Search For Exotic Tau-decays

The Crystal Ball detector at the Doris II storage ring at DESY was used to search for the exotic decay processes tau -> e gamma, tau -> e pi0, tau -> e eta. No signal was observed. We obtained the following 90% CL upper limits on the branching fractions:B(tau -> e gamma)< 2.0x10^(-4),B(tau -> e pi0) < 1.4x10^(-4),B(tau -> e eta) < 2.4x10^(-4)

Measurement of pi0 and eta meson production in e+e- annihilation at sqrt(s) near 10 GeV

We present a study of inclusive pi0 and eta production in e+e- annihilation at sqrt(s)=(approx) 10 GeV. Our analysis is based on integrated luminosities of 46.2 pb-1 taken at the Y(1S) resonance and 42.1 pb-1 taken in the neighboring continuum. We measure the inclusive pi0 and eta spectra for direct Y(1S) -> 3 g decays and continuum processes e+ e- -> q qbar and obtain the following mean particle multiplicities per event: Continuum:=3.64+-0.21+-0.36, =0.22+-0.04+-0.03Y(1S) -> 3g:=3.39+-0.14+-0.34, =0.35+-0.04+-0.04We compare our results with predictions of different fragmentation models and with other measurements performed in e+e- annihilation at similar center-of-mass energies

Inclusive J/Psi production in decays of B mesons

The production of J/Psi in B meson decays has been measured on the Y(4S) resonance using the Crystal Ball detector at the e+e- storage ring DORIS II. The J/Psi is identified by its e+e- decay mode. We obtain a branching ratio of BR(B->J/Psi X)=(1.12+-0.33+-0.25)% in good agreement with theoretical predictions based on color suppression. The J/Psi momentum distribution is observed to be peaked at high values. This implies a substantial contribution from direct B meson decays to the J/Psi. In addition upper limits on J/Psi production in Y(1S) and Y(2S) decays and in continuum processes are determined

First observation of the reaction gamma gamma -> pi2 -> pi0 pi0 pi0

The Crystal Ball detector has been used at the DORIS II storage ring at DESY to study the reaction gamma gamma -> pi0 pi0 pi0 in the pi0 pi0 pi0 invariant mass range from 850 MeV/c 2 to 2600 MeV/c 2. An enhancement around 1750 MeV/c 2 is attributed to the pi2(1670) resonance. The observed pi0 pi0 invariant mass distribution and the pi0 angular distributions are consistent with those expected for the decay chain pi2 -> pi0 f2(1270) -> pi0 pi0 pi0. From our measurements we find the following resonance parameters: two photon partial width Gamma(gamma gamma)(pi2) = (1.41+.0.23+.0.28)keV, mass M(pi2)=(1742+-31+-49)MeV/c 2 and total width Gamma(tot)(pi2)=(236+.49+.36)MeV

Observation of the exclusive decay B -> e nu D * and search for B -> e nu pi0

The Crystal Ball detector at the e+e- storage ring DORIS II has been used to analyze exclusive semileptonic decays of B mesons produced at Y(4S) energies. The decay B -> e nu D* has been observed with a branching ratio of (7.0+-1.8+-1.4)% using the pi0 D decay mode of the D*. In addition we have searched for the exclusive semileptonic decay B+- -> e+- nu pi0. We find an upper limit on B+- -> e+- nu pi0 of 0.22% at the 90% CL

*Measurement of the Branching Ratios for the Decays Tau->Hadron Pi-0-Nu and Tau->Hadron Pi-0-Pi-0-Nu

Contains fulltext : 29793.pdf (publisher's version ) (Open Access

The Electron Spectrum From B-meson Decays

The Crystal Ball Collaboration has measured the energy spectrum of electrons from semileptonic B meson decays at the e+ e– storage ring DORIS II. Branching ratios and weak mixing angles of the Kobayashi-Maskawa matrix are determined using several models for the hadronic matrix elements. We obtain the branching ratio for semileptonic B decays to charmed states BR(B -> e nu Xc )=(11.7+-0.4+-1.0)%. Our result for the corresponding Kobayashi-Maskawa matrix element is |Vcb |=0.052+-0.006. The model dependence of both results is included in the error. We have not observed semileptonic B decays to non-charmed mesons. Analyzing the measured electron spectrum above 2.4 GeV, where no b->c decays contribute, we find BR(B -> e nu Xu )/BR(B -> e nu Xc )<6.5% at the 90% confidence level.this corresponds to an upper limit |V ub /V cb |