arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 109 records · Page 6Linked to original sources

arXiv2011

Search for b --> u Transitions in B^{+-} --> [K^{-+} pi^{+-} pi0]_D K^{+-} Decays

We present a study of the decays B^{+-} --> D K^{+-} with D mesons reconstructed in the K+pi-pi0 or K-pi+pi0 final states, where D indicates a D0 or a anti-D0 meson. Using a sample of 474 million BBbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC we obtain R^{+} = (5^{+12}_{-10}(stat) ^{+2}_{-4}(syst))\times10^{-3} and R^{-} = (12^{+12}_{-10}(stat) ^{+3}_{-5}(syst))\times10^{-3}, from which we extract the upper limits at 90% probability: R^+<23\times10^{-3} and R^-<29\times10^{-3}. Using these measurements, we obtain an upper limit for the ratio rB of the magnitudes of the b --> u and b --> c amplitudes r_B<0.13 at 90% probability.

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arXiv2011

Measurement of the B^0 --> pi^-ell^+nu and B^+ --> eta^(')ell^+nu Branching Fractions, the B^0 --> pi^-ell^+nu and B^+ --> eta ell^+nu Form-Factor Shapes, and Determination of |V_{ub}|

We report the results of a study of the exclusive charmless semileptonic decays, $B^{+} \rightarrow η^{(\prime)} \ell^{+} ν$ and $B^{0} \rightarrow π^{-} \ell^{+} ν$, undertaken with approximately 464 million $\ensuremath{B\kern 0.18em\bar{\kern -0.18em B}}$ pairs collected at the $Υ(4S)$ 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 $B^{+} \rightarrow η\ell^{+} ν$ and $B^{0} \rightarrow π^{-} \ell^{+} ν$ 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 ${\ensuremath{\cal B}}(B^{+} \rightarrow η\ell^{+} ν)$ $ = (0.36 \pm 0.05_{stat} \pm 0.04_{syst}) \times 10^{-4}$ and ${\ensuremath{\cal B}}(B^{0} \rightarrow π^- \ell^{+} ν)$ $ = (1.42 \pm 0.05_{stat} \pm 0.07_{syst}) \times 10^{-4}$. We also measure ${\ensuremath{\cal B}}(B^{+} \rightarrow η^{\prime} \ell^{+} ν)$ $ = (0.24 \pm 0.08_{stat} \pm 0.03_{syst}) \times 10^{-4}$. We obtain values for the magnitude of the CKM matrix element $\ensuremath{|V_{ub}|}$ using three different QCD calculations.

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arXiv2011

Search for CP Violation in the Decay D+/- -> Ks pi+/-

We report on a search for CP violation in the decay $ D^\pm \to K^0_{\scriptscriptstyle S} π^\pm $ using a data set corresponding to an integrated luminosity of $ 469\,\,fb^{-1} $ collected with the \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 CPviolating decay rate asymmetry $A_{CP}$ is determined to be $(-0.44 \pm 0.13 \mathrm{(stat)} \pm 0.10 \mathrm{(syst)})%$, consistent with zero at 2.7 $σ$ and with the standard model prediction of $(-0.332 \pm 0.006)%$. This is currently the most precise measurement of this parameter.

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arXiv2011

Measurement of the mass and width of the Ds1(2536)+ meson

The decay width and mass of the Ds1(2536)+ meson are measured via the decay channel Ds1+ -> D*+KS0 using 385 fb^-1 of data recorded with the BABAR detector in the vicinity of the Y(4S) resonance at the PEP-II asymmetric-energy electron-positron collider. The result for the decay width is 0.92 +- 0.03 (stat) +- 0.04 (syst) MeV. For the mass, a value of 2535.08 +- 0.01 +- 0.15 MeV/c^2 is obtained. The mass difference between the Ds1+ and the D*+ is measured to be 524.83 +- 0.01 +- 0.04 MeV/c^2, representing a significant improvement compared to the current world average. The unnatural spin-parity assignment for the Ds1+ meson is confirmed.

