Using the ARGUS detector at the
e
+
e
− storage ring DORIS II at DESY, we have made two measurements of the mixing parameter
χ
d
using kaons as flavour tags. Using
D
∗+ K
±
correlations we found
χ
d
...= 0.20 ± 0.13 ± 0.12 and from the study of
(D
∗+ℓ
−) K
±
correlations we obtained
χ
d
= 0.19 ± 0.07 ± 0.09. The branching ratio for
B → D
∗+ X
has been updated:
Br(
B → D
∗+ X) = (19.6 ± 1.9)
%. We have also determined the average multiplicity of charged kaons in
B
0 decays to be 0.78 ± 0.08.
We report the results of a study of the exclusive charmless semileptonic decays, B^0 --> pi^- l^+ nu, B^+ --> pi^0 l^+ nu, B^+ --> omega l^+ nu, B^+ --> eta l^+ nu and B^+ --> eta^' l^+ nu, (l = e or ...mu) undertaken with approximately 462x10^6 B\bar{B} pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q^2, the square of the momentum transferred to the lepton-neutrino pair, for B^0 --> pi^- l^+ nu, B^+ --> pi^0 l^+ nu, B^+ --> omega l^+ nu and B^+ --> eta l^+ nu. From these distributions, we extract the form-factor shapes f_+(q^2) and the total branching fractions BF(B^0 --> pi^- l^+ nu) = (1.45 +/- 0.04_{stat} +/- 0.06_{syst})x10^-4 (combined pi^- and pi^0 decay channels assuming isospin symmetry), BF(B^+ --> omega l^+ nu) = (1.19 +/- 0.16_{stat} +/- 0.09_{syst})x10^-4 and BF(B^+ --> eta l^+ nu) = (0.38 +/- 0.05_{stat} +/- 0.05_{syst})x10^-4. We also measure BF(B^+ --> eta^' l^+ nu) = (0.24 +/- 0.08_{stat} +/- 0.03_{syst})x10^-4. We obtain values for the magnitude of the CKM matrix element V_{ub} by direct comparison with three different QCD calculations in restricted q^2 ranges of B --> pi l^+ nu decays. From a simultaneous fit to the experimental data over the full q^2 range and the FNAL/MILC lattice QCD predictions, we obtain |V_{ub}| = (3.25 +/- 0.31)x10^-3, where the error is the combined experimental and theoretical uncertainty.
We present an analysis of exclusive charmless semileptonic B-meson decays based on 377 million BBbar pairs recorded with the BABAR detector at the Upsilon(4S) resonance. We select four event samples ...corresponding to the decay modes B0 --> pi- l+ nu, B+ --> pi0 l+ nu, B0 --> rho- l+ nu, and B+ -> rho0 l+ nu, and find the measured branching fractions to be consistent with isospin symmetry. Assuming isospin symmetry, we combine the two pi l nu samples, and similarly the two rho l nu samples, and measure the branching fractions BF(B0 --> pi- l+ nu) = (1.41 +- 0.05 +- 0.07) x 10^-4 and BF(B0 --> rho- l+ nu) = (1.75 +- 0.15 +- 0.27) x 10^-4, where the errors are statistical and systematic. We compare the measured distribution in q^2, the momentum transfer squared, with predictions for the form factors from lattice QCD calculations and light-cone sum rules, and determine the CKM matrix element |V_ub|. From a simultaneous fit to B --> pi l nu data and FNAL/MILC lattice QCD results, we obtain |V_ub| = (2.95 +- 0.31) x 10^-3 from B --> pi l nu, where the uncertainty is the combined experimental and theoretical error.
We report a search for CP violation in the decay \tau- -> \pi - \K^0_S (>= 0 \pi 0) \nu_\tau\ using a dataset of 437 million \tau\ lepton pairs, corresponding to an integrated luminosity of 476 ...fb^{-1}, collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings. The CP-violating decay-rate asymmetry is determined to be (-0.45 +/- 0.24 +/- 0.11)%, approximately three standard deviations from the Standard Model prediction of (0.33 +/- 0.01)%.
We report the observation of the baryonic B decay B0bar --> Lambda_c^+ anti-Lambda K- with a significance larger than 7 standard deviations based on 471x10^6$ BBbar pairs collected with the BABAR ...detector at the PEP-II storage ring at SLAC. We measure the branching fraction for the decay B0bar --> Lambda_c^+ anti-Lambda K- to be (3.8 \pm 0.8_{stat} \pm 0.2_{sys} \pm 1.0_{Lambda_c^+})x10^{-5}. The uncertainties are statistical, systematic, and due to the uncertainty in the Lambda_c^+ branching fraction. We find that the Lambda_c^+ K^- invariant mass distribution shows an enhancement above 3.5 GeV/c^2.
