Highlights from the GRAPES-3 Experiment on Galactic Cosmic Ray Measurements

The GRAPES-3 experiment, located in Ooty, India (11.0° N, 76.7° E, 2200 m a.s.l.) comprises a dense array of 400 plastic scintillator detectors and a 560 m$^2$ area muon telescope to measure electromagnetic and muonic components of cosmic ray showers. The experiment could successfully measure the cosmic ray proton spectrum in the energy range of 50 TeV - 1.3 PeV, providing an overlap with direct measurements. The relative proton fraction was determined using muon multiplicity distributions. A spectral hardening was observed above 165 TeV, challenging the simple power-law description extending to the knee energy. Additionally, we have observed both small and large scale cosmic ray anisotropies. We observed two significant small-scale anisotropic features at a median energy of 16 TeV using the time-scrambling method, consistent with results from the HAWC and ARGO-YBJ experiments. However, for the observation of large-scale anisotropy, we used an iterative maximum-likelihood approach for retrieving attenuated signals which occurs due to the limited instantaneous field of view for low latitude location of GRAPES-3. We successfully observed large scale anisotropy with a statistical significance of six standard deviations and the results are consistent with other experiments both in amplitude and phase. ... mehrWe have added another muon telescope to the experiment. The new muon telescope, covering an area of 570 m$^2$ is nearing its completion, with 75% of its modules already operational. The two muon telescopes combined will provide two times larger detection area which could result in an enhanced sensitivity particularly for the detection of PeV gamma-ray sources and mass composition measurements below 100 TeV.