# The GRAND project and GRANDProto300 experiment

## TL;DR

GRAND is a proposed large-scale observatory for ultra-high energy cosmic particles, aiming to detect neutrinos, cosmic rays, and gamma rays with unprecedented sensitivity, while GRANDProto300 serves as a validation and science precursor.

## Contribution

The paper introduces the GRAND project and its prototype, GRANDProto300, detailing their design, scientific goals, and the validation of detection concepts for ultra-high energy particles.

## Key findings

- GRANDProto300 will validate detection techniques for GRAND.
- The project aims to measure air showers from cosmic rays between 10^16.5 and 10^18 eV.
- GRAND will enable neutrino astronomy and study the origin of ultra-high energy cosmic particles.

## Abstract

The Giant Array for Neutrino Detection (GRAND) is a proposal for a giant observatory of ultra-high energy cosmic particles (neutrinos, cosmic rays and gamma rays). It will be composed of twenty subarrays of 10 000 antennas each, totaling a detection area of 200 000 km$^2$. GRAND will reach unprecedented sensitivity to neutrinos allowing to detect cosmogenic neutrinos while its sub-degree angular resolution will also make it possible to hunt for point sources and possibly start neutrino astronomy. Combined with its gigantic exposure to ultra-high energy cosmic rays and gamma rays, GRAND will be a powerful tool to solve the century-long mistery of the nature and origin of the particles with highest energy in the Universe. On the path to GRAND, the GRANDProto300 experiment will be deployed in 2020 over a total area of 200 km$^2$. It primarly aims at validating the detection concept of GRAND, but also proposes a rich science program centered on a precise and complete measurement of the air showers initiated by cosmic rays with energies between 10$^{16.5}$ and 10$^{18}$ eV, a range where we expect to observe the transition between the Galactic and extra-galactic origin of cosmic rays.