172 research outputs found

    Search for CP Violation in the decays D+ -> K_S pi+ and D+ -> K_S K+

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    A high statistics sample of photo-produced charm from the FOCUS(E831) experiment at Fermilab has been used to search for direct CP violation in the decays D+->K_S pi+ and D+ -> K_S K+. We have measured the following asymmetry parameters relative to D+->K-pi+pi+: A_CP(K_S pi+) = (-1.6 +/- 1.5 +/- 0.9)%, A_CP(K_S K+) = (+6.9 +/- 6.0 +/- 1.5)% and A_CP(K_S K+) = (+7.1 +/- 6.1 +/- 1.2)% relative to D+->K_S pi+. The first errors quoted are statistical and the second are systematic. We also measure the relative branching ratios: \Gamma(D+->\bar{K0}pi+)/\Gamma(D+->K-pi+pi+) = (30.60 +/- 0.46 +/- 0.32)%, \Gamma(D+->\bar{K0}K+)/\Gamma(D+->K-pi+pi+) = (6.04 +/- 0.35 +/- 0.30)% and \Gamma(D+->\bar{K0}K+)/\Gamma(D+->\bar{K0}pi+) = (19.96 +/- 1.19 +/- 0.96)%.Comment: 4 pages, 3 figure

    A measurement of branching ratios of D+D^+ and Ds+D^+_s hadronic decays to four-body final states containing a KSK_S

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    We have studied hadronic four-body decays of D+D^+ and Ds+D^+_s mesons with a KSK_S in the final state using data recorded during the 1996-1997 fixed-target run at Fermilab high energy photoproduction experiment FOCUS. We report a new branching ratio measurement of Γ(D+KSKπ+π+)/Γ(D+KSπ+π+π)=0.0768±0.0041±0.0032\Gamma(D^+\to K_S K^-\pi^+\pi^+)/\Gamma(D^+\to K_S \pi^+\pi^+\pi^-)=0.0768\pm0.0041\pm0.0032. We make the first observation of three new decay modes with branching ratios Γ(D+KSK+π+π)/Γ(D+KSπ+π+π)=0.0562±0.0039±0.0040\Gamma(D^+\to K_S K^+\pi^+\pi^-)/\Gamma(D^+\to K_S \pi^+\pi^+\pi^-)=0.0562\pm0.0039\pm0.0040, \Gamma(D^+\to\K_S K^+ K^-\pi^+)/\Gamma(D^+\to K_S \pi^+\pi^+\pi^-)=0.0077\pm0.0015\pm0.0009, and Γ(Ds+KSK+π+π)/Γ(Ds+KSKπ+π+)=0.586±0.052±0.043\Gamma(D^+_s\to K_S K^+\pi^+\pi^-)/\Gamma(D^+_s\to K_S K^-\pi^+\pi^+)=0.586\pm0.052\pm0.043, where in each case the first error is statistical and the second error is systematic.Comment: 4 pages, 1 table, 2 figures, submitted to Physical Review Letter

    A High Statistics Measurement of the Lambdac+ Lifetime

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    A high statistics measurement of the Lambdac+ lifetime from the Fermilab fixed-target FOCUS photoproduction experiment is presented. We describe the analysis technique with particular attention to the determination of the systematic uncertainty. The measured value of 204.6 +/- 3.4 (stat.) +/- 2.5 (syst.) fs from 8034 +/- 122 Lambdac -> pKpi decays represents a significant improvement over the present world average.Comment: Submitted to Physical Review Letter

    A Measurement of the Ds+ Lifetime

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    A high statistics measurement of the Ds+ lifetime from the Fermilab fixed-target FOCUS photoproduction experiment is presented. We describe the analysis of the two decay modes, Ds+ -> phi(1020)pi+ and Ds+ -> \bar{K}*(892)0K+, used for the measurement. The measured lifetime is 507.4 +/- 5.5 (stat.) +/- 5.1 (syst.) fs using 8961 +/- 105 Ds+ -> phi(1020)pi+ and 4680 +/- 90 Ds+ -> \bar{K}*(892)0K+ decays. This is a significant improvement over the present world average.Comment: 5 pages, 3 figures, 2 tables, submitted to PR

    Measurement of the relative branching ratio BR(\Xi_c^+ \to p^+ K^-\pi^+)\BR(\Xi_c^+ \to \Xi^- \pi^+ \pi^+)

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    We report the observation of the Cabibbo suppressed decay \Xi_c^+ \to p K^-\pi^+ using data collected with the FOCUS spectrometer during the 1996--97 Fermilab fixed target run. We find a \Xi_c^+ signal peak of 202\pm35 events. We have measured the relative branching ratios BR(\Xi^+_c\to p K^-\pi^+)/BR(\Xi^+_c\to\Xi^-\pi^+\pi^+)= 0.234 \pm 0.047 \pm 0.022 and BR(\Xi^+_c\to p \bar{K}^*(892)^0)/BR(\Xi^+_c\to p K^-\pi^+)= 0.54 \pm 0.09 \pm 0.05 .Comment: 9 pages, 4 figure

