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The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 145 records · Page 8Linked to original sources

arXiv2009

Search for the B+ -> K+vv Decay Using Semi-Leptonic Tags

We present an update of the search for the flavor-changing neutral current B+ -> K+vv decay using 351 x 10^6 BB pairs collected at the Y(4S) resonance with the BABAR detector at the SLAC PEP-II B factory. Due to the presence of two neutrinos in the final state, we require the reconstruction of the companion B in the event through the decay channel B- -> D0l-v. We find 38 candidates in the data with an expected background of 31 +/- 12. This allows us to set an upper limit on the branching fraction for B+ -> K+vv of 4.5 x 10^-5 at 90% confidence level.

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arXiv2009

Search for a low-mass Higgs boson in Y(3S)-->gamma A^0, A^0-->tau^+tau^- at BABAR

We search for a light Higgs boson, $A^0$, in the radiative decay $Υ(3S)\toγA^0$, $A^0\toτ^+τ^-$, $τ^+\to e^+ν_e \barν_τ$ or $τ^+\to μ^+ ν_μ \barν_τ$. The data sample contains 122 million $Υ(3S)$ events recorded with the \babar detector. We find no evidence for a narrow structure in the studied $τ^+τ^-$ invariant mass region of $4.03 (1.5-16)\times 10^{-5}$ across the $m_{τ^+τ^-}$ range. We also set a 90% C.L. upper limit on the $τ^+τ^-$-decay of the $η_b$ at ${\mathcal{B}}(η_b\to τ^+τ^-)<8%$.

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arXiv2009

Study of $D_{sJ}$ decays to $D^*K$ in inclusive $e^+e^-$ interactions

We observe the decays $ $D^*_{s1}(2710)^+ \to D^*K$ and $D^*_{sJ}(2860)^+ \to D^*K$ and measure their branching fractions relative to the $D K$ final state. We also observe, in the $D^*K$ mass spectrum, a new broad structure at a mass of $(3044 \pm 8_{stat} (^{+30}_{-5})_{syst})$ $MeV/c^2$ having a width $Γ=(239 \pm 35_{stat} (^{+46}_{-42})_{syst})$ $MeV$. To obtain this result we use 470 ${\rm fb}^{-1}$ of data recorded by the BaBar detector at the PEPII 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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arXiv2009

Evidence for the eta_b(1S) Meson in Radiative Upsilon(2S) Decay

We have performed a search for the eta_b(1S) meson in the radiative decay of the Upsilon(2S) resonance using a sample of 91.6 million Upsilon(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E_gamma = 609.3 {+4.6} {-4.5} (stat) +/- 1.9 (syst) MeV, corresponding to an eta_b(1S) mass of 9394.2 {+4.8} {-4.9} (stat) +/- 2.0 (syst) MeV/c^2. The branching fraction for the decay Upsilon(2S) --> gamma eta_b(1S) is determined to be [3.9 +/-1.1 (stat) {+1.1} {-0.9} (syst)] x 10^(-4). We find the ratio of branching fractions B[Upsilon(2S) --> gamma eta_b(1S)]/B[Upsilon(3S) --> gamma eta_b(1S)] = 0.82 +/- 0.24 (stat) {+0.20}{-0.19} (syst).

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arXiv2009

Study of B Meson Decays with Excited eta and eta' Mesons

Using 383 million BBbar pairs from the BaBar data sample, we report results for branching fractions of six charged B-meson decay modes, where a charged kaon recoils against a charmless resonance decaying to KKbar* or etapipi final states with mass in the range (1.2-1.8)gev/c^2. We observe a significant enhancement at the low KK*bar invariant mass which is interpreted as B+ --> eta(1475)K+, find evidence for the decay B+ --> eta(1295)K+, and place upper limits on the decays B+ --> eta(1405)K+, B+ --> f_1(1285)K+, B+ --> f_1(1420)K+, and B+ --> phi(1680)K+.

