Under the mentorship of Professor Elliot Lipeles in the Department of Physics and Astronomy, we worked on the project “Particle Physics at the Large Hadron Collider” in the PennATLAS group. Using particle processes simulated by postdoctoral researcher Prachi Atmasiddha, we used the ROOT software in C++ and Python to analyze interactions between elementary particles such as quarks and vector bosons. In order to study a specific signal occurring in the particle interaction, the “background” of additional particles and their interactions must be analyzed. We reconstructed simulated particles using methods applicable to the real ATLAS detector and compared the reconstructed results to the simulated values. Our studies focused on reconstructing particles in two distinct particle events originating from proton-proton collisions.

We conducted a study of methods for reconstructing quarks from particle jets in vector boson scattering events (VBS quarks) and calculated the percentage of quarks that were correctly assigned for each. Through testing of four different potential algorithms for selecting the proper particle jets, it was determined that sorting pairs of jets by a combination of their momenta and the angle between them led to the highest efficiency of correct matches. With this method, properties of the quarks and assigned jets such as transverse momentum or invariant mass were equal or similar.

We also examined and reconstructed W and Z bosons, with the goal of comparing and optimizing our Delphes simulation to match the official ATLAS simulation results. We did this for three outcomes of two bosons per collision, being Z to two leptons in each, and W to two quarks in one, Z to two quarks in another, and Z to two bottom quarks in the last. The quarks were grouped into fat jets so we used similar reconstruction techniques to the VBS quarks, and we sorted the leptons by transverse momentum and took the highest two momenta, along with cuts on lepton eta, transverse momentum, and delta R, with the additional requirement of the leptons (either electrons or muons) being of the same flavor. We were able to successfully reconstruct the W and Z bosons to have a similar added invariant mass as the ATLAS simulation did by both distribution and number of selected events. We also found it to be optimal to include next to leading order events to our simulation, instead of just leading order events, to better match the ATLAS results. Thank you for listening, and we hope you found our presentation interesting and informative.