AMBER ("Apparatus for Meson and Baryon Experimental Research") is a new fixed-target experiment at CERN (the European Laboratory for Particle Physics). The AMBER collaboration continues the COMPASS experiment’s goals, for studies of hadron structure and spectroscopy at the CERN M2 beam line. AMBER proposes to study several aspects of quantum chromodynamics, among which are the studies related to the pion structure, accessed by the pion-induced Drell-Yan process. These Drell-Yan measurements will be performed with both positive and negative hadron beams on nuclear targets.The Drell-Yan process consists in the quark-antiquark annihilation that takes place in high-energy hadron collisions, producing a virtual photon that decays into a pair of leptons of opposite charge. In this work, the simulation of the Drell-Yan collisions at AMBER is described. The differences between the kinematic distributions of signal (the Drell-Yan process) and minimum bias events (all hadronic interactions that may occur in the target) are studied. The hadronic cascades that are produced contain many charged pions and kaons that tend to decay into muon-neutrino pairs. The random combinatorial pairs of muons formed in this way contribute to the background in the Drell-Yan measurements. The Drell-Yan dimuon events obtained from different target configurations and different beam momenta are analysed. The distributions for the various kinematic variables are compared and the dimuon acceptance is evaluated. Some conclusions on the optimisation of the Drell-Yan measurement are drawn from the studies done. The comparison between the acceptance results of the default and compressed target configurations is essential to optimize experimental measurements. Both configurations face challenges with substantial smearing along the Z-axis, largely due to the absence of a vertex detector in the reconstruction process. To enhance the acceptance for the Tungsten target and improve measurement precision, a compressed setup is implemented and simulated, aiming to reduce smearing effects and increase overall accuracy. The analysis also evaluates the efficiency requirements of CEDAR detectors at different beam momenta.

COMPASS (Common Muon and Proton Apparatus for Structure and Spectroscopy) is a fixed-target experiment with a beam of negative pions at 190 GeV. The COMPASS setup includes 3 target materials placed sequentially along the beamline: two cells of solid ammonia (NH3) crystals embedded in a helium bath (3He and 4He); a aluminium cell (27Al) and a tungsten plug with its first 20 cm used as a target(184W). In the COMPASS dimuon mass spectra, we observe two peaks on top of a decreasing continuum: J/ψ at 3.097 GeV/c 2 and ψ(2S) at 3.686 GeV/c 2 . J/ψ and ψ(2S) are charmonium resonances made of a quark charm and an antiquark charm. The goal of this thesis is to obtain the nuclear modification factors of J/ψ production as a function of transverse momentum (pT ) and Feynman-x (xF), using COMPASS 2018 data to access Cold Nuclear Matter (CNM) effects: Parton Energy Loss; Nuclear Shadowing and Anti-shadowing and EMC effect. The purity of J/ψ signal in the COMPASS dimuon mass spectra is evaluated in a cocktail fit, considering all the physics processes in J/ψ mass region. To calculate the J/ψ differential cross-section, the acceptance is considered, given as the ratio of the number of J/ψ events reconstructed over the number of events generated by Pythia, using a model based in Non-Relativistic QCD. The acceptance is calculated in bins of transverse momentum, pT , Feynman-x, xF, and vertex position along the beamline, zvertex. The J/ψ Reconstructed Monte Carlo is compared with the real data in the range of J/ψ highest purity, obtaining discrepancies of 50 %, demonstrating that NRQCD model doesn’t describe well charmonium production at the COMPASS energies. The discrepancies are corrected, applying event reweighting in the muon laboratory variables. Finally, the differential cross-section ratios between the three target materials are calculated.

This work investigates how the removal of calorimeters could affect Drell-Yan measurements in the AMBER experiment at CERN. Through systematic Monte Carlo simulations, 8 different calorimeter configurations were studied, 4 for the Large Angle Spectrometer (LAS) and 4 for the Small Angle Spectrometer (SAS) subsystems, combining the presence or absence of ECAL1, ECAL2, HCAL1, and HCAL2. The hypothesis is that calorimeter removal should not affect the experiment, as they act only as passive elements for muon identification. To automate and simplify the simulation process across multiple scenarios, the software AMBER Simulation Chain Manager was developed, a framework enabling researchers without specialized software expertise to run complete simulation chains locally, facilitating focus on physics rather than computing complexity. The study reveals that the standard PHAST muon identification threshold of 30 /₀ is insufficient for SAS configurations without calorimeters, as MF2 alone provides only 20.78 /₀. However, when considering a reduced threshold of 20 /₀, no significant differences are observed between any setup with respect to dimuon acceptance, resolution of variables, variable distributions, and detection patterns between LAS and SAS. These results demonstrate that calorimeters can be safely removed without degrading reconstruction quality or experimental performance. However, adjustments are required either in the software, by lowering the PHAST threshold, or in the hardware, by adding material to SAS. These findings open the possibility for optimizing the detector geometry, potentially improving acceptance and efficiency while maintaining reconstruction robustness in future AMBER configurations.

A measurement of the forward-backward asymmetry (AFB) of Drell-Yan lepton pairs in pp collisions at s=7TeV is presented. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 5fb-1. The asymmetry is measured as a function of dilepton mass and rapidity in the dielectron and dimuon channels. Combined results from the two channels are presented, and are compared with the standard model predictions. The AFB measurement in the dimuon channel and the combination of the two channels are the first such results obtained at a hadron collider. The measured asymmetries are consistent with the standard model predictions. © 2012 CERN.