High Energy Astroparticle Physics at Ooty and the GRAPES-3 Experiment

Abstract

The astroparticle studies at Ooty have their roots going way back into the fifties, when studies using cosmic rays were initiated with cloud chambers of progressively larger sizes as the primary detector and measuring device to obtain properties of hadrons at high energies. This study was subsequently strengthened with the installation of a total absorption calorimeter and a modest extensive air shower array to probe the composition of the primary cosmic rays to very high energies. The discovery of pulsars provided a thrust for the exploration of these compact objects as the sources of γ-rays at TeV energies with the aid of atmospheric Cerenkov detectors in the seventies. With the rapid technological advances occurring during the subsequent years in detectors, electronics and computers, physicists world-wide were able to set up very large and remarkably sensitive experiments that were hard to imagine a decade earlier. With the increasing sophistication and complexity the modern experiments require participation of very large teams of scientists. This development has made the formation of collaboration of large number of physicists both experimental and theoretical, engineers, technicians etc., from a number of institutions and universities, a prerequisite for setting up any major experimental facility. The GRAPES-3 experiment is a collaboration of 34 scientists from 13 institutions, including 8 from India and 5 from Japan. The GRAPES-3 experiment contains a dense extensive air shower array operating with ~ 400 scintillator detectors and a 560 m 2 tracking muon detector (Em > 1 GeV), at Ooty in India. 25 % of scintillator detectors are instrumented with two fast photomultiplier tubes (PMTs) for extending the dynamic range to ~ 5x10 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 o at 30 TeV, is measured from shadow of the Moon on the isotropic flux of cosmic rays. Sensitive limit on the diffuse flux of 100 TeV γ-rays is placed by using muon detector to filter out the charged cosmic ray background. The tracking muon detector allows sensitive measurements on the 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. PACS

A combined astrophysical and dark matter interpretation of the IceCube HESE and throughgoing muon events

“…The top panel is for K = 1 (pγ) and the bottom panel is for K = 2 (pp). In each panel, we show the current 90% CL upper limits on the integrated photon flux over the whole energy range from 10 GeV to 10 8 GeV, obtained from a combination of various experiments, such as CASA-MIA [129], MILARGO [130], Fermi-LAT [131], GRAPES [132], KASCADE [133,134], ARGO [135] and HAWC [136]. We also adopted a combined best fit [137] in the 1-100 TeV region for the upper bound on photon flux based on the diffuse electron flux limit from AMS-02 [138], DAMPE [139], Fermi-LAT [140], MAGIC [141], HESS [142], and VERITAS [143], since air showers from electrons, positrons and photons behave the same.…”