We measure the rate of D0-D0bar mixing with the observable yCP=(tauKpi/tauKK)-1, where tauKK and tauKpi are respectively the mean lifetimes of CP-even D0->K+K- and CP-mixed D0->K-pi+ decays, using a ...data sample of 384/fb collected by the Babar detector at the SLAC PEP-II asymmetric-energy B Factory. From a sample of D0 and D0bar decays where the inital flavor of the decaying meson is not determined, we obtain yCP = 1.12 +/- 0.26 (stat) +/- 0.22 (sys)%, which excludes the no-mixing hypothesis at 3.3 sigma, including both statistical and systematic uncertainties. This result is in good agreement with a previous Babar measurement of yCP obtained from a sample of D*+->D0pi+ events, where the D0 decays to K-pi+, K+K-, and pi+pi-, which is disjoint with the untagged D0 events used here. Combining the two results taking into account statistical and systematic uncertainties, where the systematic uncertainties are assumed to be 100% correlated, we find yCP = 1.16 +/- 0.22 (stat) +/- 0.18 (sys)%, which excludes the no-mixing hypothesis at 4.1 sigma.
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We present measurements of the semileptonic decays B- --> D0 tau- nubar_tau, B- --> D*0 tau- nubar_tau, B0bar --> D+ tau- nubar_tau, and B0bar --> D*+ tau- nubar_tau, which are sensitive to ...non--Standard Model amplitudes in certain scenarios. The data sample consists of 232x10^6 Upsilon(4S) --> BBbar decays collected with the BaBar detector at the PEP-II e+e- collider. We select events with a D or D* meson and a light lepton (ell=e or mu) recoiling against a fully reconstructed B meson. We perform a fit to the joint distribution of lepton momentum and missing mass squared to distinguish signal B --> D(*) tau- nubar_tau (tau- --> ell- nubar_ell nu_tau) events from the backgrounds, predominantly B --> D(*) ell- nubar_ell. We measure the branching-fraction ratios R(D) == BR(B --> D tau- nubar_tau) / BR(B --> D ell- nubar_ell) and R(D*) == BR(B --> D* tau- nubar_tau) / BR(B --> D* ell- nubar_ell) and, from a combined fit to B- and B0bar channels, obtain the results R(D)=(41.6 +/- 11.7 +/- 5.2)% and R(D*)=(29.7 +/- 5.6 +/- 1.8)%, where the uncertainties are statistical and systematic. Normalizing to measured B- --> D(*)0 ell- nubar_ell branching fractions, we obtain BR(B --> D tau- nubar_tau)=(0.86 +/- 0.24 +/- 0.11 +/- 0.06)% and BR(B --> D* tau- nubar_tau)=(1.62 +/- 0.31 +/- 0.10 +/- 0.05)%, where the additional third uncertainty is from the normalization mode. We also present, for the first time, distributions of the lepton momentum, p*_ell, and the squared momentum transfer, q^2.
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We perform a study of the exclusive production of $D \bar D$, $D \bar D^*$, and $D^* \bar D^*$ in initial-state-radiation events, from $e^+ e^-$ annihilations at a center-of-mass energy near 10.58 ...GeV, to search for charmonium and possible new resonances. The data sample corresponds to an integrated luminosity of 384 $fb^{-1}$ and was recorded by the BaBar experiment at the PEP-II storage rings. The $D \bar D$, $D \bar D^*$, and $D^* \bar D^*$ mass spectra show clear evidence of several $\psi$ resonances. However, there is no evidence for $Y(4260) \to D \bar D^*$ or $Y(4260)\to D^* \bar D^*$.
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We report a study of B ± → D ∗ K ± decays with D ∗ decaying to D π 0 or D γ , using 383 × 10 6 B ¯¯¯ B pairs collected at the Υ ( 4 S ) resonance with the BABAR detector at the SLAC PEP-II B Factory. ...The D meson decays under study include a non- C P mode ( K ± π ∓ ) , C P -even modes ( K ± K ∓ , π ± π ∓ ) , and C P -odd modes ( K 0 S π 0 , K 0 S ϕ , K 0 S ω ) . We measure ratios ( R ∗ C P ± ) of branching fractions of decays to C P eigenmode states and to flavor-specific states as well as C P asymmetries ( A ∗ C P ± ). These measurements are sensitive to the unitarity triangle angle γ . We obtain A ∗ C P + = − 0.11 ± 0.09 ± 0.01 , R ∗ C P + = 1.31 ± 0.13 ± 0.04 , and A ∗ C P − = 0.06 ± 0.10 ± 0.02 , R ∗ C P − = 1.10 ± 0.12 ± 0.04 , where the first error is statistical and the second error is systematic. Translating our results into an alternative parametrization, widely used for related measurements, we obtain x ∗ + = 0.11 ± 0.06 ± 0.02 and x ∗ − = 0.00 ± 0.06 ± 0.02 . No significant C P -violating charge asymmetry is found in either the flavor-specific mode D → K ± π ∓ or in B ± → D ∗ π ± decays.
