Limits on WWZ and WW\gamma couplings from p\bar{p}\to e\nu jj X events at \sqrt{s} = 1.8 TeV

We present limits on anomalous WWZ and WW-gamma couplings from a search for WW and WZ production in p-bar p collisions at sqrt(s)=1.8 TeV. We use p-bar p -> e-nu jjX events recorded with the D0 detector at the Fermilab Tevatron Collider during the 1992-1995 run. The data sample corresponds to an integrated luminosity of 96.0+-5.1 pb^(-1). Assuming identical WWZ and WW-gamma coupling parameters, the 95% CL limits on the CP-conserving couplings are -0.33<lambda<0.36 (Delta-kappa=0) and -0.43<Delta-kappa<0.59 (lambda=0), for a form factor scale Lambda = 2.0 TeV. Limits based on other assumptions are also presented.Comment: 11 pages, 2 figures, 2 table

Limits on Anomalous WWγWW\gamma Couplings from ppˉ→Wγ+Xp\bar{p} \to W \gamma + X Events at s=1.8\sqrt{s}=1.8 TeV

We have measured the $WW\gamma$ gauge boson coupling parameters using $p\bar{p}\to \ell\nu\gamma+X$ ($\ell=e,\mu$) events at $\sqrt{s}=1.8$ TeV. The data, corresponding to an integrated luminosity of 89.1 pb^{-1}, were collected using the D0 detector at the Fermilab Tevatron Collider. The measured cross section times branching ratio for $p\bar{p} \to W\gamma+X$ with $p_T^\gamma$ > 10 GeV/c and $R_{\ell\gamma} > 0.7$ is ${11.8}^{+1.7}_{-1.6} \pm 2.0$ pb, in agreement with the Standard Model prediction. The one degree of freedom 95% confidence level limits on individual CP-conserving parameters are $-0.98<\Delta\kappa<1.01$ and $-0.33<\lambda<0.31$. Similar limits are set on the CP}violating coupling parameters.Comment: 10 pages, including two figures. Paper submitted to Phys. Rev. Let

INCLUSIVE MU AND B-QUARK PRODUCTION CROSS-SECTIONS IN P(P)OVER-BAR COLLISIONS AT ROOT-S=1.8 TEV

We report a measurement of the inclusive muon and b-quark production cross sections in pp» collisions at s=1.8 TeV using the D0 detector at the Fermilab Tevatron collider. The inclusive muon spectrum extends over the kinematic range | y|&lt;0.8 and 3.56GeV/c is extracted, and agrees with next-to-leading order QCD predictions within the experimental and theoretical uncertainties. © 1995 The American Physical Society.</pt<60gev

TOP-QUARK SEARCH WITH THE D0 1992-1993 DATA SAMPLE

We present results on the search for the top quark in pp̄ collisions at s =1.8 TeV with an integrated luminosity of 13.5±1.6 pb-1. We have considered tt̄ production in the standard model using electron and muon dilepton decay channels (tt̄→eμ+jets, ee+jets, and μμ+jets) and single-lepton decay channels (tt̄→e+jets and μ+jets) with and without tagging of b quark jets. An analysis of these data optimized for top quark masses below 140 GeV/c2 gives a lower top quark mass limit of 128 GeV/c2. An analysis optimized for higher top quark masses yields 9 events with an expected background of 3.8±0.9. If we assume that the excess is due to tt̄ production, and assuming a top quark mass of 180 GeV/c2, we obtain a cross section of 8.2±5.1 pb. © 1995 The American Physical Society

SEARCH FOR HEAVY W-BOSONS IN 1.8 TEV P(P)OVER-BAR COLLISIONS

A search for a heavy charged gauge boson, W′, using the decay channels W′ → eν and W′ → τν → eννν is reported. The data used in the analysis were collected by the DØ experiment at the Fermilab Tevatron during the 1992-93 pp collider run from an integrated luminosity of 13.9 ± 0.8 pb-1 at s=1.8 TeV. Assuming that the neutrino from W′ decay is stable and has a mass significantly less than mW′, an upper limit at the 95% confidence level is set on the cross section times branching ratio for pp → W′ → eν. A W′ with the same couplings to quarks and leptons as the standard model W boson is excluded for mW′ &lt; 610 GeV/c2. © 1995

SEARCH FOR W-BOSON PAIR PRODUCTION IN P(P)OVER-BAR COLLISIONS AT ROOT-S=1.8 TEV

The results of a search for W boson pair production in pp» collisions at s=1.8 TeV with subsequent decay to dilepton (e,ee, and) channels are presented. One event is observed with an expected background of 0.56 0.13 events with an integrated luminosity of approximately 14 pb-1. Assuming equal strengths for the WWZ and WW gauge boson coupling parameters and, limits on the CP-conserving anomalous coupling constants are -2.6&lt; &lt;2.8 and -2.1&lt; &lt;2.1 at the 95% confidence level. © 1995 The American Physical Society

SEARCH FOR SQUARKS AND GLUINOS IN P(P)OVER-BAR COLLISIONS AT ROOT-S=1.8 TEV

We present a search for events consistent with the production and decay of the squarks and gluinos of the minimal supersymmetric standard model (MSSM) in the D0 detector at the Fermilab Tevatron pp collider. We examined data for events containing large missing transverse energy and three or more jets. We observed no excess of events above the expected yield from standard model processes. For a choice of MSSM parameter values, we set a lower limit at the 95% confidence level on the mass of the gluino of 144 GeV /c2 for all squark masses and a lower limit of 212 GeV /c2 for equal squark and gluino masses. © 1995 The American Physical Society

OBSERVATION OF THE TOP-QUARK

The D0 Collaboration reports on a search for the standard model top quark in pp̄ collisions at s=1.8TeV at the Fermilab Tevatron with an integrated luminosity of approximately 50 pb-1. We have searched for tt̄ production in the dilepton and single-lepton decay channels with and without tagging of b-quark jets. We observed 17 events with an expected background of 3.8±0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2×10-6 (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measured its mass to be 199-21+19 (stat) ±22 (syst) GeV/c2 and its production cross section to be 6.4±2.2 pb. © 1995 The American Physical Society

STUDY OF THE STRONG-COUPLING CONSTANT USING W-PLUS JET PROCESSES

The ratio of the number of W+1 jet to W+0 jet events is measured with the D0 detector using data from the 1992-93 Tevatron Collider run. For the W→eν channel with a minimum jet ET cutoff of 25 GeV, the experimental ratio is 0.065±0.003stat±0.007syst. Next-to-leading order QCD predictions for various parton distributions agree well with each other and are all over 1 standard deviation below the measurement. Varying the strong coupling constant αs in both the parton distributions and the partonic cross sections simultaneously does not remove this discrepancy. © 1995 The American Physical Society