arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 181 records · Page 10Linked to original sources

arXiv2009

Direct CP, Lepton Flavor and Isospin Asymmetries in the Decays B->K(*)l+l-

We measure rate asymmetries for the rare decays B->K(*)l+l-, where l+l- is either e+e- or mu+mu-, using a sample of 384 million BBbar events collected with the Babar detector at the PEP-II e+e- collider. We find no evidence for direct CP or lepton-flavor asymmetries. For dilepton masses below the J/psi resonance, we find evidence for unexpectedly large isospin asymmetries in both B->Kl+l- and B->K*l+l-, which differ respectively by 3.2 sigma and 2.7 sigma, including systematic uncertainties, from the Standard Model expectations.

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arXiv2009

Measurement of the Semileptonic Decays B --> D tau- nubar_tau and B --> D* tau- nubar_tau

We present measurements of the semileptonic decays B- --> D0 tau- nubar_tau, B- --> D*0 tau- nubar_tau, B0bar --> D+ tau- nubar_tau, and B0bar --> D*+ tau- nubar_tau, which are sensitive to non--Standard Model amplitudes in certain scenarios. The data sample consists of 232x10^6 Upsilon(4S) --> BBbar decays collected with the BaBar detector at the PEP-II e+e- collider. We select events with a D or D* meson and a light lepton (ell=e or mu) recoiling against a fully reconstructed B meson. We perform a fit to the joint distribution of lepton momentum and missing mass squared to distinguish signal B --> D(*) tau- nubar_tau (tau- --> ell- nubar_ell nu_tau) events from the backgrounds, predominantly B --> D(*) ell- nubar_ell. We measure the branching-fraction ratios R(D) == BR(B --> D tau- nubar_tau) / BR(B --> D ell- nubar_ell) and R(D*) == BR(B --> D* tau- nubar_tau) / BR(B --> D* ell- nubar_ell) and, from a combined fit to B- and B0bar channels, obtain the results R(D)=(41.6 +/- 11.7 +/- 5.2)% and R(D*)=(29.7 +/- 5.6 +/- 1.8)%, where the uncertainties are statistical and systematic. Normalizing to measured B- --> D(*)0 ell- nubar_ell branching fractions, we obtain BR(B --> D tau- nubar_tau)=(0.86 +/- 0.24 +/- 0.11 +/- 0.06)% and BR(B --> D* tau- nubar_tau)=(1.62 +/- 0.31 +/- 0.10 +/- 0.05)%, where the additional third uncertainty is from the normalization mode. We also present, for the first time, distributions of the lepton momentum, p*_ell, and the squared momentum transfer, q^2.

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arXiv2009

Search for the decay B^+ --> K_S^0 K_S^0 pi^+

We search for charmless decays of charged B mesons to the three-body final state K_S^0 K_S^0 pi+. Using a data sample of 423.7 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector, corresponding to (465.1 +- 5.1)X10^6 BB-bar pairs, we find no significant signal and determine a 90% confidence level upper limit on the branching fraction of 5.1X10^-7.

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arXiv2009

Search for Dimuon Decays of a Light Scalar in Radiative Transitions Y(3S) -> gamma A0

The fundamental nature of mass is one of the greatest mysteries in physics. The Higgs mechanism is a theoretically appealing way to account for the different masses of elementary particles and implies the existence of a new, yet unseen particle, the Higgs boson. We search for evidence of a light scalar (e.g. a Higgs boson) in the radiative decays of the narrow Y(3S) resonance: Y(3S)->gamma A0, A0->mu+mu-. Such an object appears in extensions of the Standard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. We find no evidence for such processes in a sample of 122*10^6 Y(3S) decays collected by the BABAR collaboration at the PEP-II B-factory, and set 90% C.L. upper limits on the branching fraction product B(Y(3S)-> gamma A0)*B(A0->mu+mu-) at (0.25-5.2)*10^{-6} in the mass range 0.212<= m(A0)<=9.3 GeV. We also set a limit on the dimuon branching fraction of the eta_b meson B(eta_b->mu+mu-)<0.8% at 90% C.L. The results are preliminary.

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arXiv2009

Observation of B Meson Decays to omegaK* and Improved Measurements for omegarho and omega f_0

We present measurements of B meson decays to the final states omegaK*, omegarho, and omega f_0, where K* indicates a spin 0, 1, or 2 strange meson. The data sample corresponds to 465x10^6 BBbar pairs collected with the BABAR detector at the PEP-II e+e- collider at SLAC. B meson decays involving vector-scalar, vector-vector, and vector-tensor final states are analyzed; the latter two shed new light on the polarization of these final states. We measure the branching fractions for nine of these decays; five are observed for the first time. For most decays we also measure the charge asymmetry and, where relevant, the longitudinal polarization f_L.

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arXiv2009

Measurements of time-dependent CP asymmetries in B0 --> D()+D()- decays

We present new measurements of time-dependent CP asymmetries for B0 --> D(*)+D(*)- decays using (467 +/- 5) X 10^6 BB pairs collected with the BaBar detector located at the PEP-II B Factory at the Stanford Linear Accelerator Center. We determine the CP-odd fraction of the B0 --> D*+D*- decays to be R_perp = 0.158 +/- 0.028 +/- 0.006 and find CP asymmetry parameters for the CP-even component of the decay S_+ = -0.76 +/- 0.16 +/- 0.04 and C_+ = 0.00 +/- 0.12 +/- 0.02. We measure S = -0.63 +/- 0.36 +/- 0.05 and C = -0.07 +/- 0.23 +/- 0.03 for B0 --> D+D-, S = -0.62 +/- 0.21 +/- 0.03 and C = 0.08 +/- 0.17 +/- 0.04 for B0 --> D*+D-$, and S = -0.73 +/- 0.23 +/- 0.05 and C = 0.00 +/- 0.17 +/- 0.03 for B0 --> D+D*-. For the B0 --> D*+/-D-/+ decays, we also determine the CP-violating asymmetry A = 0.008 +/- 0.048 +/- 0.013. In each case, the first uncertainty is statistical and the second is systematic. The measured values for the asymmetries are all consistent with the Standard Model.

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arXiv2009

Evidence for B+ -> K0bar K+

We present measurements of the branching fraction and fraction of longitudinal polarization for the decay B+ -> K*0bar K*+ with a sample of 467 +/- 5 million BBbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at the SLAC National Accelerator Laboratory. We obtain the branching fraction Br(B+ -> K*0bar K*+) = (1.2 +/- 0.5 +/- 0.1) x 10^{-6} with a significance of 3.7 standard deviations including systematic uncertainties. We measure the fraction of longitudinal polarization f_L = 0.75+0.16-0.26 +/- 0.03. The first error quoted is statistical and the second is systematic.

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arXiv2009

Angular Distributions in the Decays B -> K* l+l-

We use a sample of 384 million BBbar events collected with the Babar detector at the PEP-II e+e- collider to study angular distributions in the rare decays B -> K* l+l-, where l+l- is either e+e- or mu+mu-. For low dilepton invariant masses, m(l+l-)<2.5 GeV/c^2, we measure a lepton forward-backward asymmetry AFB=0.24 (+0.18,-0.23) +/- 0.05 and K* longitudinal polarization FL=0.35 +/- 0.16 +/- 0.04$. For m(l+l-)>3.2$ GeV/c^2, we measure AFB=0.76 (+0.52,-0.32) +/- 0.07 FL=0.71 (+0.20,-0.22) +/- 0.04.

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arXiv2009

Measurements of ${\cal B}(\bar{B}^0 \to Λ_{c}^{+} \bar{p})$ and ${\cal B}(B^- \to Λ_{c}^{+} \bar{p} π^-)$ and Studies of $Λ_{c}^{+}π^-$ Resonances

We present an investigation of the decays $\bar{B}^0 \to Λ_{c}^{+} \bar{p}$ and $B^- \to Λ_{c}^{+} \bar{p} π^-$ based on $383\times10^6$ $Υ(4S) \to B\bar{B}$ decays recorded with the BABAR detector. We measure the branching fractions of these decays; their ratio is ${\cal B}(B^- \to Λ_{c}^{+} \bar{p} π^-) / {\cal B}(\bar{B}^0 \to Λ_{c}^{+} \bar{p}) = 15.4 \pm 1.8 \pm 0.3$. The $B^- \to Λ_{c}^{+} \bar{p} π^-$ process exhibits an enhancement at the $Λ_{c}^{+} \bar{p}$ threshold and is a laboratory for searches for excited charm baryon states. We observe the resonant decays $\bar{B}^- \to Σ_{c}(2455)^{0} \bar{p}$ and $B^- \to Σ_{c}(2800)^{0} \bar{p}$ but see no evidence for $B^- \to Σ_{c}(2520)^{0} \baver{p}$. This is the first observation of the decay $B^- \to Σ_{c}(2800)^{0} \bar{p}$; however, the mass of the observed excited $Σ_{c}^{0}$ state is $(2846\pm8\pm10)MeV/c^2$, which is somewhat inconsistent with previous measurements. Finally, we examine the angular distribution of the $B^- \to Σ_{c}(2455)^{0} \bar{p}$ decays and measure the spin of the $Σ_{c}(2455)^{0}$ baryon to be 1/2, as predicted by the quark model.

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arXiv2009

Measurement of time dependent CP asymmetry parameters in B0 meson decays to omega K0S, eta'K0, and pi0K0S

We present measurements of the time-dependent CP-violation parameters S and C in the decays omega K0S, eta'K0, reconstructed as eta'K0S and eta'K0L, and pi0K0S. The data sample corresponds to the full BABAR dataset of 467 x 10^6 BB pairs produced at the PEP-II asymmetric-energy e+e- collider at the Stanford Linear Accelerator Center. The results are S_{omega K0S} = 0.55^{+0.26}_{-0.29} +/- 0.02, C_{omega K0S} = -0.52^{+0.22}_{-0.20} +/- 0.03, S_{eta' K0} = 0.57 +/- 0.08 +/- 0.02, C_{eta' K0} = -0.08 +/- 0.06 +/- 0.02, S_{pi0 K0S} = 0.55 +/- 0.20 +/- 0.03, and C_{pi0 K0S} = 0.13 +/- 0.13 +/- 0.03, where the first errors are statistical and the second systematic. These results are consistent with our previous measurements and the world average of sin2beta measured in B0 -> J/psi K0S.

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arXiv2008

Study of hadronic transitions between Y states and observation of Y(4S)-> eta Y(1S) decay

We present a study of hadronic transitions between Y(mS) (m=4,3,2) and Y(nS) (n=2,1) resonances based on 347.5\invfb of data taken with the BABAR detector at the PEP-II storage rings. We report the first observation of Y(4S)-> eta Y(1S) decay with a branching fraction BR((Y(4S)->eta Y(1S))=(1.96+-0.06_{stat} +-0.09_{syst}) x 10^{-4} and measure the ratio of partial widths Gamma(Y(4S)->etaY(1S))/Gamma(Y(4S)->pi+pi-Y(1S))=2.41+- 0.40_{stat}+- 0.12_{syst}. We set 90% CL upper limits on the ratios Gamma(Y(2S)->etaY(1S))/Gamma(Y(2S)->pi+pi-Y(1S))<5.2 x10^{-3}$ and Gamma(Y(3S)->etaY(1S))/Gamma(Y(3S)->pi+pi-Y(1S))<1.9x10^{-2}. We also present new measurements of the ratios Gamma(Y(4S)->pi+pi-Y(2S))/Gamma(Y(4S)->pi+pi-Y(1S))=1.16+- 0.16_{stat}+- 0.14_{syst} and Gamma(Y(3S)->pi+pi-Y(2S))/Gamma(Y(3S)->pi+pi-Y(1S))=0.577+- 0.026_{stat}+- 0.060_{syst}.

