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BABAR Collaboration

Publications and source records attributed to BABAR Collaboration.

At least 55 records · Page 3Linked to original sources

Measurement of Time-dependent CP-Violating Asymmetries in B^0 -> K^0_S K^0_S K^0_S Decays

We present preliminary measurements of the CP asymmetry parameters in B^0 -> K^0_S K^0_S K^0_S decays, reconstructing two of the K^0_S into pi^+pi^- and one into pi^0pi^0. In a sample of 227M $B\bar B$ pairs collected by the BABAR detector at the PEP-II B-Factory at SLAC, we find the CP parameters to be S = -0.25^{+0.68}_{-0.61} (stat) +/- 0.05 (syst) and C = 0.56^{+0.34}_{-0.43} (stat) +/- 0.04 (syst). Combining this result with the previous BABAR measurement, obtained from events with three K^0_S decaying into pi^+pi^-, we get S = -0.63^{+0.32}_{-0.28} (stat) +/- 0.04(syst) C = -0.10 +/- 0.25 (stat) +/- 0.05 (syst)

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Measurement of Time-dependent CP-Violating Asymmetries in B0 -> K+K-K0L Decays

We present preliminary measurements of the CP asymmetry parameters and CP content in B0 --> K+K-K0L decays, with B0 --> phi K0L events excluded. In a sample of 227 M B bar B pairs collected by the BaBar detector at the PEP-II B Factory at SLAC, we find the CP parameters to be S = 0.07 +/- 0.28 (stat) {+0.11} {-0.12} (syst) C = 0.54 +/- 0.22 (stat) {+0.08} {-0.09} (syst) where the first error is statistical and the second is systematic. Estimating the fraction of CP-odd final states from angular moments analysis in the K+K-K0S CP-conjugate final state, f_{odd} (K+K-K0L) = 0.92 +/- 0.07 (stat) +/- 0.06 (syst) we determine sin 2beta_{eff} = 0.09 +/- 0.33, (stat) {+0.13} {-0.14} (syst) +/- 0.10 (syst CP-cont)

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Branching Fraction for B0 -> pi- l+ nu and Determination of |Vub| in Upsilon(4S) -> B0 B0bar Events Tagged by B0bar -> D(*)+ l- nubar

We report preliminary results from a study of the charmless exclusive semileptonic decay B0 -> pi- l+ nu based on the data collected at the Upsilon(4S) resonance using the BABAR detector at SLAC. The analysis uses events in which the signal B meson recoils against a B meson that has been reconstructed in a semileptonic decay B0bar -> D(*)+ l- nubar. We extract the total branching fraction BF(B0 -> pi- l+ nu) = (1.03 +/- 0.25(stat.) +/- 0.13(syst.)) x 10^-4 and the partial branching fractions in three bins of q^2, the invariant mass squared of the lepton-neutrino system. From the partial branching fractions and theoretical predictions for the form factors, we determine the magnitude of the CKM matrix element |Vub|. We find |Vub| = (3.3 +/- 0.4(stat.) +/- 0.2(syst.) +0.8/-0.4(FF)) x 10^-3, where the last error is due to normalization of the form factor.

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Branching Fraction for B+ -> pi0 l+ nu, Measured in Upsilon(4S) -> B Bbar Events Tagged by B- -> D0 l- nubar (X) Decays

We report a preliminary branching fraction of (1.80 +/- 0.37(stat.) +/- 0.23(syst.)) x 10^-4 for the charmless exclusive semileptonic B+ -> pi0 l+ nu decay, where l can be either a muon or an electron. This result is based on data corresponding to an integrated luminosity of 81 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses BBbar events that are tagged by a B meson reconstructed in the semileptonic B- -> D0 l- nubar (X) decays, where X can be either a gamma or a pi0 from a D* decay.

