We present results from a search for anomalous WW and WZ production in ppbar collisions at sqrt(s) = 1.8 TeV. We used ppbar->evjjX events observed during the 1992-1993 run of the Fermilab Tevatron collider, corresponding to an integrated luminosity of 13.7 +- 0.7 pb^-1. A fit to the transverse momentum spectrum of the W boson yields direct limits on the CP-conserving anomalous WWgamma and WWZ coupling parameters of -0.9 < delta kappa < 1.1 (with lambda = 0) and -0.6 < lambda < 0.7 (with delta kappa = 0) at the 95% confidence level, for a form factor scale Lambda = 1.5 TeV, assuming that the WWgamma and WWZ coupling parameters are equal.

We present a search for pair produced top squarks, the supersymmetric partners of the top quark, using the D0 detector at the Fermilab Tevatron $p\overline{p}$ collider. We consider a scenario in which the lighter of the two top squarks ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}$ decays with 100% branching fraction to a charm quark and the lightest neutralino ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}$ yielding a signal of two acollinear jets with missing transverse energy. We observe 3 events while we expect $3.5\ifmmode\pm\else\textpm\fi{}1.2$ events from the known standard model processes. We exclude at the 95% confidence level a significant region of the ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}}$- ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}}$ parameter space. The highest ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}}$ value we exclude is $93\mathrm{GeV}{/c}^{2}$ with a corresponding ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}}$ value of $8\mathrm{G}\mathrm{e}\mathrm{V}/{c}^{2}$.

We have searched for associated production of the lightest chargino (W) over tilde(1) and next-to-lightest neutralino (Z) over tilde(2) of the minimal supersymmetric standard model in p (p) over bar collisions at root s = 1.8 TeV using the DO detector at the Fermilab Tevatron collider. Data corresponding to an integrated luminosity of 12.5 +/- 0.7 pb(-1) were examined for events containing three isolated leptons. No evidence for (W) over tilde(1) (Z) over tilde(2) pair production was found. Limits on sigma((W) over tilde(1) (Z) over tilde(2))B((W) over tilde(1)-->lv (Z) over tilde(1))B((Z) over tilde(2)-->l (l) over bar (Z) over tilde(1)) are presented.

We have searched for associated production of the lightest chargino ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{W}}_{1}$ and next-to-lightest neutralino ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}_{2}$ of the minimal supersymmetric standard model in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8$ TeV using the D0 detector at the Fermilab Tevatron collider. Data corresponding to an integrated luminosity of $12.5\ifmmode\pm\else\textpm\fi{}0.7{\mathrm{pb}}^{\ensuremath{-}1}$ were examined for events containing three isolated leptons. No evidence for ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{W}}_{1}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}_{2}$ pair production was found. Limits on $\ensuremath{\sigma}({\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{W}}_{1}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}_{2})B({\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{W}}_{1}\ensuremath{\rightarrow}l\ensuremath{\nu}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}_{1})B({\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}_{2}\ensuremath{\rightarrow}l\overline{l}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}_{1})$ are presented.

A study of the particle multiplicity between jets with large rapidity separation has been performed using the DO detector at the Fermilab Tevatron p (p) over bar Collider operating at root s = 1.8 TeV. A significant excess of low-multiplicity events is observed above the expectation for color-exchange processes. The measured fractional excess is 1.07 +/- 0.10(stat)(-0.13)(+0.25) (syst)%, which is consistent with a strongly interacting color-singlet (colorless) exchange process and cannot be explained by electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on the fraction of dijet events with color-singlet exchange, independent of the rapidity gap survival probability.