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arXiv2008

Measurements of the Semileptonic Decays $\Bb\to D\ell\nub$ and $\Bb\to D^*\ell\nub$ Using a Global Fit to $D X\ell\nub$ Final States

Semileptonic $\bar{B}$ decays to $DX\ell\barν$ ($\ell=e$ or $mu$) are selected by reconstructing $D0\ell$ and $D^+\ell$ combinations from a sample of 230 million $Υ(4S) \to B\bar{B}$ decays recorded with the BaBar detector at the PEPII $e^+e^-$ collider at SLAC. A global fit to these samples in a 3-dimensional space of kinematic variables is used to determine the branching fractions $\mathcal{B}(B^- \to D0\ell\barν) = (2.34 \pm 0.03 \pm 0.13) %$ and $\mathcal{B}(B^- \to D^{*0}\ell\barν) = (5.40 \pm 0.02 \pm 0.21) %$,where the errors are statistical and systematic, respectively. The fit also determines form factor parameters in a HQET-based parameterization, resulting in $ρ_D2 = 1.20 \pm 0.04 \pm 0.07$ for $\bar{B} \to D\ell\barν$ and $ρ_{D^*}2 = 1.22 \pm 0.02 \pm 0.07$ for $\bar{B} \to D^*\ell\barν$ These values are used to obtain the product of the CKM matrix element $|V_{cb}|$ times the form factor at the zero recoil point for both $\bar{B} \to D\ell\barν$ decays, $\mathcal{G}(1)|V_{cb}| = (43.1 \pm 0.8 \pm 2.3)\times 10^{-3}$, and for $\bar{B} \to D^*\ell\barν$ decays, $\mathcal{F}(1)|V_{cb}| = (35.9 \pm 0.2 \pm 1.2)\times 10^{-3}$.

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arXiv2008

Search for the Lepton-Flavor Violating Decays Upsilon(3S) -> e tau and Upsilon(3S) -> mu tau

Charged lepton-flavor violating processes are extremely rare in the Standard Model, but they may occur in several beyond-the-Standard Model theories, including Supersymmetry or models with leptoquarks or compositeness. We present a search for such processes in a sample of 117M Upsilon(3S) decays recorded with the BaBar detector. We place upper limits on the branching fractions BF(Upsilon(3S) -> e tau) < 5.0e-6 and BF(Upilon(3S) -> mu tau) < 4.1e-6 at 90% confidence level. These results are used to place lower limits on the mass scale of beyond-the-Standard Model physics contributing to lepton-flavor violating decays of the Upsilon(3S).

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arXiv2008

Observation of the bottomonium ground state in the decay Upsilon(3S) -> gamma eta_b

We report the results of a search for the bottomonium ground state eta_b(1S) in the photon energy spectrum with a sample of (109 +/- 1) million of Upsilon(3S) recorded at the Upsilon(3S) energy with the BABAR detector at the PEP-II B factory at SLAC. We observe a peak in the photon energy spectrum at E_gamma = 921.2 {+2.1} {-2.8} (stat) +/- 2.4(syst) MeV with a significance of 10 standard deviations. We interpret the observed peak as being due to monochromatic photons from the radiative transition Upsilon(3S) -> gamma eta_b(1S). This photon energy corresponds to an eta_b(1S) mass of $9388.9 {+3.1} {-2.3} (stat) +/- 2.7(syst) MeV/c2. The hyperfine Upsilon(1S)-eta_b(1S) mass splitting is 71.4 {+2.3} {-3.1} (stat) +/- 2.7(syst) MeV/c2. The branching fraction for this radiative Upsilon(3S) decay is estimated to be (4.8 +/- 0.5(stat) +/- 1.2 (syst)) x 10^(-4).

