2 research outputs found
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Search for b-->u transitions in B- --> DK- and B- --> D*K- Decays
We report results from an updated study of the suppressed decays B{sup -} --> DK{sup -} and B{sup -} --> D*K{sup -} followed by D --> K{sup +}{pi}{sup -}, where D{sup (*)} indicates a D{sup (*)0} or a {anti D}{sup (*)0} meson, and D{sup *} --> D{tau}{sup 0} or D{sup *} --> D{gamma}. These decays are sensitive to the CKM unitarity triangle angle {gamma} due to interference between the b --> c transition B{sup -} --> D{sup (*)0}K{sup -} followed by the double Cabibbo-suppressed decay D{sup 0} --> K{sup +}{pi}{sup -}, and the b --> u transition B{sup -} --> {anti D}{sup (*)0}K{sup -} followed by the Cabibbo-favored decay {anti D}{sup 0} --> K{sup +}{pi}{sup -}. We also report an analysis of the decay B{sup -} --> D{sup (*)}{pi}{sup -} with the D decaying into the doubly Cabibbo-suppressed mode D --> K{sup +}{pi}{sup -}. Our results are based on 467 million {Upsilon}(4S) --> B{anti B} decays collected with the BABAR detector at SLAC. We measure the ratios R{sup (*)} of the suppressed ([K{sup +}{pi}{sup -}]{sub D}K{sup -}/{pi}{sup -}) to favored ([K{sup -}{pi}{sup +}]{sub D}K{sup -}/{pi}{sup -}) branching fractions as well as the CP asymmetries A{sup (*)} of those modes. We see indications of signals for the B{sup -} --> DK{sup -} and B{sup -} --> D{sup *}{sub D{pi}{sup 0}}K{sup -} suppressed modes, with statistical significances of 2.1 and 2.2{sigma}, respectively, and we measure: R{sub DK} = (1.1 {+-} 0.6 {+-} 0.2) x 10{sup -2}, A{sub DK} = -0.86 {+-} 0.47 {sup +0.12}{sub -0.16}, R{sup *}{sub (D{pi}{sup 0})K} = (1.8 {+-} 0.9 {+-} 0.4) x 10{sup -2}, A{sup *}{sub (D{pi}{sup 0})K} = +0.77 {+-} 0.35 {+-} 0.12, R{sup *}{sub (D{gamma})K} = (1.3 {+-} 1.4 {+-} 0.8) x 10{sup -2}, A{sup *}{sub (D{gamma})K} = +0.36 {+-} 0.94 {sup +0.25}{sub -0.41}, where the first uncertainty is statistical and the second is systematic. we use a frequentist approach to obtain the magnitude of the ratio r{sub B} {equivalent_to} {vert_bar}A(B{sup -} --> {anti D}{sup 0}K{sup -})/A(B{sup -} --> D{sup 0}K{sup -}){vert_bar} = (9.5{sup +5.1}{sub -4.1})%, with r{sub B} < 16.7% at 90% confidence level. In the case of B{sup -} --> D{sup *}K{sup -} we find r{sup *}{sub B} {equivalent_to} {vert_bar}A(B{sup -} --> {anti D}{sup *0}K{sup -})/A(B{sup -} --> D{sup *0}K{sup -}){vert_bar} = (9.6{sup +3.5}{sub 5.1})%, with r{sup *}{sub B} < 15.0% at 90% confidence level
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Measurement of mixing parameters using D^0 \to K_S^0 \pi^ \pi^- and D^0 \to K_S^0 K^ K^- decays
We report a direct measurement of D{sup 0}-{bar D}{sup 0} mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D{sup 0} {yields} K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and, for the first time, D{sup 0} {yields} K{sub S}{sup 0}K{sup +}K{sup -} decays. The low-momentum pion {pi}{sub s}{sup +} in the decay D*{sup +} {yields} D{sup 0}{pi}{sub s}{sup +} identifies the flavor of the neutral D meson at its production. Using 468.5 fb{sup -1} of e{sup +}e{sup -} colliding-beam data recorded near {radical}s = 10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x = [1.6 {+-} 2.3 (stat.) {+-} 1.2 (syst.) {+-} 0.8 (model)] x 10{sup -3}, and y = [5.7 {+-} 2.0 (stat.) {+-} 1.3 (syst.) {+-} 0.7 (model)] x 10{sup -3}. These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing