Giles Barr

Abstract:

The decay rate of the long-lived neutral K meson into the e +e-e+e- final state has been measured with the NA48 detector at the CERN SPS. Using data collected in 1998 and 1999, a total of 200 events has been observed with negligible background. This observation corresponds to a branching ratio of Br(KL→ e+e-e+e-)=(3.30±0.24 stat±0.23syst±0.10norm) ×10-8. © 2005 Elsevier B.V. All rights reserved.

Abstract:

Using data taken during the year 2000 with the NA48 detector at the CERN SPS, a search for the CP violating decay KS→3π⁰ has been performed. From a fit to the lifetime distribution of about 4.9 million reconstructed K⁰/K̄⁰→3π⁰ decays, the CP violating amplitude η000=A(KS→3π⁰)/ A(KL→3π⁰) has been found to be Re(η000)=-0.002±0.011±0.015 and Im(η000)=-0.003±0. 013±0.017. This corresponds to an upper limit on the branching fraction of Br(KS→3π⁰)<7.4×10^-7 at 90% confidence level. The result is used to improve knowledge of Re(ε) and the CPT violating quantity Im(δ) via the Bell-Steinberger relation. © 2005 Elsevier B.V. All rights reserved.

Abstract:

We present a measurement of the relative branching ratio of the decay K⁰ → π^±e^±νγ (Ke3γ) with respect to K⁰ → π^±e^±ν (Ke3 + K e3γ) decay. The result is based on observation of 19 000 K e3γ and 5.6 × 10⁶ Ke3 decays. The value of the branching ratio is Br(Ke3γ⁰, E γ* > 30 MeV, θeγ* > 20°)/Br(Ke3⁰) = (0.964±0.008 -0.009^+0.011)%. This result agrees with theoretical predictions but is at variance with a recently published result. © 2004 Elsevier B.V. All rights reserved.

Abstract:

This report describes the focusing solenoid for the proposed Muon Ionization Cooling Experiment (MICE) [1]. The focusing solenoid consists of a pair of superconducting solenoids that are on a common bobbin. The two coils, which have separate leads, may be operated in the same polarity or at opposite polarity. This report discusses the superconducting magnet design and the cryostat design for the MICE focusing module. Also discussed is how this superconducting magnet can be. integrated with a pair of small 4.2 K coolers.

Abstract:

The semileptonic decay of the neutral K meson, KL0→π± e∓ν (Ke3), was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector (f+(q2)), scalar (fS) and tensor (fT) interactions were measured. The linear slope of the vector form factor λ+=0.0284±0.0007±0.0013 and values for the ratios |fS/f+(0)|=0.015-0.010+0.007±0.012 and |fT/f+(0)|=0.05-0.04+0. 03±0.03 were obtained. The values for fS and fT are consistent with zero. Assuming only vector-axial-vector couplings, λ+=0.0288±0. 0004±0.0011 and a good fit consistent with pure V-A couplings were obtained. Alternatively, a fit to a dipole form factor yields a pole mass of M=859±18 MeV, consistent with the K*(892) mass. © 2004 Elsevier B.V. All rights reserved.