501 research outputs found

    Determination of the B -> D^*+l-nu Decay Width and |V_{cb}|

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    We determine the CKM matrix element |Vcb| using a sample of 3.33 million BBbar events in the CLEO detector at CESR. We determine the yield of reconstructed B --> D*+ l nu decays as a function of w = v_B . v_D*, and from this we obtain the differential decay rate d\Gamma/dw. By extrapolating the differential decay rate to w=1, the kinematic point at which the D* is at rest relative to the B, we extract the product |Vcb| F(1), where F(1) is the form factor at w=1 and is predicted accurately by theory. We find |Vcb| F(1) = 0.0424 +- 0.0018(stat.) +- 0.0019(syst.). We also integrate the differential decay rate over w to obtain B(B --> D*+ l nu) = (5.66 +- 0.29 +- 0.33)%. All results are preliminary.Comment: Contribution to XXXth International Conference on High Energy Physics, July 2000, Osaka, Japa

    Observation of the Omega_c Charmed Baryon at CLEO

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    The CLEO detector at the CESR collider has used 13.7 fb^{-1} to search for the production of Omega_c (css-ground state) in e^{+}e^{-} collisions at sqrt{s} = 10.6 GeV The modes used to study the Omega_c are Omega- pi+, Omega- pi+ pi0, Xi- K- pi+ pi+, Xi0 K- pi+, and Omega- pi+ pi+ pi-. We observe 40.4 +- 9.0(stat) combined events at a mass of 2694.6 +- 2.6(stat) +- 2.4(syst) MeV. We have also measured the \sigma * Br of the above modes for xp > 0.5 to be 11.3 +- 3.9 +- 2.3 fb, 47.6 +- 18.0 +- 2.8 fb, 45.1 +- 23.2 +- 4.1 fb, 18.2 +- 10.6 +- 3.8 fb, and <5.1 fb @ 90 % CL, respectively.Comment: Submitted to XXXth International Conference on High Energy Physics, July 2000, Osaka, Japa

    Recent Results From CLEO on D0-D0Bar Mixing, CP Violation in D0 Decays, and D*+ Width

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    We present preliminary results of several analyses searching for the effects of CP violation and mixing in the decay of D0D^0 mesons. We find no evidence of CP asymmetry in five different two-body decay modes of the D0D^0 to pairs of light pseudo-scalar mesons: ACP(K+Kβˆ’)=(+0.05Β±2.18Β±0.84)A_{CP}(K^+ K^-) = (+0.05 \pm 2.18 \pm 0.84)% , ACP(Ο€+Ο€βˆ’)=(+2.0Β±3.2Β±0.8)A_{CP}(\pi^+ \pi^-) = (+2.0 \pm 3.2 \pm 0.8)% , ACP(KS0Ο€0)=(+0.1Β±1.3)A_{CP}(K^0_{\rm S} \pi^0) = (+0.1 \pm 1.3)%, ACP(Ο€0Ο€0)=(+0.1Β±4.8)A_{CP}(\pi^0 \pi^0) = (+0.1 \pm 4.8)%, and ACP(KS0KS0)=(βˆ’23Β±19)A_{CP}(K^0_{\rm S} K^0_{\rm S}) = (-23 \pm 19)%. We present the first measurement of the rate of wrong-sign D0β†’K+Ο€βˆ’Ο€0D^0 \to K^+ \pi^- \pi^0 decay: R=0.0043βˆ’0.0010+0.0011Β±0.0007R = 0.0043^{+0.0011}_{-0.0010} \pm 0.0007. We also describe a measurement of the mixing parameter yCP=ΔΓ2Ξ“y_{CP}= {\Delta\Gamma\over 2 \Gamma} by searching for a lifetime difference between the CP neutral Kβˆ’Ο€+K^{-}\pi^{+} final state and the CP even K+Kβˆ’K^+K^- and Ο€+Ο€βˆ’\pi^+\pi^- final states. Under the assumption that CP is conserved we find yCP=βˆ’0.011Β±0.025Β±0.014y_{CP} = -0.011 \pm 0.025 \pm 0.014. Finally, we present our measurement of the \dstarp width: 96Β±4Β±2296 \pm 4 \pm 22~keeV.Comment: 6 pages, Proceedings of the Fourth International Conference on B Physics & CP Violatio

