Professor Brian Foster OBE, FRS

Abstract:

The results of a search for T and CP violation in B⁰-B̄⁰ mixing were presented. A same-sign dilepton asymmetry was obtained which was used to to extract the modulus of the ratio of complex mixing parameters. The background dilution correction was measured using data from full dilepton sample. The uncertainity on the ratio resulted in a ±3% multiplicative error.

Abstract:

A new technique involving the time-difference distribution of a tagged sample of fully reconstructed neutral B decays was used to determine the B0-B̄0 mixing frequency Δmd. The obtained result is consistent with the current world average and a recent BABAR measurement with a dilepton sample.

Abstract:

An overview is given on the measurement of the time dependence of B0-B̄0 mixing using data collected with the BABAR detector at the PEP-II asymmetric energy e+e- collider operated at or near the Υ(4S) resonance. The result is the single most precise measurements to date and is consistent with a recent BABAR measurement with a fully reconstructed B0 sample, as well as the world average of previous measurements.

Abstract:

New measurements of Ds+ and Ds*+ meson production rates from B decays and from qq̄ continuum events near the Y(4S) resonance are presented. Using 20.8 fb-1 of data on the Y(4S) resonance and 2.6 fb-1 off-resonance, we find the inclusive branching fractions B(B→Ds+ X)=(10.93±0.19±0.58±2.73)% and B(B→Ds*+X)=(7.9±0.8±0.7 ±2.0)%, where the first error is statistical, the second is systematic, and the third is due to the Ds+→φπ+ branching fraction uncertainty. The production cross sections σ(e+e- →Ds+X) × B(Ds+→φπ+)=7.55±0.20 ±0.34 pb and σ(e+e-→Ds *±X) × B(Ds+→φπ+) = 5.8±0.7±0.5 pb are measured at center-of-mass energies about 40 MeV below the Y(4S) mass. The branching fractions ΣB(B→Ds(*)+ D̄(*))=(5.07±0.14±0.30±1.27)% and ∑B(B→Ds*+D̄(*)) =(4.1±0.2±0.4±1.0)% are determined from the Ds(*)+ momentum spectra. The mass difference m(Ds+)-m(D+)=98.4±0.1 ±0.3 MeV/c2 is also measured.

Abstract:

A search has been made for lepton-flavor-violating interactions of the type e⁺p→lX, where l denotes a μ or τ with high transverse momentum, at a center-of-mass energy √s of 300 GeV with an integrated luminosity of 47.7 pb^-1 using the ZEUS detector at HERA. No evidence was found for lepton-flavor violation and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below √s, limits are set on λeq1βlq, where λeq1 is the coupling of the LQ to an electron and a first-generation quark q1 and βlq is the branching ration of the LQ to l and a quark. For LQ masses exceeding √s, limits are set on the four-fermion contact-interaction term λeqα λlqβ/M² LQ for leptoquarks that couple to an electron and a quark qα and also to l and a quark qβ. Some of the limits are also applicable to lepton-flavor-violating processes mediated by squarks in R-parity-violating supersymmetric models. In some cases involving heavy quarks and especially for l=τ, the ZEUS limits are the most stringent published to date.