Optimisation studies for the pion-induced Drell-Yan measurement at the AMBER experiment

The AMBER experiment is a future fixed-target experiment at SPS, CERN. It was recently approved, and one of the first phase physics goals is to study the pion-induced Drell-Yan process. The Drell-Yan process is a hard process where a quark-antiquark annihilation originates a virtual photon that decays in the final state to a pair of oppositely charged leptons. This process allows privileged access to the pion structure. At AMBER the valence, sea, and gluon contributions in the pion will be characterised with unprecedented accuracy, using high-intensity pion beams of both charges impinging in different nuclear targets. The AMBER setup is based on the COMPASS one but introduces significant upgrades to the existing spectrometer. Thus, the optimisation of the AMBER Drell-Yan detector is currently being studied and is a goal of this work. We introduce the AMBER Monte Carlo simulation chain. We start by simulating the physics process, followed by the simulation of the spectrometer and the response of the detector, and finally by allowing the reconstruction of the data. We will study the impact of the introduction of a vertex detector and how different positions, geometry, and segmentation affect the results. In our study, the silicon microstrips detector FVTX seems to be the most solid option. The choice is based on the values obtained for the dimuon mass and vertex position resolutions, as well as on the global acceptance for dimuons.