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arXiv2011

Measurement of CP observables in B+- --> D_CP K+- decays and constraints on the CKM angle gamma

Using the entire sample of 467 million Y(4S) --> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC, we perform a "GLW" analysis of B+- --> D K+- decays, using decay modes in which the neutral D meson decays to either CP-eigenstates or non-CP-eigenstates. We measure the partial decay rate charge asymmetries for CP-even and CP-odd D final states to be A_CP+ = 0.25+-0.06+-0.02 and A_CP- = -0.09+-0.07+-0.02, respectively, where the first error is the statistical and the second is the systematic uncertainty. The parameter A_CP+ is different from zero with a significance of 3.6 standard deviations, constituting evidence for direct CP violation. We also measure the ratios of the charged-averaged B partial decay rates in CP and non-CP decays, R_CP+ = 1.18+-0.09+-0.05 and R_CP- = 1.07+-0.08+-0.04. We infer frequentist confidence intervals for the angle gamma of the (db) unitarity triangle, for the strong phase difference delta_B, and for the amplitude ratio r_B, which are related to the B- --> DK- decay amplitude by r_Be^{i(delta_B-gamma)} = A(B- --> anti-D0 K^-)/A(B- --> D0 K-). Including statistical and systematic uncertainties, we obtain 0.24<r_B<0.45 (0.06<r_B<0.51) and, modulo 180 degrees, 11.3 degrees < gamma < 22.7 degrees or 80.9 degrees < gamma < 99.1 degrees or 157.3 degrees < gamma < 168.7 degrees (7.0 degrees < gamma < 173.0 degrees) at the 68% (95%) confidence level.

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arXiv2011

Measurement of the B -> Dbar()D()K branching fractions

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.

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arXiv2011

Search for the Rare Decay B->K nu nubar

We present a search for the rare decays B+ -> K+ nu nubar and B0 -> K0 nu nubar using 459 million BBbar pairs collected with the BaBar detector at the SLAC National Accelerator Laboratory. Flavor-changing neutral-current decays such as these are forbidden at tree level but can occur through one-loop diagrams in the Standard Model (SM), with possible contributions from new physics at the same order. The presence of two neutrinos in the final state makes identification of signal events challenging, so reconstruction in the semileptonic decay channels B -> D(*) l nu of the B meson recoiling from the signal B is used to suppress backgrounds. We set an upper limit at the 90% confidence level of 1.3 x 10^{-5} on the total branching fraction for B+ -> K+ nu nubar, and 5.6 x 10^{-5} for B0 -> K0 nu nubar. We additionally report partial branching fractions in two ranges of di-neutrino mass squared for B+ -> K+ nu nubar.

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arXiv2011

Measurement of the Absolute Branching Fractions for $D^-_s\!\rightarrow\!\ell^-\barν_{\ell}$ and Extraction of the Decay Constant $f_{D_s}$

The absolute branching fractions for the decays $D^-_s\!\rightarrow\!\ell^-\barν_{\ell}$ ($\ell=e$, $μ$, or $τ$) are measured using a data sample corresponding to an integrated luminosity of 521 fb$^{-1}$ collected at center of mass energies near 10.58 GeV 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 $e^+e^-$ collider at SLAC. The number of $D^-_s$ mesons is determined by reconstructing the recoiling system $DKXγ$ in events of the type $e^+e^-{\rightarrow}DKXD^{*-}_s$, where $D^{*-}_s\rightarrow D^-_sγ$ and $X$ represents additional pions from fragmentation. The $D^-_s\!\rightarrow\!\ell^-\barν_{\ell}$ events are detected by full or partial reconstruction of the recoiling system $DKXγ\ell$. The branching fraction measurements are combined to determine the $D^-_s$ decay constant $f_{D_s} = (258.6 \pm 6.4 \pm 7.5)$ MeV, where the first uncertainty is statistical and the second is systematic.

