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A. F. Zarnecki

Publications and source records attributed to A. F. Zarnecki.

31 records · Page 2Linked to original sources
arXiv2004

CP Studies of the Higgs Sector

The CP structure of the Higgs sector will be of great interest to future colliders. The measurement of the CP properties of candidate Higgs particles will be essential in order to distinguish models of electroweak symmetry breaking, and to discover or place limits on CP-violation in the Higgs sector. In this report we briefly summarize various methods of determining the CP properties of Higgs bosons at different colliders and identify areas where more study is required. We also provide an example of a synergy between the LHC, an e+e- Linear Collider and a Photon Collider, for the examination of CP-violation in a Two-Higgs-Doublet-Model.

hep-ph↗
arXiv2003

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.

hep-ph↗
arXiv2003

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%.

hep-ph↗
arXiv2003

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.

hep-ph↗
arXiv2002

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 LO estimate. Using a realistic luminosity spectrum and performing a detector simulation, we find that Gamma(h -> gamma gamma)Br(h -> bb) can be measured with an accuracy better than 2% after one year of photon collider running.

hep-ph↗
arXiv2002

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.

hep-ph↗
arXiv2002

Study of the Higgs-boson decays into WW and ZZ at the Photon Collider

Production of the Standard Model Higgs-boson at the Photon Collider at TESLA is studied for the Higgs-boson masses above 150 GeV. Simulation of signal and background processes takes into account realistic luminosity spectra and detector effects. In the considered mass range, large interference effects are expected in the W+W- decay channel. By reconstructing W+W- and ZZ final states, not only the h->gamma gamma partial width can be measured, but also the relative phase of the scattering amplitude. This opens a new window for the precise determination of the Higgs-boson couplings. Models with heavy, fourth-generation fermions and with enlarged Higgs sector (2HDM (II)) are considered.

hep-ph↗
arXiv2002

Physics at large p_T^2 and Q^2: Summary

We summarize the results presented in the `Physics at large p_T^2 and Q^2' working group at the DIS'2002 Workshop. Higgs searches, precision measurements as well as searches for physics beyond the Standard Model at current and future experiments are reviewed.

hep-ph↗
arXiv2002

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.

hep-ph↗
arXiv2001

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.

hep-ph↗
arXiv2000

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.

hep-ph↗
arXiv2000

Leptoquark signal from global analysis

Data from HERA, LEP and the Tevatron, as well as from low energy experiments are used to constrain the Yukawa couplings for scalar and vector leptoquarks in the Buchmuller-Ruckl-Wyler effective model. In the limit of very high leptoquark masses constraints on the coupling to the mass ratio l/M are derived using the contact-interaction approximation. For finite masses the coupling limits are studied as a function of the leptoquark mass. Some leptoquark models are found to describe the existing experimental data much better than the Standard Model. Increase in the global probability observed for models including S_1 or ~V_o leptoquark production/exchange corresponds to more than a 3 sigma effect. Assuming that a real leptoquark signal is observed, calculated is an allowed region in the l-M plane. The leptoquark signal is mostly resulting from the new data on the atomic parity violation in cesium, but is also supported by recent LEP2 measurements, unitarity violation in the CKM matrix and HERA high-Q^2 results.

hep-ph↗