Giles Barr

Abstract:

This report describes the channel of superconducting solenoids for the proposed international Muon Ionization Cooling Experiment (MICE). MICE consists of two cells of a SFOFO cooling channel that is similar to that studied in the level 2 study of a neutrino factory[1], MICE also consists of two detector solenoids at either end of the cooling channel section. The superconducting solenoids for MICE perform three functions. The coupling solenoids, which are large solenoids around 201.25 MHz RF cavities, couple the muon beam between the focusing sections as it passes along the cooling channel. The focusing solenoids are around the liquid hydrogen absorber that reduces the momentum of the muons in all directions. These solenoids generate a gradient field along the axis as they reduce the beta of the muon beam before it enters the absorber. Each detector solenoid system consists of five coils that match the muon beam coming to or from an absorber to a 4.0 T uniform solenoidal field section that that contains the particle detectors at the ends of the experiment. There are detector solenoids at the beginning and at the end of the experiment. This report describes the parameters of the eighteen superconducting coils that make up the MICE magnetic channel.

Abstract:

A search for the decay KS → π⁰γγ has been made using the NA48 detector at the CERN SPS. Using data collected in 1999 during a 40-hour run with a high-intensity KS beam, an upper limit for the branching ratio BR(KS → π⁰γγ, z ≥ 0.2) < 3.3 x 10^-7 has been obtained at 90% confidence level, where z = m²γγ/mKO². © 2003 Published by Elsevier Science B.V.

Abstract:

The KS → γγ decay rate has been measured with the NA48 detector using a high intensity short neutral beam from the CERN SPS. The measured branching ratio BR(KS → γγ) = (2.78 ± 0.06stat ± 0.04syst) x 10^-6, obtained from 7461 ± 172 KS → γγ events, is significantly higher than the O(p⁴) prediction of chiral perturbation theory. Using a KL beam the ratio Γ(KL → γγ)/Γ(KL → π⁰π⁰π⁰) = (2.81 ± 0.02syst) ×10^-3 has been measured. © 2002 Elsevier Science B.V. All rights reserved.

Abstract:

The KL → π+π-e +e- and KS → π+π -e+e- decay modes have been studied in detail using the NA48 detector at the CERN SPS. Based on the data collected during the 1998 and 1999 run periods, a sample of 1162 KL → π +π-e+e- candidates has been observed with an expected background level of 36.9 events, yielding the branching ratio measurement BR(KL → π+π -e+e-) = (3.08 ± 0.20) × 10 -7. The distribution of events in the sinφ cosφ variable, where φ is the angle between the π+π- and the e+e- decay planes in the kaon centre of mass, is found to exhibit a large CP-violating asymmetry with the value Aφ = (14.2 ± 3.6)%. For the KS → π+π -e+e- decay channel, 621 candidates have been identified in the 1999 data sample with an estimated background contribution of 0.7 event. The corresponding branching ratio has been determined to be BR(K S → π+π-e+e-) = (4.71 ± 0.32) × 10-5. The combined value of this measurement with the published 1998 result is BR(KS → π +π-e+e-) = (4.69 ± 0.30) × 10-5. No asymmetry is observed in this decay mode. Our results are in good agreement with theoretical predictions based on a phenomenological description of radiative kaon decays. The form factor parameters a1/a2 and g̃M1 in the K L → π+π-e+e- direct emission process as well as the value of the K0 charge radius have been extracted from the data.