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Register a new userMeasurement of the anomalous like-sign dimuon charge asymmetry with 9 fb^-1 of p pbar collisions
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We present an updated measurement of the anomalous like-sign dimuon charge asymmetry Aslb for semi-leptonic $b$-hadron decays in 9.0 fb^-1 of p pbar collisions recorded with the D0 detector at a center-of-mass energy of sqrt{s} = 1.96 TeV at the Fermilab Tevatron collider. We obtain Aslb = (-0.787 +- 0.172(stat) +- 0.093 (syst))%. This result differs by 3.9 standard deviations from the prediction of the standard model and provides evidence for anomalously large CP violation in semi-leptonic neutral B decay. The dependence of the asymmetry on the muon impact parameter is consistent with the hypothesis that it originates from semi-leptonic b-hadron decays.
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The DO collaboration has measured the like-sign dimuon charge asymmetry in $p bar{p}$ collisions at the Fermilab Tevatron collider. The result is significantly different from the standard model expectation of CP violation in mixing. In this paper we consider the possible causes of this asymmetry and identify one standard model source not considered before. It decreases the discrepancy of the like-sign dimuon charge asymmetry with the standard model prediction, although does not eliminate it completely.
We present an overview of the measurements of the like-sign dimuon charge asymmetry by the DO Collaboration at the Fermilab Tevatron proton-antiproton Collider. The results differ from the Standard Model prediction of CP violation in mixing and interference of B^0 and B^0_s by 3.6 standard deviations.
At the Fermilab Tevatron proton-antiproton ($pbar{p}$) collider, high-mass electron-neutrino ($e u$) pairs are produced predominantly in the process $p bar{p} rightarrow W(rightarrow e u) + X$. The asymmetry of the electron and positron yield as a function of their pseudorapidity constrain the slope of the ratio of the $u$- to $d$-quark parton distributions versus the fraction of the proton momentum carried by the quarks. This paper reports on the measurement of the electron-charge asymmetry using the full data set recorded by the Collider Detector at Fermilab in 2001--2011 and corresponding to 9.1~fb$^{-1}$ of integrated luminosity. The measurement significantly improves the precision of the Tevatron constraints on the parton-distribution functions of the proton. Numerical tables of the measurement are provided.
A surprisingly large charge symmetry violation of the sea quarks in the nucleon has been proposed in a recent article by Boros et al. as an explanation of the discrepancy between neutrino (CCFR) and muon (NMC) nucleon structure function data at low x. We show that these models are ruled out by the published CDF W charge asymmetry measurements, which strongly constrain the ratio of d and u quark momentum distributions in the proton over the x range of 0.006 to 0.34. This constraint also limits the systematic error from possible charge symmetry violation in the determination of sin^2(theta) from nu-N scattering experiments.
We present measurements of the tWb coupling form factors using information from electroweak single top quark production and from the helicity of W bosons from top quark decays in ttbar events. We set upper limits on anomalous tWb coupling form factors using data collected with the D0 detector at the Tevatron ppbar collider corresponding to an integrated luminosity of 5.4 fb^-1.
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