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arXiv2010

Measurement of partial branching fractions of inclusive charmless B meson decays to K+, K0, and pi+

We present measurements of partial branching fractions of $B \rightarrow K^+ X$, $B \rightarrow K^0 X$, and $B \rightarrow π^+ X$, where $X$ denotes any accessible final state above the endpoint for B decays to charmed mesons, specifically for momenta of the candidate hadron greater than 2.34 (2.36) GeV for kaons (pions) in the B rest frame. These measurements are sensitive to potential new-physics particles which could enter the $b \rightarrow s(d)$ loop transitions. The analysis is performed on a data sample consisting of $383 \times 10^6$ $B \bar{B}$ pairs collected with the BaBar detector at the PEP-II $e^+e^-$ asymmetric energy collider. Our results are in agreement with standard model predictions and exclude large enhancements of the inclusive branching fraction due to sources of new physics.

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arXiv2010

Observation of new resonances decaying to $Dπ$ and $D^*π$ in inclusive $e^+e^-$ collisions near $\sqrt{s}=$10.58 GeV

We present a study of the $D^+π^-$, $D^0π^+$, and $D^{*+}π^-$ systems in inclusive $e^+e^- \rightarrow c\bar{c}$ interactions in a search for new excited $D$ meson states. We use a dataset, consisting of $\sim$454 fb$^{-1}$, collected at center-of-mass energies near 10.58 GeV by the BABAR detector at the SLAC PEP-II asymmetric-energy collider. We observe, for the first time, candidates for the radial excitations of the $D^0$, $D^{*0}$, and $D^{*+}$, as well as the L=2 excited states of the $D^0$ and $D^+$, where $L$ is the orbital angular momentum of the quarks.

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arXiv2010

A Search for the Decay B^0 -> gamma gamma

We report the result of a search for the rare decay B^0 -> gamma gamma in 426 fb-1 of data, corresponding to 226 million B^0 \bar{B}^0 pairs, collected on the Upsilon(4S) resonance at the PEP-II asymmetric-energy e+e- collider using the BABAR detector. We use a maximum likelihood fit to extract the signal yield and observe 21^{+13}_{-12} signal events with statistical significance of 1.9 sigma. This corresponds to a branching fraction B(B^0 -> gamma gamma) = (1.7 +- 1.1(stat.) +- 0.2(syst.)) x 10^-7. Based on this result, we set a 90% confidence level upper limit of B(B^0 -> gamma gamma) < 3.3 x 10^-7.

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arXiv2010

Study of B --> pi l nu and B --> rho l nu Decays and Determination of |V_ub|

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 B --> pi l nu samples, and similarly the two B --> 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 QCD calculations and determine the CKM matrix element |V_ub|. Based on the measured partial branching fraction for B --> pi l nu in the range q^2 < 12 GeV^2 and the most recent LCSR calculations we obtain |V_ub| = (3.78 +- 0.13 +0.55-0.40) x 10^-3, where the errors refer to the experimental and theoretical uncertainties. From a simultaneous fit to the data over the full q^2 range and the FNAL/MILC lattice QCD results, we obtain |V_ub| = (2.95 +- 0.31) x 10^-3 from B --> pi l nu, where the error is the combined experimental and theoretical uncertainty.

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arXiv2010

Measurement of D0-antiD0 mixing parameters using D0 -> K0S pi+ pi- and D0 -> KS0 K+ K- decays

We report a direct measurement of $D^0-overline{D}^0$ mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of $D^0 \rightarrow K_S^0 π^+ π^-$ and, for the first time, $D^0 \rightarrow K_S^0 K^+ K^-$ decays. The low-momentum pion $π_s^+$ in the decay $D^{*+} \rightarrow D^0 π_s^+$ identifies the flavor of the neutral $D$ meson at its production. Using 468.5 fb$^{-1}$ of $e^+e^-$ colliding-beam data recorded near $\sqrt s = 10.6$~GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters $x= [1.6 \pm 2.3 ({\rm stat.}) \pm 1.2 ({\rm syst.}) \pm 0.8 ({\rm model}) ] \times10^{-3}$, and $y= [5.7 \pm 2.0 ({\rm stat.}) \pm 1.3 ({\rm syst.}) \pm 0.7 ({\rm model}) ]\times 10^{-3}$. These results provide the best measurement to date of $x$ and $y$. The knowledge of the value of $x$, in particular, is crucial for understanding the origin of mixing.