We present results from a search for anomalous WW and WZ production in ppbar collisions at sqrt(s) = 1.8 TeV. We used ppbar->evjjX events observed during the 1992-1993 run of the Fermilab Tevatron collider, corresponding to an integrated luminosity of 13.7 +- 0.7 pb^-1. A fit to the transverse momentum spectrum of the W boson yields direct limits on the CP-conserving anomalous WWgamma and WWZ coupling parameters of -0.9 < delta kappa < 1.1 (with lambda = 0) and -0.6 < lambda < 0.7 (with delta kappa = 0) at the 95% confidence level, for a form factor scale Lambda = 1.5 TeV, assuming that the WWgamma and WWZ coupling parameters are equal.

We report on a search for right-handed W bosons (WR) with mass greater than 200GeV/c2. We used data collected with the D0 detector at the Fermilab Tevatron p¯p collider at √s=1.8TeV to search for WR decays into an electron and a massive right-handed neutrino W±R→e±NR. Using the inclusive electron data, we set mass limits independent of the NR decay: mWR>650GeV/c2 and mWR>720GeV/c2 at the 95% confidence level, valid for mNR<12mWR and mNR≪mWR, respectively. The latter also represents a new lower limit on the mass of a heavy left-handed W boson (W′) decaying into eν. In addition, limits on mWR valid for larger values of the NR mass are obtained assuming that NR decays to an electron and two jets.Received 21 December 1995DOI:https://doi.org/10.1103/PhysRevLett.76.3271©1996 American Physical Society

We present results from a search for anomalous $\mathrm{WW}$ and $\mathrm{WZ}$ production in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{TeV}$. We used $p\overline{p}\ensuremath{\rightarrow}e\ensuremath{\nu}\mathrm{jjX}$ events observed during the 1992--1993 run of the Fermilab Tevatron collider, corresponding to an integrated luminosity of $13.7\ifmmode\pm\else\textpm\fi{}0.7{\mathrm{pb}}^{\ensuremath{-}1}$. A fit to the transverse momentum spectrum of the $W$ boson yields direct limits on the CP-conserving anomalous $\mathrm{WW}\ensuremath{\gamma}$ and $\mathrm{WWZ}$ coupling parameters of $\ensuremath{-}0.9l\ensuremath{\Delta}\ensuremath{\kappa}l1.1$ (with $\ensuremath{\lambda}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$) and $\ensuremath{-}0.6l\ensuremath{\lambda}l0.7$ (with $\ensuremath{\Delta}\ensuremath{\kappa}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$) at the 95% confidence level, for a form factor scale $\ensuremath{\Lambda}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.5\phantom{\rule{0ex}{0ex}}\mathrm{TeV}$, assuming that the $\mathrm{WW}\ensuremath{\gamma}$ and $\mathrm{WWZ}$ coupling parameters are equal.

This study reports the first measurement of the azimuthal decorrelation between jets with pseudorapidity separation up to five units. The data were accumulated using the D0 detector during the 1992-1993 collider run of the Fermilab Tevatron at root s = 1.8 TeV. These results are compared to next-to-leading order (NLO) QCD predictions and to two leading-log approximations (LLA) where the leading-log terms are re-summed to all orders in alpha(S). The final state jets as predicted by NLO QCD show less azimuthal decorrelation than the data. The parton showering LLA Monte Carlo HERWIG describes the data well; an analytical LLA prediction based on Balitsky-Fadin-Kuraev-Lipatov resummation shows more decorrelation than the data.

We have studied J/psi production in p (p) over bar collisions at root s = 1.8 TeV with the DO detector at Fermilab using mu(+)mu(-) data. We have measured the inclusive J/psi production cross section as a function of J/psi transverse momentum, p(T). For the kinematic range p(T) > 8 GeV/c and \eta\ < 0.6 we obtain sigma(p (p) over bar --> J/psi + X) . Br(J/psi --> mu(+)mu(-)) = 2.08 +/- 0.17(stat) +/- 0.46(syst) nb. Using the muon impact parameter we have estimated the fraction of J/psi mesons coming from B meson decays to be f(b) = 0.35 +/- 0.09(stat) +/- 0.10(syst) and inferred the inclusive b production cross section. From the information on the event topology the fraction of nonisolated J/psi events has been measured to be f(nonisol) = 0.64 +/- 0.08(stat) +/- 0.06(syst). We have also obtained the fraction of J/psi events resulting from radiative decays of chi(c) states, f(chi) = 0.32 +/- 0.07(stat) +/- 0.07(syst). We discuss the implications of our measurements for charmonium production processes.

