Search for Flavor Changing Neutral Currents K

Search for Flavor Changing Neutral Currents K

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Published: 1988

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We report on a search for the flavor-changing neutral-current decays K/sub L/° .-->. .pi.°ee/sup /minus//, K/sub L/° .-->. ee/sup /minus// and K/sub L/° .-->. .mu./sup +-/e/sup /minus plus//. Limits obtained for these processes are BR(K/sub L/° .-->. .pi.°e+e/sup /minus//) 3.2 x 10/sup /minus/7/, BR(K/sub L/° .--. e+e/sup /minus//) 1.2 x 10/sup /minus/9/, BR(K/sub L/° .--. .mu./sup +-/e/sup /minus plus//)


Updated Search for the Flavor-Changing Neutral-Current Decay $D0̂ \to \mu+̂ \mu-̂$

Updated Search for the Flavor-Changing Neutral-Current Decay $D0̂ \to \mu+̂ \mu-̂$

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Published: 2010

Total Pages: 8

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We report on a search for the flavor-changing neutral-current decay D° →??− in p{bar p} collisions at √s = 1.96TeV using 360 pb−1 of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. A displaced vertex trigger selects long-lived D° candidates in the?+?−,?+?−, and K−?+ decay modes. We use the Cabibbo-favored D° → K−?+ channel to optimize the selection criteria in an unbiased manner, and the kinematically similar D° →?+?− channel for normalization. We set an upper limit on the branching fraction?(D° →?+?−)


Search for the Flavor-changing Neutral Current Decay K Sup + Yields. Pi. Sup +. Nu. Nu

Search for the Flavor-changing Neutral Current Decay K Sup + Yields. Pi. Sup +. Nu. Nu

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Published: 1990

Total Pages: 10

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The observation that flavor-changing neutral currents (FCNC) in weak decays are highly suppressed was first explained by Glashow, Iliopoulos and Maiani in 1970, and their idea has since become a cornerstone of the Standard Model. They proposed a model of the weak interaction that included a then new fourth quark and which, in a natural way, allowed the existence of a neutral vector boson without inducing FCNC's at tree level. Thus the couplings of the neutral intermediary{hor ellipsis}cause no embarrassment.'' In higher order through, decays like K →?l{bar l} can proceed. Measurements of such processes provide a detailed test of the Standard Model since definite predictions for their rates can be calculated. Conversely, if no contradictions are found and the standard model is assumed to describe the physics, measurements limit the allowed values of the parameters of the model. As is often the case in studying processes that are highly suppressed and heretofore unseen, improvements in the sensitivity of experiments allow the possibility for the discovery of new physics that exhibits a similar experimental signature. This paper describes experiment 787 at Brookhaven which is expected to address some of these issues. The status and future of the experiment will be described here. The main goal of E787 is to measure the rate of K →?+?{bar {nu}} at the standard model level. In addition, the experiment has sensitivity to other FCNC decays of the charged kaon, in particular the decays K+ →?+?+?− and K+ →?+??


Search for Flavor-changing Neutral Current and Lepton-flavor Violating Decays of D[sup 0] --] [ell][sup +] [ell][sup -].

Search for Flavor-changing Neutral Current and Lepton-flavor Violating Decays of D[sup 0] --] [ell][sup +] [ell][sup -].

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Published: 2004

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The authors report on a search for the flavor-changing neutral current decays D[sup 0] --> e[sup +]e[sup -] and D[sup 0] --> [mu][sup +][mu][sup -], and the lepton-flavor violating decay D[sup 0] --> e[sup [+-]][mu][sup [-+]]. The measurement is based on 122 fb[sup -1] of data collected by the BABAR detector at the PEP-II asymmetric e[sup +]e[sup -] collider. No evidence is found for any of the decays. The upper limits on the branching fractions, at the 90% confidence level, are 1.2 x 10[sup -6] for D[sup 0] --> e[sup +]e[sup -], 1.3 x 10[sup -6] for D[sup 0] --> [mu][sup +][mu][sup -], and 8.1 x 10[sup -7] for D[sup 0] --> e[sup [+-]][mu][sup [-+]].