Observation of
نویسندگان
چکیده
We have studied two-body charmless hadronic decays of B mesons into the nal states K and K. Using 9.7 million B B pairs collected with the CLEO II detector, we observe the decays B ? ! K ? and B 0 ! K 0 with the following branching fractions: ?1:7) 10 ?6. We also see evidence for the decays B 0 ! K 0 and B ? ! K ?. However, since the statistical signiicance is not overwhelming for these modes we determine upper limits of < 12:310 ?6 3 The phenomenon of CP violation can be accommodated in the Standard Model (SM) by a complex phase in the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix 1]. Whether this phase is the only source of CP violation in nature remains an open experimental question. Studies of charmless B meson decays will certainly play an important role in constraining the CKM matrix and testing the SM picture of CP violation. Flavor Changing Neutral Currents (FCNC) are forbidden to rst order in the SM. Second order loop diagrams, known as penguin and box diagrams, can generate eeective FCNC which lead to b ! s transitions. These processes are of considerable interest because they are sensitive to V ts , the CKM matrix element which will be very diicult to measure in direct decays of the top quark. They are also sensitive to non-Standard Model physics 2], since charged Higgs bosons, new gauge bosons or supersymmetric particles can contribute via additional loop diagrams. Among nal states produced by the gluonic penguin, b ! sg, decay modes in which a gluon splits into two strange quarks, g ! s s, play a special role since they cannot be produced by any other b decay with comparable rate, thus providing an unambiguous signature for the gluonic penguin. As illustrated in Fig. 1, a particularly clean nal state is produced when the kaon includes the spectator quark and no pions are emitted. In this Letter we present B b W t g s s s K (*) the rst signiicant measurements of exclusive charmless hadronic decays B ! K and B ! K. Measurements of other charmless hadronic decay modes by CLEO are discussed elsewhere 3]. The data set used in this analysis was collected with the CLEO detector at the Cornell Electron Storage Ring (CESR). It consists of 9:13 fb ?1 taken at the (4S) (on-resonance), corresponding to …
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تاریخ انتشار 2007