Search for CP Violation in the Decay D+/- -> Ks pi del Amo Sanchez, P.; Lees, J.P.; Poireau, V. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
08/2011, Letnik:
83, Številka:
7
Journal Article
Odprti dostop
We report on a search for $C\!P$ violation in the decay $ D^\pm \to K^0_{\scriptscriptstyle S} \pi^\pm $ using a data set corresponding to an integrated luminosity of $ 469\,\mbox{\,fb}^{-1} $ ...collected 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 PEP-II asymmetric energy $e^+e^-$ storage rings. The $C\!P$-violating decay rate asymmetry $A_{C\!P}$ is determined to be $(-0.44 \pm 0.13 \mathrm{(stat)} \pm 0.10 \mathrm{(syst)})%$, consistent with zero at 2.7 $\sigma$ and with the standard model prediction of $(-0.332 \pm 0.006)%$. This is currently the most precise measurement of this parameter.
We report the results of a study of the exclusive charmless semileptonic decays, $B^{+} \rightarrow \eta^{(\prime)} \ell^{+} \nu$ and $B^{0} \rightarrow \pi^{-} \ell^{+} \nu$, undertaken with ...approximately 464 million $\ensuremath{B\kern 0.18em\bar{\kern -0.18em B}}$ pairs collected at the $\Upsilon(4S)$ resonance with the ${{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}}}$ detector. The analysis uses events in which the signal $B$ decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions for $B^{+} \rightarrow \eta \ell^{+} \nu$ and $B^{0} \rightarrow \pi^{-} \ell^{+} \nu$ decays in three and twelve bins of $q^2$, respectively, from which we extract the $f_+(q^2)$ form-factor shapes and the total branching fractions ${\ensuremath{\cal B}}(B^{+} \rightarrow \eta \ell^{+} \nu)$ $ = \left(0.36 \pm 0.05_{stat} \pm 0.04_{syst} \right) \times 10^{-4}$ and ${\ensuremath{\cal B}}(B^{0} \rightarrow \pi^- \ell^{+} \nu)$ $ = \left(1.42 \pm 0.05_{stat} \pm 0.08_{syst} \right) \times 10^{-4}$. We also measure ${\ensuremath{\cal B}}(B^{+} \rightarrow \eta^{\prime} \ell^{+} \nu)$ $ = \left(0.24 \pm 0.08_{stat} \pm 0.03_{syst} \right) \times 10^{-4}$. We obtain values for the magnitude of the CKM matrix element $\ensuremath{|V_{ub}|}$ using three different QCD calculations.
We present a measurement of the branching fractions of the 22 decay channels of the B0 and B+ mesons to Dbar(*)D(*)K, where the D(*) and Dbar(*) mesons are fully reconstructed. Summing the 10 neutral ...modes and the 12 charged modes, the branching fractions are found to be B(B0 -> Dbar(*)D(*)K) = (3.68 +- 0.10 +- 0.24)% and B(B+ -> Dbar(*)D(*)K) = (4.05 +- 0.11 +- 0.28)%, where the first uncertainties are statistical and the second systematic. The results are based on 429 fb^-1 of data containing 471.10^6 BBbar pairs collected at the Y(4S) resonance with the BaBar detector at the SLAC National Accelerator Laboratory.
We report on analyses of tau lepton decays $\tau^- \to \eta K^- \nu_{\tau}$ and $\tau^- \to \eta \pi^- \nu_{\tau}$, with $\eta \to \pi^+ \pi^- \pi^0$, using 470 fb$^{-1}$ of data from the Babar ...experiment at PEP-II, collected at center-of-mass energies at and near the $\Upsilon(4S)$ resonance. We measure the branching fraction for the $\tau^- \to \eta K^- \nu_{\tau}$ decay mode, $\Br(\tau^- \to \eta K^- \nu_{\tau}) = (1.42\pm0.11\text{(stat)}\pm0.07\text{(syst)})\times10^{-4}$, and report a 95% confidence level upper limit for the second-class current process $\tau^- \to \eta \pi^- \nu_{\tau}$, $\Br(\tau^- \to \eta \pi^- \nu_{\tau}) < 9.9\times10^{-5}$.
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