The neutral kaon decays to \pi^+ \pi^- \pi^0: a detailed analysis of the CPLEAR data

A detailed analysis of neutral kaons decaying to is presented based on the complete data set containing half a million events. Time-dependent decay rate asymmetries are measured between initially tagged and and for different regions of the phase space. These asymmetries, resulting from the interference between the CP-conserving decay amplitude of and the decay amplitude of – either CP-violating or CP-conserving – allow the determination of the parameters (CP-violating) and (CP-conserving), and also of the main isospin components of the decay amplitude. The branching ratio of (CP-conserving) is deduced directly from . In addition, we extract the slope parameters describing the energy dependence of the Dalitz plot. The whole set of our results fits well within the current phenomenological picture of the neutral-kaon system including CP violation and Chiral Perturbation Theory (ChPT). Received: 13 March 1998 / Published online: 3 September 1998     

Quasi-free \pi^0 photoproduction from the bound nucleon

Differential cross-sections for quasi-free photoproduction from the proton and neutron bound in the deuteron have been measured for MeV at using the Glasgow photon tagger at MAMI, the Mainz 48 cm cm NaI(Tl) photon detector and the Göttingen SENECA recoil detector. For the proton measurements made with both liquid-deuterium and liquid-hydrogen targets allow direct comparison of free photoproduction cross-sections as extracted from the bound-proton data with experimental free cross-sections which are found to be in reasonable agreement below 320 MeV. At higher energies the free cross-sections extracted from quasi-free data are significantly smaller than the experimental free cross-sections and theoretical predictions based on multipole analysis. For the first time, free neutron cross-section have been extracted in the -region. They are also in agreement with the predictions from multipole analysis up to 320 MeV and significantly smaller at higher photon energies.Received: 28 May 2003, Published online: 27 January 2004PACS: 13.60.Le Meson production - 14.20.Dh Protons and neutrons - 25.20.Lj Photoproduction reactionsK. Kossert: Part of the Doctoral Thesis.,Present address: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany.Present address F. Wissmann: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany. Present address B. Seitz: II. Physikalisches Institut der Universität Gießen, Germany.     

Large-p_T inclusive \pi^0 cross sections and next-to-leading-order QCD predictions

We review the phenomenology of production at large transverse momentum in proton-induced collisions. Uncertainties in the next-to-leading-order predictions of Quantum Chromodynamics are discussed. The comparison with data reveals that the disagreement between theory and experiment lies essentially in an overall normalization factor. The situation for production is contrasted with that of prompt-photon production in hadronic collisions. Received: 7 October 1999 / Published online: 17 February 2000     

Multiplicities of \pi^0, \eta,\rm K^0 and of charged particles in quark and gluon jets

We compared the multiplicities of and of charged particles in quark and gluon jets in 3-jet events, as measured by the OPAL experiment at LEP. The comparisons were performed for distributions unfolded to 100% pure quark and gluon jets, at an effective scale which took into account topological dependences of the 3-jet environment. The ratio of particle multiplicity in gluon jets to that in quark jets as a function of for or was found to be independent of the particle species. This is consistent with the QCD prediction that the observed enhancement in the mean particle rate in gluon jets with respect to quark jets should be independent of particle species. In contrast to some theoretical predictions and previous observations, we observed no evidence for an enhancement of meson production in gluon jets with respect to quark jets, beyond that observed for charged particles. We measured the ratio of the slope of the average charged particle multiplicity in gluon jets to that in quark jets, C, and we compared it to a next-to-next-to-next-to leading order calculation. Our result, is about one standard deviation higher than the perturbative prediction. Received: 31 March 2000 / Published online: 25 September 2000     

Final State Strong Interaction Constraints on Weak {D^0 \to K^0_S \pi^+ \pi^-} Decay Amplitudes

Weak decay tree and annihilation-t-channel W-exchange amplitudes for the ${D^0 \to K^0_S \pi^+ \pi^-}$ process are calculated using quasi two-body QCD factorization approach and unitarity constraints. Final state strong Kπ and ππ interactions in S, P and D waves are described through corresponding form factors including many resonances. Preliminary results compare well with the effective mass distributions of the Belle and BABAR Collaboration analyses.     

Electromagnetic corrections in the anomaly sector and the \pi^0 lifetime

The framework for computing radiative corrections in ChPT in the anomaly sector is set up. Application to the lifetime of the and the possibility to extract information on m _d -m _u from precision data is discussed.Received: 30 September 2002, Published online: 22 October 2003PACS: 11.30.Rd Chiral symmetries - 12.15.Ff Quark and lepton masses and mixing - 12.39.Fe Chiral Lagrangians     

Pion correlations and resonance effects in \bar{p}p annihilation to 4\pi^0 at rest

We study correlations in the exclusive reaction at rest with complete reconstruction of the kinematics for each event. The inclusive distribution is fairly flat at small invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while the stochastic HBT mechanism is not supported by the present findings. Received: 26 February 2002 / Revised version: 22 July 2002 / Published online: 30 August 2002