1,712 research outputs found

    Angular distributions in the decay B -> K*l(+)l(-)

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    We use a sample of 384 X 10(6) B (B) over bar 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(ee) 3.2 GeV/c(2), we measure A(FB) = 0.76(-0.32)(+0.52) +/- 0.07 F-L = 0.71(-0.22)(+0.20) +/- 0.04

    Measurement of the Branching Fractions of B̅ →D**l-ν̅ l Decays in Events Tagged by a Fully Reconstructed B Meson

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    We report a measurement of the branching fractions of B̅ →D**l-ν̅ l decays based on 417 fb-1 of data collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e+e- storage rings. Events are selected by fully reconstructing one of the B mesons in a hadronic decay mode. A fit to the invariant mass differences m(D(*)π)-m(D(*)) is performed to extract the signal yields of the different D** states. We observe the B̅ →D**l-ν̅ l decay modes corresponding to the four D** states predicted by heavy quark symmetry with a significance greater than 5 standard deviations including systematic uncertainties

    Measurement of the Branching Fractions of (B)over-bar -> D**l(-)(v)over-bar(l) Decays in Events Tagged by a Fully Reconstructed B Meson

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    We report a measurement of the branching fractions of B -> D**l(-)(v) over bar (l) decays based on 417 fb(-1) of data collected at the Y(4S) resonance with the BABAR detector at the PEP-II e(+) e(-) storage rings. Events are selected by fully reconstructing one of the B mesons in a hadronic decay mode. A fit to the invariant mass differences m(D-(*())pi) - (m(D-(*())) is performed to extract the signal yields of the different D** states. We observe the (B) over bar -> D**l(-)(v) over bar (l) decay modes corresponding to the four D** states predicted by heavy quark symmetry with a significance greater than 5 standard deviations including systematic uncertainties

    Search for lepton-number violating B + → X -l + l ′ + decays

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    We report on a search for eleven lepton-number violating processes B+→X-l+l′+ with X-=K-, π-, ρ-, K*-, or D- and l+/l′+=e+ or μ+, using a sample of 471±3 million BB̄ events collected with the BABAR detector at the PEP-II e+e- collider at the SLAC National Accelerator Laboratory. We find no evidence for any of these modes and place 90% confidence level upper limits on their branching fractions in the range (1.5-26)×10-7. © 2014 American Physical Society

    CMS pixel detector: Overview

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    An overview of the compact muon solenoid pixel detector effort is presented. Pixel detectors are being built for use at the large hadron collider beginning in the year 2007. It is reported that a good progress is made in 2002 on the critical issues of readout chip and token bit manager design, bump bonding and sensor testing. (Edited abstract) 8 Refs

    A Search for the Rare Decays B→πl+l− and B0→ηl+l−

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    We present the results of a search for the rare flavor-changing neutral-current decays B --> pi l+l- (pi=pi+/-, pi0 and l = e,mu) and B0 --> eta l+l- using a sample of e+e- --> Y(4S) BB decays decays corresponding to 428 fb^-1 of integrated luminosity collected by the BABAR detector. No significant signal is observed, and we set an upper limit on the isospin and lepton-flavor averaged branching fraction of BF(B --> pi l+l-) eta l+l-) pi+ e+e-, B0 --> pi0 e+e-, B+ --> pi+ mu+mu-, B0 --> pi0 mu+mu-, B0 --> eta e+e-, and B0 --> eta mu+mu-

    Search for the rare decays B ---> K l+ l- and B ---> K* l+ l-

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    We present results from a search for the flavor-changing neutral current decays B --> Kl(+)l(-) and B --> K*l(+)l(-), where l(+)l(-) is either an e(+)e(-) or mu(+)mu(-) pair. The data sample comprises 22.7 x 10(6) Y (4S) --> BB decays collected with the BABAR detector at the PEP-II B Factory. We obtain the 90% C. L. upper limits B (B --> Kl(+)l(-)) K*l(+)l(-)) Ke(+/-) mu(-/+) and B --> K* e(+/-) mu(-/+)

    Measurement of lepton mass squared moments in B →Xc l ν ̄l decays with the Belle II experiment

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    We present measurements of the first to fourth moments of the lepton mass squared q2 of B→Xc l ν ̄l decays for l=e, μ and with Xc a hadronic system containing a charm quark. These results use a sample of electron-positron collisions at the Υ(4S) resonance corresponding to 62.8 fb-1 of integrated luminosity and collected by the Belle II 2 experiment in 2019 and 2020. To identify the Xc system and reconstruct q2, one of the B mesons from an Υ(4S)→BB ̄ decay is fully reconstructed in a hadronic decay mode using a multivariate B tagging algorithm. We report raw and central moments for q2>1.5 GeV2/c4 up to q2>8.5 GeV2/c4, probing up to 77% of the accessible B→Xc l ν ̄l phase space. This is the first measurement of moments in the experimentally challenging range of [1.5,2.5] GeV2/c4. The results can be used for a new determination of |Vcb| using inclusive B→Xc l ν ̄l decays

    Direct CP, lepton flavor, and isospin asymmetries in the decays B -> K((*))l(+)l(-)

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    We measure branching fractions and integrated rate asymmetries for the rare decays B -> K((*))l(+)l(-), where l(+)l(-) is either e(+)e(-) or mu(+)mu(-), using a sample of 384x10(6) BB events collected with the BABAR detector at the PEP-II e(+)e(-) collider. We find no evidence for direct CP or lepton-flavor asymmetries. However, 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

    Measurement of the (B)over-bar lifetime and the B-0(B)over-bar(0) oscillation frequency using partially reconstructed (B)over-bar(0)-> D*+ l-(v)over-bar(l) decays

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    We present a simultaneous measurement of the (B) over bar (0) lifetime tau(B0) and B-0(B) over bar (0) oscillation frequency Delta m(d). We use a sample of about 50 000 partially reconstructed (B) over bar (0)-> D(*+)l(-)nu(l) decays identified with the BABAR detector at the PEP-II e(+)e(-) storage ring at SLAC. The flavor of the other B meson in the event is determined from the charge of another high-momentum lepton. The results are tau(B0) = (1.504 +/- 0.013(stat)(-0.013)(+0.018)(syst)) ps, Delta m(d) = (0.511 +/- 0.007(stat)(-0.006)(+0.007)(syst)) ps(-1)
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