Electroproduction of Dijets at Small Jet Separation

Dijet production in deep-inelastic scattering (DIS) in the range 150 < Q^2 < 35000 GeV^2 has been measured by the H1 collaboration using the Durham jet algorithm in the laboratory frame. QCD calculations in next-to-leading order (NLO) are found to give a good description of the data when requiring a small minimum jet separation, which selects a dijet sample containing 1/3 of DIS events in contrast to approximately 1/10 with more typical jet analyses.Comment: On behalf of the H1 collab., X International Workshop on Deep-Inelastic Scattering, DIS 2002, Cracow, 30 April - 4 May 2002, 4 pages, to be published in Acta Phys. Pol.

Tests of QCD: Summary of DIS 2000

This summary of the working group 2 of DIS 2000 encompasses experimental and theoretical results of jet physics, open and bound state heavy flavour production, prompt photon production, next-to-leading order QCD calculations and beyond, instantons, fragmentation, event shapes, and power corrections, primarily from deep-inelastic scattering and photoproduction at HERA, but also from the LEP and Tevatron colliders.Comment: 16 pages, LaTeX, including 8 PostScript figures. Talk given at the 8th International Workshop on Deep-Inelastic Scattering (DIS2000), 25th-30th April 2000, Liverpool, England, to appear in the proceeding

Photoproduction of WHWH signal at electron-proton Colliders

We present the photoproduction of an intermediate mass Higgs (IMH) boson associated with a $W$ boson at the future electron-proton colliders using bremsstrahlung photon beam or laser backscattered photon beam. With bremsstrahlung photon beam the search for the IMH boson is unfavorable because of the small signal rate. But with laser photon beam the search is viable due to a much larger rate, and provided that the $B$-identification is efficient and $m(b\bar b)$ measurement has a good resolution.Comment: 12 pages, using RevTex2.0, figures not included, NUHEP-TH-93-2

Search for Chargino and Neutralino Production at sqrt(s) = 192-209 GeV at LEP

Approximately 438 pb-1 of e+e- data from the OPAL detector, taken with the LEP collider running at centre-of-mass energies of 192-209 Gev, are analyzed to search for evidence of chargino pair production, e+e- -> tilde chi^+_1 tilde chi^-_1, or neutralino associated production, e+e- -> tilde chi^0_2 tilde chi^0_1. Limits are set at the 95% confidence level on the product of the cross-section for the process e+e- -> tilde chi^+_1 tilde chi^-_1 and its branching ratios to topologies containing jets and missing energy, of jest with a lepton and missing energy, and on the product of the cross-section for e+e- -> tilde chi^0_2 tilde chi^0_1 and its branching ratio to jets. R-parity conservation is assumed throughout this paper. When these results are interpreted in the context of the Constrained Minimal Supersymmetric Standard Model, limits are also set on the masses of the tilde chi^+-_1, tilde chi^0_1 and tilde chi^0_2, and regions of the parameter space of the model are ruled out. Nearly model-independent limits are also set at the 95% confidence level on sigma(e+e- -> tilde chi^+_1 tilde chi^-_1) with the assumption that each chargino decays via a W boson, and on sigma(e+e- -> tilde chi^0_2 tilde chi^0_1) with the tilde chi^0_2 assumed to decay via a Z^0.Comment: 33 pages, 13 figures, Submitted to Eur Phys J.

Jets in Hadron-Hadron Collisions

In this article, we review some of the complexities of jet algorithms and of the resultant comparisons of data to theory. We review the extensive experience with jet measurements at the Tevatron, the extrapolation of this acquired wisdom to the LHC and the differences between the Tevatron and LHC environments. We also describe a framework (SpartyJet) for the convenient comparison of results using different jet algorithms.Comment: 68 pages, 54 figure

QCD and QED Corrections to Higgs Boson Production in Charged Current epep Scattering

First order QCD and leading QED corrections to Higgs boson production in the channel $e^-p \to \nu H^0 X; H^0 \to b\bar{b}$ are calculated for the kinematical conditions at LEP $\otimes$ LHC (\sqrt{s} = 1360 \GeV) and the interesting mass range 80 < M_H < 150 \GeV. In the DIS scheme the QCD corrections (not including the corrections to the branching ratio, which are well-known) are found to be about 1\% for the total cross section and $-13\%$ to $-10\%$ for the observable cross section as defined by appropriate cuts. The latter results depend on the definition of these cuts. The QED corrections amount to about $-5\%$. Also obtainable with anonymous ftp from gluon.hep.physik.uni-muenchen.de.Comment: latex, 16 pages + 9 pages figures in PostScript (included

Production of Supersymmetric Higgs Bosons at LEP x LHC

Within the Minimal Supersymmetric Standard Model (MSSM), we study the production of the neutral scalar and pseudoscalar as well as the charged Higgs bosons together with fermions or sfermions in deep inelastic $ep$ scattering at $\sqrt{s}=1.6$ TeV. We focus on the parameter space where a Higgs particle is likely to be invisible at LEP2 and LHC. Although we choose gaugino/higgsino mixing scenarios that maximize the corresponding production rates we find only for the production of the scalar Higgs bosons in the non-supersymmetric channels non-negligible cross sections of the order of $10^2$ fb.Comment: 8 pages, LATEX, 4 figures (not included). The complete paper (including figures) can be obtained at ftp://ftp.physik.uni-wuerzburg.de/pub/preprint/WUE-ITP-95-004.ps.g