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arXiv2009

Observation of the baryonic B-decay B0bar -> Lambda_c^+ antiproton K^- pi^+

We report the observation of the baryonic B-decay B0bar -> Lambda_c^+ antiproton K^- pi^+, excluding contributions from the decay B0bar -> Lambda_c^+ anti-Lambda K^-. Using a data sample of 467*10^6 BBbar pairs collected with the BABAR detector at the PEP-II storage ring at SLAC, the measured branching fraction is (4.33 +/- 0.82_stat +/- 0.33_syst +/- 1.13_Lambda_c^+)*10^-5. In addition we find evidence for the resonant decay B0bar -> Sigma_c(2455)^++ antiproton K^- and determine its branching fraction to be (1.11 +/- 0.30_stat +/- 0.09_syst +/- 0.29_Lambda_c^+)*10^-5. The errors are statistical, systematic, and due to the uncertainty in the Lambda_c^+ branching fraction. For the resonant decay B0bar -> Lambda_c^+ antiproton K^*0 we obtain an upper limit of 2.42*10^-5 at 90% confidence level.

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arXiv2009

Measurement of branching fractions of B decays to K1(1270)pi and K1(1400)pi and determination of the CKM angle alpha from B0 --> a1(1260)+/- pi-/+

We report measurements of the branching fractions of neutral and charged B meson decays to final states containing a K_1(1270) or K_1(1400) meson and a charged pion. The data, collected with the BaBar detector at the SLAC National Accelerator Laboratory, correspond to 454 million B Bbar pairs produced in e^+ e^- annihilation. We measure the branching fractions BF(B^0 --> K_1(1270)^+ π^- + K_1(1400)^+ π^-) = 3.1^{+0.8}_{-0.7} x10^{-5} and BF(B^+ --> K_1(1270)^0 π^+ + K_1(1400)^0 π^+) = 2.9^{+2.9}_{-1.7} x10^{-5} (<8.2 x10^{-5} at 90% confidence level), where the errors are statistical and systematic combined. The B^0 decay mode is observed with a significance of 7.5σ, while a significance of 3.2σis obtained for the B^+ decay mode. Based on these results, we estimate the weak phase α= (79 +/- 7 +/- 11)^{\circ} from the time dependent CP asymmetries in B^0 --> a_1(1260)^{+/-} π^{-/+} decays.

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arXiv2009

Precise measurement of the e+ e- to pi+ pi- (gamma) cross section with the Initial State Radiation method at BABAR

A precise measurement of the cross section of the process e+ e- to pi+ pi- (gamma) from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using 232 fb^-1 of data collected with the BABAR detector at e+ e- center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e+ e- to mu+ mu- gamma (gamma). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the pi pi cross section measured from threshold to 1.8 GeV is (514.1 +-2.2(stat} +-3.1(syst}) x 10^{-10}.

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arXiv2009

Search for b-> u transitions in B0 -> D0 K*0 decays

We present a study of the decays B0 -> D0 K*0 and B0 -> barD0 K*0 with K*0 -> K+pi-. The D0 and the barD0 mesons are reconstructed in the final states f=K+pi-, K+pi-pi0, K+pi-pi+pi- and their charge conjugates. Using a sample of 465 million BBbar pairs collected with the Babar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we measure the ratio R_{ADS}=[Gamma(barB0 -> [f]_D barK*0)+Gamma(B0 -> [bar{f}]_D K*0)]/ [Gamma(barB0 -> [bar{f}]_D barK*0)+Gamma(B0 -> [f]_D K*0)] for the three final states. We do not find significant evidence for a signal and set the following limits at 95% probability: R_{ADS}(Kpi)<0.244, R_{ADS}(Kpipi0)<0.181 and R_{ADS}(Kpipipi)<0.391. From the combination of these three results, we find that the ratio rS between the b -> u and the b -> c amplitudes lies in the range [0.07,0.41] at 95% probability.

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arXiv2009

A Search for Invisible Decays of the Upsilon(1S)

We search for invisible decays of the Upsilon(1S) meson using a sample of 91.4 x 10^{6} Upsilon(3S) mesons collected at the BaBar/PEP-II B-factory. We select events containing the decay Upsilon(3S) -> pi+ pi- Upsilon(1S) and search for evidence of an undetectable Upsilon(1S) decay recoiling against the dipion system. We set an upper limit on the branching fraction BR(Upsilon(1S) -> invisible) < 3.0 x 10^{-4} at the 90% confidence level.

