Constraints on R-parity Violation from Precision Electroweak Measurements
We constrain the size of R-parity violating couplings using precision electroweak data.
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arXiv subjects
Oleg Lebedev
Publications and source records attributed to Oleg Lebedev.
Universal Torsion-Induced Interaction from Large Extra Dimensions
We consider the Kaluza-Klein (KK) scenario in which only gravity exists in the bulk. Without the assumption of symmetric connection, the presence of brane fermions induces torsion. The result is a universal axial contact interaction that dominates those induced by KK gravitons. This enhancement arises from a large spin density on the brane. Using a global fit to Z-pole observables, we find the 3 sigma bound on the scale of quantum gravity to be 28 TeV for n=2. If Dirac or light sterile neutrinos are present, the data from SN1987A increase the bound to \sqrt{n}M_S >= 210 TeV.
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Constraining New Physics with Vertex Corrections
We discuss how new physics not encompassed within the STU oblique correction framework can be constrained from precision electroweak measurements via vertex corrections to Z-pole observables.
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Constraints on Two-Higgs Doublet Models at Large tan{beta} from W and Z decays
We study constraints on type-II two Higgs doublet models at large tan{beta} from LEP/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 mass. For tan{beta}=100 we obtain the 1 sigma classical (Bayesian) bounds of m_{H+} > 670 GeV (370 GeV) and 1 > m_{h0}/m_{A0} > 0.68 (0.64). The 2 sigma bounds are weak. Currently, the Tevatron experimental limits on lepton universality violation in W decay provide no significant constraint on the Higgs sector.
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Constraints on R-parity violating couplings from LEP/SLD hadronic observables
We analyze the one loop corrections to hadronic Z decays in an R-parity violating extension to the Minimal Supersymmetric Standard Model (MSSM). Performing a global fit to all the hadronic observables at the Z-peak, we obtain stringent constraints on the R-violating couplings constants lambda' and lambda''. As a result of the strong constraints from the b asymmetry parameters A_b and A_FB(b), we find that the couplings lambda'{i31}, lambda'{i32}, and lambda''{321} are ruled out at the 1 sigma level, and that lambda'{i33} and lambda''{33i} are ruled out at the 2 sigma level. We also obtain Bayesian confidence limits for the R-violating couplings.
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Constraints on R-parity violating couplings from lepton universality
We analyze the one loop corrections to leptonic W and Z decays in an R-parity violating extension to the Minimal Supersymmetric Standard Model (MSSM). 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}| < 0.42 and |lambda'_{23k}| < 0.50 at the 2 sigma level. Bounds from W decays are less stringent: |lambda'_{33k}| < 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 Upsilon invisible width.
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B Decays as a Probe of Spontaneous CP-Violation in SUSY Models
We consider phenomenological implications of susy models with spontaneously broken CP-symmetry. In particular, we analyze CP-asymmetries in B decays and find that the predictions of these models are vastly different from those of the SM. These features are common to NMSSM-like models with an arbitrary number of sterile superfields and the MSSM with broken R-parity.
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Constraining SUSY Models with Spontaneous CP-Violation via B->ψK_s
We study CP-violating effects in $B\to ψK_{s}$ decay within minimal supersymmetric models with spontaneous CP-violation. We find that the CP-asymmetry predicted by the Standard Model in this decay, $\sin 2β\geq 0.4$, cannot be accommodated in these models without violating the bound on the neutron electric dipole moment. This result holds for NMSSM-like models with an arbitrary number of sterile superfields. Further implications of the scenario are discussed.
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Probing Spontaneous CP-Violation in Supersymmetric Models via B-Decays
We study implications of spontaneous CP-violation in minimal susy models for CP-asymmetries in rare $B,\bar B$-decays. In particular, we estimate characteristic values of the angles of the unitarity triangle and show that sizeable CP-violating effects result from $B-\bar B$ mixing only. Significant deviations from the SM predictions are pointed out.
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On the invisible decays of the Upsilon and J/Psi resonances
We estimate the most important corrections to the branching ratios for the invisible decays of quarkonium states, arising from possible extensions of the standard model. Among the possibilities considered are the presence of extra Z-bosons, minimal supersymmetric extensions of the standard model with R-parity violation, and decays into goldstinos. Prospects of detecting these corrections at existing and future B-factories and tau-charm factories are discussed.
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