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A Study of Production and Decays of Omega_c0 Baryons at BABAR

Production and decay of $Ω_c^0$ baryons is studied with $\sim230 \mathrm{fb}^{-1}$ of data recorded with the BABAR detector at the PEP-II $e^+e^-$ asymmetric-energy storage ring at SLAC. The $Ω_c^0$ is reconstructed through its decays into $Ω^-π^+$, $Ω^-π^+π^+π^-$, and $Ξ^-K^-π^+π^+$ final states. The invariant mass spectra are presented and the signal yields are extracted. Ratios of branching fractions are measured relative to the $Ω^-π^+$ mode \frac{{\cal B}(Ξ^-K^-π^+π^+)}{{\cal B}(Ω^-π^+)} &= 0.31 \pm 0.15\mathrm{(stat.)} \pm 0.04\mathrm{(syst.)}, \frac{{\cal B}(Ω^-π^+π^+π^-)}{{\cal B}(Ω^-π^+)} &< 0.30\qquad (90%\mathrm{CL}). The momentum spectrum (not corrected for efficiency) of $Ω_c^0$ baryons is extracted from decays into $Ω^-π^+$, establishing the first observation of $Ω_c^0$ production from B decays.

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Measurement of the B+ --> p pbar K+ Branching Fraction and Study of the Decay Dynamics

With a sample of 232x10^6 Upsilon(4S) --> BBbar events collected with the BaBar detector, we study the decay B+ --> p pbar K+ excluding charmonium decays to ppbar. We measure a branching fraction Br(B+ --> p pbar K+)=(6.7+/-0.5+/-0.4)x10^{-6}. An enhancement at low ppbar mass is observed and the Dalitz plot asymmetry suggests dominance of the penguin amplitude in this B decay. We search for a pentaquark candidate Theta*++ decaying into pK+ in the mass range 1.43 to 2.00 GeV/c2 and set limits on Br(B+ --> Theta*++pbar)xBr(Theta*++ --> pK+) at the 10^{-7} level.

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Search for B --> Ds(*) Phi

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, the branching fractions for these decays are expected to be highly suppressed, since they proceed through annhilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BaBar detector at SLAC. We find no evidence for these decays, and we set 90% confidence level upper limits on the branching fractions BF(B- --> Ds- Phi) < 1.8x10^(-6) BF(B- --> Ds*- Phi) < 1.1x10^(-5). These results are consistent with Standard Model expectations.

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Improved Measurement of the CKM Angle alpha Using B0->rho+rho- Decays

We present results from an analysis of B0 -> rho+rho- using 232 million Upsilon(4S) decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We measure the longitudinal polarization fraction f_L = 0.978 +- 0.014 (stat) +0.021 -0.029 (syst) and the CP-violating parameters SLong = -0.33 +- 0.24 (stat) +0.08 -0.14 (syst) and CLong = -0.03 +- 0.18 (stat) +- 0.09 (syst). Using an isospin analysis of B -> rho rho decays we determine the unitarity triangle alpha. The solution compatible with the Standard Model is alpha = (100 +- 13) degrees.

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Search for the Decay tau to seven pion (pizero)

A search for the decay of the tau lepton to seven charged pions and one or zero pizero mesons was performed using the BaBar detector at the PEP-II asymmetric-energy e+e- collider. The analysis uses 232.2 fb-1 of data at center-of-mass energies on or near the Y(4S) resonance. We observe 24 events with an expected background of 21.6+-1.3 events. Without evidence for a signal, we calculate an upper limit of BR(tau- --> 4pi- 3pi+ (pizero) nu_tau) < 3.0*10^-7 at 90 % confidence level. This is an improvement by nearly an order of magnitude over the previously established limit. In addition, we set upper limits for the exclusive decays tau- --> 4pi- 3pi+ nu_tau and tau- --> 4pi- 3pi+ pizero nu_tau.

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Search for the Rare Decays B+ --> D(*)+K0s

We report on the search for the rare decays $B^+ \to D^{(*)+} K^0_{s}$ in approximately 226 million $Y(\rm 4S)\to b\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $B$ factory at SLAC. We do not observe any significant signal and we set 90% confidence level upper limits on the branching fractions, ${\ensuremath {{\cal B}(\Bp{\to}D^{+}K^0})}$ $<0.5 \times 10^{-5}$ and ${\ensuremath {{\cal B}(\Bp{\to}D^{*+}K^0})}$ $<0.9 \times 10^{-5}$.

