Search for high-energy gamma-ray emissionand upgrade of the GAMMA experiment on Mt. Aragats

¹ Alikhanyan National Laboratory, Yerevan, Armenia
² state Engineering University of Armenia, Yerevan, Armenia
³ P.N. Lebedev Physical Institute of the RAS, Moscow, Russia
⁴ LUPM, Université Montpellier 2, CNRS/IN2P3, Montpellier, France
⁵ Department of Physics, University of Michigan, Ann Arbor, USA
⁶ Warsaw University of Technology, Branch in Plock, Poland
⁷ CERN, Geneva, Switzerland
⁸ Centre d'Études Nucléaires de Bordeaux-Gradignan, Gradignan, France
⁹ DESY, Zeuthen, Germany
¹⁰ Department of Physics, Southern University, Baton Rouge, USA

^a corresponding author
^b e-mail: romenmartirosov@rambler.ru

Abstract

We present the current status of the search for possible diffuse orlocalized gamma-ray emission at energies above about 100 TeV with the GAMMA air shower detector which is located at 3200 m a.s.l. on Mt. Aragats, Armenia. For this search we select muon-poor extensive air showers detected by GAMMA.We discuss ongoing studies of improved criteria for the selection ofmuon-poor showers, taking into account the geometry of the muon underground detector array in 2004–2011. A modernization of the muon array was completed between October 2011 and February 2012. Sixty additional muon scintillation detectors were installed and are now taking data. They will improvethe the selection of muon-poor showers, the primary energy estimation, and should also yield improved information on the mass composition.