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(s)
Cutajar, Michael
Type
Thesis
Abstract
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.
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.
Date Issued
2012
Date Awarded
2012-09
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Colling, David
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)