Speaker
Maria Teresa Grippo
(P)
Description
A search of the Standard Model (SM) Higgs boson production in association with a vector boson, W or Z, has been performed at LHC, using data collected with the CMS detector during 2011 and 2012, corresponding, respectively, to an integrated luminosity of 5 fb-1 at a centre-of-mass energy of 7 TeV, and 19.5 fb-1 at 8 TeV. In spite of its lower cross section compared to gluon fusion and vector boson fusion processes, the associated production represents an interesting channel for the low-mass Higgs boson search, thanks to the presence of highly energetic leptons coming from the decay of vector bosons which suppress the most relevant SM backgrounds. The low-mass Higgs decay search is performed in the di-τ decay mode, which has the second highest branching ratio after the decay in b quarks and it is easier to be identified. Each τ can decay into an electron, a muon or hadronically (τh). The final states studied have three or four leptons: in the WH channel the search is performed in eμτh, μμτh, eτhτh and μτhτh final states, where W decays into electron or muon; in the ZH channel, the Z decays into a pair of electrons or muons, and the Higgs boson is searched in the final states eμ, eτh, μτh and τhτh. The estimate of the background has been made on data and is based on a fake rate technique. The data analysed show no evidence of Higgs boson and are compatible with the SM expected background. Upper limits at 95% confidence lebel have been set for the SM Higgs production cross section times the decay branching ratio in the mass range 110 < mH < 145 GeV.
