We present the results of a search in p¯p collisions at s=1.8 TeV for the top quark decaying to a charged Higgs boson (H±). We search for dilepton final states from the decay chain tt¯→HH (or HW, or WW) + bb¯→ll+X. In a sample of 19.3 pb−1 collected during 1992-93 with the Collider Detector at Fermilab, we observe 2 events with a background estimation of 3.0 ± 1.0 events. Limits at 95% C.L. in the (Mtop,MH±) plane are presented. For the case Mtop<MW+Mb, we exclude at 95% C.L. the entire (Mtop,MH±) plane for the branching ratio B(H→τν) larger than 75%. We also interpret the results in terms of the parameter tan β of two-Higgs-doublet models.
We have used 19 pb**-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to dijets. We exclude at 95% confidence level models containing the following new particles: axigluons with mass between 200 and 870 GeV, excited quarks with mass between 80 and 570 GeV, and color octet technirhos with mass between 320 and 480 GeV.
We report the observation and measurement of the rate of diffractive dijet production at the Fermilab Tevatron p¯p collider at s=1.8TeV. In events with two jets of ET>20GeV, 1.8<|η|<3.5, and η1η2>0, we find that the diffractive to nondiffractive production ratio is RJJ=[0.75±0.05(stat)±0.09(syst)]%. By comparing this result, in combination with our measured rate for diffractive W boson production reported previously, with predictions based on a hard partonic pomeron structure, we determine the pomeron gluon fraction to be fg=0.7±0.2.
We present a study of events with Z bosons and hadronic jets produced in $\overline{p}p$ collisions at a center-of-mass energy of 1.8 TeV. The data consist of 6708 $Z \rightarrow e~+e~-$ decays from 106 pb$~{-1}$ of integrated luminosity collected using the CDF detector at the Tevatron Collider. The Z $+ \ge n$ jet cross sections and jet production properties have been measured for n = 1 to 4. The data compare well to predictions of leading order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.
We present a study of events with W bosons and hadronic jets produced in pbar p collisions at a center of mass energy of 1.8 TeV. The data consist of 51400 W^+/- -> e^+/- nu decay candidates from 108 pb^-1 of integrated luminosity collected with the CDF detector at the Tevatron Collider. The cross sections and jet production properties have been measured for W + \geq 1 to \geq 4 jet events. The data are compared to predictions of leading order QCD matrix element calculations with added gluon radiation and simulated fragmentation.
We report on a search for second generation leptoquarks (Phi_2) using a data sample corresponding to an integrated luminosity of 110 pb^{-1} collected at the Collider Detector at Fermilab. We present upper limits on the production cross section as a function of Phi_2 mass, assuming that the leptoquarks are produced in pairs and decay into a muon and a quark with branching ratio beta. Using a Next-to-Leading order QCD calculation, we extract a lower mass limit of M_{\Phi_2} > 202 (160) GeV$/c^{2} at 95% confidence level for scalar leptoquarks with beta=1(0.5).
We present a search for new heavy particles, $X$, which decay via $X \to WZ \to e\nu +jj$ in $p{\bar p}$ collisions at $\sqrt{s}$ = 1.8 TeV. No evidence is found for production of $X$ in 110 pb$^{-1}$ of data collected by the Collider Detector at Fermilab. Limits are set at the 95% C.L. on the mass and the production of new heavy charged vector bosons which decay via $W'\to WZ$ in extended gauge models as a function of the width, $\Gamma (W')$, and mixing factor between the $W'$ and the Standard Model $W$ bosons.
We determine the fraction of events with double parton (DP) scattering in a single ppbar collision at sqrt{s}=1.96 TeV in samples of photon + 3 jet and photon + b/c jet + 2 jet events collected with the D0 detector and corresponding to an integrated luminosity of about 8.7 fb^{-1}. The DP fractions and effective cross sections (sigma_eff) are measured for both event samples using the same kinematic selections. The measured DP fractions range from 0.21 to 0.17, with effective cross sections in the photon + 3 jet and photon + b/c jet + 2 jet samples of sigma_eff^incl = 12.7 +- 0.2 (stat) +- 1.3 (syst) mb and sigma_eff^HF = 14.6 +- 0.6 (stat) +- 3.2 (syst) mb, respectively.
Forum