arXiv subjects
Publications and source records attributed to J-M. Poutissou.
We report on a search for the free decay component of pi- stopped in water and light materials. A non-zero value of this would be an indication of anomalous nu_e contamination to the nu_e and nu_mu_bar production at stopped-pion neutrino facilities. No free decay component of pi- was observed in water, Beryllium, and Aluminum, for which upper limits were established at 8.2E-4, 3.2E-3, and 7.7E-3, respectively.
An upper limit on the branching ratio for the decay K+ --> e+ nu mu+ mu- is set at 5.0 x 10^{-7} at 90% confidence level, consistent with predictions from chiral perturbation theory.
We have observed the rare decay K+ --> pi+ mu+ mu- and measured the branching ratio Gamma(K+ --> pi+ mu+ mu-)/Gamma(K+ --> all) = (5.0 +/- 0.4 (stat.) +/- 0.7 (sys.) +/- 0.6 (theor.)) x 10^{-8}. We compare this result with predictions from chiral perturbation theory and estimates based on the decay K+ --> pi+ e+ e-.
An upper limit on the branching ratio for the decay $K^+ \! \rightarrow \! π^+ ν\overlineν$ is set at $2.4 \times 10^{-9}$ at the 90\% C.L. using pions in the kinematic region $214~{\rm MeV}/c < P_π< 231~{\rm MeV}/c$. An upper limit of $5.2 \times 10^{-10}$ is found on the branching ratio for decays $K^+ \! \rightarrow \! π^+ X^0$, where $X^0$ is any massless, weakly interacting neutral particle. Limits are also set for cases where $M_{X^0}>0$.