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The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 325 records · Page 18Linked to original sources

arXiv2006

Measurement of B Decays to phi K gamma

We search for the decays B- -> phi K- gamma and B0bar -> phi K0bar gamma in a data sample of 228 million BBbar pairs collected at the Upsilon(4S) resonance with the BaBar detector. We measure the branching fraction B(B- -> phi K- gamma) = (3.5 +/- 0.6 +/- 0.4) x 10^-6 and set an upper limit B(B0bar -> phi K0bar gamma) < 2.7 x 10^-6 at the 90% confidence level. We also measure the direct CP asymmetry in B- -> phi K- gamma, A_CP = (-26 +/- 14 +/- 5)%. The uncertainties are statistical and systematic, respectively.

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arXiv2006

Measurement of the B -> pi l nu Branching Fraction and Determination of |Vub| with Tagged B Mesons

We report a measurement of the B -> pi l nu branching fraction based on 211 fb-1 of data collected with the BABAR detector. We use samples of B0 and B+ mesons tagged by a second B meson reconstructed in a semileptonic or hadronic decay, and combine the results assuming isospin symmetry to obtain BF(B0 -> pi- l+ nu) = (1.33 +/- 0.17(stat) +/- 0.11(syst)) x 10^-4. We determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vub| by combining the partial branching fractions measured in ranges of the momentum transfer squared and theoretical calculations of the form factor. Using a recent lattice QCD calculation, we find |Vub| = (4.5 +/- 0.5(stat) +/- 0.3(syst) +0.7/-0.5(FF)) x 10^-3, where the last error is due to the normalization of the form factor.

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arXiv2006

Observation of the Exclusive Reaction e+e- -> phi eta at sqrt{s}=10.58 GeV

We report the observation of $\e^+e^-\to ϕη$ near $\sqrt{s}$ = 10.58 GeV with 6.5 $σ$ significance in the $K^+K^-γγ$ final state in a data sample of 224 $fb^{-1}$ collected by the BaBar experiment at the PEP-II $e^+e^-$ storage rings. We measure the restricted radiation-corrected cross section to be $σ(\e^+e^- \to ϕη) =$$2.1\pm 0.4 (\mathrm{stat})\pm 0.1(\mathrm{syst}) \mathrm{fb}$ within the range $|\cosθ^*| < 0.8$, where $θ^*$ is the center-of-mass polar angle of the $ϕ$ meson. The $ϕ$ meson is required to be in the invariant mass range of 1.008 $< m_ϕ <$ 1.035 \gevcc. The radiation-corrected cross section in the full $\cosθ^*$ range is extrapolated to be $2.9\pm 0.5 (\mathrm{stat})\pm 0.1(\mathrm{syst}) \mathrm{fb}$.

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arXiv2006

Measurement of the Branching Fraction and Time-Dependent CP Asymmetry in the Decay B0->D+D-Ks

We study the decay B0->D*+D*-Ks using (230 +/- 2) x 10^{6} BBbar pairs collected by the Babar detector at the PEP-II B factory. We measure a branching fraction B(B0->D*+D*-Ks)=(4.4\pm0.4\pm0.7)\times 10^{-3} and find evidence for the decay B0->D*- D+_{s1}(2536) with a significance of $4.6σ$. A time-dependent CP asymmetry analysis is also performed to study the possible resonant contributions to B0->D*+D*-Ks and the sign of cos2beta . Our measurement indicates that there is a sizable resonant contribution to the decay B0->D*+D*-Ks from a unknown $D^+_{s1}$ state with large width, and that cos2beta is positive at the 94 % confidence level under certain theoretical assumptions.

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arXiv2006

Observation of a New D_s Meson Decaying to D K at a Mass of 2.86 GeV/c^2

We observe a new D_s meson with mass (2856.6 +/- 1.5_{stat.} +/- 5.0_{syst.}) MeV/c^2 and width (48 +/- 7_{stat.} +/- 10_{syst.}) MeV decaying into D^0 K^+ and D^+K^0_S. In the same mass distributions we also observe a broad structure with mass (2688 +/- 4_{stat.} +/- 3_{syst.}) MeV/c^2 and width (112 +/- 7_{stat.} +/- 36_{syst.}) MeV. To obtain this result we use 240 fb^-1 of data recorded by the BaBar detector at the PEP-II asymmetric-energy e^+e^- storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.

