LHCb

Abstract:

A new radiation hard pipelined readout chip is being developed for the LHCb-experiment. Appropriate design measures have been taken to ensure the radiation hardness against total ionising dose effects in excess of 45 Mrad, as well as radiation effects induced by single particles. (C) 2003 Elsevier B.V. All rights reserved.

Abstract:

We study the decays B⁺ → ηcK⁺ and B⁰ → ηcK⁰, where the ηc is reconstructed in the KS⁰K ^±π^∓ and K⁺K^- π⁰ decay modes. Results are based on a sample of 86 B B̄ pairs collected with the BABAR detector at the SLAC e⁺e^- B Factory. We measure the product of branching fractions B(B⁺ → ηcK⁺) ×B(ηc→KK̄π)= (7.40±0.50±0.70)×10^-5 and B(B ⁰→ηcK⁰) ×B(ηc→KK̄π)=(6.48±0.85±0.71) ×10^-5, where the first error is statistical and the second is systematic, In addition, we search for B → ηcK events with ηc→2(K⁺K^-) and ηc→ φφ and determine the ηc decay branching fraction ratios B(ηc →(K⁺K^-)) /B(ηc→KK̄π)=(2.3±0.7±0.6) ×10^-2 and B(ηc→φφ) /B(ηc→KK̄π)=(5.5±1.4±0.5) ×10^-2.

Abstract:

A test of the benchmark QED process e⁺e^- → γγ(γ) is reported, using the data collected with the DELPHI detector at LEP 2. The data analysed were recorded at centre-of-mass energies ranging from 161 GeV to 208 GeV and correspond to a total integrated luminosity of 656.4 pb^-1. The Born cross-section for the process e ⁺e^- → γγ(γ) was determined, confirming the validity of QED at the highest energies ever attained in electron-positron collisions. Lower limits on the parameters of a number of possible deviations from QED, predicted within theoretical frameworks expressing physics beyond the Standard Model, were derived. © Springer-Verlag/ Società Italiana di Fisica 2004.