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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Measurement of indirect CP-violating asymmetries in D 0 →K + K - and D 0 →π + π - decays at CDF

We report a measurement of the indirect CP-violating asymmetries (A Γ ) between effective lifetimes of anticharm and charm mesons reconstructed in D 0 →K + K - and D 0 →π + π - decays. We use the full data set of proton-antiproton collisions collected by the Collider Detector at Fermilab experiment and corresponding to 9.7 fb -1 of integrated luminosity. The strong-interaction decay D *+ →D 0 π + is used to identify the meson at production as D 0 or D ¯0 . We statistically subtract D 0 and D ¯0 mesons originating from b-hadron decays and measure the yield asymmetry between anticharm and charm decays as a function of decay time. We measure A Γ (K + K - )=(-0.19±0.15(stat)±0.04(syst))%and A Γ (π + π - )=(-0.01±0.18(stat)±0.03(syst))%. The results are consistent with the hypothesis of CP symmetry and their combination yields A Γ =(-0.12±0.12)%.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of central exclusive π⁺ π⁻ production in p p ¯ collisions at √s = 0.9 and 1.96 TeV at CDF

We measure exclusive π⁺ π⁻ production in proton-antiproton collisions at center-of-mass energies √s = 0.9 and 1.96 TeV in the Collider Detector at Fermilab. We select events with two oppositely charged particles, assumed to be pions, with pseudorapidity |η| < 1.3 and with no other particles detected in |η| < 5.9. We require the π⁺ π⁻ system to have rapidity |y| < 1.0. The production mechanism of these events is expected to be dominated by double pomeron exchange, which constrains the quantum numbers of the central state. The data are potentially valuable for isoscalar meson spectroscopy and for understanding the pomeron in a region of transition between nonperturbative and perturbative quantum chromodynamics. The data extend up to dipion mass M(π⁺ π⁻) = 5000 MeV / c² and show resonance structures attributed to f₀ and f₂ (1270) mesons. From the π⁺ π⁻ and K⁺K⁻ spectra, we place upper limits on exclusive χ c0 (3415) production.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for new physics in high p T like-sign dilepton events at CDF II

We present a search for new physics in events with two high p T leptons of the same electric charge, using data with an integrated luminosity of 6.1 fb -1 . The observed data are consistent with standard model predictions. We set 95% C.L. lower limits on the mass of doubly-charged scalars decaying to like-sign dileptons, m H ±± > 190 - 245 GeV/c 2 , depending on the decay mode and coupling.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of R = B(t --> Wb)/B(t -->Wq) in Top-Quark-Pair Decays Using Dilepton Events and the Full CDF Run II Data Set

We present a measurement of the ratio of the top-quark branching fractions R = B(t --> Wb)/B(t --> Wq) where q represents any quark flavor, in events with two charged leptons, imbalance in total transverse energy, and at least two jets. The measurement uses proton–antiproton collision data at center-of-mass energy 1.96 TeV, corresponding to an integrated luminosity of 8.7 fb -1 collected with the Collider Detector at Fermilab during Run II of the Tevatron. We measure R to be 0.87 ± 0.07, and extract the magnitude of the top-bottom quark coupling to be |Vtb| = 0.93 ± 0.04, assuming three generations of quarks. Under these assumptions, a lower limit of |Vtb| > 0.85(0.87) at 95 (90) percent credibility level is set.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