Browsing by Author "Lebedev, O."
Now showing 1 - 12 of 12
Results Per Page
Sort Options
- Constraining new physics with vertex correctionsTakeuchi, Tatsu; Lebedev, O.; Loinaz, William (1999)
- Constraints on gauged B-3L(tau) and related theoriesChang, Lay Nam; Lebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2001-04-01)
- Constraints on gauged B-3L(tau) and related theoriesChang, Lay Nam; Lebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2001-04-01)We consider extensions of the standard model with an extra U(1) gauge boson that couples to B- (alphaL(e), + betaL(mu) + gammaL(tau)) with alpha + beta + gamma =3. We show that the extra gauge boson necessarily mixes with the Z, leading to potentially significant corrections to the Zf(f) over bar vertex. The constraints on the size of this correction imposed by the Z-pole data from CERN LEP and SLD are derived.
- Constraints on R-parity violating couplings from CERN LEP and SLAG SLD hadronic observablesLebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2000-07-01)We analyze the one loop corrections to hadronic Z decays in an R-parity violating extension to the minimal supersymmetric standard model. Performing a global fit to all the hadronic observables at the Z peak, we obtain stringent constraints on the R-violating coupling constants lambda' and lambda". The presence of these couplings worsens the agreement with the data relative to the standard model. The strongest constraints come from the b asymmetry parameters A(b) and A(FB)(b) From a classical statistical analysis we find that the couplings lambda'(131), lambda'(132), and lambda"(321) are ruled out at the 1 sigma level, and that lambda'(133) and lambda"(33i) are ruled out at the 2 sigma level. A Bayesian statistical analysis weakens the bounds, but the corresponding chi(2)'s are uncomfortably large, rendering the relevance of the Bayesian bounds suspect.
- Constraints on R-parity violating couplings from CERN LEP and SLAG SLD hadronic observablesLebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2000-07-01)
- Constraints on R-parity violating couplings from lepton universalityLebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2000-06-01)
- Constraints on R-parity violating couplings from lepton universalityLebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2000-07-01)We analyze the one loop corrections to leptonic W and Z decays in an R-parity violating extension to the minimal supersymmetric standard model. We find that lepton universality violation in the Z line-shape variables alone would strengthen the bounds on the magnitudes of the lambda' couplings, but a global fit on all data leaves the bounds virtually unchanged at \lambda'(33k)\less than or equal to 0.42 and \lambda'(23k)\less than or equal to 0.50 at the 2 sigma level. Bounds from W decays are less stringent: \lambda'(33k)\less than or equal to 2.4 at 2 sigma, as a consequence of the weaker Fermilab experimental bounds on lepton universality violation in W decays. We also point out the potential of constraining R-parity violating couplings from the measurement of the Y invisible width.
- Constraints on R-parity violation from precision electroweak measurementsTakeuchi, Tatsu; Lebedev, O.; Loinaz, William (World Scientific, 2001-01-01)
- Constraints on two-Higgs-doublet models at large tan beta from W and Z decaysLebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2000-09-01)
- Constraints on two-Higgs-doublet models at large tan beta from W and Z decaysLebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2000-09-01)We study constraints on type-II two-Higgs-doublet models at large tan beta from CERN LEP and SLD Z-pole data and from lepton universality violation in W decay. We perform a global fit and find that, in the context of Z decay, the LEP-SLD experimental values for lepton universality violation, R-b, and A(b) all somewhat disfavor the model. Contributions from the neutral-Higgs sector can be used to constrain the scalar-pseudoscalar Higgs mass splittings. Contributions from the charged-Higgs sector allow us to constrain the charged-Higgs boson mass. For tan beta=100 we obtain the 1 sigma classical (Bayesian) bounds of m(H+/-) greater than or equal to 670 GeV (370 GeV) and 1 greater than or equal to m(h)0/m(A)0/(alpha = beta) =m(H)0/m(A)0/(alpha=0) greater than or equal to 0.68 (0.64). The 2 sigma bounds are weak. Currently, the Fermilab Tevatron experimental limits on lepton universality violation in W decay provide no significant constraint on the Higgs sector.
- Universal torsion induced interaction from large extra dimensionsTakeuchi, Tatsu; Chang, Lay Nam; Lebedev, O.; Loinaz, William (American Institute of Physics, 2001-01-01)
- Universal torsion-induced interaction from large extra dimensionsChang, Lay Nam; Lebedev, O.; Loinaz, William; Takeuchi, Tatsu (American Physical Society, 2000-10-30)