[en] A new analysis of parity violation in atomic cesium has led to an improved value of the weak charge, Q_W(Cs)=-72.06±0.46. The implications of this result for constraining the Peskin-Takeuchi parameters S and T and for guiding searches for new Z bosons are discussed. (c) 1999 The American Physical Society

[en] There are theoretical and phenomenological motivations that there may exist additional heavy Z^' bosons with family nonuniversal couplings. Flavor mixing in the quark and lepton sectors will then lead to flavor changing couplings of the heavy Z^', and also of the ordinary Z when Z-Z^' mixing is included. The general formalism of such effects is described, and applications are made to a variety of flavor changing and CP-violating tree and loop processes. Results are described for three specific cases motivated by a specific heterotic string model and by phenomenological considerations, including cases in which all three families have different couplings, and those in which the first two families, but not the third, have the same couplings. Even within a specific theory the results are model dependent because of unknown quark and lepton mixing matrices. However, assuming that typical mixings are comparable to the Cabibbo-Kobayashi-Maskawa matrix, processes such as coherent μ-e conversion in a muonic atom, K⁰-K(bar sign)⁰ and B-B(bar sign) mixing, ε, and ε^'/ε lead to significant constraints on Z^' bosons in the theoretically and phenomenologically motivated range M_Z^'∼1 TeV. (c) 2000 The American Physical Society

[en] The 1999 precision electroweak data from CERN LEP and SLC persist in showing some slight discrepancies from the assumed standard model, mostly regarding b and c quarks. We show how their mixing with exotic heavy quarks could result in a more consistent fit of all the data, including two unconventional interpretations of the top quark. (c) 2000 The American Physical Society

[en] 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 λ^' couplings, but a global fit on all data leaves the bounds virtually unchanged at |λ_33k^'|≤0.42 and |λ_23k^'|≤0.50 at the 2σ level. Bounds from W decays are less stringent: |λ_33k^'|≤2.4 at 2σ, 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 Υ invisible width. (c) 2000 The American Physical Society

[en] We continue our previous work on the flavor-conserving leptonic decays of the Z boson with neutral heavy leptons (NHL close-quote s) in the loops by considering box, vertex, and self-energy diagrams for the muon decay. By inclusion of these loops (they contribute to the input parameter M_W), we can probe the full parameter space spanned by the so-called flavor-conserving mixing parameters ee_mix,μμ_mix,ττ_mix. We show that only two diagrams from each class (box, vertex, and self-energy) are important; further, after renormalization only two box diagrams open-quotes survive close-quote close-quote as dominant. We compare the results of our analysis with the existing work in this field and conclude that flavor-conserving decays have certain advantages over traditionally considered flavor-violating ones. copyright 1997 The American Physical Society

[en] We present a measurement of the differential cross section as a function of transverse momentum of the Z boson in pp(bar sign) collisions at √(s)=1.8 TeV using data collected by the DOe experiment at the Fermilab Tevatron Collider during 1994-1996. We find good agreement between our data and the next-to-next-to-next-leading-logarithmic resummation prediction and extract values of the non-perturbative parameters for the resummed prediction from a fit to the differential cross section. (c) 2000 The American Physical Society

[en] We have made a detailed study of the signals expected at CERN LEP 2 from charged scalar bosons whose dominant decay channels are into four fermions. The event rates as well as kinematics of the final states are discussed when such scalars are either pair produced or are generated through a tree-level interaction involving a charged scalar, the W, and the Z. The backgrounds in both cases are discussed. We also suggest the possibility of reconstructing the mass of such a scalar at LEP 2. copyright 1997 The American Physical Society

[en] We study constraints on type-II two-Higgs-doublet models at large tan β 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 β=100 we obtain the 1σ classical (Bayesian) bounds of m_H^±≥670 GeV (370 GeV) and 1≥m_h⁰/m_A⁰|_α=β=m_H⁰/m_A⁰|_α=0≥0.68 (0.64). The 2σ bounds are weak. Currently, the Fermilab Tevatron experimental limits on lepton universality violation in W decay provide no significant constraint on the Higgs sector. (c) 2000 The American Physical Society

[en] We present a new determination of the strong coupling constant α_s through the scaling violations in the fragmentation functions for charged pions, charged kaons, and protons. In our fit we include the latest e⁺e^- annihilation data from CERN LEP1 and SLAC SLC on the Z-boson resonance and older, yet very precise data from SLAC PEP at center-of-mass energy √(s) = 29 GeV. A new world average of α_s is given. (orig.)

[en] The direct production rates of D-wave charmonia in the decays of Z⁰ are evaluated. The color-octet production processes Z⁰→³D_J(c bar c)q bar q are shown to have distinctively large branching ratios as compared with other D-wave charmonium production mechanisms under a proper assumption. This may suggest a crucial channel to test the color-octet mechanism as well as to observe the D-wave charmonium states in Z⁰ decays. In addition, a signal for the ³D_J charmonium states with a large transverse momentum at the Fermilab Tevatron should be observed. copyright 1997 The American Physical Society