A determination of sin2θ w and the lepton and quark electroweak couplings frome + e − data

Published data on lepton pair and quark pair final states ine ⁺ e ^? annihilation have been analysed in a self consistent way to yield values for the lepton and quark weak vector and axial vector couplings. Generation universality has been tested for the leptons and under the assumption of the standard model of the weak interaction, the parameter sin²θ _w has been determined separately for the lepton and quark sector. In the renormalisation scheme α,G _μ and sin²θ _w , the result for the lepton final states is sin²θ _w = 0.212±0.014 and for the hadron final states, sin²θ _w = 0.236±0.015. The combined result for this single parameter in the model is sin²θ _w = 0.223±0.011±0.007, corresponding tom _Z =93.0 _?1.8 ^+2.0 GeV.     

New determination of quark mixing angles and phase

The Kobayashi-Maskawa angles and phase are determined with accuracy using recent B meson lifetime measurements together with the CP violation parameters of the K⁰ system. We get 0.032?sinθ₂?0.125, 0?sinθ₃?0.06, 140°?δ?179° (δ in the second quadrant). some implications, namely possible large B⁰-$\text{B}$⁰ mixing, are discussed.     

On the determination of sin2θw in semileptonic neutrino interactions

It is shown that if sin²θ_w is measured in semileptonic neutrino interactions then, contrary to a claim in the literature, the error due to unknown dynamical (higher-twist) corrections to the QCD parton model is small provided an isoscalar target is used. The largest contributions to σ_nc and σ_cc are related by isospin invariance alone. Neglecting heavy quarks and Kobayashi-Maskawa (KM) mixing, the parton model is only needed for very small terms and introduces an uncertainty in sin²θ_w which is probably less than 1%. There is a much larger theoretical error due to uncertainties in the element U_cs of the KM matrix and in the strange quark distribution. With the full range 0.80 ? | U_cs | 0.98 which is allowed phenomenologically, these uncetainties give δsin²θ_w = ± 0.008. There is also an error of ±0.004 due to uncertainties in |U_dc| and |U_du|.     

Results from the NOMAD experiment

The NOMAD experiment has sought ν_μ ? ν_τ oscillations by looking for the emergence of τ^? in events from the CERN SPS neutrino beam. With some improvements in the techniques of analysis in relation to the results published previously and with the inclusion of data from the 1998 run, no evidence for the oscillations has been found, which results in an updated limit on the oscillation probability [P(ν_μ → ν_τ) < 0.5 × 10^?3 at a 90% C.L.]. The corresponding limit on the oscillation mixing angle is given by sin²2θ_μτ < 1.0 × 10^?3 for large Δm ². By using a 1% contamination of ν_e in the neutrino beam, we can also rule out ν _e ? ν_τ oscillations and constrain the probability of the relevant transition as P(ν _e → ν_τ) < 3 × 10^?2 at a 90% C.L. (sin²2θ _eτ < 6 × 10^?2 at large Δm ²).     

A measurement of the neutral current electroweak parameters using the fermilab narrow band neutrino beam

We report a measurement of the electroweak parameters sin₂θ ^w and ? based on the ratios of neutral current to charged current events measured in the Fermilab narrow-band neutrino beam at energies of 30–240 GeV. The data are fully corrected for radiative effects, heavy-quark production, and other effects. The best value for sin₂θ ^w obtained, sin₂θ ^w =0.239±0.011, is consistent with the most recent values fromW andZ production, as well as from other neutrino experiments.     

Anti-Su(5)

We discuss ordinary as well as supersymmetric SU(5) ×?(1) models in the hope of accomodating acceptable τ_p and sin²θ_W. The ordinary SU(5) ×?(1) model does not have the monopole. The supersymmetric SU(5) ×?(1) model can be unified in SO(10).     

Heavy particle effects in grand unified theories with fine-structure constant matching

We note the presence of very significant mismatchings in α(M_w) in some GUT predictions where superheavy particle effects have been included, and adopt a new method to correct them leading to new solutions for the GUT coupling, τ_p or sin²θ_w. An SO(10) model with a grand desert is also noted to yield τ_p ≅ 10³²−10³³ yr and sin²θ_w = 0.225−0.235.     

Status of the Chorus experiment

The CHORUS experiment at CERN searches for ν_μ ? ν_τ oscillations by looking for τ decays from charged-current ν_τ interactions. The emulsion target of the detector, having a resolution of about a micron, enables the detection of the decay topology of the τ. After having analyzed a sample of 126000 events containing an identified muon and 7500 purely hadronic events, no ν_τ candidate has been found. This result translates in a limit on the mixing angle sin²2θ_μτ < 8 × 10^?4 at 90% C.L. for large Δm _μτ ² .     

Gluon effects and nonet mixing in the current quark picture

The effects on the meson mass spectrum of gluon interactions, and in particular of quark annihilation diagrams, are investigated in the current quark framework. The resulting mixing scheme leads to mixing angles θp ? ?13° and θ_V ? ? 52° for the pseudoscalar and vector nonets respectively, in moderate agreement with present data on radiative decays. For virtual electromagnetic processes additional gluon diagrams play a role. In η → 3π the net effect is to almost double the current algebra prediction, while in ω → 2π the ω → ?⁰ transition amplitude is correctly predicted in both sign and magnitude. The relation between the Hamiltonian approach and the U(1) problem, as formulated in terms of axial divergences, is briefly discussed.     

Experimental constraints on weak mixing angles in the six quark scheme

Experimental results on charm production by neutrinos and onB meson decays are used to derive bounds on the quark mixing anglesθ ₂ andθ ₃ in the six quark model of Kobayashi and Maskawa.     

