Working group report: High energy and collider physics

Abstract

This is a summary of the projects undertaken by the Working Group I on High Energy Collider Physics at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8) held at the Indian Institute of Technology, Mumbai, January 5-16, 2004. The topics covered are (i) Higgs searches (ii) supersymmetry searches (iii) extra dimensions and (iv) linear collider.The projects undertaken in the Working Group I on High Energy and Collider Physics can be classified into the categories (i) Higgs searches (ii) supersymmetry searches (iii) extra dimensions and (iv) linear collider. The reports on the projects are given below under these headings.1 Higgs searches Potential of Associated Higgs Production in LHC throughτ -pair modeParticipants: P.Agrawal and K.Mazumdar 1 At LHC, the Standard Model Higgs production in association with W-boson, pp → W H is very interesting, though in general the total production rate is dominated by gluon-gluon fusion process. There is a strong indication that the Higgs boson is not very heavy and the experimental search for Higgs mass, m H ≤ 150 GeV/c 2 is comparatively more difficult. In any case it is desirable to study all possibilities for detection of Higgs boson in this mass range to strengthen the significance of discovery via 'golden' modes. This has motivated us to probe less studied modes of Higgs boson decays via WH production. Once the Higgs boson is discovered at LHC these final states will have to be studied for confirmation anyway.The LHC experiments, both CMS and ATLAS, have special trigger algorithm at the first level (LEVEL 1) based on calorimetric information for selecting hadronic decays of τ in the final state [1]. The tau-decay modes of Supersymmetric Higgs bosons have been particularly studied for this purpose. The narrowness of a jet as in the case of hadronic tau decays has been utilised in discrimenating the transverse profile of jets. The tracker information is used at a later stage for decision at a higher level and hence leptonic decays of τ cannot be used for trigger. Of course the leptonic decays of W-boson (only electron and muon final states) can be chosen for trigger in inclusive isolated electron/muon mode. But the background is likely to be overwhelming in that case. Hence we try the possibility of triggering the signal with the taus from the Higgs decay. This situation can be effectively utilised for the decay mode H → τ + τ − in the Higgs boson mass range m H ≤ 140 GeV/c 2 where the branching ratio is not too small, though below 10%. According to the 'trigger menu' of CMS experiment there are two possibilities for events with at least one τ in the final state. For 95% efficiency of signal selection (SUSY Higgs decay to tau final state) the kinematic thresholds are as follows. 1.Inclusive τ -jet with jet transverse energy ≥ 86 GeV. 2. Double τ -jets with the transverse energy of each jet ≥ 59 GeV. It remains to be checked through simulation the efficiency in the signal channel after these requirements. We need to study the spectrum of transverse momen...