The tau lepton decays to hadrons (65% of the time) or to an electron or a muon (the other 35%). In addition to that, there is also a large amount of missing momentum as the neutrinos and neutralinos do not interact with the detector and escape undetected. The bottom quark produces a collimated beam of hadrons, called a jet. The signature of the signal is characterised by the presence of two bottom quarks and two tau leptons in the final state. 2, and reflects a certain type of configuration of the SUSY parameters.įigure 2: A top squark pair is produced in a proton-proton collision, leading to pairs of bottom quarks and tau leptons accompanied by neutrinos and neutralinos. This SUSY process (the "signal”) is quite unique, as schematically illustrated in Fig. The neutralino is assumed to be the lightest superparticle and can potentially be a candidate for dark matter. In this study we have investigated scenarios where the top squark undergoes a cascade decay, producing a bottom quark (b), a tau lepton (□), a neutrino (□), and a neutralino. Given that they might be within wide ranges, the production of massive SUSY particles in proton-proton collisions can result in a diverse variety of experimental signatures, arising from their decay products. The masses of the SUSY particles, as well as various other parameters of the theory, are unknown and have to be determined experimentally. Grefe, “Unstable Gravitino Dark Matter – Prospects for Indirect and Direct Detection”, arXiv:1111.6779. We look for it in all possible ways ( Searching for top squarks with CMS data ) to make sure we do not leave any stone unturned.įigure 1: The Standard Model and SUSY particle content. Hence, it is of great importance to probe the existence of the top squark. Since the Higgs boson primarily interacts with massive particles, the heaviest known particles, the top quark and its superpartner (top squark), play a central role in solving the Higgs boson mass problem. The theory also provides potential candidates for explaining dark matter. The interactions of SUSY particles with the Higgs boson mitigates its mass problem. This discrepancy can potentially be addressed by a supersymmetric (SUSY) extension of the theory, which complements the SM particles with SUSY counterparts, as shown in Fig. However its value has been measured to be 125 GeV, by the ATLAS and CMS experiments. The mass of the Higgs boson calculated in the SM framework can be arbitrarily large because of certain effects known as quantum fluctuations. However, the SM has a few serious shortcomings, such as the Higgs boson mass problem. The measurement of the ratio of the decay rate of W bosons to τ leptons and muons, R( τ/ μ), constitutes an important test of this axiom.The standard model (SM) of particle physics, is the most successful theory describing the behaviour of elementary particles and their interactions. A fundamental axiom of this theory is the universality of the couplings of the different generations of leptons to the electroweak gauge bosons. The standard model of particle physics encapsulates our best current understanding of physics at the smallest scales.
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