    Observation of New States Decaying into Lambda_c^+pi-pi+

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    Using 13.7 fb^{-1} of data recorded by the CLEO detector at CESR, we investigate the spectrum of charmed baryons which decay into Lambda_c^+ pi^- pi^+ and are more massive than the Lambda_{c1} baryons. We find evidence for two new states: one is broad and has an invariant mass roughly 480 MeV above that of the Lambda_c^+; the other is narrow with an invariant mass of 596 +- 1 +- 2 MeV above the Lambda_c^+ mass. These results are preliminary.Comment: Contributed to XXXth International Conference on High Energy Physics, July 2000, Osaka, Japa

    Study of Two-Body B Decays to Kaons and Pions: Observation of B->pi+pi-, B-> K+-pi0, and B-> K0pi0 Decays

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    We have studied charmless hadronic decays of B mesons into two-body final states with kaons and pions and observe three new processes with the following branching fractions: BR(B-> pi+ pi-) = (4.3^{+1.6}_{-1.4} \pm 0.5) \times 10^{-6}, BR(B-> K0 pi0) = (14.6^{+5.9+2.4}_{-5.1-3.3}) \times 10^{-6}, and BR(B-> K+- pi0) = (11.6^{+3.0+1.4}_{-2.7-1.3}) \times 10^{-6}. We also update our previous measurements for the decays B->K+- pi-+ and B-> K0 pi+-.Comment: 10 pages, 3 figure

    Study of charmless hadronic B decays into the final states KΟ€,ππK\pi, \pi\pi, and KK, with the first observation of Bβ†’Ο€+Ο€βˆ’B \to \pi^+ \pi^- and Bβ†’K0Ο€0B\to K^0\pi^0

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    We have studied charmless hadronic decays of B mesons into two-body final states with kaons and pions. We present preliminary results based on 9.66 million BBΛ‰B\bar{B} pairs collected with the CLEO detector. We have made the first observation of the decay Bβ†’Ο€+Ο€βˆ’B \to \pi^+\pi^-, with the branching fraction of Br(Bβ†’Ο€+Ο€βˆ’)=(4.7βˆ’1.5+1.8Β±0.6)Γ—10βˆ’6Br(B \to \pi^+ \pi^-) = (4.7^{+1.8}_{-1.5} \pm 0.6) \times 10^{-6}. We have also observed for the first time the decay Bβ†’K0Ο€0B \to K^0\pi^0 with the branching fraction of Br(Bβ†’K0Ο€0)=(14.8βˆ’5.1βˆ’3.3+5.9+2.4)Γ—10βˆ’6Br(B \to K^0 \pi^0) = (14.8^{+5.9+2.4}_{-5.1-3.3}) \times 10^{-6}, thus completing the set of four KΟ€K\pi branching fraction measurements. We present improved measurements for the decays Bβ†’KΒ±Ο€βˆ“B\to K^{\pm}\pi^{\mp}, BΒ±β†’K0π±B^{\pm}\to K^0\pi^{\pm}, and BΒ±β†’KΒ±Ο€0B^{\pm}\to K^{\pm}\pi^0. We use these and other charmless hadronic B decays to make a first determination of the value of the weak phase Arg(Vubβˆ—)=Ξ³=113βˆ˜βˆ’23∘+25∘{\rm Arg}(V^*_{ub})=\gamma = {113^\circ}^{+25^\circ}_{-23^\circ}.Comment: Leppho99 conference submission. All results are preliminar

    Comparison of D to K0L pi and D to K0S pi Decay Rates

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    We present preliminary measurements of D to K^0_L pi and D to K^0_S pi branching fractions using 281 pb^{-1} of psi(3770) data at the CLEO-c experiment. We find that BF(D^0 to KS pi^0) is larger than BF(D^0 to KL pi^0), with an asymmetry of R(D^0) = 0.122 +- 0.024 +- 0.030. For BF(D^+ to KS pi^+) and BF(D^+ to KL pi^+), we observe no measureable difference; the asymmetry is R(D^+) = 0.030 +- 0.023 +- 0.025. Under reasonable theoretical assumptions, these measurements imply a value for the D^0 to K^+- pi^-+ strong phase that is consistent with zero. The results presented in this document are preliminary.Comment: 17 pages postscript,also available through http://www.lepp.cornell.edu/public/CONF/2006, Conrtibuted to ICHEP0

