Professor Brian Foster OBE, FRS

Abstract:

We have studied the B^±→J/ψπ^± and B^±→J/ψK^± decays using a 20.7 fb^-1 data set collected with the BABAR detector. We observe a signal of 51±10 B^±→J/ψπ^± events and determine the ratio B(B^± →J/ψπ^±)/B(B^±→J/ψ K^±) to be [3.91±0.78(stat)±0.19(syst)]%. The CP-violating charge asymmetries for the B^±→J/ψπ^± and B^±→J/ψK^± decays are determined to be Aπ=0.01±0.22(stat)±0.01(syst) and AK =0.003±0.030(stat)±0.004(syst).

Abstract:

The photon-proton total cross section has been measured in the process e⁺ p → e⁺ γp → e⁺ X with the ZEUS detector at HERA. Events were collected with photon virtuality Q² < 0.02 GeV² and average γp center-of-mass energy Wγp = 209 GeV in a dedicated run, designed to control systematic effects, with an integrated luminosity of 49 nb^-1. The measured total cross section is σtot ^γp = 174 ± 1 (stat.) ± 13 (syst.) μb. The energy dependence of the cross section is compatible with parameterizations of high-energy pp and pap data. © 2002 Elsevier Science B.V. All rights reserved.

Abstract:

Dijet differential cross sections for the reaction e+ p → e+ + jet + jet + X in the photoproduction regime have been measured with the ZEUS detector at HERA using an integrated luminosity of 42.7 pb-. The cross sections are given for photon-proton centre-of-mass energies in the range 134 < W < 277 GeV. The differential cross sections as a function of the dijet mass, MJJ, and of the dijet angular variables have been measured for 47 < MJJ < 160 GeV and compared to next-to-leading-order QCD calculations. The dijet events in the region 75 < MJJ < 100 GeV have been used to derive a 95% C.L. upper limit on the cross section for Z0 photoproduction of σ e+p→e+Z0X < 5.9 pb. Upper limits on the photoproduction of new heavy resonances decaying into two jets are also presented for masses in the range between 60 GeV and 155 GeV. © 2002 Elsevier Science B.V. All rights reserved.

Abstract:

The dijet cross section in photoproduction has been measured with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb-1. The events were required to have a virtuality of the incoming photon, Q2, of less than 1 GeV2 and a photon-proton centre-of-mass energy in the range 134 < Wγp < 277 GeV. Each event contains at least two jets satisfying transverse-energy requirements of ETjet1 > 14 GeV and ETjet2 > 11 GeV and pseudorapidity requirements of -1 < ηjet1,2 < 2.4. The measurements are compared to next-to-leading-order QCD predictions. The data show particular sensitivity to the density of partons in the photon, allowing the validity of the current parameterisations to be tested.

Abstract:

The branching fraction of the exclusive decays B0 → K*0γ and B+ → K*+γ measured from a sample of BB̄ decays collected with the BABAR detector at the PEP-II asymetric e+e- collider was discussed. It was found that the weighted average of the measured CP-violating charged asymmetries was Acp(B → K*γ) = -0.044 + 0.076 (stat) ± 0.012 (syst). The results showed the CP-violating charge asymmetry to be constrained to -0.170 < Acp(B → K*γ) < 0.082 at 90% C.L.