Evidence for CP violation in B0-->J/psipi0 decays

We present measurements of the branching fraction and time-dependent CP asymmetries in B0-->J/psipi0 decays based on 466 x 10(6) Upsilon(4S)-->BB over events collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We measure the CP asymmetry parameters S= -1.23+/-0.21(stat)+/-0.04(syst) and C= -0.20+/-0.19(stat)+/-0.03(syst), where the measured value of (S, C) is 4.0 standard deviations from (0, 0) including systematic uncertainties. The branching fraction is determined to be B(B0-->J/psipi0)=[1.69+/-0.14(stat)+/-0.07(syst)]x10(-5).     

Observation of tree-level B decays with ss production from gluon radiation

We report on our search for decays proceeding via a tree-level b-->c quark transition in which a gluon radiates into an ss[over ] pair. We present observations of the decays B;{-}-->D_{s};{+}K;{-}pi;{-} and B[over ];{0}-->D_{s};{+}K_{S};{0}pi;{-} and evidence for B;{-}-->D_{s};{+}K;{-}K;{-} and set upper limits on the branching fractions for B[over ];{0}-->D_{s};{+}K_{S};{0}pi;{-} and B;{-}-->D_{s};{+}K;{-}K;{-} using 383x10;{6} Upsilon(4S)-->BB[over ] events collected by the BABAR detector at SLAC. We present evidence that the invariant mass distributions of D_{s};{+}K;{-} pairs from B;{-}-->D_{s};{+}K;{-}pi;{-} decays are inconsistent with the phase-space model, suggesting the presence of charm resonances lying below the D_{s};{+}K;{-} threshold.     

Measurements of partial branching fractions for B-->Xulnu and determination of |Vub|

We present partial branching fractions for inclusive charmless semileptonic B decays B[over ]-->X_{u}lnu[over ], and the determination of the Cabibbo-Kobayashi-Maskawa matrix element |V_{ub}|. The analysis is based on a sample of 383 x 10;{6} Upsilon(4S) decays into BB[over ] pairs collected with the BABAR detector at the SLAC PEP-II e;{+}e;{-} storage rings. We select events using the invariant mass M_{X} of the hadronic system, the invariant mass squared, q;{2}, of the lepton and neutrino pair, the kinematic variable P+, or one of their combinations. We then determine partial branching fractions in limited regions of phase space: DeltaB=(1.18+/-0.09_{stat}+/-0.07_{syst}+/-0.01_{theor})x10;{-3} (M_{X}<1.55 GeV/c;{2}), DeltaB=(0.95+/-0.10_{stat}+/-0.08_{syst}+/-0.01_{theor})x10;{-3} (P+<0.66 GeV/c), and DeltaB=(0.81+/-0.08_{stat}+/-0.07_{syst}+/-0.02_{theor})x10;{-3} (M_{X}<1.7 GeV/c;{2}, q;{2}>8 GeV;{2}/c;{4}). Corresponding values of |V_{ub}| are extracted using several theoretical calculations.     

Observation of B+-->a1+(1260)K0 and B0-->a1-(1260)K+

We present branching fraction measurements of the decays B(+)-->a(1)(+)(1260)K(0) and B(0)-->a(1)(-)(1260)K(+) with a(1)(+/-)(1260)-->pi(-/+)pi(+/-)pi(+/-). The data sample corresponds to 383 x 10(6) BB pairs produced in e(+)e(-) annihilation through the Upsilon(4S) resonance. We measure the products of the branching fractions B(B(+)-->a(1)(+)(1260)K(0)B(a(1)(+)(1260)-->pi(-)pi(+)pi(+))=(17.4+/-2.5+/-2.2) x 10(-6) and B(B(0)-->a(1)(-)(1260)K(+)B(a(1)(-)(1260)-->pi(+)pi(-)pi(-)) = (8.2+/-1.5+/-1.2) x 10(-6). We also measure the charge asymmetries A(ch)(B(+)-->a(1)(+)(1260)K(0) = 0.12+/-0.11+/-0.02 and A(ch)(B(0)-->a(1)(-)(1260)K+) = -0.16+/-0.12+/-0.01. The first uncertainty quoted is statistical and the second is systematic.     

Search for production of invisible final states in single-photon decays of Υ(1S)

We search for single-photon decays of the Υ(1S) resonance, Υ → γ + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A?, or a pair of dark matter particles, χχ. Both A? and χ are assumed to have zero spin. We tag Υ(1S) decays with a dipion transition Υ(2S) → π?π?Υ(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m(A?) ≤ 9.2 GeV and m(χ) ≤ 4.5 GeV in the sample of 98 × 10? Υ(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.     

Slow magnetic order-order transition in the spin chain antiferromagnet Ca3Co2O6

Using powder neutron diffraction, we have discovered an unusual magnetic order-order transition in the Ising spin chain compound Ca3Co2O6. On lowering the temperature, an antiferromagnetic phase with a propagation vector k=(0.5,-0.5,1) emerges from a higher temperature spin density wave structure with k=(0,0,1.01). This transition occurs over an unprecedented time scale of several hours and is never complete.     

The use of PDE centres in the local RBF Hermitian method for 3D convective-diffusion problems

In this work an extension is proposed to the Local Hermitian Interpolation (LHI) method; a meshless numerical method based on interpolation with small and heavily overlapping radial basis function (RBF) systems. This extension to the LHI method uses interpolation functions which themselves satisfy the partial differential equation (PDE) to be solved. In this way, a much improved reconstruction of partial derivatives can be obtained, resulting in significantly improved accuracy in many cases.     

Improved measurement of CP violation in neutral B decays to cc[over]s

We present updated measurements of time-dependent CP asymmetries in fully-reconstructed neutral B decays to several CP eigenstates containing a charmonium meson. The measurements use a data sample of (383+/-4)x10(6) Upsilon(4S)-->BB[over] decays collected with the BABAR detector at the PEP-II B factory. We determine sin2beta = 0.714+/-0.032(stat)+/-0.018(syst) and |lambda|=0.952+/-0.022(stat)+/-0.017(syst).     

Search for the rare decay B-->pil+ l-

We have performed a search for the flavor-changing neutral-current decays B-->pil+ l-, where l+ l- is either e+ e- or mu+ mu-, using a sample of 230 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector. We observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be B(B-->pil+ l-)<9.1 x 10(-8) at 90% confidence level. We also search for the lepton-flavor-violating decays B-->pie+/- mu-/+ and measure an upper limit on the isospin-averaged branching fraction of B(B-->pie+/- mu-/+)<9.2 x 10(-8) at 90% confidence level.