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arXiv2008

Search for B0 -> K+ K-

We report the results of a search for the decay B0 -> K*+ K*- with a sample of 454 +/- 5 million BBbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at the Stanford Linear Accelerator Center. We obtain an upper limit at the 90% confidence level on the branching fraction for Br(B0 -> K*+ K*-) < 2.0 x 10^{-6}, assuming the decay is fully longitudinally polarized.

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arXiv2008

Search for the highly suppressed decays B- -> K+ pi- pi- and B- -> K- K- pi+

We report a search for the decays B- -> K+ pi- pi- and B- -> K- K- pi+, which are highly suppressed in the Standard Model. Using a sample of (467 +/- 5) x 10^6 BBbar pairs collected with the BaBar detector, we do not see any evidence of these decays and determine 90% confidence level upper limits of BF(B- -> K+ pi- pi-) < 9.5 x 10^-7 and BF(B- -> K- K- pi+) < 1.6 x 10^-7 on the corresponding branching fractions, including systematic uncertainties.

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arXiv2008

Observation of B0 -> chi_c0K0 and evidence for B+ -> chi_c0K+

We present the observation of the decay B0 -> chi_c0K*0 as well as evidence of B+ -> chi_c0K*+, with an 8.9 and a 3.6 standard deviation significance, respectively, using a data sample of 454 million Y(4S) -> BB decays collected with the BaBar detector at the PEP-II B meson factory located at the Stanford Linear Accelerator Center (SLAC). The measured branching fractions are: B(B0 -> chi_c0K*0) = (1.7 +/- 0.3 +/- 0.2) * 10^{-4} and B(B+ -> chi_c0K^*+) = (1.4 +/- 0.5 +/- 0.2) * 10^{-4}, where the first quoted errors are statistical and the second are systematic. We obtain a branching fraction upper limit of B(B+ -> chi_c0K*+) < 2.1 * 10^{-4} at the 90% confidence level.

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arXiv2008

Search for the Z(4430)^- at BABAR

We report the results of a search for $Z(4430)^-$ decay to $J/ψπ^-$ or $ψ(2S)π^-$ in $B^{-,0}\to \jpsiπ^- K^{0,+}$ and $B^{-,0}\to \psitwos π^- K^{0,+}$ decays. The data were collected with the BABAR detector at the SLAC PEP-II asymmetric-energy $e^+e^-$ collider operating at center of mass energy 10.58 \gev, and the sample corresponds to an integrated luminosity of 413 fb$^{-1}$. Each $Kπ$ mass distribution exhibits clear $K^{\ast}(892)$ and $K^{\ast}_2(1430)$ signals, and the efficiency-corrected spectrum is well-described by a superposition of the associated Breit-Wigner intensity distributions, together with an $S$-wave contribution obtained from the LASS $I=1/2$ $Kπ$ scattering amplitude measurements. Each $Kπ$ angular distribution varies significantly in structure with $Kπ$ mass, and is represented in terms of low-order Legendre polynomial moments. We find that each $J/ψπ$ or $ψ(2S)π$ mass distribution is well-described by the reflection of the measured $Kπ$ mass and angular distribution structures. We see no significant evidence for a $Z(4430)^-$ signal for any of the processes investigated, neither in the total $J/ψπ$ or $ψ(2S)π$ mass distribution, nor in the corresponding distributions for the regions of $Kπ$ mass for which observation of the $Z(4430)^-$ signal was reported. We obtain branching fraction upper limits ${\cal{B}}(B^-\to Z^-\bar{K^0}, Z^-\to J/ψπ^-)<1.5\times 10^{-5}$, ${\cal{B}}(B^0\to Z^-K^+, Z^-\to J/ψπ^-)<0.4\times 10^{-5}$, ${\cal{B}}(B^-\to Z^-\bar{K^0}, Z^-\to ψ(2S)π^-)<4.7\times 10^{-5}$, and ${\cal{B}}(B^0\to Z^-K^+, Z^-\to ψ(2S)π^-)<3.1\times 10^{-5}$ at 95% confidence level, where the $Z(4430)^-$ mass and width have been fixed to the reported central values.

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