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arXiv2006

Observation of B+ --> K0bar K+ and B0 --> K0 K0bar

We report observations of the b --> d penguin-dominated decays B+ --> K0bar K+ and B0 --> K0 K0bar in approximately 350 million Upsilon(4S) --> BBbar decays collected with the BaBar detector. We measure the branching fractions B(B+ --> K0bar K+) = (1.61 +/- 0.44 +/- 0.09) * 10^-6 and B(B0 --> K0 K0bar) = (1.08 +/- 0.28 +/- 0.11) * 10^-6, and the CP-violating charge asymmetry A_{CP}(K0bar K+) = 0.10 +/- 0.26 +/- 0.03. Using a vertexing technique previously employed in several analyses of all-neutral final states containing kaons, we report the first measurement of time-dependent CP-violating asymmetries in B0 --> K0 K0bar, obtaining S = -1.28 +0.80/-0.73 +0.11/-0.16 and C = -0.40 +/- 0.41 +/- 0.06. We also report improved measurements of the branching fraction B(B+ --> K0 pi+) = (23.9 +/- 1.1 +/- 1.0) * 10^-6 and CP-violating charge asymmetry A_{CP}(K0 pi+) = -0.029 +/- 0.039 +/- 0.010.

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arXiv2006

A Structure at 2175 MeV in $e^+ e^- \to ϕf_0(980)$ Observed via Initial-State Radiation

We study the initial-state-radiation processes $e^+ e^- \to K^+ K^-π^+π^-γ$ and $e^+ e^- \to K^+ K^-π^0π^0γ$ using an integrated luminosity of 232 fb$^{-1}$ collected at the $Υ(4S)$ mass with the BaBar detector at SLAC. Even though these reactions are dominated by intermediate states with excited kaons, we are able to study for the first time the cross section for $e^+ e^- \to ϕ(1020) f_{0}(980)$ as a function of center-of-mass energy. We observe a structure near threshold consistent with a $1^{--}$ resonance with mass $m = 2.175 \pm 0.010\pm 0.015 GeV/c^2$ and width $Γ= 58\pm 16\pm 20 MeV$. We observe no Y(4260) signal and set a limit of $BR_{Y\toϕπ^+π^-}\cdotΓ^{Y}_{ee}<0.4$ eV (90% confidence level), which excludes some models.

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arXiv2006

Measurement of CP-Violating Asymmetries in $B^0\to(ρπ)^0$ Using a Time-Dependent Dalitz Plot Analysis

We report a measurement of CP-violating asymmetries in $B^0\to(ρπ)^0\toπ^+π^-π^0$ decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 347 million $Υ(4S) \to B\bar{B}$ decays, collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure 26 coefficients of the bilinear form factor terms occurring in the time-dependent decay rate of the \Bz meson and derive the physically relevant quantities from these coefficients. In particular we find a three standard deviation evidence of direct CP-violation in $B^0\toρ^\pmπ^\mp$ decays, with systematic uncertainties included. We also achieve a constraint of the angle $α$ of the Unitarity Triangle. All results presented are preliminary.

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arXiv2006

Measurement of the Absolute Branching Fractions B to Dpi, D*pi, D**pi with a Missing Mass Method

We present branching fraction measurements of charged and neutral B decays to Dpi-, D*pi- and D**pi- with a missing mass method, based on a sample of 231 million Y(4S)-->BBar pairs collected by the BaBar detector at the PEP-II e+e- collider. One of the B mesons is fully reconstructed and the other one decays to a reconstructed charged pion and a companion charmed meson identified by its recoil mass, inferred by kinematics. Here D** refers to the sum of all the non-strange charm meson states with masses in the range 2.2-2.8 Gev/c2.

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arXiv2006

Branching Fraction Measurements of Charged B Decays to K+K+K-, K+pi+K-, K+K+pi- and K+pi+pi- Final States

Branching fraction and asymmetry measurements of charmless $B^+\to K^{*+}h^+_1h^-_2$ (where $h_{1,2}$ = $K$, $π$) decays are presented, using a data sample of 232 million $Υ(4S) \to$ $BB$ decays collected with the BaBar detector at the SLAC PEP-II asymmetric-energy $B$ factory. Using a maximum likelihood fit, the following branching fraction results were obtained: ${\cal B}$($B^+ \to K^{*+}K^+ K^-)$ = (36.2 $\pm$ 3.3 $\pm$ 3.6) $\times$ 10$^{-6}$ and ${\cal B}$($B^+$ $\to$ $K^{*+}π^+π^-$) = (75.3 $\pm$ 6.0 $\pm$ 8.1) $\times$ 10$^{-6}$. Upper limits were set for ${\cal B}$($B^+$ $\to$ $K^{*+}π^+ K^-$) $<$ 11.8 $\times$ 10$^{-6}$ and ${\cal B}$($B^+$ $\to$ $K^{*+}K^+ π^-$) $<$ 6.1 $\times$ 10$^{-6}$ at 90% confidence level. The charge asymmetries for the decays $B^+ \to K^{*+}K^+ K^-$ and $B^+$ $\to$ $K^{*+}π^+π^-$ were measured to be ${\cal A}_{K^*KK} = 0.11 \pm 0.08 \pm 0.03$ and ${\cal A}_{K^*ππ} = 0.07 \pm 0.07 \pm 0.04$, respectively. The first error quoted on branching fraction and asymmetry measurements is statistical and the second systematic.

