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Register a new userRecent NA48 results on rare kaon decays
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C. Cheshkov
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Recent NA48 results from detailed studies of $K_{L,S}to pi^+ pi^- e^+ e^-$ and $K_Stopi^0 gammagamma$ decay modes are presented. The results are based on the data collected with the NA48 detector at the CERN SPS during the 1998-199 9 and 2000 data taking periods, respectively. Prospects for future results on charged kaon decays are briefly described.
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While measuring the ratio R_K = Gamma(K+e2(gamma))/Gamma(K+mu2(gamma)), the KLOE Collaboration has studied the radiative process Ke2gamma. The ratio of the width for the Ke2gamma decay with a positively polarized photon from structure-dependent radiation to the inclusive Kmu2(gamma) width is found to be 1.484(68) 10-5. The observed radiation spectrum agrees with predictions from chiral perturbation theory and is in contrast with predictions based on the light front quark model. This result reduces the contribution to systematic uncertainties on measurements of R_K. In a separate study, KLOE has measured the ratio of the radiative Ke3gamma decay width to the inclusive Ke3(gamma) width to be 924(28) 10-5. The distribution in energy and angle of the radiative photon has been analyzed in an attempt to isolate the signature from interference of the inner-bremsstrahlung and structure-dependent amplitudes.
The NA48/2 Collaboration at CERN has accumulated and analysed unprecedented statistics of rare kaon decays in the $K_{e4}$ modes: $K_{e4}(+-)$ ($K^pm to pi^+ pi^- e^pm u$) and $K_{e4}(00)$ ($K^pm to pi^0 pi^0 e^pm u$) with nearly one percent background contamination. It leads to the improved measurement of branching fractions and detailed form factor studies. New final results from the analysis of 381 $K^pm to pi^pm gamma gamma$ rare decay candidates collected by the NA48/2 and NA62 experiments at CERN are presented. The results include a decay rate measurement and fits to Chiral Perturbation Theory (ChPT) description.
We report on recent results on radiative and electroweak penguin B decays at Belle at KEKB accelerator.
We review recent experimental progress in the domain of rare radiative, semileptonic and leptonic B decays. The statistical precision attained for these decays has reached a level where they start to impose meaningful constraints on the Cabibbo-Kobayashi-Maskawa matrix, which are complementary to those obtained from hadronic decays. While the current data indicate no deviations from Standard Model predictions, there is still some room for new physics in these decays.
This review presents the analysis of leptonic and semileptonic kaon decays data done by the FlaviaNet Kaon Working group, as described in FlaviaNet Note of October 2008. Data include all recent results by BNL-E865, KLOE, KTeV, ISTRA+, and NA48. Experimental results are critically reviewed and combined, taking into account theoretical (both analytical and numerical) constraints on the semileptonic kaon form factors. We report on a very accurate determination of Vus as well as on many other tests of the SM which can be performed with leptonic and semileptonic kaon decays.
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