P. Depommier

Radiative Muon Capture on Hydrogen and the Induced Pseudoscalar Coupling

Next to the hydrogen atom, the µ − p system is the most fundamental lepton-hadron system; therefore it can be used to test and extend our basic knowledge of the weak semi-leptonic interaction between leptons and quarks. Radiative muon capture (RMC) is much more sensitive than ordinary muon capture (OMC) to the induced pseudoscalar coupling constant of the weak semi-leptonic current because of the much larger range of momentum transfers which can occur in RMC. A status report on TRIUMF E452, Radiative Muon Capture on Hydrogen, which is anticipating a 10% measurement of this coupling constant, is presented.

Apparatus for a search for T-violating muon polarization in stopped-kaon decays

Abstract The detector built at KEK to search for T-violating transverse muon polarization in K + → π 0 μ + ν μ ( K μ 3 ) decay of stopped kaons is described. Sensitivity to the transverse polarization component is obtained from reconstruction of the decay plane by tracking the μ+ through a toroidal spectrometer and detecting the π0 in a segmented CsI(Tl) photon calorimeter. The muon polarization was obtained from the decay positron asymmetry of muons stopped in a polarimeter. The detector included features which minimized systematic errors while maintaining high acceptance.

Test of exotic scalar and tensor couplings in K+→π0e+ν decay

Abstract The form factors of the decay K + → π 0 e + ν ( K e 3 + ) have been measured with stopped kaons. Axa0Dalitz plot containing 4.1×10 4 events was analyzed. A comparison of the observed Dalitz plot with a Monte Carlo simulation determined the ratio of the strengths of possible scalar and tensor couplings to that of the vector coupling, f S / f + (0)=−0.002±0.026(stat)±0.014(syst) and f T / f + (0)=−0.01±0.14(stat)±0.09(syst). These values are consistent with the standard model prediction of zero, and disagree with a previous experiment. The analysis also yielded the coefficient of the q 2 term in the vector form factor to be λ + =0.0278±0.0026(stat)±0.0030(syst).

Measurement of Γ(Kμ3)/Γ(Ke3) ratio using stopped positive kaons

Abstract The ratio of the K + → π 0 μ + ν ( K μ 3 + ) and K + → π 0 e + ν ( K e 3 + ) decay widths, Γ ( K μ 3 )/ Γ ( K e 3 ), has been measured with stopped positive kaons. K μ 3 + and K e 3 + samples containing 2.4×10 4 and 4.0×10 4 events, respectively, were analyzed. The Γ ( K μ 3 )/ Γ ( K e 3 ) ratio was obtained to be 0.671±0.007(stat.)±0.008(syst.) calculating the detector acceptance by a Monte Carlo simulation. The coefficient of the q 2 dependent term of the f 0 form factor was also determined to be λ 0 =0.019±0.005(stat.)±0.004(syst.) with the assumption of μ – e universality in K l 3 + decay. The agreement of our result with the λ 0 value obtained from K μ 3 + Dalitz plot analyses supports the validity of the μ – e universality.

CsI(Tl) photon detector with PIN photodiode readout for a Kμ3 T-violation experiment

Abstract The π0 detector constructed for the T-violation search experiment E246 at KEK is described. It consists of 768 CsI(Tl) crystals with PIN photodiode readout. The crystals are assembled in a tight barrel with holes for muons entering the magnetic spectrometer. The design and performance of the calorimeter are presented. The average light yield of 11u2008000xa0p.e./MeV and average equivalent noise level of 63xa0keV (bench test) were obtained for the CsI(Tl) modules used in the calorimeter. The coherent noise was found to be about 11xa0keV per a module. A readout electronics has been specifically developed for the high counting rate environment of the experiment. A π0 invariant mass resolution of 9.9xa0MeV (σ) was obtained for the whole detector, including regions around the muon holes. A time resolution of 3.8xa0ns (rms) was achieved in the photon energy range of 10–200xa0MeV.

Measurement of P(mu)xi in polarized muon decay

The quantity P_{mu}^{pi}xi, where xi is one of the muon decay parameters and

Test of exotic scalar and tensor interactions in K(e3) decay using stopped positive kaons

P_{mu}^{pi}

Search for the parity-forbidden heavy-particle width Γ′dα of the Ex = 3.562 MeV state in 6Li

is the degree of muon polarization in pion decay, has been measured. The value P_{mu}^{pi}xi = 1.0003 +- 0.0006 stat. +- 0.0038 syst. was obtained. This result agrees with previous measurements but is over a factor of two more precise. It also agrees with the Standard Model prediction for P_{mu}^{pi}xi and thus leads to restrictions on left-right symmetric models.

Precise measurement of parity violation in polarized muon decay

The form factors of the decay K+ → π0e+νe (Ke3) have been determined from the comparison of the experimental and Monte Carlo Dalitz distributions containing about 105Ke3 events. The following values of the parameters were obtained: λ+=0.0278±0.0017 (stat.)±0.0015 (syst.), |fS/f+(0)|=0.0040±0.0160 (stat.)±0.0067 (syst.), and |fT/f+(0)|=0.019±0.080 (stat.)±0.038 (syst.). Both scalar fS and tensor fT form factors are consistent with the Standard Model predictions of zero values.

First measurement of the T-violating muon polarization in the decay K+→μ+νγ

Abstract Alpha-particle capture by deuterium has been investigated at excitation energies in 6 Li close to the J π = 0 + , T = 1, E x , = 3.562 MeV state. A search for resonance γ-rays from this state has yielded a negative result and an upper limit for the heavy-particle width Γ ′ d α ≦ 0.017 eV.