Leptoquark Searches at Future Colliders

Leptoquark searches are considered for future experiments at HERA, Tevatron, LHC, TESLA and THERA. Expected exclusion limits from direct leptoquark searches (leptoquark pair production and single leptoquark production) are compared with indirect limits expected from the contact interaction analysis. Strongest limits on the leptoquark masses and couplings are expected from high luminosity LHC data. If the leptoquark signal suggested by the existing data is detected at LHC, with mass below 1 TeV, TESLA will be an ideal place to study leptoquark properties, provided that the leptoquark Yukawa coupling is not too small.Comment: Paper submitted to ICHEP'2000 (abstract #451); 20 pages, 8 figures, 4 table

Contact Interactions, Large Extra Dimensions and Leptoquarks at THERA

The sensitivity of THERA to different models of "new physics" has been studied, both for the contact interaction approximation and for the resonance production. For contact interaction models conserving parity, scales up to about 18 TeV can be explored at THERA, extending considerably beyond the existing bounds. Significant improvement of existing limits is also expected for models with large extra dimensions. Effective Plank mass scales up to about 2.8 TeV can be probed. THERA will be the best machine to study leptoquark properties, for leptoquark masses up to about 1 TeV. It will be sensitive to the leptoquark Yukawa couplings down to lambda ~ 0.01.Comment: 23 pages, 9 figures, 7 table

EUDET Telescope Geometry and Resolution Studies

Construction of EUDET pixel telescope will significantly improve the test beam infrastructure for the ILC vertex detector studies. The telescope, based on the Monolithic Active Pixel Sensors (MAPS), will consist of up to six readout planes and will be initially installed at an electron beam line at DESY. A dedicated study was performed to understand the position measurement in the telescope and optimize its performance by suggesting the best plane setup. The approach based on the analytical track fitting method allows for determination of the expected measurement uncertainty and for comparison of different telescope setups without time consuming event simulation. The proposed method also turns out to be little sensitive to the possible telescope misalignment.Comment: 36 pages, 33 figure

Two-photon Width and Phase Measurement from the SM Higgs Decays into WW and ZZ

Production of the Standard Model Higgs-boson at the photon collider at TESLA is studied for the Higgs-boson masses above 170 GeV. By reconstructing WW and ZZ final states, not only the h to gamma-gamma partial width but also the phase of the scattering amplitude can be measured. This opens a new window onto the precise determination of the Higgs-boson couplings.Comment: Presented at the International Workshop on Linear Colliders LCWS(2002), Jeju, Kore

Measurement of the MSSM Higgs-bosons production in gamma gamma -> A,H -> b bbar at the Photon Collider at TESLA

Results from a realistic simulation of the heavy MSSM Higgs-bosons A and H production, gamma gamma -> A,H -> b bbar, at the Photon Collider at TESLA are reported. In the scenario where a light SM-like Higgs boson h exists, we study (following M. Muehlleitner et al.) Higgs bosons A and H for masses M_A=200,250,300,350 GeV and tan(beta)=7. This scenario corresponds to parameters region not accessible at LHC or at the first stage of the e^+ e^- collider. NLO estimation of background, analysis of overlaying events, realistic b-tagging and corrections for escaping neutrinos were performed. The statistical precision of the cross-section measurement is estimated to be 8-20%.Comment: 12 pages, 8 figures. Submitted to International Europhysics Conference on High Energy Physics EPS 2003, Aachen, Germany, abstract 60

The SM Higgs-boson production in gamma gamma -> h -> bb at the Photon Collider at TESLA

Measuring the Gamma(h -> gamma gamma)Br(h -> bb) decay at the photon collider at TESLA is studied for a Standard Model Higgs boson of mass m_h = 120 GeV. The main background due to the process gamma gamma -> QQ(g), where Q = b,c, is estimated using the NLO QCD program (G. Jikia); the results obtained are compared with the corresponding LO estimate. Using a realistic luminosity spectrum and performing a detector simulation with the SIMDET program, we find that the Gamma(h -> gamma gamma)Br(h -> bb) decay can be measured with an accuracy better than 2% after one year of photon collider running.Comment: 11 pages, 7 figures; minor changes, references added; submitted to ICHEP'200

Light Higgs-boson production at the Photon Collider at TESLA with an improved background analysis

Measurement of the Gamma(h -> gamma gamma)Br(h -> b bbar) at the Photon Collider at TESLA is studied for the Standard Model Higgs boson with mass of 120 to 160 GeV. The NLO estimation of background, analysis of overlaying events, realistic b-tagging and corrections for escaping neutrinos were performed. We find that for M_h = 120-160 GeV the Gamma(h -> gamma gamma)Br(h -> b bbar) can be measured with a statistical accuracy of 2-7% after one year of the Photon Collider running.Comment: 12 pages, 8 figures. Submitted to International Europhysics Conference on High Energy Physics EPS 2003, Aachen, Germany, abstract 59

Extended analysis of the MSSM Higgs boson production at the Photon Collider

New analysis of the heavy, neutral MSSM Higgs bosons H and A production at the Photon Collider is presented for M_A = 200, 250, 300 and 350 GeV in the parameter range corresponding to the so called "LHC wedge" and beyond. The expected precision of the cross section measurement for the process gamma+gamma->A,H->b+bbar and the "discovery reach" of the Photon Collider are compared for different MSSM scenarios. The analysis takes into account all relevant theoretical and experimental issues which could affect the measurement. For MSSM Higgs bosons A and H, for M_A = 200-350 GeV and tan(beta)=7, the statistical precision of the cross-section determination is estimated to be 8-34%, after one year of Photon Collider running, for four considered MSSM parameters sets. As heavy neutral Higgs bosons in this scenario may not be discovered at LHC or at the first stage of the e+e- collider, an opportunity of being a discovery machine is also studied for the Photon Collider.Comment: Presented at the International Linear Collider Workshop LCWS05, Stanford, US

Measurement of the Higgs-boson CP properties using decays into WW and ZZ at the Photon Collider

Higgs-boson production at the Photon Collider at TESLA is studied for masses from 180 to 350 GeV, using realistic luminosity spectra and detector simulation. Parity of the SM Higgs-boson can be verified from the measurement of the interference effects in the W+ W- decay channel and of the angular correlations in the decays of W+ W- and ZZ pairs. SM-like Two Higgs Doublet Model (2HDM II) and model with the generic higgs couplings are considered.Comment: Paper submitted to EPS'2003 (abstract nr 605). 28 pages, 20 figure

Model-Independent Determination of CP Violation from Angular Distributions in Higgs Boson Decays to WW and ZZ at the Photon Collider

The model-independent determination of the Higgs-boson CP properties at the Photon Collider at TESLA has been studied in detail, for masses between 200 and 350 GeV, using realistic luminosity spectra and detector simulation. We consider a generic model with the CP violating Higgs tensor couplings to gauge bosons. We introduce a new variable describing angular distributions of the secondary WW and ZZ decay products which is very sensitive to the CP properties of the Higgs-boson. Understanding of the detector performance turns out to be crucial, as the influence of the acceptance corrections is similar to the effects of CP violation. From the combined measurement of invariant mass distributions and various angular distributions the phase describing a CP violation can be determined to about 50 mrad after one year of Photon Collider running.Comment: 10 pages, 8 figure