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arXiv2006

Measurement of CP Asymmetries and Branching Fractions in B -> pi pi and B -> K pi decays

We present preliminary measurements of the CP asymmetries and branching fractions for B -> pi pi and B -> K pi decays. A total of 347 million BBbar events collected by the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC are used for these results. We find Spipi = -0.53 +- 0.14 +-0.02, Cpipi = -0.16 +- 0.11 +- 0.03, AKpi = -0.108 +- 0.024 +- 0.008, BF(B0 -> pi0 pi0) = (1.48 +- 0.26 +- 0.12) x 10^-6, BF(B+ -> pi+pi0) = (5.12 +- 0.47 +- 0.29) x 10^-6, BF(B+ -> K+pi0) = (13.3 +- 0.56 +- 0.64) x 10^-6, Cpi0pi0 = -0.33 +- 0.36 +- 0.08, Apipi0 = -0.019 +- 0.088 +- 0.014, AKpi0 = 0.016 +- 0.041 +- 0.012. The measured values of Spipi and Cpipi imply that CP conservation in B0 -> pi+ pi- decays is excluded at the 3.6 sigma level. From these results we present bounds on the CKM angle alpha.

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arXiv2006

A Study of the DsJ(2317) and DsJ(2460) Mesons in Inclusive ccbar Production Near sqrt(s) = 10.6 GeV

A study of the $D_{sJ}^*(2317)^+$ and $D_{sJ}(2460)^+$ mesons in inclusive $c\bar{c}$ production is presented using 232 ${\rm fb}^{-1}$ of data collected by the BaBar experiment near $\sqrt{s} = 10.6$ \gev. Final states consisting of a $D_s^+$ meson along with one or more $π^0$, $π^\pm$, or $γ$ particles are considered. Estimates of the mass and limits on the width are provided for both mesons and for the $D_{s1}(2536)^+$ meson. A search is also performed for neutral and doubly-charged partners of the $D_{sJ}^*(2317)^+$ meson.

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arXiv2006

Measurement of the CP Asymmetry and Branching Fraction of B^0 to rho^0 K^0

We present a measurement of the branching fraction and time-dependent CP asymmetry of B^0 to rho^0 K^0. The results are obtained from a data sample of 227 10^6 Y4S to BB_ decays collected with the BaBar detector at the PEP2 asymmetric-energy B Factory at SLAC. From a time-dependent maximum likelihood fit yielding 111+/-19 signal events we find B(B^0 to rho^0 K^0)=(4.9+/-0.8+/-0.9) 10^-6, where the first error is statistical and the second systematic. We report the measurement of the CP parameters S=0.20+/-0.52+/-0.24 and C=0.64+/-0.41+/-0.20.

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arXiv2006

Study of B --> D^()D_s(J)^() Decays and Measurement of D_s^- and D_sJ(2 460)^- Branching Fractions

We present branching fraction measurements of twelve B meson decays of the form B --> D^(*)D_s(J)^(*). The results are based on Y(4S) decays in BBbar pairs. One of the B mesons is fully reconstructed and the other decays to two charm mesons, of which one is reconstructed, and the mass and momentum of the other is inferred by kinematics. Combining these results with previous exclusive branching fraction measurements, we determine BR(D_s^- --> phi pi^-) = (4.62 +/- 0.36_stat. +/- 0.51_syst.)%, BR(D_sJ(2460)^- --> D_s^*- pi^0) = (56 +/- 13_stat. +/- 9_syst.)% and BR(D-sJ(2460)^- --> D_s^- gamma) = (16 +/- 4_stat. +/- 3_syst.)%.

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arXiv2006

Search for the decay B0 --> K0_S K0_S K0_L

We present the first search for the decay B0 --> K0_S K0_S K0_L using a data sample of 232 million B Bbar pairs. We find no statistically significant evidence for the non-resonant component of this decay. Our central value for the branching fraction, assuming the true Dalitz distribution is uniform and excluding the phi resonance, is B(B0 --> K0_S K0_S K0_L) = (2.4 +2.7 -2.5 +/- 0.6) x 10^{-6} where the errors are statistical and systematic, respectively. We set a single-sided Bayesian upper limit of B(B0 --> K0_S K0_S K0_L) < 7.4 x 10^{-6} at 90% confidence level using a uniform prior probability for physical values. Assuming the worst-case true Dalitz distribution, where the signal is entirely in the region of lowest efficiency, the 90% confidence level upper limit is B(B0 --> K0_S K0_S K0_L) < 16 x 10^{-6}.

