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Title: Search for supersymmetric neutral Higgs bosons decaying to τ pairs in the e + τ-jet final state with calibration using Z → ττ events at CMS
Author: Cutajar, Michael
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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A search for the neutral Higgs bosons,φ , of the Minimal Supersymmetric Standard Model (MSSM) decaying to τ pairs in proton-proton collisions at √s = 7 TeV is performed. The e + τ-jet final state is considered in data corresponding to 2.1 fb-1 of integrated luminosity collected by the Compact Muon Solenoid detector. The search is performed separately in the inclusive channel, sensitive to both gg → φ and gg → b [Symbol appears here. To view, please open pdf attachment]φ production, and the b-tagged channel which maximises sensitivity to gg → b [Symbol appears here. To view, please open pdf attachment]φ. No significant excess of events over the predicted Standard Model backgrounds is observed. Upper limits are set on the φ → + τ+τ- production cross section, σ(pp → φ+X) x B( φ → τ+τ- ). Cross sections greater than 18 and 1.3 pb are excluded at 95% confidence level for mA = 100 and mA = 400 GeV respectively. The limits are interpreted as constraints on tan β in the mhmax scenario of the MSSM: Values of tan β greater than 12 and 40 are excluded at 95% confidence level for mA = 100 and mA = 400 GeV respectively. The inclusive channel is found to have the greatest tan β sensitivity at large mA and the b-tagged channel to have greatest sensitivity at small mA. The τ-jet reconstruction is calibrated using Z → τ+τ- events. A measurement of the Z → τ+τ- cross section in the e + τ-jet final state using the same dataset as the Higgs search yields σ (pp → Z + X) . B(Z → τ+τ-) = 1.06+0.05 -0.04(stat.) ± 0.07(syst.) ± 0.05(lumi.) nb. The result is in good agreement with the Standard Model prediction of 0.972 ± 0.042 nb at next-to-next-to-leading order. This measurement provides a cross check of the methods used in the φ → τ+τ- search.
Supervisor: Colling, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available