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Search for B --> K nu anti-nu decays Aubert, B.; Bona, M.; Karyotakis, Y. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
2008, Volume:
78
Journal Article
We present a search for the decays $B \to K^{*} \nu \bar{\nu}$ using 454$\times10^{6}$ $B \bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the $mbox{\slshape B\kern-0.1em{\smaller ...A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}}$ detector at the SLAC PEP-II $B$-Factory. We first select an event sample where one $B$ is reconstructed in a semileptonic or hadronic mode with one charmed meson. The remaining particles in the event are then examined to search for a $B \to K^{*} \nu \bar{\nu}$ decay. The charged $K^{*}$ is reconstructed as $ K^{*+} \to K^0_{\scriptscriptstyle S} \pi^{+}$ or $ K^{*+} \to K^{+} \pi^{0}$; the neutral $K^{*}$ is identified in the $K^{*0} \to K^{+} \pi^{-}$ mode. We establish upper limits at 90% confidence level of $\matchal{B}(B^{+} \to K^{*+} \nu \bar{\nu}) < 8 \times 10^{-5}$, $\matchal{B}(B^{0} \to K^{*0} \nu \bar{\nu}) < 12 \times 10^{-5}$, and $\matchal{B}(B \to K^{*} \nu \bar{\nu}) < 8 \times 10^{-5}$.
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Study of the decay Ds+ --> K+ K- e+ nu Aubert, B.; Bona, M.; Karyotakis, Y. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
2008, Volume:
78
Journal Article
Using 214 fb-1 of data recorded by the Babar detector at the PEPII electron-positron collider, we study the decay Ds+ --> K+ K- e+ nu. Except for a small S-wave contribution, the events with K+K- ...masses in the range 1.01-1.03 GeV/c2 correspond to phi mesons. For Ds+ --> phi e+ nu decays, we measure the relative normalization of the Lorentz invariant form factors at q2=0, rV=V(0)/A1(0)=1.849 +/- 0.060 +/- 0.095, r2=A2(0)/A1(0)=0.763 +/- 0.071 +/- 0.065 and the pol e mass of the axial-vector form factors mA=(2.28^{+0.23}_{-0.18}+/- 0.18) GeV/c2. Within the same K+K- mass range, we also measure the relative branching fraction B(Ds+ --> K + K- e+ nu)/B(Ds+ --> K+ K- pi+)=0.558 +/- 0.007 +/- 0.016, from which we obtain the total branching fraction B(Ds+ --> phi e+ nu) = (2.61 +/- 0.03 +/- 0.08 +/- 0.15)* 10^{-2}. By comparing this value with the predicted decay rate, we extract A1(0) = 0.607 +/- 0.011 +/- 0.019 +/- 0.018. The stated uncertainties are statistical, systematic, and from external inputs.
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We measure the time-dependent CP asymmetry in B0 --> K_S0 pi0 gamma decays for two regions of K_S0-pi0 invariant mass, m(K_S0 pi0), using the final BABAR data set of 467 x 10^6 BBbar pairs collected ...at the PEP-II e+e- collider at SLAC. We find 339 +/- 24 B0 --> K*0 gamma candidates and measure S_{K* gamma} = -0.03 +/- 0.29 +/- 0.03 and C_{K* gamma} = -0.14 +/- 0.16 +/- 0.03. In the range 1.1 < m(K_S0 pi0) < 1.8 GeV/c^2 we find 133 +/- 20 B0 --> K_S0 pi0 gamma candidates and measure S_{K_S0 pi0 gamma} = -0.78 +/- 0.59 +/- 0.09 and C_{K_S0 pi0 gamma} = -0.36 +/- 0.33 +/- 0.04. The uncertainties are statistical and systematic, respectively.
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We present the observation of the decay B0 -> chi_c0K*0 as well as evidence of B+ -> chi_c0K*+, with an 8.9 and a 3.6 standard deviation significance, respectively, using a data sample of 454 million ...Y(4S) -> BB decays collected with the BaBar detector at the PEP-II B meson factory located at the Stanford Linear Accelerator Center (SLAC). The measured branching fractions are: B(B0 -> chi_c0K*0) = (1.7 +/- 0.3 +/- 0.2) * 10^{-4} and B(B+ -> chi_c0K^*+) = (1.4 +/- 0.5 +/- 0.2) * 10^{-4}, where the first quoted errors are statistical and the second are systematic. We obtain a branching fraction upper limit of B(B+ -> chi_c0K*+) < 2.1 * 10^{-4} at the 90% confidence level.
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