    Charged Track Multiplicity in B Meson Decay

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    We have used the CLEO II detector to study the multiplicity of charged particles in the decays of B mesons produced at the Ξ₯(4S)\Upsilon(4S) resonance. Using a sample of 1.5 x 10^6 B meson pairs, we find the mean inclusive charged particle multiplicity to be 10.71 +- 0.02 +0.21/-0.15 for the decay of the pair. This corresponds to a mean multiplicity of 5.36 +- 0.01 +0.11/-0.08 for a single B meson. Using the same data sample, we have also extracted the mean multiplicities in semileptonic and nonleptonic decays. We measure a mean of 7.82 +- 0.05 +0.21/-0.19 charged particles per BBΛ‰B\bar{B} decay when both mesons decay semileptonically. When neither B meson decays semileptonically, we measure a mean charged particle multiplicity of 11.62 +- 0.04 +0.24/-0.18 per BBΛ‰B\bar{B} pair.Comment: 11 pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

    Measurement of B9Upsilon(5S) to Bs(*) Bs(*)bar Using phi Mesons

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    Knowledge of the Bs decay fraction of the Y(5S) resonance, fs, is important for Bs meson studies at the Y(5S) energy. Using data collected by the CLEO III detector at CESR consisting of 0.423 1/fb on the Y(5S) resonance, 6.34 1/fb on the Y(4S) and 2.32 1/fb in the continuum below the Y(4S), we measure B(Y(5S)-> phi X)=(13.2+/- 0.7 ^{+2.2}_{-1.4})% and B(Y (4S)-> phi X)=(7.1 +/- 0.1 +/- 0.6)%, the ratio of the two rates is (1.9 +/- 0.1 ^{+0.3}_{-0.2}). This is the first measurement of the phi meson yield from the Y(5S). Using these rates, and a model dependent estimate of B(Bs -> phi X), we measure fs=(27.3 +/- 3.2 ^{+14.6}_{-~6.1})%. We update our previous, independent measurement of this branching fraction using the inclusive Ds yields to be (21.8 +/- 3.4 ^{+8.5}_{-4.2})%, due to changes in the Ds+βˆ’>phiΟ€+D_s^+ -> phi \pi^+ branching fraction and a better estimate of the number of hadronic events. We also report the total Y(5S) hadronic cross section above continuum to be sigma(e^+e^- -> Y(5S))=(0.301 +/- 0.002 +/- 0.039) nb. This allows us to extract the fraction of B mesons as (58.9+/-10.0+/-9.2)%, equal to 1-fs. Averaging the three methods gives a model dependent result of fs=(26^{+7}_{-4})%.Comment: 23 pages postscript,also available through http://www.lns.cornell.edu/public/CONF/2006/, Contributed to ICHEP0

    Radiative Decays of the Upsilon(1S) to gamma pi^0 pi^0, and gamma eta eta and gamma pi^0 eta

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    We report on a study of exclusive radiative decays of the Upsilon(1S) resonance into the final states gamma pi^0 pi^0, gamma eta eta and gamma pi^0 eta, using 1.13 inverse femto-barn of e^+ e^- annihilation data collected at sqrt(s)= 9.46 GeV with the CLEO III detector operating at the Cornell Electron Storage Ring. In the channel gamma pi^0 pi^0, we measure the branching ratio for the decay mode Upsilon(1S) to gamma f_2(1270) to be (10.5 \pm 1.6 (+ 1.9)(-1.8)) x 10^-5. We place upper limits on the product branching ratios for the isoscalar resonances f_0(1500) and f_0(1710) for the pi^0 pi^0 and eta-eta decay channels. We also set an upper limit on the Upsilon(1S) radiative decay into pi^0 eta.Comment: 8 pages postscript,also available through http://www.lns.cornell.edu/public/CLNS/2005/, Submitted to PR
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