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Measurement of Branching Fraction and Dalitz Distribution for B0->D(*)+/- K0 pi-/+ Decays

We present measurements of the branching fractions for the three-body decays B0 -> D(*)-/+ K0 pi^+/-$ and their resonant submodes $B0 -> D(*)-/+ K*+/- using a sample of approximately 88 million BBbar pairs collected by the BABAR detector at the PEP-II asymmetric energy storage ring. We measure: B(B0->D-/+ K0 pi+/-)=(4.9 +/- 0.7(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K0 pi+/-)=(3.0 +/- 0.7(stat) +/- 0.3 (syst)) 10^{-4} B(B0->D-/+ K*+/-)=(4.6 +/- 0.6(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K*+/-)=(3.2 +/- 0.6(stat) +/- 0.3 (syst)) 10^{-4} From these measurements we determine the fractions of resonant events to be : f(B0-> D-/+ K*+/-) = 0.63 +/- 0.08(stat) +/- 0.04(syst) f(B0-> D*-/+ K*+/-) = 0.72 +/- 0.14(stat) +/- 0.05(syst)

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The $\epem\toπ^+π^-π^+π^-$, $K^+K^-π^+π^-$, and $K^+K^- K^+K^- $ Cross Sections at Center-of-Mass Energies 0.5--4.5 \gev Measured with Initial-State Radiation

We study the process $e^+e^-\toπ^+π^-π^+π^-γ$, with a hard photon radiated from the initial state. About 60,000 fully reconstructed events have been selected from 89 $fb^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy, so that these data can be compared with the corresponding direct $e^+e^-$ measurements. From the $4π$-mass spectrum, the cross section for the process $e^+e^-\toπ^+π^-π^+π^-$ is measured for center-of-mass energies from 0.6 to 4.5 $GeV/c^2$. The uncertainty in the cross section measurement is typically 5%. We also measure the cross sections for the final states $K^+ K^- π^+π^-$ and $K^+ K^- K^+ K^-$. We observe the $J/ψ$ in all three final states and measure the corresponding branching fractions. We search for X(3872) in $J/ψ(\toμ^+μ^-) π^+π^-$ and obtain an upper limit on the product of the $e^+e^-$ width of the X(3872) and the branching fraction for $X(3872) \to J/ψπ^+π^-$.

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Search for the Radiative Penguin Decays B+ -> rho+ gamma, B0 -> rho0 gamma, and B0 -> omega gamma

A search for the decays B --> rho(770) gamma and B0 --> omega(782)gamma is performed on a sample of 211x10^6 Y(4S)->BBbar events collected by the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring. No evidence for the decays is seen. We set the following limits on the individual branching fractions: BF(B --> rho+ gamma)<1.8 x 10^-6, BF(B --> rho0 gamma)<0.4 x 10^-6, and BF(B --> omega gamma)<1.0 x 10^-6 at the 90% confidence level (C.L.). We use the quark model to limit the combined branching fraction BFbar[B --> (rho/omega) gamma]<1.2 x 10^-6, from which we determine a constraint on the ratio of Cabibbo-Kobayashi-Maskawa matrix elements |V_td|/|V_ts|.

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Measurement of Branching Fractions and Charge Asymmetries for Exclusive B Decays to Charmonium

We report measurements of branching fractions and charge asymmetries of exclusive decays of neutral and charged B mesons into two-body final states containing a charmonium state and a light strange meson. The charmonium mesons considered are J/Psi, Psi(2S) and Chi_c1, and the light meson is either K or K*. We use a sample of about 124 million BBbar events collected with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center.

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Constraints on rB and gamma in B+- -> D(*)0K+- decays by a Dalitz analysis of D0 -> Ks pi+ pi-

We report on a study of direct CP violation in the decay B- -> D(*)0 K- with a Dalitz analysis of the D0 -> Ks pi- pi+ decay using a sample of 227 million BBbar pairs collected by the BaBar detector. Reference to the charge-conjugate state is implied here. We constrain the amplitude ratio rB=|A(B- -> D0bar K-)|/|A(B- -> D0 K-)| to be <0.19 at the 90% confidence level and rB*=|A(B- -> D*0bar K-)|/|A(B- -> D*0 K-)| = 0.155 +0.070-0.077 +/- 0.040 +/- 0.020 and we measure the relative strong phase deltaB=(114 +/- 41 +/- 8 +/- 10) deg and deltaB*=(303 +/- 34 +/- 14 +/- 10) deg between the amplitudes A(B- -> D(*)0bar K-) and A(B- -> D(*)0 K-). From these samples we measure gamma =(70 +/- 26 +/- 10 +/- 10) deg. The first error is statistical, the second error accounts for experimental uncertainties and the third error reflects the Dalitz model uncertainty. For this preliminary result we have quoted confidence intervals obtained with a Bayesian technique assuming a uniform prior in rB, gamma and deltaB.

