36 research outputs found
Precise Measurement of the Pi+ -> Pi0 e+ nu Branching Ratio
Using a large acceptance calorimeter and a stopped pion beam we have made a
precise measurement of the rare Pi+ -> Pi0 e+ Nu,(pi_beta) decay branching
ratio. We have evaluated the branching ratio by normalizing the number of
observed pi_beta decays to the number of observed Pi+ -> e+ Nu, (pi_{e2})
decays. We find the value of Gamma(Pi+ -> Pi0 e+ Nu)/Gamma(total) = [1.036 +/-
0.004(stat.) +/- 0.004(syst.) +/- 0.003(pi_{e2})] x 10^{-8}$, where the first
uncertainty is statistical, the second systematic, and the third is the pi_{e2}
branching ratio uncertainty. Our result agrees well with the Standard Model
prediction.Comment: 4 pages, 5 figures, 1 table, revtex4; changed content; updated
analysi
Search for the lepton-family-number nonconserving decay \mu -> e + \gamma
The MEGA experiment, which searched for the muon- and electron-number
violating decay \mu -> e + \gamma, is described. The spectrometer system, the
calibrations, the data taking procedures, the data analysis, and the
sensitivity of the experiment are discussed. The most stringent upper limit on
the branching ratio of \mu -> e + \gamma) < 1.2 x 10^{-11} was obtained
Precise Measurement of the Pion Axial Form Factor in the Pi+ -> e+ nu gamma Decay
We have studied radiative pion decays Pi+ -> e+ nu gamma in three broad
kinematic regions using the PIBETA detector and a stopped pion beam. Based on
Dalitz distributions of 42,209 events we have evaluated absolute Pi -> e nu
gamma branching ratios in the three regions. Minimum chi^2 fits to the integral
and differential (E(e+),E(gamma)) distributions result in the axial-to-vector
weak form factor ratio of gamma = F_A/F_V = 0.443(15),or F_A = 0.0115(4) with
F_V = 0.0259. However, deviations from Standard Model predictions in the
high-E(gamma)/low-E(e+) kinematic region indicate the need for further
theoretical and experimental work.Comment: 5 pages, 4 figures, 1 table, revtex