Search for Doubly Cabibbo-suppressed D Sup + Decays PDF Download

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Languages : en
Pages : 4

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Preliminary results of a search for the doubly Cabibbo-suppressed D decays D+ 2!?+?−? + D+ 2!?+?°, in the MarkIII detector at SPEAR are presented. Theoretical arguments suggest that these decays may be enhanced relative to Cabibbo-allowed D+ decays. Use of hadronically tagged D+D− events produced in the decay of the? (3770), reduce backgrounds significantly, allowing the isolation of three candidate events in the?+?+?− final state and a limit on the relative decay rate of the?+?°channel. 4 refs., 2 figs.

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Languages : en
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We present results of a search for D[sup 0]-[bar D][sup 0] mixing and a measurement of R[sub D], the ratio of doubly Cabibbo-suppressed decays to Cabibbo-favored decays, based on an analysis of D[sup 0][yields] K[sup+][pi][sup -] decays in 57.1 fb[sup -1] of data collected at or just below the[Upsilon](4S) resonance with the BABAR detector at the PEP-II collider. Our results are compatible with no mixing and no CP violation. At the 95% confidence level, allowing for CP violation, we find the mixing parameters x[prime][sup 2]

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Languages : en
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This report summarizes results from Fermilab experiment E791 on D[sup 0]-[anti D][sup 0] mixing and doubly Cabibbo-suppressed decays of the D[sup +] meson. In order to search for D[sup 0]-[anti D][sup 0] mixing, the authors use only D[sup 0] mesons from D[sup *+] decays in which case the charge of the pion from the D[sup *+] decay identifies the charm quantum number of the D[sup 0] at birth. When the D[sup 0] decays, the charge of the kaon identifies the charm quantum number and this way one can tell if mixing has occurred. This kind of search can be carried out by CLEO II as well and their conclusion was that there is some evidence of a wrong sign signal (0.77 [+-] 0.25 [+-] 0.25)% of the right sign signal. However, because of a lack of lifetime information, they cannot distinguish between doubly Cabibbo-suppressed decays which are expected at the level of the observed signal and mixing. They use their excellent lifetime sensitivity to obtain separate limits. During the past year, the authors have been working on extracting D[sup +] doubly Cabibbo-suppressed decay signals from E791's data sample. These decays are interesting both because they have never been observed and because definite predictions have been made about their rates, based on models of D mesons and their decay mechanisms. Preliminary analyses of 1/3 of the data have now been completed. Figure 3 shows the Cabibbo-favored signal D[sup +] [yields] K[sup [minus]][pi][sup +][pi][sup +] and the next figure shows the signal in the doubly Cabibbo-suppressed mode D[sup +] [yields] K[sup +][pi][sup [minus]][pi][sup [minus]].

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Languages : en
Pages : 322

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The doubly Cabibbo suppressed decayed D → K+?{sup −}?+, D+ → K+?°and D+ → K*+?° are searched for in a 9.56 pb{sup −1} data sample of e+e{sup −} annihilation events collected near the?(3770) resonance with the Mark 3 detector at the SPEAR storage ring, at the Stanford Linear Accelerator Center. These rare weak decays are naively expected at a rate of tan4?{sub c} relative to corresponding Cabibbo allowed decays. In the context of presently accepted models of hadronic weak decays, however, they are anticipated to be enhanced, making their experimental detection feasible in the Mark 3 data set. The experimentally simplest decay channel D+ → K+?{sup −}?+ is searched for inclusively through conventional analysis techniques. A signal of approximately 2.5? significance is obtained. An independent analysis is performed to establish examples of this decay of D+ → K+?° and K*+?° by full reconstruction of D+D{sup −} events. Exploiting the two body kinematics of?(3770) → D{bar D}, this second approach obtains significantly smaller backgrounds than the inclusive study. Consistent with the inclusive results, three D+ → K+?{sup −}?+ candidate events are observed. No events are observed for either D+ → K+?° or K*+?°. The branching fraction for D+ → K+?{sup −}?+ is measured, and limits are established on the branching fractions for D+ → K+?° and K*+?°. These results are used to confront the theoretical predictions from models of the weak hadronic decays of charmed mesons.

