Direct Higgs production and jet veto at hadron colliders ∗

We consider Higgs boson production through gluon–gluon fusion in hadron collisions, when a veto is applied on the transverse momenta of the accompanying hard jets. We compute the QCD corrections to this process at NLO and NNLO, and present numerical results at the Tevatron and the LHC. CERN–TH/2002-123 June 2002 Talk given by M. Grazzini at the XXXVIIth Rencontres de Moriond, QCD and Hadronic interactions, Les Arc1800, France On leave of absence from INFN, Sezione di Firenze, Florence, Italy. Partially supported by Fundación Antorchas and Conicet. The search for the Higgs boson is one the main experimental challenges in high-energy physics. In the near future this search will be carried out at hadron colliders, the Tevatron and the LHC. LEP has established at 95% confidence-level that the mass MH of the SM Higgs boson is larger than 114.1 GeV [1], whereas precision electroweak measurements indicate that the Higgs boson should be light (MH ∼< 200 GeV). At the Tevatron and the LHC, various channels [2, 3] can be exploited to search for the Higgs boson in this mass window. Direct Higgs production followed by the decay H → W W , ZZ is relevant for a Higgs boson with mass 140∼<MH ∼< 190 GeV. In particular, the decay mode W W ∗ → llνν̄ is quite important [2, 3, 4, 5], since it is cleaner than W W ∗ → lνjj, and the decay rate H → W W ∗ is higher than H → ZZ by about one order of magnitude. An important background for the direct Higgs signal H → W W ∗ → llνν̄ is tt̄ production (tW production is also important at the LHC), where t → lν̄b, thus leading to b jets with high pT in the final state. If the b quarks are not identified, a veto cut on the transverse momenta of the jets accompanying the final-state leptons turns out to be essential, both at the Tevatron [2, 5] and at the LHC [3, 4], to cut the hard b jets arising from this background process. Here we study the effect of a jet veto on the signal, or, more precisely, on the cross section for direct Higgs production. The events that pass the veto selection are those with p T < p veto T , where p T is the transverse momentum of any final-state jets, defined by a cone algorithm. The cone size R of the jets will be fixed at the value R = 0.4. More details of our study are presented elsewhere [6]. The vetoed cross section σ at the c.m. energy √ s can be computed through the following factorization formula: σ(s,M H ; p veto T , R) = ∑