We report the first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders. The data for the two-muon and two-jets final states were ...collected by the DO experiment, and correspond to an integrated luminosity of 94 +/- 5 pb^{-1}. Assuming that R-parity is violated via the single coupling lambda^{prime}_{211}, the number of candidate events is in agreement with expectation from the standard model. Exclusion contours are given in the (m_0,m_{1/2}) and (m_{tilde{chi}},m_{tilde{nu}}) planes for lambda^{prime}_{211}=0.09, 0.08 and 0.07.
We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of $p \bar{p}$ events corresponding to ...108.3 pb$^{-1}$ of data collected with the D{\O}detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, \bc and \bls, no evidence for signal is found. We derive cross-section limits as a function of stop (\stt), chargino (\ca), and sneutrino (\snu) masses.
The central inclusive jet cross section has been measured using a successive-combination algorithm for reconstruction of jets. The measurement uses 87.3 pb^{-1} of data collected with the D0 detector ...at the Fermilab Tevatron ppbar Collider during 1994-1995. The cross section, reported as a function of transverse momentum (pT>60 GeV) in the central region of pseudorapidity (|\eta|<0.5), exhibits reasonable agreement with next-to-leading order QCD predictions, except at low pT where the agreement is marginal.
Using the DØ detector, we have studied events produced in $\bar{p}p$ collisions that contain large forward regions with very little energy deposition (“rapidity gaps”) and concurrent jet production ...at center-of-mass energies of $\sqrt s$ = 630 and 1800 GeV. The fraction of events with forward or central jets associated with rapidity gaps is compared to predictions for hard diffraction. We also extract the momentum loss for scattered protons in such processes.
Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a ...function of the
γp centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.
We present a search for electroweak production of single top quarks in ~90 pb^-1 of data collected with the DZero detector at the Fermilab Tevatron collider. Using arrays of neural networks to ...separate signals from backgrounds, we set upper limits on the cross sections of 17 pb for the s-channel process ppbar->tb+X, and 22 pb for the t-channel process ppbar->tqb+X, both at the 95% confidence level.
We report a new measurement of the pseudorapidity (eta) and transverse-energy (Et) dependence of the inclusive jet production cross section in pbar b collisions at sqrt(s) = 1.8 TeV using 95 pb**-1 ...of data collected with the DZero detector at the Fermilab Tevatron. The differential cross section d^2sigma/dEt deta is presented up to |eta| = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.
The D0 Collaboration has measured the inclusive jet cross section in barpp collisions at square root of s = 630 GeV. The results for pseudorapidities (eta)<0.5 are combined with our previous results ...at square root of s = 1800 GeV to form a ratio of cross sections with smaller uncertainties than either individual measurement. Next-to-leading-order QCD predictions show excellent agreement with the measurement at 630 GeV; agreement is also satisfactory for the ratio. Specifically, despite a 10% to 15% difference in the absolute magnitude, the dependence of the ratio on jet transverse momentum is very similar for data and theory.
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