We have studied Jψ production in pp collisions at s = 1.8 TeV with the DØ detector at Fermilab using μ+μ− data. We have measured the inclusive Jψ production cross section as a function of Jψ transverse momentum, pT. For the kinematic range pT > 8 GeV/c and |η| < 0.6 we obtain σ(pp → Jψ + X) · Br(Jψ → μ+μ−) = 2.08 ± 0.17(stat) ± 0.46(syst) nb. Using the muon impact parameter we have estimated the fraction of Jψ mesons coming from B meson decays to be fb = 0.35 ± 0.09(stat)±0.10(syst) and inferred the inclusive b production cross section. From the information on the event topology the fraction of nonisolated Jψ events has been measured to be fnonisol = 0.64 ± 0.08(stat)±0.06(syst). We have also obtained the fraction of Jψ events resulting from radiative decays of χc states, fχ = 0.32 ± 0.07(stat)±0.07(syst). We discuss the implications of our measurements for charmonium production processes.

We report on a search for right-handed W bosons (W-R) with mass greater than 200 GeV/c(2). We used data collected with the DO detector at the Fermilab Tevatron p (p) over bar collider at root s = 1.8 TeV to search for W-R decays into an electron and a massive right-handed neutrino W-R(+/-) --> e(+/-)N(R). Using the inclusive electron data, we set mass limits independent of the N-R decay: m(WR) > 650 GeV/c(2) and m(WR) > 720 GeV/c(2) at the 95% confidence level, valid for m(NR) < 1/2-m(WR) << m(WR), respectively. The latter also represents a new lower limit on the mass of a heavy left-handed W boson (W-') decaying into e nu. In addition, limits on m(WR) valid for larger values of the N-R mass are obtained assuming that NR decays to an electron and two jets.

We have searched for a heavy neutral gauge boson, Z′, using the decay channel Z′ → ee. The data were collected with the DØ detector at the Fermilab Tevatron during the 1992–1993 pp collider run at s=1.8 TeV from an integrated luminosity of 15±1 pb−1. Limits are set on the cross section times brancing ratio for the process pp → Z′ → ee as a function of the Z′ mass. We exclude the existence of a Z′ of mass less than 490 GeV/c2, assuming a Z′ with the same coupling strengths to quarks and leptons as the standard model Z boson.

We performed a direct search for the anomalous ZZγ and Zγγ couplings by studying p¯p→ℓℓγ+X (ℓ=e,μ) events at √s=1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. A fit to the transverse energy spectrum of the photon in the signal events, based on the data set corresponding to an integrated luminosity of 14.3pb−1 ( 13.7pb−1) for the electron (muon) channel, yields the following 95% confidence level limits on the anomalous CP-conserving ZZγ couplings: |hZ30|<1.8 ( hZ40=0) and |hZ40|<0.5 ( hZ30=0), for a form-factor scale Λ=500 GeV. Limits for the Zγγ couplings and CP-violating couplings are also discussed.Received 10 March 1995DOI:https://doi.org/10.1103/PhysRevLett.75.1028©1995 American Physical Society

The distribution of the transverse energy in jets has been measured in p $($) over bar$$ p collisions at root s = 1.8 TeV using the DO detector at Fermilab. This measurement of the jet shape is made as st function of jet transverse energy in both the central and forward rapidity regions. Jets are shown to narrow both with increasing transverse energy and with increasing rapidity. Next-to-leading order partonic QCD calculations are compared to the data. Although the calculations qualitatively describe the data, they are shown to be very dependent on renormalization scale, parton clustering algorithm, and jet direction definition and they fail to describe the data in all regions consistently.