Showing papers by "Hermann Kolanoski published in 2000"
TL;DR: In this article, cross sections for elastic photoproduction of J / ψ and ϒ mesons are presented, and the energy dependence on the photon-proton center-of-mass energy W γp is analyzed in an extended range with respect to previous measurements of 26≤W −1 ≤ 285 GeV.
145 citations
TL;DR: In this article, the effect of the quark and gluon content of the photon on the di-jet cross-section was measured in tagged photoproduction at HERA using data taken with the H1 detector.
20 citations
TL;DR: In this paper, the authors measured the triple-differential dijet cross-section with the H1 detector at HERA as a function of the photon virtuality, the fraction of photon's momentum carried by the parton entering the hard scattering, xgjets, and the square of the mean transverse energy of the two highest E_t jets.
Abstract: The triple-differential dijet cross-section, d^3 sigma_{ep}/dQ2 dE_t2 dxgjets, is measured with the H1 detector at HERA as a function of the photon virtuality Q^2, the fraction of the photon's momentum carried by the parton entering the hard scattering, xgjets, and the square of the mean transverse energy, E_t2, of the two highest E_t jets. Jets are found using a longitudinal boost-invariant k_T clustering algorithm in the gamma* p center of mass frame. The measurements cover the ranges 1.6 Q^2 80 GeV$^2 in virtuality and 0.1 y 0.7 in inelasticity y. The results are well described by leading order QCD models which include the effects of a resolved component to the virtual photon. Models which treat the photon as point-like fail to describe the data. An effective leading order parton density for the virtual photon is extracted as a function of the photon virtuality, the probing scale and the parton momentum fraction. The x_gamma and probing scale dependences of the parton density show characteristic features of photon structure, and a suppression of this structure with increasing Q^2 is seen.
18 citations
TL;DR: In this article, the authors measured the di-jet event rates for deep-inelastic scattering in the kinematic domain with the H1 detector at HERA in 1994 corresponding to an integrated luminosity of about 2 pb\(^{-1}\).
Abstract: Di-jet event rates have been measured for deep-inelastic scattering in the kinematic domain \(5 \lesssim Q^2 \lesssim 100\) GeV\(^2\) and \(10^{-4} \lesssim x_{Bj} \lesssim 10^{-2}\), and for jet transverse momenta squared \(p_t^{*2}\gtrsim Q^2\). The analysis is based on data collected with the H1 detector at HERA in 1994 corresponding to an integrated luminosity of about 2 pb\(^{-1}\). Jets are defined using a cone algorithm in the photon-proton centre of mass system requiring jet transverse momenta of at least 5 GeV. The di-jet event rates are shown as a function of \(Q^2\) and \(x_{Bj}\). Leading order models of point-like interacting photons fail to describe the data. Models which add resolved interacting photons or which implement the colour dipole model give a good description of the di-jet event rate. This is also the case for next-to-leading order calculations including contributions from direct and resolved photons.
10 citations
15 Oct 2000
TL;DR: The HERA-B outer tracker as discussed by the authors consists of drift tubes folded from polycarbonate foil and is operated with Ar CF/sub 4/ CO/sub 2/ as drift gas.
Abstract: The HERA-B Outer Tracker consists of drift tubes folded from polycarbonate foil and is operated with Ar CF/sub 4/ CO/sub 2/ as drift gas. The detector has to stand radiation levels which are similar to LHC conditions. The first prototypes exposed to radiation in HERA-B suffered severe radiation damage due to the development of self-sustaining currents (Malter effect). In a subsequent extended R&D program major changes to the original concept for the drift tubes (surface conductivity, drift gas, production materials) have been developed and validated for use in harsh radiation environments. In the test program various aging effects-like Malter currents, gain loss due to anode aging and etching of the anode gold surface-have been observed and cures by tuning of operation parameters have been developed.
10 citations