Hadronic production of a Higgs boson in association with two jets at ...

1.3. Higgs searches at colliders 22m H[GeV]Figure 1.6: Higgs decay modes for an interesting range of Higgs masses [56,57]. Forlight Higgs bosons (m H 130 GeV) bb is the dominant decay mode. For all othermasses W + W − dominates, for large masses tt becomes an important cannel.above these masses the Higgs decays preferentially into W + W − . This latter channelwith leptonic W decay is much cleaner at hadron colliders since in an hadronicenvironment picking out QCD decays of the Higgs is extremely difficult due to thelarge irreducible backgrounds.The peak in the H → W + W − spectrum around m H ≈ 2m W gives a particularsensitivity to a Higgs boson in this mass range. Indeed the Tevatron has recentlyproduced results [58] which exclude a Higgs boson in the mass range 162-166 GeVat the 95% CL. This is based on the combined analysis [58] of 4.8 [59] (CDF) and5.4 [60] (D0) fb −1 data sets. The experiments investigated events with large missingtransverse energy and two oppositely charged leptons, targeting the H → W + W −signal, in which both Ws decay leptonically. The results are shown in Fig. 1.7.It should be noted that in this analysis theoretical predictions for the Higgs crosssection play a crucial role, which we will talk more about in Chapter 6. Veryrecently, [61] the combined CDF (5.9) fb −1 and D0 (6.7) fb −1 results have beenpublished, increasing the exclusion limits to 158 < m H < 175 GeV/c 2 , the resultsare summarised in Fig 1.8.