121521916
Measurement of some EAS properties using new scintillator detectors developed for the GRAPES-3 experiment
The GRAPES-3 extensive air shower (EAS) array started operation with 256 scintillator detectors at Ooty in India. Each detector is viewed by a fast photomultiplier tube (PMT) mounted at a height of 60 cm above the scintillator. However, for further expansion of the array, an alternative readout of the scintillator using wave-length shifting (WLS) fibers is employed. This resulted in improved performance with a larger photon signal and a more uniform response. With the inclusion of a second PMT, the dynamic range for particle detection has been increased to �5 � 10 3 particles m � 2 . We now use plastic scintillators, developed in-house to cut costs. The measurement of the density spectrum, shows a power law dependence with an index c = 1.57 ± 0.04. Using the zenith angle dependence of the density spectrum, an attenuation length Ka = 98–106 g cm � 2 for the EAS is obtained. These measurements are found to be consistent with the results reported earlier by other groups.
55926788
A large area muon tracking detector for ultra-high energy cosmic ray astrophysics — the GRAPES-3 experiment
Certain aspects of ultra-high energy (UHE) cosmic ray astrophysics require correlated studies on the electron and muon components of air showers, namely, the search for cosmic ray sources through g-ray astronomy and studies on the variation of the nuclear composition of primary cosmic rays with energy. While studies on the electron component provide basic information about the arrival direction and energy, it is the muon component that plays a crucial role in distinguishing primary g-rays from charged cosmic ray particles and in determining the composition. A large area (560m), tracking muon detector of the GRAPES-3 experiment, operating at Ooty in southern India, has been designed for detailed studies on both of these aspects of UHE cosmic ray astrophysics. We present here the details of the muon detector, associated electronics and the data acquisition system. A brief discussion of the potential of the muon detector is presented through simulation studies. r 2005 Elsevier B.V. All rights reserved. PACS: 98.70.Sa; 96.40.Pq; 96.40.De; 98.70.Rz; 95.55.Vj; 13.85.Tp
67815721
The angular resolution of the GRAPES-3 array from the shadows of the Moon and the Sun
Abstract The absence of a well established point source of very high energy ( ≳ 10 TeV ) γ-rays in the sky, makes the measurement of the angular resolution and the absolute pointing accuracy of an extensive air shower (EAS) array a challenging task. In the past, several groups have utilized the reduction in the isotropic flux of cosmic rays due to the shadows of the Moon and the Sun, to measure the angular resolution and the absolute pointing accuracy of their arrays. The data collected from the GRAPES-3 EAS array, over the period of 4 years from 2000 to 2003, has been used to observe the shadow of the Moon at a level of ∼ 5 σ and that of the Sun at a lower level of significance. The high density of the detectors in GRAPES-3 enabled an angular resolution of 0.7° to be obtained at energies as low as 30 TeV. The angular resolution studies were further extended by using two other techniques, namely, the even–odd and the left–right methods. All three techniques have yielded nearly identical results on the energy dependent angular resolution.
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.
55612742
Recent results from the GRAPES-3 experiment
The GRAPES-3 is a dense extensive air shower array operating with ~400 scintillator detectors and a 560 m 2 large tracking muon detector (E μ > 1 GeV), at Ooty in India. The muon detector has been used to observe acceleration of muons during thunderstorm conditions. The muon multiplicity distribution of the EAS is used to probe the composition of primary cosmic rays below 1 PeV, with an overlap with direct measurements. More recently we have explored the possibility of using the angular distribution of >1 GeV muons to identify the best from among several low- and high-energy hadronic interaction models. We have major expansion plans to enhance the sensitivity of the GRAPES-3 experiment in all of the areas listed above.
119032709
Emission of Radiation at Energies > 1014 eV: Binary X-Ray Sources SCO X-1, CYG X-1, HER X-1 and Others
122137195
Neutral charm production in 400 GeV proton-emulsion interactions
A search has been carried out for neutral charm production in 5,108 proton-emulsion interactions at 400 GeV/c. Nine charm candidates have been observed in our fiducial volume which extends from 100 μm-1,000 μm in the forward cone. One of these is a 4-prong and the others are 2-prong events with opening angle>10 mrad and momenta of both decay tracks>150 MeV/c. Search for associated charm decays was made in an extended fiducial volume around the primary stars of these nine candidates. This yielded two neutral 2-prong events, one associated with the 4-prong and the other with a 2-prong candidate. All unassociated candidates are consistent with being backgrounds due toKs, Λ decays, neutral interactions and γ conversions whereas the background to associated events is negligible. Based on the two associated decays the inclusive cross section forD0, −0 production is determined as 27±20 μb/nucleon. Detailed measurements on the 4-prong candidate lead to the identification of one decay track as an electron and another as a kaon. This is interpreted as a semi-leptonic, Cabbibo favouredD0/D−0 decay.
120893061
Models of the proton spin structure
A phenomenological model of spin sharing by the constituents of a proton is constructed, based on the recent EMC measurement of the spin dependent structure function and knowledge of the unpolarized parton densities.
119711961
Aspects of deuteron production in relativistic heavy ion collisions
One criticism of the thermodynamic model for deuteron production has been that it may not be possible for deuterons to exist inside the fireball. We give arguments why deuterons can exist inside the fireball, although they cannot exist in cold nuclear matter at normal density. We redefine the Berkeley coalescence model and show that with this redefinition, the coalescence model is rather close to the thermodynamic prescription. We show that this redefined coalescence model is equivalent to the quantum mechanical sudden approximation model considered by Kapusta. We construct the grand canonical partition function for interacting fermions up to the second virial coefficient and show that the redefined coalescence model and the simple thermodynamic model are two limits of a more complete theory.
124420840
Cosmic Ray Isotope Measurements using the Cherenkov-Rigidity Technique in ISOMAX
The Isotope Magnet Experiment, ISOMAX, which had its first flight in August 1998, is designed to measure the isotopic composition of the light elements using a complement of three major detector systems: a magnetic spectrometer, a time-of-flight (TOF) system, and two Cherenkov detectors. ISOMAX measures mass by combining the velocity measurement with charge and magnetic rigidity (momentum/charge) measurements. In the energy range from 1.1 to 1.7 GeV/nucleon, the velocity measurements are provided by two aerogel Cherenkov counters. The aerogel radiators have a nominal index-of-refraction n = 1.14 corresponding to an energy threshold of 1.08 Ge V /nucleon, which complements and extends the energy range covered by the TOF. Combining the velocity measurement with a measurement of rigidity results in a determination of isotope mass with an expected resolution of ::;: 0.25 amu. We present preliminary isotope data.
128078572
A preshower photon multiplicity detector for the WA93 experiment
Abstract A fine granularity preshower detector has been designed, fabricated and installed in the WA93 experiment for the first ever measurement of photon multiplicity in ultra-relativistic heavy ion collisions. Photons are counted by detecting the preshower signal in plastic scintillator pads placed behind a lead converter and applying a threshold on the scintillator signal to reject the minimum ionizing particles. The photon detection efficiency estimated using Monte-Carlo and beam test results is found to be ∼65–75% depending on centrality. Simulation and performance results of the detector for counting of photons and rejection of hadrons in the large multiplicity environment of ultra-relativistic heavy ion collisions are described.