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Register a new userStudy of the KL to PI+PI-GAMMA Direct Emission Vertex
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We have perfomed studies of the KL to PI+PI-GAMMA Direct Emission (DE) and Inner Bremsstrahlung (IB) vertices, based on data collected by KTeV during the 1996 Fermilab fixed target run. We find a1/a2 = -0.737 +- 0.034 GeV^2 for the DE form-factor parameter in the rho-propagator parametrization, and report on fits of the form-factor to linear and quadratic functions as well. We concurrently measure B.R.(KL to PI+PI-GAMMA, E_gamma >20 MeV)/(KL to PI+PI-) = (20.8 +- 0.3)*10^-3, and a KL to PI+PI-GAMMA DE/(DE + IB) branching ratio of 0.683 +- 0.011.
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We present new results on the related rare KL decay modes KL -> pi+ pi- gamma and KL -> pi+ pi- e+ e-. KTeV has performed the first direct measurement of the form factor for the direct emission component of KL -> pi+ pi- gamma decays, a quantity with ramifications for particular chiral models. In addition, the form factor and direct emission/inner bremsstrahlung branching ratio - also presented here - are important input parameters for the understanding of the planar-angle distribution of KL -> pi+ pi- e+ e- decays. Preliminary results indicating the presence of a T-violating asymmetry in the KL -> pi+ pi- e+ e- angular distribution are presented.
We have performed a measurement of the K^+ -> pi^+ pi^0 gamma decay and have observed 2 X 10^4 events. The best fit to the decay spectrum gives a branching ratio for direct photon emission of (4.7pm0.8pm0.3) X 10^{-6} in the pi^+ kinetic energy region of 55 to 90 MeV and requires no component due to interference with inner bremsstrahlung.
We report the measurement of the ratio $Gamma(eta to pi^+pi^-gamma)/Gamma(eta to pi^+pi^-pi^0)$ analyzing a large sample of $phi to eta gamma$ decays recorded with the KLOE experiment at the DA$Phi$NE $e^+ e^-$ collider, corresponding to an integrated luminosity of 558 pb$^{-1}$. The $eta to pi^+pi^-gamma$ process is supposed to proceed both via a resonant contribution, mediated by the $rho$ meson, and a non resonant direct term, connected to the box anomaly. The presence of the direct term affects the partial width value. Our result $R_{eta}=Gamma(eta to pi^+ pi^- gamma)/Gamma(eta to pi^+ pi^- pi^0)= 0.1838pm 0.0005_{stat} pm 0.0030_{syst}$ is in agreement with a recent CLEO measurement, which differs by more 3 $sigma$ from the average of previous results.
We report a study of the suppressed $B^-to DK^-pi^+pi^-$ and favored $B^-to Dpi^-pi^+pi^-$ decays, where the neutral $D$ meson is detected through its decays to the $K^{mp}pi^{pm}$ and CP-even $K^+K^-$ and $pi^+pi^-$ final states. The measurement is carried out using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 3.0~fb$^{-1}$. We observe the first significant signals in the CP-even final states of the $D$ meson for both the suppressed $B^-to DK^-pi^+pi^-$ and favored $B^-to Dpi^-pi^+pi^-$ modes, as well as in the doubly Cabibbo-suppressed $Dto K^+pi^-$ final state of the $B^-to Dpi^-pi^+pi^-$ decay. Evidence for the ADS suppressed decay $B^{-}to DK^-pi^+pi^-$, with $Dto K^+pi^-$, is also presented. From the observed yields in the $B^-to DK^-pi^+pi^-$, $B^-to Dpi^-pi^+pi^-$ and their charge conjugate decay modes, we measure the value of the weak phase to be $gamma=(74^{+20}_{-19})^{rm o}$. This is one of the most precise single-measurement determinations of $gamma$ to date.
We present a new result on the K^+ --> pi^+ pi^0 gamma decay measurement using stopped kaons. The best fit to the decay spectrum comprised of 10k events gives a branching ratio for the direct photon emission of [3.8+-0.8(stat)+-0.7(syst)] times 10^{-6} in the pi^+ kinetic energy region of 55 to 90 MeV. This result has been obtained with the assumption that there is no component due to interference with the inner bremsstrahlung.
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