University of Minnesota
School of Physics & Astronomy

Academic Calendar

Tuesday, November 3rd 2015
10:00 am:
Thesis Defense in PaN 120
Speaker: Tambe Ebai Norbert, University Of Minnesota
Subject: Search for massive long-lived neutral particles decaying to photons and large missing transverse energy using the Compact Muon Solenoid(CMS) particle detector.
This the public portion of Mr. Norbert's defense. His advisor is Yuichi Kubota.

The Standard Model (SM) despite its unmatched success in describing visible matter in the universe does not describe massive long-lived neutral particles. Therefore any sign of a massive long-lived neutral particle at the Large Hadron Collider(LHC) for example, would be an indication for new physics. Many models Beyond the SM like Gauge Mediated Supersymmetry Breaking Models(GMSB), Split SUSY models, Hidden Valley models and Large Extra Dimension models predict the existence of a massive long-lived neutral particle which decays into a photon and a gravitino.
Capitalizing on the excellent timing resolution of the Electromagnetic Calorimeter(ECAL) of the CMS detector, this thesis presents the search for events whose final state consist of at least one photon with late arrival time at ECAL compared to photons produced directly from proton-proton collisions at the LHC and large missing transverse energy in data recorded by the CMS detector from proton-proton collisions at 8 TeV center of mass energy in 2012. This data corresponds to 19.1/fb total integrated luminosity.
A photon from the decay of a massive long-lived neutral particle arrives late at ECAL due to the long lifetime of the massive long-lived neutral particle and is detectable using timing measurements of photons by ECAL. The large missing energy is used to infer the presence of an undetectable particle like the gravitino produced along with the photon from the decay of the massive long-lived neutral particle. The search covers particle lifetimes ranging from 3 to 40 nanoseconds(10^-9s).

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