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arXiv2009

Measurement of Semileptonic B Decays into Orbitally Excited Charmed Mesons

We present a study of B decays into semileptonic final states containing charged and neutral $D_1(2420)$ and $D_2^*(2460)$. The analysis is based on a data sample of $208 fb^{-1}$ collected at the $Υ(4S)$ resonance with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. With a simultaneous fit to four different decay chains, the semileptonic branching fractions are extracted from measurements of the mass difference $Δm=m(D**)-m(D)$ distributions. Product branching fractions are determined to be $BR(B^+ -> D_1^0 \ell^+ ν_{\ell}) x BR(D_1^0 -> D*^+ π^-) = (2.97 +/- 0.17 +/- 0.17) x 10^{-3}$, $BR(B^+ -> D_2^{*0} \ell^+ ν_{\ell}) x BR(D_2^{*0} -> D^{(*)+} π^-) = (2.29 +/- 0.23 +/- 0.21) x 10^{-3}$, $BR(B^0 -> D_1^- \ell^+ ν_{\ell}) x BR(D_1^- -> D*^0 π^-) = (2.78 +/- 0.24 +/- 0.25) 10^{-3}$ and $BR(B^0 -> D_2^{*-} \ell^+ ν_{\ell}) x BR(D_2^{*-} -> D^{(*)0} π^-) = (1.77 +/- 0.26 +-/ 0.11) 10^{-3}$. In addition we measure the branching ratio $Γ(D_2^* -> D π^-)/Γ(D_2^* -> D^{(*)} π^-) = 0.62 +/- 0.03 +/- 0.02$.

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arXiv2009

Search for a Narrow Resonance in e+e- to Four Lepton Final States

Motivated by recent models proposing a hidden sector with $\sim$GeV scale force carriers, we present a search for a narrow dilepton resonance in 4 lepton final states using $536fb^{-1}$ collected by the BaBar detector. We search for the reaction, $e^+e^-\to W^\prime W^\prime\to(l^+l^-)(l^{\prime+}l^{\prime-})$, where the leptons carry the full 4-momentum and the two dilepton pair invariant masses are equal. We do not observe a significant signal and we set 90% upper limits of $σ(e^+e^-\to W^\prime W^\prime\to(e^+e^-)(e^+e^-))<(15-70) ab$, $σ(e^+e^-\to W^\prime W^\prime\to(e^+e^-)(μ^+μ^-))<(15-40) ab$, and $σ(e^+e^-\to W^\prime W^\prime\to(μ^+μ^-)(μ^+μ^-))<(11-17) ab$ in the $W^\prime$ mass range between 0.24 and 5.3GeV. Under the assumption that the $W^\prime$ coupling to electrons and muons is the same, we obtain a combined upper limit of $σ(e^+e^-\to W^\prime W^\prime\to(l^+l^-)(l^{\prime+}l^{\prime-}))<(25-60) ab$. Using these limits, we constrain the product of the SM-dark sector mixing and the dark coupling constant in the case of a non-Abelian Higgsed dark sector.

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arXiv2009

Observation and study of baryonic B decays: B -> D() p pbar, D() p pbar pi, and D(*) p pbar pi pi

We present a study of ten B-meson decays to a D(*), a proton-antiproton pair, and a system of up to two pions using BaBar's data set of 455x10^6 BBbar pairs. Four of the modes (B0bar -> D0 p anti-p, B0bar -> D*0 p anti-p, B0bar -> D+ p anti-p pi-, B0bar -> D*+ p anti-p pi-) are studied with improved statistics compared to previous measurements; six of the modes (B- -> D0 p anti-p pi-, B- -> D*0 p anti-p pi-, B0bar -> D0 p anti-p pi- pi+, B0bar -> D*0 p anti-p pi- pi+, B- -> D+ p anti-p pi- pi-, B- -> D*+ p anti-p pi- pi-) are first observations. The branching fractions for 3- and 5-body decays are suppressed compared to 4-body decays. Kinematic distributions for 3-body decays show non-overlapping threshold enhancements in m(p anti-p) and m(D(*)0 p) in the Dalitz plots. For 4-body decays, m(p pi-) mass projections show a narrow peak with mass and full width of (1497.4 +- 3.0 +- 0.9) MeV/c2, and (47 +- 12 +- 4) MeV/c2, respectively, where the first (second) errors are statistical (systematic). For 5-body decays, mass projections are similar to phase space expectations. All results are preliminary.

