In this paper we present a precise measurement of the total ZZ production cross section in pp collisions at {surd}s= 1.96 TeV, using data collected with the CDF II detector corresponding to an integrated luminosity of approximately 6 fb-1. The result is obtained by combining separate measurements in the four-charged (llll), and two-charged-lepton and two-neutral-lepton (llvv) decay modes of the Z. The combined measured cross section for pp {to} ZZ is 1.64^(+0.44)_(-0.38) pb. This is the most precise measurement of the ZZ production cross section in 1.96 TeV pp collisions to date.
We measure exclusive $pi^+pi^-$ production in proton-antiproton collisions at center-of-mass energies $sqrt{s}$ = 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 $|eta| < 1.3$ and with no other particles detected in $|eta| < 5.9$. We require the $pi^+pi^-$ 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 $M(pi^+pi^-)$ = 5000 MeV/$c^2$ and show resonance structures attributed to $f_0$ and $f_2(1270)$ mesons. From the $pi^+pi^-$ and $K^+K^-$ spectra, we place upper limits on exclusive $chi_{c0}(3415)$ production.
Diboson production ($WW+WZ+ZZ$) has been observed at the Tevatron in hadronic decay modes dominated by the $WW$ process. This paper describes the measurement of the cross section of $WZ$ and $ZZ$ events in final states with large $mett$ and using $b$-jet identification as a tool to suppress $WW$ contributions. Due to the limited energy resolution, we cannot distinguish between partially hadronic decays of $WZ$ and $ZZ$, and we measure the sum of these processes. The number of signal events is extracted using a simultaneous fit to the invariant mass distribution of the two jets for events with two $b$-jet candidates and events without two $b$-jet candidates. We measure a cross section $sigma(pbar{p}to WZ,ZZ) = 5.8^{+3.6}_{-3.0}$ pb, in agreement with the standard model.
The leptonic asymmetry in semileptonic ttbar decays is measured with the CDF detector using the full Tevatron Run II dataset, which corresponds to 9.4 fb^-1 of integrated luminosity. The measured asymmetry is extrapolated to the full kinematic range and the measured value of A_FB^lep = 0.094^+0.032_-0.029 is compared to the NLO prediction A_FB^lep = 0.038 +/- 0.003.
We present the results of a search for pair production of a heavy top-like (t) quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb-1 collected by the CDF II detector in pp collisions at {surd}s = 1.96 TeV. We perform parallel searches for t to Wb and t to Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t quark mass, we set upper limits on the t bar{t} production cross section and exclude a standard model fourth-generation t quark decaying to W b (W q) with mass below 358 (340) GeV/c2 at 95% CL.
The latest results of the ATLAS experiment for the production of a top-quark pair in association with a photon using proton-proton collision data from the LHC at a centre-of-mass energy of 13 TeV are summarised here. This includes inclusive and differential cross-sections measurements performed in single-lepton and dilepton final states in a fiducial volume corresponding to the experimental acceptance.
T. Aaltonen
,B. Alvarez Gonzalez
,S. Amerio
.
(2011)
.
"Measurement of ZZ production in leptonic final states at {surd}s of 1.96 TeV at CDF"
.
Matteo Bauce
هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا