Working group report: Collider Physics

This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.     

Z decay constraints on supersymmetric particles revisited

The allowed regions in the chargino-gluino mass plane are mapped out using the latestZ decay data from experiments. The determination of these masses in future experiments will uniquely fix the neutralino mass spectrum for a fixedv ₁/v ₂. Since the usual two-fold ambiguity is removed by LEP data for gluino masses upto 200 GeV. Constraints have also been placed on neutralino masses.     

Signature of heavy charged Higgs boson at LHC in the 1 and 3 prong hadronic tau decay channels

We have done a fast simulation analysis of the H^± signal at LHC in 1 and 3 prong hadronic τ-jet channels along with a tt̄ background. The τ polarization was effectively used to suppress the background in both channels. Combining this with appropriate cuts on p_T of the τ-jet, the missing E_T and the azimuthal angle between them reduces the background below the signal level. Consequently, one gets a viable H^± signal up to a mass range of 600–700 GeV at moderate to large tanβ.     

Exact solution of the neutralino mass matrix

The eigenvalue problem for the neutralino mass matrix has been solved exactly and the eigenvalues are expressed in terms of thev ₁/v ₂, chargino and gluino masses which are directly measurable. An analytical formula for the lightest neutralino mass as a function of the above parameters is obtained. Formulae for the photino, zino and neutral higgsino contents of each of the physical neutralino mass eigenstates states have been found. Taking into account these formulae it has been possible to predict the upper (lower) bound on the mass of zino (photino) dominant neutralino states, including the lightest one. The neutralino-gluino and neutralino-chargino mass planes have also been constrained by using the latest LEP data.     

Physics beyond Standard Model: Working group 3 report

This is a summary of the beyond the Standard Model (including model building) working group of the WHEPP-X workshop held at Chennai from January 3 to 15, 2008. Participants: Neelima Agarwal, S K Agarwalla, C S Aulakh, A Belyaev, S S Biswal, B Bhattacharjee, G Bhattacharyya, L Calibbi, D Choudhury, E J Chun, D Das, A De Roeck, N G Deshpande, E Dudas, A Giri, D Grellshceid, R Godbole, S Goswami, M Guchait, M Hirsch, R Kaul, B Kodrani, M C Kumar, A Kundu, Y Mambrini, P Mathews, B Mellado, R Mohanta, S Mohanty, A Nyffeler, S Pakvasa, M K Parida, M Passera, C Petridou, S Poddar, P Poulose, A Rajaraman, G Rajasekaran, V Ravindran, Kumar Rao, D P Roy, Probir Roy, K A Saheb, V H Satheeshkumar, T Schwetz, A Tripathi, R Vaidya and S Vempati     

Focus point SUSY at the LHC revisited

The estimation of the backgrounds for gluino signals in focus point supersymmetry is extended by including the backgrounds from the production of four third generation quarks in the analysis. We find that these backgrounds are negligible if one uses the strong selection criteria proposed in the literature (including this analysis) for heavy gluino searches. Softer selection criteria often recommended for lighter gluino searches yield backgrounds that are small but numerically significant. We have also repeated the more conventional background calculations and compared our results with the other groups. We find that the size of the total residual background estimated by different groups using different event generators and hard kinematical cuts agree approximately. In view of the theoretical uncertainties in the leading order signal and background cross sections mainly due to the choice of the QCD scale, the gluino mass reach at the LHC cannot be pinpointed. However, requiring a signal with ≥3 tagged b-jets (instead of the standard choice of ≥2) it is shown that gluino masses close to 2 TeV can be probed at the LHC for a range of reasonable choices of the QCD scale for an integrated luminosity of 300 fb^-1. PACS 11.30.Pb; 12.60.Jv; 14.80.Ly; 95.35.+d