Unique solution for the weak neutral current coupling constants in purely leptonic interactions

By combining results from the MARK-J at PETRA on Bhabha scattering, μ⁺μ^- and τ⁺τ^- production with recent world data from neutrino-electron scattering experiments, we determine unique values for the leptonic weak neutral current coupling constants g_V and g_A in the framework of electroweak models containing a single Z⁰. In contrast to previous analyses, we only use data from purely leptonic interactions, and therefore avoid the inherent uncertainties resulting from the use of hadronic targets. From the MARK-J data alone in the context of the standard SU(2) ? U (1) model of Glashow, Weinberg and Salam, we find sin²θ_W=0.24±0.11.     

Neutrino masses and mixings based on a special set of quark mass matrices (II)

In the framework of a 6×6 neutrino mass matrix with the standard seesaw mechanism, simple empirical forms are used for the leptonic Dirac mass submatrices which exhibit hierarchical chiral symmetry-breaking structure with just six parameters, as suggested by our previous work with quark mass matrices. Through a Monte Carlo analysis of Euler angle rotations applied to diagonal forms for the right-handed Majorana mass submatrix, we generate scatter plots in the δm ₂₃ ² vs sin²2θ ₂₃ and δm ₁₃ ² vs sin²2θ ₁₃ oscillation planes for a fixed point in the nonadiabatic MSW band. Only a small, statistically insignificant, segment of the 23 mixing plane exists corresponding to depletions of both the solarv _e and atmosphericv _μ fluxes; however, for such solutions the righthanded Majorana submatrix exhibits a hierarchical chiral symmetry-breaking form remarkably similar to that for the Dirac submatrices.     

SU(2)×U(1) effects in e+e− annihilation: Generalized charge asymmetry

The observability of the SU(2)×U(1) electroweak charge asymmetry effects in e⁺e^? annihilation at $\text{s}\text{=29}\text{GeV}$ is addressed in the context of a Feynman-Field type fragmentation model. We assume three colors of five flavored quarks and one heavy lepton τ. We neglect, at this time, the hard gluon bremsstrahlung events. We take b→c+X as the b-decay mode and we assume all τ's and heavy hadrons decay within the resolution of the detector so thatonly light hadrons and leptons are detected. Allowing all these decays to occur, we then compute the expected front-back asymmetry of negatively charged particles weighted with zⁿ for z?0.0175, where n = 0.5, 1…, 7, 10, and z is the light-cone momentum fraction. We find, for example, that such an asymmetry is ≈5% for n=2for sin²θ_w=0.236 and Λ_{QCD=0.34 GeV}. In other words, due to the large number of charge particles produced per event, this SU(2)×U(1) charge asymmetry may be accessible experimentally in e⁺e^? → X already at PEP and PETRA energies.     

Hartree-Fock-calculation of parity-violation in cesium

We present a relativistic Hartree-Fock calculation of the parity violatingE1-matrixelement of the 6s?7s transition in cesium. Our resultE1= ?8.4·10^?12 iea ₀ for sin² θ _w = 0.22 is in good agreement with the experimental value. We also give a general discussion of the consequences of a violation of discrete symmetries for the solutions of the Dirac equation.     

How to compare the SU(5) value of sin2θw with experiments?

We establish the relation between κsin²θ_w to be found from neutral-current experiments and sin²θ_w(Q) for Q=M_W predicted by grand unified theories. We then calculate sin²θ_W(M_W) in the minimal SU(5) model taking the M_W as well as M_x threshold effects into account. We find that these two threshold effects on sin²θ_W(M_W) cancel with each other and sin²θ_W(M_W)=0.211± 0.005.     

From a new smell to a new flavour −BdBd mixing,CP violation and new physics

Using the preliminary data on B_dB̄_d mixing from ARGUS, and the standard model with three families, we infer a lower bound on the top quark mass of 50–70 GeV; also, B_sB̄_s mixing has to be close to maximal. We discuss how the prospects for observing CP violation in B⁰ decays are enhanced and sketch alternative scenarios for new physics.     

The\overline {MS} and on-shell renormalization schemes in the analysis of neutrino scattering experiments

The relationship between the \(\overline {MS} \) and on-shell renormalization schemes is discussed and the correction, for finite top quark mass, to the formula connecting sin² θ _W =1?M _W ² /M _Z ² and sin² \(\widehat\theta _W (M_W )\) is given. A table is presented to allow easy conversion. The relative sensitivity, to the top quark and Higgs masses, of the two definitions, when extracted from semi-leptonic neutrino scattering experiments is considered.     

Estimation ofv μ→v τ oscillation parameters in the E-564 hybrid experiment

The limits on the parameters of thev _μ→v _τ oscillations are obtained in the E-564 hybrid experiment: Δm ²≦4.5 eV² and sin²(2θ)≦6.0·10^?2 (90% CL). A possibility of direct observation of τ-lepton decays in the nuclear emulsion vertex detector allowed the sensitivity of this experiment to the parameters of the oscillations to be increased.     

Seasonal and energy dependence of solar neutrino vacuum oscillations

We make a global vacuum neutrino oscillation analysis of solar neutrino data, including the seasonal and energy dependence of the recent Super-Kamiokande 708-day results. The best fit parameters for ν_e oscillations to an active neutrino are δm²=4.42×10⁻¹⁰ eV², sin²2θ=0.93. The allowed mixing angle region is consistent with bi-maximal mixing of three neutrinos. Oscillations to a sterile neutrino are disfavored. Allowing an enhanced hep neutrino flux does not significantly alter the oscillation parameters.