Giles Barr

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.

Abstract:

We present a new measurement of the branching ratio R of the decay K L→ pi;±e∓ν, denoted as Ke3, relative to all charged KL decays with two tracks, based on data taken with the NA48 detector at the CERN SPS. We measure R=0.4978±0. 0035. From this we derive the Ke3 branching fraction and the weak coupling parameter |Vus| in the CKM matrix. We obtain |Vus|f+(0)=0. 2146±0.0016, where f+(0) is the vector form factor in the Ke3 decay. © 2004 Published by Elsevier B.V.

Abstract:

A time-of-flight system based on 46 multigap glass resistive plate chambers has operated for 2 years in the HARP experiment at the CERN PS. The system covers an area of 10m(2) and comprises 368 readout channels. Systematic checks of the RPC performance are presented as well as preliminary results on its particle identification capabilities. (C) 2004 Elsevier B.V. All rights reserved.