Based on the full BABAR data sample of 466.5 million BB¯ pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to ...distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B→Xueν decays from the CKM-favored B→Xceν decays, and from various other backgrounds, and determine the total semileptonic branching fraction B(B→Xeν)=(10.34±0.04stat±0.26syst)%, averaged over B± and B0 mesons. We determine the spectrum and branching fraction for charmless B→Xueν decays and extract the CKM element |Vub|, by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1 GeV/c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element |Vub| are presented, with the lower limit on the electron momentum varied from 0.8 GeV/c to the kinematic endpoint. We determine |Vub| using each of these different calculations and find, |Vub|=(3.794±0.107exp −0.219 SF+0.292 −0.068 theory+0.078)×10−3 (De Fazio and Neubert), (4.563±0.126exp −0.208 SF+0.230 −0.163 theory+0.162)×10−3 (Bosch, Lange, Neubert, and Paz), (3.959±0.104exp −0.154 SF+0.164 −0.079 theory+0.042)×10−3 (Gambino, Giordano, Ossola, and Uraltsev), (3.848±0.108exp −0.070 theory+0.084)×10−3 (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.
We propose a simple explanation for the increase of approximately 3 MeV/c2 in the mass value of the X(3872) obtained from D{sup *0} {bar D}{sup 0} decay relative to that obtained from decay to ...J/{psi}{pi}{sup +}{pi}{sup -} If the total width of the X(3872) is 2-3 MeV, the peak position in the D{sup *0} {bar D}{sup 0} invariant mass distribution is sensitive to the final state orbital angular momentum because of the proximity of the X(3872) to D{sup *0} {bar D}{sup 0} threshold. We show that for total width 3 MeV and one unit of orbital angular momentum, a mass shift {approx}3 MeV/c2 is obtained; experimental mass resolution should slightly increase this value. A consequence is that spin-parity 2{sup -} is favored for the X(3872).
The processes e+e−→KS0K±π∓π0 and e+e−→KS0K±π∓η are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb−1 of data collected with ...the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from K*0(Kπ)0, K*(892)±(Kπ)∓, and KS0K±ρ∓ are studied. The J/ψ is observed in all of these channels, and corresponding branching fractions are measured.
We report a Dalitz plot analysis of charmless hadronic decays of charged B mesons to the final state KS0π+π0 using the full BABAR data set of 470.9±2.8 million BB¯ events collected at the Υ(4S) ...resonance. We measure the overall branching fraction and CP asymmetry to be B(B+→K0π+π0)=(31.8±1.8±2.1−0.0+6.0)×10−6 and ACP(B+→K0π+π0)=0.07±0.05±0.03−0.03+0.02, where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for B+→K0π+π0. We find first evidence of a CP asymmetry in B+→K*(892)+π0 decays: ACP(B+→K*(892)+π0)=−0.52±0.14±0.04−0.02+0.04. The significance of this asymmetry, including systematic and model uncertainties, is 3.4 standard deviations. We also measure the branching fractions and CP asymmetries for three other intermediate decay modes.
Here we perform the first measurement on the D0-D0 mixing parameters using a time-dependent amplitude analysis of the decay D0→π+π-π0. The data were recorded with the BABAR detector at center-of-mass ...energies at and near the $Y$(4S) resonance, and correspond to an integrated luminosity of approximately 468.1 fb-1. The neutral D meson candidates are selected from D*(2010)+→D0π$+\atop{s}$ decays where the flavor at the production is identified by the charge of the low-momentum pion, π$+\atop{s}$. The measured mixing parameters are x=(1.5±1.2±0.6)% and y=(0.2±0.9±0.5)%, where the quoted uncertainties are statistical and systematic, respectively.
Using a sample of (470.9±2.8)×106 BB¯ pairs, we measure the decay branching fraction B(B0→D*−π+π−π+)=(7.26±0.11±0.31)×10−3, where the first uncertainty is statistical and the second is systematic. ...Our measurement will be helpful in studies of lepton universality by measuring B(B0→D*−τ+ντ) using τ+→π+π−π+ν¯τ decays, normalized to B(B0→D*−π+π−π+).
We study the process e+e- -> pi+pi-pi+pi-gamma, with a photon emitted from the initial-state electron or positron, using 454.3 fb^-1 of data collected with the BABAR detector at SLAC, corresponding ...to approximately 260,000 signal events. We use these data to extract the non-radiative sigma(e+e- ->pi+pi-pi+pi-) cross section in the energy range from 0.6 to 4.5 Gev. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.
We present a measurement of the asymmetry ACP between same-sign inclusive dilepton samples scriptl+scriptl+ and scriptl-scriptl- (scriptl=e, mu ) from semileptonic B decays in Y(4S) arrow right BB- ...events, using the complete data set recorded by the BABAR experiment near the Y(4S) resonance, corresponding to 471x106 BB- pairs. The asymmetry ACP allows comparison between the mixing probabilities P(B-0 arrow right B0) and P(B0 arrow right B-0), and therefore probes CP and T violation. The result, ACP=-3.9+ or -3.5(stat) + or -1.9(syst)x10-3, is consistent with the standard model expectation.
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