Alec Aivazis edited untitled.tex  over 9 years ago

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\textit{Oh, Given the high precision of analysis techniques implemented at the LHC at Cern, there has been increasing opportunity to discover theories beyond the current model of fundamental physics. One such theory for physics “beyond the Standard Model” is known as Supersymmetry and proposes  an empty article!} additional symmetry to be added to space-time, allowing for a family of particles that are an exact duplicate (except for this quantity, labeled R) to those found in the Standard Model. Associated with the extension is a corresponding conservation law in supersymmetric interactions known as ‘R-parity’ [Super Primer]. R-parity conserving decays have been in high focus since they provide an explanation for the massive amount of dark energy foundr, estimated to be close to 73\% [LSP][DM Primer]. Since R needs to be conserved, the lightest supersymmetric particle (LSP for short) would not be able to decay to any other particle other than itself and would explain the massive amount of seemingly stable dark matter [LEP, 8]. For this reason, there has been a large effort to look for data that resemble R-parity conserving modes, without much attention towards R-parity violating decays.   Over the past two years, I performed an analysis looking for data that resembles a signal that is consistent with a supersymmetric decay. My target process is a supersymmetric top decaying to oppositely charged W-bosons one of which decays to a positive muon and an anti-b quark, and the second decays to a b-quark and negatively charged muon. I chose to look for a particular decay that resembles a standard model interaction with well understood backgrounds because I assumed that the process would behave similarly, except for this additional symmetry which I ignored as part of the analysis. Therefore, I chose a process whose major backgrounds were well modeled using current Monte Carlo methods.    One variable that affects the rate at which this occurs is the mass of the supersymmetric top quark [Baryogensis]. Since this quantity has not be measured, the goal of my research was to to calculate a cutoff mass at which I can say there is enough data to prove/disprove the theory at a mass lower than a certain value. I did this by performing a comparison between the expected numbers if the theory were true to the numbers found in the data sample. Since the probability at which the decay happens decreases as the supersymmetric top mass increase, there should be a point at which the numbers flip from being too high to too low. The point at which this flip occurs is the “cutoff” point where I can say below which the data does not have enough events to support the theory.   The data came from the latest set published by the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider at CERN in Switzerland. At the core of the design is a superconducting solenoid magnet that is 6m in diameter,13m long, and generates a 4T field which is used to determine the charge of the particle. On the outside of the magnet is an electromagnetic calorimeter (ECAL) which is designed to measure electromagnetic deposits. After the products of the decay have passed through the ECAL, they reach the hadronic calorimeter (HCAL) which absorbs most of the energy left in the collision. The particles that do make it through the HCAL are either neutrinos or muons. The muons are detected and collected in a separate configuration around the magnet composed of a drift tube and cathode-strip detector [CMS].  The result of this analysis will provide future researchers with a better sense of possible values for the mass of the supersymmetric top and possibly allow for the creation of more specialized detectors that focus on higher mass regions than the calculated cutoff.     Annotated Bibliography  Super primer: http://arxiv.org/abs/hep-ph/9709356  DM primer: http://arxiv.org/abs/1006.2483  Baryogensis by RPV: http://arxiv.org/abs/hep-ph/0605263  LSP as dark matter candidate: http://arxiv.org/abs/hep-ph/0607301  Physics detectors at LHC: http://arxiv.org/abs/hep-ex/0512057  Measurement of ttbar: http://arxiv.org/abs/1406.5375  Stops and neutrino mass hierarchy: http://arxiv.org/abs/1401.7989  previous serches for R-parity violation: http://arxiv.org/abs/1310.3598  Dark matter considering MSSM: http://arxiv.org/abs/astro-ph/0609126  general summary of susy searches: http://arxiv.org/abs/hep-ex/0411002  You can get started by \textbf{double clicking} this text block and begin editing. You can also click the \textbf{Insert} button below to add new block elements. Or you can \textbf{drag and drop an image} right onto this text. Happy writing!