Universiẗat, Diss., 2002--München.

Three types of rare radiative meson decays are studied. The first type is the weak kaon decay [special characters omitted] The interest here is this decay's sensitivity to the loop-level and hence quantum structure of the standard model. Both short-distance and long-distance effects are considered, as well as possible contributions from horizontal gauge bosons. The second decay type studied is electromagnetic η decays into neutral pions, specifically [special characters omitted] and [special characters omitted] The main interest here is possible signals for electromagnetic charge-conjugation violation. The modelling method used is vector meson dominance. The third type studied is electromagnetic η decays into charged pions, specifically [special characters omitted] and [special characters omitted] The interest here is chiral perturbation theories that incorporate vector mesons. / Graduate

Brookhaven National Laboratory experiment E949 was designed to search for the rare K meson decay K⁺ → π⁺ , neutrino, and anti-neutrino, a decay sensitive to physics beyond the Standard Model. While previous data analyses dealt with the high π⁺ momentum region accessible for this reaction, this thesis concentrates on the lower range between 140 and 199 MeV/c. Analysis of this low π⁺ momentum region was performed to search for additional evidence of the process K⁺ → π⁺, neutrino, and anti-neutrino. A blind analysis technique was used to avoid bias when developing the selection criteria used to suppress the competing background processes. The blind analysis technique was based on identifying background sources a priori and only examining the signal region once all selection criteria and background estimates had been finalized. The background estimates were performed using a technique known as a "bifurcation method", which relied on using two uncorrelated selection criteria to suppress each background source. The analysis of an exposure of 1.71 x 10¹² K⁺ decays resulted in an observation of three events with an estimated background of 0.927 ± 0.168(stat.)⁺³²⁰-₀.₂₃₇(sys.) events and a single event sensitivity of (4.28 ± 0.43)x 10-¹⁰. Using a likelihood method, the three candidate events observed here were combine with the previous E787 and E949 results, yielding a branching ratio of ϐ(K⁺ → π⁺, neutrino, and anti-neutrino decay of (1.73+1.15-1.05) x 10⁻¹⁰ at the 68% confidence level. This branching ratio is consistent with the prediction of the Standard Model, (0.85 ± 0.07) x 10⁻¹⁰. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Techn. Universiẗat, Diss., 2003--Darmstadt.

No description available.

The purpose of this investigation was to study the scattering processes of K+ mesons with neutrons. In order to do such a study one must first make certain basic assumptions about the type of interaction involved and then proceed to calculate physically meaningful qualities which describe the processes. Thus, the problem is this: assuming the validity of Feynman's rules for these strongly interacting particles, calculate the differential and total scattering cross sections for the interaction of scalar K+ mesons and neutrons.

Techn. Universiẗat, Diss., 2000--Darmstadt.

The CLAS Collaboration is using the p(e, e′ K+ p)π- reaction to perform a measurement of the induced polarization of the electroproduced Λ(1116). The parity-violating weak decay of the Λ into pπ- (64%) allows extraction of the recoil polarization of the Λ. The present study uses the CEBAF Large Acceptance Spectrometer (CLAS) to detect the scattered electron, the kaon, and the decay proton. CLAS allows for a large kinematic acceptance in Q2 (0.8 ≤ Q2 ≤ 3.5 GeV2 ), W (1.6 ≤ W ≤ 3.0 GeV), as well as the kaon scattering angle. In this experiment a 5.499 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The goal is to map out the kinematic dependencies for this polarization observable to provide new constraints for theoretical models of the electromagnetic production of kaon-hyperon final states. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, SAPHIR, and GRAAL, these data are needed in a coupled-channel analysis to identify previously unobserved s-channel resonances.

No description available.

<p>In recent years, the strangeness production reactions in NN collisions have attracted a considerable amount of interest. These reactions are expected to provide valuable information on the manifestation of Quantum chromodynamics (QCD) in the nonperturbative region. For example, the &phi; meson is expected to probe the admixture of strange quark pairs in the nucleon wave function. The near-threshold reactions are expected to provide valuable information about the meson-meson, meson-baryon,</p><p>and hyperon-nucleon interactions.</p><p>We report the differential and total cross sections for the pp &rarr; ppKK/&phi; reaction at Tp= 2.567 (below the &phi; meson threshold) and 2.83 GeV (above the &phi; meson threshold). We use detailed model descriptions to fit a variety of one dimensional distributions in order to separate the pp &rarr; pp&phi; cross section from that of non- &phi; production. The differential spectra show that higher partial waves represent the majority of the pp &rarr; pp &phi; total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave &phi;p enhancement near threshold. On the other hand, strong preferences to the low Kp and Kpp invariant masses are observed in non- kaon pair productions. The cusp effect in the KK distribution at the K0 K0 threshold is clear and some evidence is also found for coupling between the Kp and K0n channels. Beside of the mentioned reactions, we also show the preliminary results for the search for a possible Kpp bound state in the pp &rarr; pK&Lambda; reaction at Tp=2.567 GeV.</p> / Dissertation