Higgs boson searches in the CMS experiment in the γγ, ZZ and WW channels.

par Dr Hugues Brun (Universidad de Oviedo)

vendredi 8 févr. 2013, 14:00 → 15:00 Europe/Paris

Auditorium M. Vivargent (LAPP)

The Standard Model of particle physics successfully explains the majority of experimental high energy physics data. The masses of the W and Z, the vector bosons of the weak interaction, have their origin in a spontaneous breaking of the gauge symmetry. This symmetry breaking is performed, using the Brout-Englert-Higgs mechanism, by introducing a new scalar field, whose quantum, the Higgs boson is actively searched at the LHC. Direct searches at LEP have excluded the Higgs boson with masses lower than 114 GeV/c2, and those at Tevatron have led to an exclusion of masses between 147 and 173 GeV/c2. The fit of precision electroweak measurements constrains the Higgs boson mass to be less than 158 GeV/c2 (all these limits and constraints are at 95% confidence level). I will present in this seminar Higgs boson searches in CMS through the three most powerful decays channel at low Higgs boson masses : H ➝ γγ, H ➝ ZZ ➝ 4l and H➝WW➝ 2l 2ν. The reconstruction and identification of final state particles are very important in the H ➝ γγ and H ➝ ZZ ➝ 4l analyses, where the Higgs mass resolution have a strong effect on the sensitivity. In the H➝WW➝ 2l 2ν channel, the search of signal imposes to understand several backgrounds which have the same final state. I will explain the features and the analyses strategy of each channel. I will also detail the key-points of these three analyses. In July 2012, the two LHC experiments, ATLAS and CMS, both announced the discovery of a new particle with a mass near 125 GeV/c2. I will finally show the last public results obtained in CMS with the 2012 data and then their compatibility with the Standard Model Higgs boson.