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arXiv2010

Evidence for direct CP violation in the measurement of the Cabibbo-Kobayashi-Maskawa angle gamma with B-+ --> D() K()-+ decays

We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle $γ$ through a Dalitz plot analysis of neutral $D$ meson decays to $K_S^0 π^+ π^-$ and $K_S^0 K^+ K^-$ produced in the processes $B^\mp \to D K^\mp$, $B^\mp \to D^{*} K^\mp$ with $D^* \to D π^0,D γ$, and $B^\mp \to D K^{*\mp}$ with $K^{*\mp} \to K_S^0 π^\mp$, using 468 million $B\bar{B}$ pairs collected by the BABAR detector at the PEP-II asymmetric-energy $e^+e^-$ collider at SLAC. We measure $γ=(68 \pm 14 \pm 4 \pm 3)^\circ$ ({\rm mod $180^\circ$}), where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the uncertainty in the description of the neutral $D$ decay amplitudes. This result is inconsistent with $γ= 0$ (no direct CP violation) with a significance of 3.5 standard deviations.

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arXiv2010

Search for f_J(2220) in radiative J/psi decays

We present a search for f_J(2220) production in radiative J/psi -> gamma f_J(2220) decays using 460 fb-1 of data collected with the BABAR detector at the SLAC PEP-II e+e- collider. The f_J(2220) is searched for in the decays to K+K- and KsKs. No evidence of this resonance is observed, and 90% confidence level upper limits on the product of the branching fractions for J/psi -> gamma f_J(2220), f_J(2220) -> K+K- and J/psi -> gamma f_J(2220), f_J(2220) -> KsKs as a function of spin and helicity are set at the level of 10-5. These values are below the central values reported by the Mark III experiment.

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arXiv2010

Search for CP violation using $T$-odd correlations in $D^0 \to K^+ K^- π^+ π^-$ decays

We search for CP violation in a sample of $4.7\times10^4$ Cabibbo-suppressed $D^0 \to K^+ K^- π^+ π^-$ decays. We use 470{\rm fb}^{-1} of data recorded by the BaBar detector at the PEPII asymmetric-energy $e^+e^-$ storage rings running at center-of-mass energies near 10.6 GeV. CP violation is searched for in the difference between the $T$-odd asymmetries, obtained using triple product correlations, measured for $D^0$ and $\bar D^0$ decays. The measured CP violation parameter is ${\cal A}_T = (1.0 \pm 5.1_{\sta}\pm 4.4_{\sys}) \times 10^{-3}$.

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arXiv2010

Observation of the Rare Decay B0 --> KsK+/-pi-/+

We report an analysis of charmless hadronic decays of neutral B mesons to the final state KsK+/-pi-/+, using a data sample of (465 +/- 5) x 10^6 BB-bar events collected with the BABAR detector at the Y(4S) resonance. We observe an excess of signal events with a significance of 5.2 standard deviations including systematic uncertainties and measure the branching fraction to be BF(B0 --> KsK+/-pi-/+) = (3.2 +/- 0.5 +/- 0.3) x 10^-6, where the uncertainties are statistical and systematic, respectively.

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arXiv2010

Exclusive Production of $D^+_sD^-_s$, $D^{+}_sD^-_s$, and $D^{+}_sD^{*-}_s$ via $e^+ e^-$ Annihilation with Initial-State-Radiation

We perform a study of exclusive production of$D^+_sD^-_s$, $D^{*+}_sD^-_s$, and $D^{*+}_sD^{*-}_s$ final states in initial-state-radiation events from $e^+ e^-$ annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium $1^{--}$ states. The data sample corresponds to an integrated luminosity of 525 $fb^{-1}$ and was recorded by the BaBar experiment at the PEP-II storage ring. The $D^+_sD^-_s$, $D^{*+}_sD^-_s$, and $D^{*+}_sD^{*-}_s$ mass spectra show evidence of the known $ψ$ resonances. Limits are extracted for the branching ratios of the decays $X(4260)\to D^{(*)+}_sD^{(*)-}_s$.

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