Observation of the Decay B=> J/psi eta K and Search for X(3872)=> J/psi eta

We report the observation of the $B$ meson decay $B^\pm\to J/\psi \eta K^\pm$ and evidence for the decay $B^0\to J/\psi \eta K^0_S$, using {90} million $BBbar$ events collected at the \ensuremath{\Upsilon{(4S)}}\xspace resonance with the $BaBar$ detector at the PEP-II $e^+ e^-$ asymmetric-energy storage ring. We obtain branching fractions of $\cal{B}$$(B^\pm\to J/\psi \eta K^{\pm}$)=$(10.8\pm 2.3(\rm{stat.})\pm 2.4(\rm{syst.}))\times 10^{-5}$ and $\cal{B}$$(B^0\to J/\psi\eta K_{\rm{S}}^{0}$)=$(8.4\pm 2.6(\rm{stat.})\pm 2.7(\rm{syst.}))\times 10^{-5}$. We search for the new narrow mass state, the X(3872), recently reported by the Belle Collaboration, in the decay B^\pm\to X(3872)K^\pm, X(3872)\to \jpsi \eta and determine an upper limit of $\cal{B}$(B^\pm \to X(3872) K^\pm \to \jpsi \eta K^\pm) $<7.7\times 10^{-6}$ at 90% C.L.Comment: 7 pages and two figures, submitted to Phys. Rev. Lett

Search for lepton-flavor violation in the decay tau(-)-> l(-)l(+)l-

A search for the lepton-flavor-violating decay of the tau into three charged leptons has been performed using 91.5 fb(-1) of data collected at an e(+)e(-)center-of-mass energy around 10.58 GeV with the BABAR detector at the SLAC storage ring PEP-II. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1-3)x10(-7) at 90% confidence level

J/Ψ production via initial state radiation in e+e -→ μ+μ-γ at an e +e- center-of-mass energy near 10.6 GeV

We have studied the process e+e -→μ+μ-γ at a center-of-mass energy near the γ(4S) resonance for a μ+μ- invariant mass range near the J/Ψ mass and measured the cross section σ(e+e-→J/Ψ γt →μ +μ-γ). The data set, corresponding to an integrated luminosity of 88.4 fb-1, was collected using the BABAR detector at the SLAC PEP-II collider. From the measured cross section we extract the product Γ(J/Ψ→e+e-)B(J/ Ψ→μ+μ-) = 0.330±0.008±0.007 keV. Using the world averages for B(J/Ψ →μ+μ - and B(J/Ψ→e+e-), we derive the J/Ψ electronic and total widths: Γ(J/Ψ→e+e -) = 5.61 ±0.20 keV and Γ = 94.7 ± 4.4 keV. © 2004 The American Physical Society

Observation of the decay B--&gt;J/psietaK and search for X(3872)--&gt;J/psieta.

We report the observation of the B meson decay B+/- --&gt;J/psietaK+/- and evidence for the decay B0--&gt;J/psietaK0S, using 90 x 10(6) BB; events collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II e+e- asymmetric-energy storage ring. We obtain branching fractions of B(B+/- --&gt;J/psietaK+/-) = [10.8 +/- 2.3(stat) +/- 2.4(syst)] x 10(-5) and B(B0--&gt;J/psietaK0S) = [8.4 +/- 2.6(stat) +/- 2.7(syst)] x 10(-5). We search for the new narrow mass state, the X(3872), recently reported by the Belle Collaboration, in the decay B+/- --&gt;X(3872)K+/-,X(3872)--&gt;J/psieta and determine an upper limit of B[B +/- --&gt;X(3872)K+/- --&gt;J/psietaK+/-] &lt; 7.7 x 10(-6) at 90% confidence level

Measurement of the B+/B0 production ratio from the Υ(4S) meson using B+ → J/ψK+ and B 0 → J/ψKS0 decays

We report a measurement of the production ratio of charged and neutral B mesons from Υ(4S) decays based on the ratio of efficiency-corrected yields for the charmonium modes J/ψK+ and J/ψKs0 with 81.9 fb-1 of data collected with the BABAR detector on the Υ(4S) resonance at 10.580 GeV. We find a value of 1.006 ±0.036(stat)±0.031(syst) for the ratio R+/0= Γ(Υ(4S) → B+B-)/Γ(Υ(4S)→ B0B̄0). © 2004 The American Physical Society

Measurement of the electron energy spectrum and its moments in inclusive B→Xeν decays

We report a measurement of the inclusive electron energy spectrum for semileptonic decays of B mesons in a data sample of 52 million γ(45)→BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We determine the branching fraction, first, second, and third moments of the spectrum for lower cutoffs on the electron energy between 0.6 and 1.5 GeV. We measure the partial branching fraction to be B(B→Xeν,Ee&gt;0.6 GeV)= [10.36±0. 06(stat.)±0.23(sys.)]%. © 2004 The American Physical Society

Measurement of the B+/B0 production ratio from the Υ(4S) meson using B+ → J/ψK+ and B 0 → J/ψKS0 decays

We report a measurement of the production ratio of charged and neutral B mesons from Υ(4S) decays based on the ratio of efficiency-corrected yields for the charmonium modes J/ψK+ and J/ψKs0 with 81.9 fb-1 of data collected with the BABAR detector on the Υ(4S) resonance at 10.580 GeV. We find a value of 1.006 ±0.036(stat)±0.031(syst) for the ratio R+/0= Γ(Υ(4S) → B+B-)/Γ(Υ(4S)→ B0B̄0). © 2004 The American Physical Society

Branching fraction measurements of B → ηcK decays

We study the decays B+ → ηcK+ and B0 → ηcK0, where the ηc is reconstructed in the KS0K ±π∓ and K+K- π0 decay modes. Results are based on a sample of 86 B B̄ pairs collected with the BABAR detector at the SLAC e+e- B Factory. We measure the product of branching fractions B(B+ → ηcK+) ×B(ηc→KK̄π)= (7.40±0.50±0.70)×10-5 and B(B 0→ηcK0) ×B(ηc→KK̄π)=(6.48±0.85±0.71) ×10-5, where the first error is statistical and the second is systematic, In addition, we search for B → ηcK events with ηc→2(K+K-) and ηc→ φφ and determine the ηc decay branching fraction ratios B(ηc →(K+K-)) /B(ηc→KK̄π)=(2.3±0.7±0.6) ×10-2 and B(ηc→φφ) /B(ηc→KK̄π)=(5.5±1.4±0.5) ×10-2

J/Ψ production via initial state radiation in e+e -→ μ+μ-γ at an e +e- center-of-mass energy near 10.6 GeV

We have studied the process e+e -→μ+μ-γ at a center-of-mass energy near the γ(4S) resonance for a μ+μ- invariant mass range near the J/Ψ mass and measured the cross section σ(e+e-→J/Ψ γt →μ +μ-γ). The data set, corresponding to an integrated luminosity of 88.4 fb-1, was collected using the BABAR detector at the SLAC PEP-II collider. From the measured cross section we extract the product Γ(J/Ψ→e+e-)B(J/ Ψ→μ+μ-) = 0.330±0.008±0.007 keV. Using the world averages for B(J/Ψ →μ+μ - and B(J/Ψ→e+e-), we derive the J/Ψ electronic and total widths: Γ(J/Ψ→e+e -) = 5.61 ±0.20 keV and Γ = 94.7 ± 4.4 keV. © 2004 The American Physical Society