Giles Barr

Abstract:

A first level trigger system based on a 40 MHz digital pipeline has been developed for the CERN NA48 [1] experiment, aiming at measuring CP violation in K-0 --> 2 pi decays.The outputs of the 13340 cells of the 10 m(3) liquid krypton calorimeter are summed into 64 X and 64 Y projection strips and continuously digitised with 40 MHz FADCs.This information is used to reconstruct at each clock cycle and for the two calorimeter projections, the number of clusters, the impact time of each of them (with a precision of about 3 ns), their total energy and the first and second moments of the energy distribution.Based on the quantities listed above, a programmable look-up table system subsequently computes online the longitudinal position of the kaon decay vertex and performs an event selection.The system is described.

Abstract:

We have searched for the proton decay mode p → ν K⁺ using the one-kiloton Soudan 2 high resolution calorimeter. Contained events obtained from a 3.56 kiloton-year fiducial exposure through June 1997 are examined for occurrence of a visible K⁺ track which decays at rest into μ⁺ ν or π⁺ π⁰. We found one candidate event consistent with background, yielding a limit, τ/B(p → ν K⁺) > 4.3 × 10³¹ years at 90% CL with no background subtraction. © 1998 Published by Elsevier Science B.V. All rights reserved.

Abstract:

The full data set of the NA31 experiment at CERN has been used to analyse the decay mode K^OL → e⁺ e^-γγ. A signal of 47 events has been observed with an estimated background of 6.9 events. The total number of kaon decays in the decay volume was determined to be (2.1 ± 0.1stat) · 10⁹. This corresponds to a branching ratio of (8.0 ± 1.5^+1.4-1.2)· 10^-7. © 1998 Published by Elsevier Science B.V.

Abstract:

In a preliminary version of the NA48 experiment at the CERN SPS, in which an iron-scintillator sandwich calorimeter was used as a photon detector, the ratio of KL → πμνγ and KL → πμν decays was measured. The branching ratio BR(KL → πμνγ,E*γ ≥30 MeV)/(KL → πμν) is found to be (2.08 ± 0.17^+0.16-0.21) × 10^-3, where the first error is statistical and the second systematic. The result is in agreement with theoretical predictions. © 1998 Elsevier Science B.V.