Cosmic ray tests for the QS1 module of the new small wheel in the ATLAS experiment -and- prospects on the search for heavy vector triplet bosons in the leptonic decay channels with the ATLAS experiment at the HL-LHC

The ATLAS detector at the LHC, CERN, will be upgraded after the current data taking period (Run 2). The ATLAS detector has to under go a series of upgrades in order to fulfill the needed performance at improved LHC conditions. The LHC will stop for the second time between 2019-2020, period of time during which the ATLAS detector is going to upgrade its muon subdetector. This upgrade is the New Small Wheel (NSW), which will replace part of it send cap muon spectrometer. The NSW will be comprised of two detection systems, the Micro Megas and the small-strip Thin Gap Chambers (sTGC), the latest is being constructed in Chile by a joint collaboration between PUC and UTFSM. After the construction, the chambers are tested before being shipped to CERN. The muon detection efficiency is calculated using cosmic muons. A trigger system is used as part of the setup, which checks for coincidences between plastic scintillator arrays placed on top and below the detectors in order to distinguish muons from background signals. A DAQ system is used to callibrate the electronics and measure muon hits. The whole system has been set up and has already been used to test one module that was successfully sent to CERN and integrated into the first wedge. Prospects were made for searches for new heavy SSM Z and W bosons at the last stage of the LHC (2024-2032), called High Luminosity LHC (HL-LHC), which is expected to run at √s = 14 TeV and collect 3000 fb−1 of data. These studies are based on MC simulations, and are used as benchmark for other models. The response of the upgraded ATLAS detector as well as pile-up collisions were simulated. SSM Z bosons are searched for in the dilepton final states, where it is expected to observe a signal with a more than five significance value at an invariant mass of 6.4 TeV, and exclude masses up to 6.5 TeV. SSMW0 bosons are searched for in the lepton plus neutrino final state, where itis expected to observe a signal with a more than five significance value at an invariant mass of 7.7 TeV, and exclude masses up to 7.9 TeV.
Tesis (Master in Physics)--Pontificia Universidad Católica de Chile, 2018