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arXiv2006

A Search for B+ --> tau+ nu Recoiling Against B- --> D0 l- nubar X

We present a search for the decay $B^{+} \to τ^{+} ν_τ$ using 288 fb-1 of data collected at the $Υ(4S)$ resonance with the BaBar detector at the SLAC PEP-II $B$-Factory. A sample of events with one reconstructed semileptonic B decay is selected, and in the recoil a search for $B^{+} \to τ^{+} ν_τ$ signal is performed. The $τ$ is identified in the following channels: {τ^+ \to e^+ ν_e \nutb}, {τ^+ \to μ^+ ν_μ \nutb}, {τ^+ \to π^+ \nutb} and {τ^+ \to π^+ π^0 \nutb}. We measure a branching fraction of $\mathcal{B}(B^{+} \to τ^{+} ν_τ)=(0.88^{+0.68}_{-0.67}({stat.}) \pm 0.11 ({syst.})) \times 10^{-4}$ and extract an upper limit on the branching fraction, at the 90% confidence level, of $\mathcal{B}(B^{+} \to τ^{+} ν_τ) < 1.8 \times 10^{-4}$. We calculate the product of the $B$ meson decay constant and $|\Vub|$ to be $f_{B}\cdot|\Vub| = (7.0^{+2.3}_{-3.6}({stat.})^{+0.4}_{-0.5}({syst.}))\times10^{-4}$ GeV \.

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arXiv2006

Measurements of the B to D* Form Factors Using the Decay B0 --> D* e nu_e

We measure the dependence of $\bar B^0 \to D^{*+}e^-\barν_e$ on the decay angles and momentum transfer. The data sample consists of $\sim 86 \times 10^6$ $B\bar B$-pairs accumulated on the $Υ(4{\rm S})$ resonance by the BABAR detector at the asymmetric $e^+ e^-$ collider PEP-II. We specify the three form factors by two ratios $R_1$ and $R_2$, and by a single parameter $ρ^2$ characterizing the polynomial representing $h_{A_1}$, the function which describes the momentum-transfer dependence of the form factor $A_1$. We determine $R_1$, $R_2$, and $ρ^2$ using an unbinned maximum likelihood fit to the full decay distribution. The results are $R_1=1.396\pm 0.060\pm 0.035\pm 0.027$, $R_2=0.885\pm 0.040\pm 0.022\pm 0.013$, and $ρ^2=1.145\pm 0.059\pm 0.030\pm 0.035$. The stated uncertainties are the statistical from the data, statistical from the size of the Monte Carlo sample and the systematic uncertainty, respectively. In addition, based on this measurement, we give an updated value for the CKM matrix element $|V_{cb}|$.

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arXiv2006

Precise Branching Ratio Measurements of the Decays D0-->pi- pi+ pi0 and D0-->K- K+ pi0

Using 232 fb-1 of e+e- collision data recorded by the BaBar experiment, we measure the ratios of three-body Cabibbo-suppressed decay rates of the D^0 meson relative to that of the Cabibbo-favored decay: B(D0 --> pi- pi+ pi0)/ B(D0 --> K- pi+ pi0) = (10.59 +/- 0.06 +/- 0.13).10^{-2} and B(D0 --> K- K+ pi0)/ B(D0 --> K- pi+ pi0) = (2.37 +/- 0.03 +/- 0.04). 10^{-2}, where the errors are statistical and systematic respectively. The precisions of these measurements are significantly better than those of the current world average values.We note that the second result differs significantly from the current world average value. Using the PDG-2006 value for D0 --> K- pi+ pi0 branching fraction, we obtain, B(D0 --> pi- pi+ pi0) = (1.493 +/- 0.008 +/- 0.018 +/- 0.053). 10^{-2}, B(D0 --> K- K+ pi0) = (0.334 +/- 0.004 +/- 0.006 +/- 0.012). 10^{-2}, where the errors are statistical, systematic, and due to the uncertainty of B(D0 --> K- pi+ pi0). The average squared matrix elements for both of the singly Cabibbo-suppressed decays are roughly a factor of sin^2 θ_C smaller than that for the Cabibbo-favored decay and are therefore, in contrast to the corresponding two-body modes, consistent with the naive expectations.

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