Observation of the decay B-->J/psietaK and search for X(3872)-->J/psieta

We report the observation of the B meson decay B+/- -->J/psietaK+/- and evidence for the decay B0-->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+/- -->J/psietaK+/-) = [10.8 +/- 2.3(stat) +/- 2.4(syst)] x 10(-5) and B(B0-->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+/- -->X(3872)K+/-,X(3872)-->J/psieta and determine an upper limit of B[B +/- -->X(3872)K+/- -->J/psietaK+/-] < 7.7 x 10(-6) at 90% confidence level.     

Search for the rare leptonic decay B+-->mu(+)nu(mu)

We have performed a search for the rare leptonic decay B+-->mu(+)nu(mu) with data collected at the Upsilon(4S) resonance by the BABAR experiment at the PEP-II storage ring. In a sample of 88.4 x 10(6) BB pairs, we find no significant evidence for a signal and set an upper limit on the branching fraction B(B+-->my(+)nu(my))< 6.6 x 10(-6) at the 90% confidence level.     

Measurement of the CP asymmetry amplitude sin2beta with B0 mesons

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 x 10(6) Upsilon(4S)-->B(-)B decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B(0) or B(-0) from its decay products. The amplitude of the CP asymmetry, which in the standard model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta=0.741+/-0.067(stat)+/-0.034(syst) and |lambda|=0.948+/-0.051(stat)+/-0.030(syst). The magnitude of lambda is consistent with unity, in agreement with the standard model expectation of no direct CP violation in these modes.     

Evidence of a broad structure at an invariant mass of 4.32 GeV/c2 in the reaction e+e- --> pi+pi-psi(2S) measured at BABAR

We present a measurement of the cross section of the process e(+)e(-)-->pi(+)pi(-)psi(2S) from threshold up to 8 GeV center-of-mass energy using events containing initial-state radiation, produced at the SLAC PEP-II e(+)e(-) storage rings. The study is based on 298 fb(-1) of data recorded with the BABAR detector. A structure is observed in the cross section not far above threshold, near 4.32 GeV. We also investigate the compatibility of this structure with the Y(4260) previously reported by this experiment.     

Observation of decays B0-->Ds(*)+ pi- and B0-->Ds(*)- K+

We report the observation of decays B{0}-->D{s}{(*)+}pi- and B{0}-->D{s}{(*)-}K+ in a sample of 230 x 10(6) Upsilon(4S)-->BB[over] events recorded with the BABAR detector at the SLAC PEP-II asymmetric-energy e+ e- storage ring. We measure the branching fractions B(B{0}-->D{s}{+}pi-)=(1.3+/-0.3(stat)+/-0.2(syst))x10(-5), B(B{0}-->D{s}{-} K+)=(2.5+/-0.4(stat)+/-0.4(syst))x10(-5), B(B{0}-->D{s}{*+}pi-)=(2.8+/-0.6(stat)+/-0.5(syst))x10(-5), and B(B{0}-->D{s}{*-}K+)=(2.0+/-0.5(stat)+/-0.4(syst))x10(-5). The significances of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is the first observation of B{0}-->D{s}{+}pi-, B{0}-->D{s}{*+}pi-, and B{0}-->D{s}{*-}K+ decays.     

Measurement of the Time-Dependent CP Asymmetry in B;{0}-->D_{CP};{(*)}h;{0} Decays

We report a measurement of the time-dependent CP-asymmetry parameters S and C in color-suppressed B{0}-->D{(*)0}h{0} decays, where h{0} is a pi{0}, eta, or omega meson, and the decays to one of the CP eigenstates K+K-, K{S}{0}pi{0}, or K{S}{0}omega. The data sample consists of 383 x 10{6} Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The results are S=-0.56+/-0.23+/-0.05 and C=-0.23+/-0.16+/-0.04, where the first error is statistical and the second is systematic.     

Measurement of CP-violating asymmetries in B0-->D*(+/-)D(-/+)

We present updated measurements of CP-violating asymmetries in the decays B0-->D*(+/-)D(-/+) and B0-->D+D- using (383+/-4) x 10(6)B(B) pairs collected by the BABAR detector at the SLAC PEP-II B factory. We determine the time-integrated CP asymmetry A(D*(+/-)D(-/+))=0.12+/-0.06+/-0.02, and the time-dependent asymmetry parameters to be C(D*+D-)=0.18+/-0.15+/-0.04, S(D*+D-)=-0.79+/-0.21+/-0.06, C(D*-D+)=0.23+/-0.15+/-0.04, S(D*-D+)=-0.44+/-0.22+/-0.06, C(D+D-)=0.11+/-0.22+/-0.07, and S(D+D-)=-0.54+/-0.34+/-0.06, where the first uncertainty is statistical and the second is systematic.     

Observation of B0 meson decay to a 1 +/(1260)pi /+

We present a measurement of the branching fraction of the decay B(0)-->a1 (+/)(1260)pi(/+) with a1 (+/)(1260)-->pi(/+)pi(+/)pi(+/). The data sample corresponds to 218 x 10(6) BB[over ] pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We measure the branching fraction Beta(B(0)-->a1(+/)(1260)pi(/+))Beta(a1(+/)(1260)-->pi(/+)pi(+/)pi(+/)) = (16.6+/1.9+/1.5) x 10(-6), where the first error quoted is statistical and the second is systematic.     

Measurement of the spin of the omega(-) hyperon

A measurement of the spin of the Omega(-) hyperon produced through the exclusive process Xi(c)(0)-->Omega(-)K(+) is presented using a total integrated luminosity of 116 fb(-1) recorded with the BABAR detector at the e(+)e(-) asymmetric-energy B factory at SLAC. Under the assumption that the Xi(c)(0) has spin 1/2, the angular distribution of the Lambda from Omega(-)-->LambdaK(-) decay is inconsistent with all half-integer Omega(-) spin values other than 3/2. Lower statistics data for the process Omega(c)(0)-->Omega(-)pi(+) from a 230 fb(-1) sample are also found to be consistent with Omega(-) spin 3/2. If the Xi(c)(0) spin were 3/2, an Omega(-) spin of 5/2 could not be excluded.