Search for Long-Lived Neutral Particles in Final States with a Muon and Multi-Track Displaced Vertex with the ATLAS Detector at the Large Hadron Collider

This work presents the result of a search for a new long-lived neutral particle decaying into a muon and charged hadrons in proton-proton collisions at a centre-of-mass energy of 7 TeV with a total integrated luminosity of 4.4 inverse femtobarn, using the ATLAS detector located at the Large Hadron Collider (LHC). Many extensions to the current Standard Model of particle physics predict the existence of such new particles, including the neutralino in an R-parity violating supersymmetry scenario. In this search, a set of selection criteria has been established to be sensitive to this kind of signal, in addition to evaluating the background in a data-driven manner. No excess of events above the expected background is observed with the collected data and limits are set on the squark pair production cross section, multiplied by the branching ratio for a squark to decay, via a long-lived neutralino, to a muon and charged hadrons, as a function of the neutralino lifetime. In addition, we present a study on two-track displaced vertex, produced from the decays of long-lived V0. This is done with data from the proton-proton collisions at a centre-of-mass energy of 8 TeV.