121643346
Study on nuclear composition of cosmic rays around the knee utilizing muon multiplicity with GRAPES-3 experiment at Ooty
The composition and energy spectrum of primary cosmic rays (PCRs) are the only observables available at ultra-high energies to understand the nature of sources accelerating protons and other nuclei to 1000 TeV and beyond. These observables have been measured up to 1000 TeV, directly with detectors flown aboard balloons and satellites. The measurements at > 1000  TeV are obtained indirectly, from ground based observations of extensive air showers (EAS). However, their interpretation depends on rather inadequate knowledge of hadronic interactions at > 1000  TeV . The GRAPES-3 experiment has been designed to study the EAS at ∼ 30  TeV to provide a sizable overlap with the results from direct measurements, enabling selection of a suitable model of hadronic interactions. We present here the salient features of GRAPES-3 experiment and some details of muon multiplicity distributions (MMDs) observed with a 560 m2 muon detector as a function of shower size ( N e ) fro analysis of 560 days of data. A comparison of GRAPES-3 results with direct measurements over the energy region 100 – 1000 TeV is presented to show the suitability of hadronic interaction generator “SIBYLL” for the interpretation of EAS data. We presented the energy spectrum of five nuclear groups (H, He, N, Al and Fe) with good statistics for 100 – 10, 000 TeV.
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.
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
119032709
Emission of Radiation at Energies > 1014 eV: Binary X-Ray Sources SCO X-1, CYG X-1, HER X-1 and Others
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.
8205449
The quark gluon plasma: Lattice computations put to experimental test
I describe how lattice computations are being used to extract experimentally relevant features of the quark gluon plasma. I deal specifically with relaxation times, photon emissivity, strangeness yields, event-by-event fluctuations of conserved quantities and hydrodynamic flow. Finally I give evidence that the plasma is rather liquid-like in some ways.
118245922
Cygnus experiment at Los Alamos
The Cygnus experiment at Los Alamos National Laboratory has been designed to study, with high angular accuracy, point sources of gamma rays of energy above 1014 eV. The experimental detector consists of an air shower array to observe gamma-ray showers and a shielded, large-area track detector to study the muon content of the showers. In this paper we present preliminary data from the array and describe its performance.
119240200
Properties of the SU(Nc) Gluon Plasma
We investigate the deconfinement transition in SU(Nc) gauge theories, and properties of the deconfined phase. A detailed lattice study of SU(4) and SU(6) gauge theories are conducted, and finite volume and cutoff effects on thermodynamic observables are studied. The scaling of the deconfinement transition point with lattice spacing is used to calculate the scale, Lambda_MSbar. The continuum estimates of the thermodynamic quantities are used to study properties of the gluon plasma. In particular, the approach to conformal limit is studied. We do not find any evidence of a strongly coupled, conformal phase in these theories.
123088134
Proton optical model potential at sub-Coulomb energies for medium weight nuclei
The ($p$,$n$) reaction excitation functions for eleven nuclei from $A=45 \mathrm{to} 80$ measured at proton energies below \ensuremath{\sim}5 MeV have been analyzed utilizing the optical model. The real potential parameters used in the present work have been obtained by suitably combining the proton optical model parameters determined between 3 and 60 MeV. Large energy dependence of the real potential at energies below 5 MeV has been observed. The imaginary potential depths determined in the present analysis exhibit an anomalous behavior when plotted as a function of mass number $A$. By utilizing the low and intermediate energy proton data, an attempt has been made to obtain a "global" set of optical parameters in the proton energy range between 4 and 180 MeV, for medium weight nuclei.
118808591
A soluble statistical model for nuclear fragmentation
The statistical model of Chase and Mekjian, which offers an analytic solution for the canonical ensemble of non-interacting fragments, is investigated for it's thermodynamic behavior. Various properties of the model, which exhibits a first-order phase transition, are studied. The effects of finite particle number are investigated. Three extensions of the model are considered, excluded volume, Coulomb effects and inclusion of isospin degrees of freedom. A formulation of a microcanonical version of the model is also presented.