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A search for the decay $B^+ \to K^+ ν\barν$

We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ ν\barν$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of ${\mathcal B}(B^+ \to K^+ ν\barν)<5.2 \times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of ${\mathcal B}(B^+ \to π^+ ν\barν)<1.0 \times 10^{-4}$ using only the hadronic B reconstruction method.

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Search for B+/- --> [K-/+ pi+/-]_D K+/- and upper limit on the b --> u amplitude in B+/- --> D K+/-

We search for B+/- --> [K^-/+ pi+/-]_D K+/- decays, where [K-/+ pi+/-]_D indicates that the K-/+ pi+/- pair originates from the decay of a D0 or D0bar. Results are based on 120 million Upsilon(4S) --> B Bbar decays collected with the BaBar detector at SLAC. We set an upper limit on the ratio R_Kpi = {Gamma(B+ --> [K- pi+]_D K+) + Gamma(B- --> [K+ pi-]_D K-)}/ {Gamma(B+ --> [K+ pi-]_D K+) + Gamma(B- --> [K- pi+]_D K-)} < 0.026 (90% C.L.). This constrains the amplitude ratio r_B = |A(B- --> D0bar K-)/A(B- --> D0 K-)| < 0.22 (90% C.L.), consistent with expectations. The small value of r_B favored by our analysis suggests that the determination of the Cabibbo-Kobayashi-Maskawa phase gamma from B --> D K will be difficult.

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Measurement of CP-Asymmetries for the Decays B+/- to D_cp Kstar+/- with the BABAR Detector

Using a sample of 227 million $Υ(4S) \to B \bar{B}$ events collected with the $BABAR$ detector at the PEP-II $B$ Factory in 1999--2004, we study $B^- \to D^0 K^*(892)^-$ decays where $K^{*-} \to K^0_S π^-$ and $D^0 \to K^-π^+, K^- π^+ π^0, K^-π^+ π^+ π^-$ (non-CP final states), $K^+ K^-, π^+ π^- (CP+$ eigenstates), $K^0_S~π^0, K^0_S ϕ$ and $K^0_S ω(CP-$ eigenstates). The partial rate charge asymmetries $\mathcal{A}_{CP}$ and the ratios $\mathcal{R}_{CP}$ defined in the literature as the sum of the $B^+$ and $B^-$ partial rates to a charged $K^*$ and a $D^0 CP$-eigenstate divi ded by the $B \to D^0 K^*$ decay rate, %of the \ensuremath{\Bu}\xspace\xspace m \ensuremath{\to}\xspace \Dcp \ensuremath{K^*}\xspacepm branch ing fractions summed over %\B charge to the \ensuremath{B^-}\xspace \xspace\ensuremath{\to}\xspace \ensuremath{D^0}\xspace \ensu remath{K^{*-}}\xspace branching fraction are sensitive to the angle $γ$ of the CKM unitarity triangle. We measure: \mathcal{A}_{CP+} &=&-0.09 \pm 0.20 (stat.) \pm 0.06 (syst.) \mathcal{A}_{CP-} &=& -0.33 \pm 0.34 (stat.) \pm 0.10 (syst.) (+1.15 \pm 0.12) \cdot (\mathcal{A}_{CP-} - \mathcal{A}_{CP+}) \mathcal{R}_{CP+} &=& +1.77 \pm 0.37 (stat.) \pm 0.12 (syst.) \mathcal{R}_{CP-} &=& +0.76 \pm 0.29 (stat.) \pm 0.06 (syst.) ^{- 0.04}_{-\ 0.14} The third uncertainty quoted for the CP- measurements reflects possible interference effects in the final states with $ϕ$ and $ω$ resonances. All results are preliminary.

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