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Languages : en
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Using the CLEO-II data set we have searched for the Cabibbo-suppressed decays B[sup 0][yields] D*[sup+]D*[sup -]. For the decay B[sup 0][yields] D*[sup+]D*[sup -], we observe one candidate signal event, with an expected background of 0.022[+-] 0.011 events. This yield corresponds to a branching fraction of[Beta](B[sup 0][yields] D*[sup+]D*[sup -])= (5.3[sub -3.7][sup+7.1](stat)[+-] 1.0(syst)) x 10[sup -4] and an upper limit of[Beta](B[sup 0][yields] D*[sup+]D[sup -])

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Languages : en
Pages : 11

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This report summarizes results from Fermilab experiment E791 on D°-{anti D}° mixing and doubly Cabibbo-suppressed decays of the D meson. In order to search for D°-{anti D}° mixing, the authors use only D° mesons from D{sup *+} decays in which case the charge of the pion from the D{sup *+} decay identifies the charm quantum number of the D° at birth. When the D° decays, the charge of the kaon identifies the charm quantum number and this way one can tell if mixing has occurred. This kind of search can be carried out by CLEO II as well and their conclusion was that there is some evidence of a wrong sign signal (0.77 ± 0.25 ± 0.25)% of the right sign signal. However, because of a lack of lifetime information, they cannot distinguish between doubly Cabibbo-suppressed decays which are expected at the level of the observed signal and mixing. They use their excellent lifetime sensitivity to obtain separate limits. During the past year, the authors have been working on extracting D+ doubly Cabibbo-suppressed decay signals from E791s̀ data sample. These decays are interesting both because they have never been observed and because definite predictions have been made about their rates, based on models of D mesons and their decay mechanisms. Preliminary analyses of 1/3 of the data have now been completed. Figure 3 shows the Cabibbo-favored signal D+ → K−?+?+ and the next figure shows the signal in the doubly Cabibbo-suppressed mode D+ → K+?−?−.

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Languages : en
Pages : 7

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Author: Jonathan Freeman Labs
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Category : Mesons
Languages : en
Pages : 660

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Author: Dirk Hufnagel
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Category : Mesons
Languages : en
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Abstract: We present a data analysis using 124.3 fb−1 of data from the BaBar detector. The analysis is a measurement of the branching fractions for the singly Cabibbo-suppressed decay mode BF([meson] [to] [pion] [pion]0) = (1.21 " 0.10 (stat.) " 0.08 (sys.) " 0.08 (pdg)) x 10−3 and for the doubly Cabibbo-suppressed decay mode BF([meson]+ [to] [kaon]+ [pion]0)= (2.11 " 0.43 (stat.) " 0.15 (sys.) " 0.16 (pdg)) x 10−4, where the first error is statistical, the second is systematic and the last is due to the D absolute branching fraction scale.

Author: Michael Galante Wilson
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Languages : en
Pages : 187

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Analyzing D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} decays, herein are presented the methods and results of a search for D{sup 0}-{bar D}{sup 0} mixing, a measurement of the branching ratio R {equivalent_to} {Lambda}(D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0})/{Lambda}(D{sup 0} {yields} K{sup -}{pi}{sup +}{pi}{sup 0}), and measurements of the contributions from D{sup 0} {yields} K{sup +}{rho}{sup -}, K*{sup +}{pi}{sup -}, K*{sup 0}{pi}{sup 0}; 230.4 fb{sup -1} of data collected from the BABAR detector at the PEP-II collider during 2000-2004 (Runs 1-4) are analyzed. An event-level tagging technique is developed, which facilitates the accurate determination of doubly Cabibbo-suppressed resonance contributions by suppressing background from Cabibbo-favored decays. The branching ratio is measured as R = (0.214 {+-} 0.008 (stat) {+-} 0.008 (syst))%, with (46.1 {+-} 3.3 (stat) {+-} 2.9 (syst))% of D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} decays proceeding through the channel D{sup 0} {yields} K*{sup +}{pi}{sup -}. The data are consistent with the null-D-mixing hypothesis at a confidence level of 10%, and the expected value of {+-} {radical}(x{sup 2} + y{sup 2}) is measured as -0.013 {+-} 0.010 (stat), indicating negative interference between mixing and doubly Cabibbo-suppressed decay. The expected value of the integrated mixing rate is (x{sup 2} + y{sup 2})/2 = (0.013 {+-} 0.013 (stat))%.