Limits on axion and light Higgs boson production in Y(1S) decays

We have searched for axion and light Higgs boson production in the channel Y(1S) → (a0 or h0)+gamma, where the non-interacting axion a0 and the Higgs boson h0 do not decay in the detector. We find no evidence for an axion and give an upper limit, Br(Y(1S) -> a0 gamma) <4.0x10(-5) (90% CL), for long-lived axions. Combining our limit with the previous search in J/Psi decays, we are able to rule out the axion in the standard model with first order QCD corrections. Our Y(1S) data also rule out a Higgs boson with mass m<86 MeV

Measurement of pi0 pi0 production in two-photon collisions

The reaction e+e- -> e+e- pi0 pi0 has been analyzed using 97 pb-1 of data taken with the Crystal Ball detector at the DESY e-e+ storage ring DORIS II at beam energies around 5.3 GeV. For the first time we have measured the cross section for gamma gamma -> pi0 pi0 for pi0 pi0 mvariant masses ranging from threshold to about 2 GeV. We measure an approximately flat cross section of about 10 nb for W=m(pi0 pi0)<0.8 GeV, which is below 0.6 GeV, in good agreement with a theoretical prediction based on an unitarized Born-term model. At higher invariant masses we observe formation of the f2(1270) resonance and a hint of the f0(975). We deduce the following two-photon widths: Gamma(gamma gamma)(f2(1270))=3.19±0.16±0.280.29 keV and Gamma(gamma gamma)(f0(975))<0.53 keV at 90% C.L. The decay-angular distributions show the pi0 pi0 system to be dominantly spin 0 for W<0.7 GeV and spin 2, helicity 2 in the f2(1270) region, with helicity 0 contributing at most 22% (90% C.L.)

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

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