A data-driven method to estimate the antiproton background in the Mu2e experiment

The Mu2e experiment at Fermilab will search for the Charged Lepton Flavour Violating process of coherent, neutrinoless muon to electron conversion in the field of an aluminum nucleus. Observation of a CLFV process would provide unambiguous evidence for BSM physics. The key features of the Mu2e experiment are: a high intensity pulsed negative muon beam, and a superconducting solenoid system with a gradient magnetic field to form and guide the intense muon beam to the target. The Mu2e physics data taking is expected to begin in 2027. One of the background processes in Mu2e is antiprotons annihilating in the stopping target to produce signal like electrons. It is a relatively small background with large uncertainty due to the lack of antiproton production cross section information for the Mu2e proton beam energy of 8 GeV. I have developed a novel methodology to estimate the antiproton background in-situ. This forms the main theme of the thesis. At Mu2e energies, antiproton annihilation in the stopping target is the only source of events with multiple, simultaneous particle trajectories. From Geant4 simulations, only about 0.2% of the simulated antiproton annihilation events have a signal-like electron. Meanwhile,5% of events have multiple reconstructible particle tracks per event. Therefore, I devised a methodology to reconstruct the multi-track events and estimate the antiproton background by exploiting the large ratio of the production rates of the two final states.