Final results for the SM Higgs-boson production at the Photon Collider

Abstract

Feasibility of the precise measurement of the SM Higgs-boson production cross section gamma+gamma->h->b+bbar at the Photon Collider is studied in detail for M_h=120-160 GeV. All relevant experimental and theoretical issues, which could affect the measurement, are taken into account. The study is based on the realistic gamma-gamma luminosity spectra simulation. The heavy-quark background gamma+gamma->Q+Qbar(+g) is estimated using the NLO QCD results. Other background processes, which were neglected in earlier analyses, are also studied: gamma+gamma->W+W, gamma+gamma->tau+tau and light-quark pair production gamma+gamma->q+qbar. The contribution from the so-called overlaying events, gamma+gamma->hadrons, is taken into account. The non-zero beam crossing angle and the finite size of colliding bunches are included in the event generation. The detector simulation and realistic b-tagging are used. Criteria of event selection are optimized separately for each considered Higgs-boson mass. In spite of the significant background contribution and deterioration of the invariant mass resolution due to overlaying events, precise measurement of the Higgs-boson production cross section is still possible. For the Standard-Model Higgs boson with mass of 120 to 160 GeV the corresponding partial width Gamma(h->gamma+gamma)BR(h->b+bbar) can be measured with a statistical accuracy of 2.1-7.7% after one year of the Photon Collider running. The systematic uncertainties of the measurement are estimated to be of the order of 2%.