    Measurement of the D+ and Ds+ decays into K+K-K+

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    We present the first clear observation of the doubly Cabibbo suppressed decay D+ --> K-K+K+ and the first observation of the singly Cabibbo suppressed decay Ds+ --> K-K+K+. These signals have been obtained by analyzing the high statistics sample of photoproduced charm particles of the FOCUS(E831) experiment at Fermilab. We measure the following relative branching ratios: Gamma(D+ --> K-K+K+)/Gamma(D+ --> K-pi+pi+) = (9.49 +/- 2.17(statistical) +/- 0.22(systematic))x10^-4 and Gamma(Ds+ --> K-K+K+)/Gamma(Ds+ --> K-K+pi+) = (8.95 +/- 2.12(statistical) +2.24(syst.) -2.31(syst.))x10^-3.Comment: 10 pages, 8 figure

    A Non-parametric Approach to the D+ to K*0bar mu+ nu Form Factors

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    Using a large sample of D+ -> K- pi+ mu+ nu decays collected by the FOCUS photoproduction experiment at Fermilab, we present the first measurements of the helicity basis form factors free from the assumption of spectroscopic pole dominance. We also present the first information on the form factor that controls the s-wave interference discussed in a previous paper by the FOCUS collaboration. We find reasonable agreement with the usual assumption of spectroscopic pole dominance and measured form factor ratios.Comment: 14 pages, 5 figures, and 2 tables. We updated the previous version by changing some words, removing one plot, and adding two tables. These changes are mostly stylisti

    Search for Λc+pK+π\Lambda_c^+ \to p K^+ \pi^- and Ds+K+K+πD_s^+ \to K^+ K^+ \pi^- Using Genetic Programming Event Selection

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    We apply a genetic programming technique to search for the double Cabibbo suppressed decays Λc+pK+π\Lambda_c^+ \to p K^+ \pi^- and Ds+K+K+πD_s^+ \to K^+ K^+ \pi^-. We normalize these decays to their Cabibbo favored partners and find BR(\text{BR}(\Lambda_c^+ \to p K^+ \pi^-)/BR()/\text{BR}(\Lambda_c^+ \to p K^- \pi^+)=(0.05±0.26±0.02)) = (0.05 \pm 0.26 \pm 0.02)% and BR(\text{BR}(D_s^+ \to K^+ K^+ \pi^-)/BR()/\text{BR}(D_s^+ \to K^+ K^- \pi^+)=(0.52±0.17±0.11)) = (0.52\pm 0.17\pm 0.11)% where the first errors are statistical and the second are systematic. Expressed as 90% confidence levels (CL), we find <0.46< 0.46 % and <0.78 < 0.78% respectively. This is the first successful use of genetic programming in a high energy physics data analysis.Comment: 10 page

    New Measurements of the D+ to K* mu nu Form Factor Ratios

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    Using a large sample of D+ to K- pi+ mu+ nu decays collected by the FOCUS photoproduction experiment at Fermilab, we present new measurements of two semileptonic form factor ratios: rv and r2. We find rv = 1.504 \pm 0.057 \pm 0.039 and r2 = 0.875 \pm 0.049 \pm 0.064. Our form factor results include the effects of the s-wave interference discussed in a previous paper.Comment: 12 pages, 5 figure

    Study of the D^0 \to pi^-pi^+pi^-pi^+ decay

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    Using data from the FOCUS (E831) experiment at Fermilab, we present new measurements for the Cabibbo-suppressed decay mode D0ππ+ππ+D^0 \to \pi^-\pi^+\pi^-\pi^+. We measure the branching ratio Γ(D0π+ππ+π)/Γ(D0Kπ+ππ+)=0.0914±0.0018±0.0022\Gamma(D^0 \to\pi^+\pi^- \pi^+\pi^-)/\Gamma(D^0 \to K^-\pi^+\pi^-\pi^+) = 0.0914 \pm 0.0018 \pm 0.0022. An amplitude analysis has been performed, a first for this channel, in order to determine the resonant substructure of this decay mode. The dominant component is the decay D0a1(1260)+πD^0 \to a_1(1260)^+ \pi^-, accounting for 60% of the decay rate. The second most dominant contribution comes from the decay D0ρ(770)0ρ(770)0D^0 \to \rho(770)^0\rho(770)^0, with a fraction of 25%. We also study the a1(1260)a_1(1260) line shape and resonant substructure. Using the helicity formalism for the angular distribution of the decay D0ρ(770)0ρ(770)0D^0 \to \rho(770)^0\rho(770)^0, we measure a longitudinal polarization of PL=(71±4±2)P_L = (71 \pm 4\pm 2)%.Comment: 38 pages, 8 figures. accepted for publication in Physical Review
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