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

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Experimental upper limits for the hadronic transitions Υ(2S)→ηΥ\Upsilon (2S)\to \eta \Upsilon(1S) and Υ(2S)→π0Υ\Upsilon (2S)\to \pi^0\Upsilon(1S)

Using the Crystal Ball detector at thee+e− storage ring DORIS-II, we have searched for the hadronic transitions Υ(2S)→ηΥ(1S) and Υ(2S)→π0Υ(1S) in exclusive decays where the Υ(1S) decays into ane+e− or aµ+µ- pair and the η and π0 are detected by their decay modes η→γγ, η→γγ and π0→γγ. From the number of observed events we derive, after consideration of possible background sources, upper limits on the branching ratiosB(Υ(2S)→ηΥ(1S))<0.7% andB(Υ(2S)→π0Υ(1S))<0.8% at the 90% confidence level

Spin Analysis of the χ(b\chi(b) States

Angular correlations in the cascade reaction e+e−→Υ(2S)→γχb, χb→γΥ, Υ→μ+μ− or Υ→e+e−, have been used for the first time to investigate the spins of the χb states. The results support the χb spins predicted by the potential models of heavy quarkonia

The Michel Parameter For the Decay Tau -> e nu nubar

The Crystal Ball detector at the Doris II storage ring at DESY has been used to study the electron energy spectrum of the decay tau -&gt; e nu nubar. In the standard model the Lorentz structure of the decay matrix element is of the well known V-A type, resulting in a Michel parameter of p=0.75. Our spectrum is found to be consistent with this value. A fit yields the value of 0.64+-0.06+-0.07

Measurement of the Decay of the Y(1S) and Y(2S) Resonances To Muon Pairs

Using the Crystal Ball detector at the e+e-storage ring DORIS II, we have measured the branching fraction to muon pairs B(mu-mu) of the UPSILON(1S) and UPSILON(2S) resonances and for the first time the product of the muonic partial width GAMMA(mu-mu) and the branching fraction to electrons B(ee) for both resonances. We obtain B(mu-mu) (1S) = (2.31 +/- 0.12 +/- 0.10)%, GAMMA(mu-mu) (1S) . B(ee) (1S) = (31.2 +/- 1.6 +/- 1.7) eV, and B(mu-mu) (2S) = (1.22 +/- 0.28 +/- 0.19)%, GAMMA(mu-mu) (2S) . B(ee) (2S) = (6.5 +/- 1.5 +/- 1.0) eV. Inserting the present world average value of B(ee) (1S) = (2.52 +/- 0.17)%, we determine the muonic partial width of the UPSILON(1S) as GAMMA(mu-mu) (1S) = (1.24 +/- 0.06 +/- 0.11) keV. In addition, we present the first indication of the expected interference between mu-pair production in the continuum and in UPSILON(1S) decays

Measurement of the Properties of the eta' and Search For Other Resonances In Gamma-gamma -> eta pi0 pi0

The reaction e+e- -> e+e- eta pi0 pi0 has been observed with the Crystal Ball detector at the DORIS II storage ring at DESY. The eta pi0 pi0 mass spectrum is dominated by the eta', and the two-photon width Gamma(eta' -> gamma gamma) is determined to be 4.6+-0.4+-0.6 keV. Limits on Gamma(X ->gamma gamma) x B(X -> eta pi pi) are given for other possible states

The Michel parameter for the decay τ→\tau \toν

The Crystal Ball detector at the Doris II storage ring at DESY has been used to study the electron energy spectrum of the decay τ→evv̄. In the standard model the Lorentz structure of the decay matrix element is of the well known V-A type, resulting in a Michel parameter of p=0.75. Our spectrum is found to be consistent with this value. A fit yields the value of 0.64±0.07

Search For Radiative B-meson Decays

The Crystal Ball detector at the e+ e- storage ring DORIS-II has been used to search for radiative B meson decays, especially of the type b --> s-gamma. No monoenergetic gamma-lines have been found in the inclusive photon spectrum from UPSILON(4S) decays, and upper limits are obtained for radiative decays of B mesons to various strange mesons and to the D*. Integrating the photon spectrum over the corresponding energy range, we find BR (B--> gamma-X) < 2.8 x 10(-3), at 90% confidence level for the mass range 892 MeV less-than-or-equal-to M(X) less-than-or-equal-to 2045 MeV