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arXiv2009

Measurement of D0-D0bar Mixing using the Ratio of Lifetimes for the Decays D0->K-pi+ and K+K-

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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arXiv2009

Measurement and interpretation of moments in inclusive semileptonic decays Bbar --> X_c l- nubar

We present results for the moments of observed spectra in inclusive semileptonic B-meson decays to charm hadrons Bbar --> X_c l- nubar. Moments of the hadronic-mass and the combined mass-and-energy spectra for different minimum electron or muon momenta between 0.8 and 1.9 GeV/c are obtained from a sample of 232x10^{6} Y(4S) --> B Bbar events, collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We also present a re-evaluation of the moments of electron-energy spectra and partial decay fractions BR(Bbar --> X_c e- nubar for minimum electron momenta between 0.6 and 1.5 GeV/c based on a sample of 51x10^{6} Y(4S) --> B Bbar events. The measurements are used for the extraction of the total decay fraction, the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V_cb|, the quark masses m_b and m_c, and four heavy-quark QCD parameters in the framework of a Heavy Quark Expansion (HQE). We find BR(Bbar --> X_c l- nubar) = (10.64 +/- 0.17 +/- 0.06)% and |V_cb| = (42.05 +/- 0.45 +/- 0.70) x 10^{-3}.

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arXiv2009

Search for B-meson decays to b1rho and b1K*

We present a search for decays of $B$ mesons to final states with a $b\_1$ meson and a $ρ$ or $K^*(892)$ meson. The search is based on a data sample consisting of 465 million $B\kern 0.18em{\kern -0.18em B}{}$ pairs collected by the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the SLAC National Accelerator Laboratory. We do not observe any statistically significant signal. The upper limits we set on the branching fractions range from 1.4 to $8.0 \times 10^{-6}$ at the 90% confidence level (C.L.), including systematic uncertainties.

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arXiv2009

Dalitz Plot Analysis of D_s+ -> pi+ pi- pi+

A Dalitz plot analysis of approximately 13,000 Ds+ decays to pi+pi-pi+ has been performed. The analysis uses a 384 fb-1 data sample recorded by the BaBar detector at the PEP-II asymmetric-energy e+e- storage ring running at center of mass energies near 10.6 GeV. Amplitudes and phases of the intermediate resonances which contribute to this final state are measured. A high precision measurement of the ratio of branching fractions is performed: BR(Ds+ -> pi+pi-pi+)/BR(Ds+ -> K+ K- pi+)=0.199 +/- 0.004 +/- 0.009. Using a model-independent partial wave analysis, the amplitude and phase of the S-wave have been measured.

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arXiv2009

Measurement of the Branching Fraction and Lambda-bar Polarization in B0 -> Lambda-bar p pi-

We present a measurement of the B0 --> Lambda-bar p pi- branching fraction performed using the BaBar detector at the PEP-II asymmetric e+e- collider. Based on a sample of 467 million BB-bar pairs we measure B(B0 --> Lambda-bar p pi-) = [3.07 pm 0.31 (stat.) pm 0.23 (syst.)] x 10^{-6}. The measured differential spectrum as a function of the dibaryon invariant mass m(Lambda p) shows a near-threshold enhancement similar to that observed in other baryonic B decays. We study the Lambda-bar polarization as a function of Lambda-bar energy in the B0 rest frame (E*_Lambda) and compare it with theoretical expectations of fully longitudinally right-polarized Lambda-bar at large E*_Lambda.

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