One of the great successes of the experimental program carried out at LEP has been to put a firm lower bound on the Higgs mass, mH>114 GeV [1], and at the same time, together with the information coming from SLD, to give a strong indirect evidence that the Higgs boson, the still missing particle of the Standard Model (SM), should be relatively light with a high probability for its mass to be below 200 GeV. The search for the Higgs boson is one of the main objective of the Tevatron and the future Large Hadron Collider (LHC), that are supposed to span all the Higgs mass regions up to 1 TeV. At hadron colliders the main Higgs production mechanism is the gluon fusion [2], a process whose knowledge is fundamental in order to put limits on the Higgs mass or, in case the Higgs is discovered, to compare the measured cross section with the SM result. Concerning the Higgs decay channels, it is quite difficult for an hadron collider to access part of the mass range favored by the LEP results, the so-called intermediate Higgs mass region 114≲mH≲160 GeV, because of the large QCD background to the dominant modes. In this region the rare decay H→γγ is the most interesting alternative to the usual decay channels.
