TeV γ -rays is placed by using muon detector to filter the charged cosmic ray background. A tracking muon detector allows sensitive measurements on coronal mass ejections and solar flares through Forbush decrease events. We have major expansion plans to enhance the sensitivity of the GRAPES-3 experiment in the areas listed above.