Observation of Exclusive Gamma Gamma Production in p pbar Collisions at sqrt{s}=1.96 TeV
ArXiv 1112.0858 (2011)
Abstract:
We have observed exclusive \gamma\gamma production in proton-antiproton collisions at \sqrt{s}=1.96 TeV, using data from 1.11 \pm 0.07 fb^{-1} integrated luminosity taken by the Run II Collider Detector at Fermilab. We selected events with two electromagnetic showers, each with transverse energy E_T > 2.5 GeV and pseudorapidity |\eta| < 1.0, with no other particles detected in -7.4 < \eta < +7.4. The two showers have similar E_T and azimuthal angle separation \Delta\phi \sim \pi; 34 events have two charged particle tracks, consistent with the QED process p \bar{p} to p + e^+e^- + \bar{p} by two-photon exchange, while 43 events have no charged tracks. The number of these events that are exclusive \pi^0\pi^0 is consistent with zero and is < 15 at 95% C.L. The cross section for p\bar{p} to p+\gamma\gamma+\bar{p} with |\eta(\gamma)| < 1.0 and E_T(\gamma) > 2.5$ GeV is 2.48^{+0.40}_{-0.35}(stat)^{+0.40}_{-0.51}(syst) pb.Publisher’s Note: Search for Bs0→μ+μ- and B0→μ+μ- Decays with CDF II [Phys. Rev. Lett. 107, 191801 (2011)]
Physical Review Letters American Physical Society (APS) 107:23 (2011) 239903
Doubly-charged Higgs bosons
Chapter in The Large Hadron Collider and Higgs Boson Research, (2011) 259-283
Abstract:
The standard model includes a Higgs weak doublet whose vacuum expectation value results in the masses of the observed particles. A number of models also predict a Higgs weak triplet, which includes a doubly-charged Higgs boson (H±±). The existence of such a boson could be inferred indirectly by its exchange in measured processes, or observed directly through its production and decay. Measurements of Bhabha scattering, tau decay, muon decay, and (g - 2)μ provide indirect limits on H±± couplings to charged leptons. Direct H±± searches have been performed in e+e- collisions at the Large Electron Positron collider (LEP) and in p-p collisions at the Fermilab Tevatron. The highest mass limits for exclusive H±± couplings to electrons and muons, and for long-lived H±±, are obtained by the Collider Detector at Fermilab (CDF), while the DELPHI detector at CERN obtains the highest mass limits for H±± couplings to taus. Future data at the Tevatron, Large Hadron Collider, and International Linear Collider will increase sensitivity to H±± mass and couplings by about an order of magnitude. © 2011 by Nova Science Publishers, Inc. All rights reserved.Measurements of branching fraction ratios and CP-asymmetries in suppressed B-→D(→K+π-)K- and B-→D(→K+π-)π- decays
Physical Review D - Particles, Fields, Gravitation and Cosmology 84:9 (2011)
Abstract:
We report the first reconstruction in hadron collisions of the suppressed decays B-→D(→K+π-)K- and B-→D(→K+π-)π-, sensitive to the Cabibbo-Kobayashi-Maskawa phase γ, using data from 7fb-1 of integrated luminosity collected by the CDF II detector at the Tevatron collider. We reconstruct a signal for the B -→D(→K+π-)K- suppressed mode with a significance of 3.2 standard deviations, and measure the ratios of the suppressed to favored branching fractions R(K)=[22.0±8.6(stat) ±2.6(syst)]×10-3, R+(K)=[42.6±13. 7(stat)±2.8(syst)]×10-3, R-(K)=[3. 8±10.3(stat)±2.7(syst)]×10-3 as well as the direct CP-violating asymmetry A(K)=-0.82±0.44(stat)±0.09(syst) of this mode. Corresponding quantities for B-→D(→K +π-)π- decay are also reported. © 2011 American Physical Society.Top-quark mass measurement using events with missing transverse energy and jets at CDF
Physical Review Letters 107:23 (2011)