Use this URL to cite or link to this record in EThOS:
Title: Searching for SUSY in events with Jets and Missing Transverse Energy using αT with the CMS Detector at the LHC
Author: Hatherell, Zoe
ISNI:       0000 0004 2728 9684
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
Availability of Full Text:
Access from EThOS:
Access from Institution:
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.
Supervisor: Nash, Jordan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral