Browsing by Author "Stadnitski, Alexi"

Vector boson scattering (VBS) is a process that occurs when vector bosons, the spin-1 fundamental particles of the Standard Model (SM), are radiated by quarks accelerated to high energies in a collider environment. These bosons may interact with each other before decaying due to their instability. This process is of interest because of its strong sensitivity to physics Beyond the Standard Model (BSM): occurring in the high-energy regime at the cutting edge of modern technology, VBS is one of few processes able to probe the coupling of the gauge fields to each other, as well as to the Higgs field, both of which are sensitive to new physics which may spoil the delicate cancellations required to maintain unitarity. In particular, the polarization states of the massive vector bosons—the W and Z, carriers of the weak interaction—are acquired as a direct consequence of electroweak symmetry breaking (EWSB). EWSB has been at the frontier of known physics since the Higgs boson was confirmed to exist in 2012. VBS has three possible decay channels: fully leptonic, semi-leptonic, and all-hadronic. We focus on the all-hadronic channel, in which each boson begets two quarks, to take advantage of its higher branching ratio: nearly half of all VBS events decay through this channel. With the Large Hadron Collider (LHC) in a period of long shutdown as it is upgraded to reach higher luminosities, one of the major steps in VBS analyses is to separate the BSM-sensitive electroweak VBS from chromodynamically-induced (QCD) diboson production, in which vector bosons do not interact; furthermore, a deeper understanding of EWSB requires the various polarization states to be distinguished from each other. To these ends, simulation is a critical component of analyses, as VBS is among the rarest processes at the LHC and overwhelmed by backgrounds with larger cross sections. We investigate the viability of employing the MadGraph5_aMC@NLO suite to generate VBS events, successfully producing electroweak, QCD, and mixed samples of all possible combinations of weak bosons: the same-sign WW, opposite-sign WW, WZ, and ZZ channels. Furthermore, we create working samples of these VBS channels with enforced polarization: both bosons longitudinally polarized, both transversely polarized, and one of each. We provide histograms that report differences in the angular distributions of the produced events, showing how to distinguish the modes of production and polarizations based on kinematic topology.