Cosmic ray proton energy spectrum below the Knee observed by the GRAPES-3 experiment

Abstract

The GRAPES-3 experiment consists of a densely packed array of 400 plastic scintillator detectors and a large area (560 m2) muon telescope. It measures cosmic rays in an energy range of several TeV to over 10 PeV with a trigger efficiency of more than 90% for proton primaries above 40 TeV, providing a substantial overlap with space based direct experiments. The scintillator array records the particle density and arrival time of the shower secondaries, which were used to estimate the shower parameters. The muon telescope is dedicated to recording the muon component in the shower. The observed muon multiplicity distributions (MMDs) were used for precise measurements of the average nuclear composition for proton, helium, nitrogen, aluminium, and iron primaries, independent of making assumptions about the primary composition. In the present work, Gold’s unfolding algorithm was used to extract the nuclear composition and obtain the proton energy spectrum with the help of simulation based on QGSJET-II-04/FLUKA hadronic interaction models. Details of the analysis and results for the extracted composition and proton energy spectrum below the Knee will be presented. © Copyright owned by the author(s) under the terms of the Creative Commons.