A search for new physics with a signature of missing energy in events with high pT jets is presented. The analysis is performed with 1.1 fb-1 of 7 TeV data taken using the Compact Muon Solenoid detector at the Large Hadron Collider in 2011. The kinematic variable α T is used to control the dominant QCD background that exhibits fake missing energy originating from mismeasurment. The remaining electroweak backgrounds are estimated using data-driven techniques through the use of two control samples. The background from boosted W decays is estimated with the use of a dedicated µ + jets control sample, while the irreducible background from Z → [Symbol appears here. To view, please open pdf attachment] is estimated using a γ + jets control sample. A shape analysis is performed across eight bins in HT , with the signal selection and the two control samples treated simultaneously in a likelihood fit. The data was found to agree very well with the Standard Model only hypothesis with a p-value of 0.56, which indicates no evidence of new physics. The results are interpreted in the scope of a possible new physics model, the Constrained Minimal Supersymmetric Standard Model. Exclusion limits are set at the 95% confidence level on the parameters m0 and m1/2 that set the mass hierarchies of the sparticles. An extension is also presented allowing additional signal into the muon control sample. The effect on the limit is negligible, although adopting a leptonic variable of the αT variable increases the ratio between signal and background events significantly. This approach is recommended for searches with higher statistics in 2012.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:560740 |
| Date | January 2012 |
| Creators | Hatherell, Zoe |
| Contributors | Nash, Jordan |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/10168 |
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