Measurement of the diffractive structure function in deep inelastic scattering at HERA

This paper presents an analysis of the inclusive properties of diffractive deep inelastic scattering events produced in $ep$ interactions at HERA. The events are characterised by a rapidity gap between the outgoing proton system and the remaining hadronic system. Inclusive distributions are presented and compared with Monte Carlo models for diffractive processes. The data are consistent with models where the pomeron structure function has a hard and a soft contribution. The diffractive structure function is measured as a function of \xpom, the momentum fraction lost by the proton, of $\beta$, the momentum fraction of the struck quark with respect to \xpom, and of $Q^2$. The \xpom dependence is consistent with the form \xpoma where $a~=~1.30~\pm~0.08~(stat)~^{+~0.08}_{-~0.14}~(sys)$ in all bins of $\beta$ and $Q^2$. In the measured $Q^2$ range, the diffractive structure function approximately scales with $Q^2$ at fixed $\beta$. In an Ingelman-Schlein type model, where commonly used pomeron flux factor normalisations are assumed, it is found that the quarks within the pomeron do not saturate the momentum sum rule.Comment: 36 pages, latex, 11 figures appended as uuencoded fil

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

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 $\gamma p$ 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.Comment: 19 pages, latex, 4 figures appended as uuencoded fil

Observation of direct processes in photoproduction at HERA

Jets in photoproduction events have been studied with the ZEUS detector for gammap centre-of-mass energies ranging from 130 to 2 50 GeV. The inclusive jet distributions give evidence for the dominance of resolved photon interactions. In the di-jet sample the direct processes are for the first time clearly isolated. Di-jet cross sections for the resolved and direct processes are given in a restricted kinematic range

Measurement of Charged and Neutral Current e-p Deep Inelastic Scattering Cross Sections at High Q2

Deep inelastic e-p scattering has been studied in both the charged current (CC) and neutral current (NC) reactions at momentum transfers squared Q(2) above 400 GeV2 using the ZEUS detector at the HERA ep collider. The CC and NC total cross sections, the NC to CC cross section ratio, and the differential cross sections d sigma/dQ(2) are presented. From the Q(2) dependence of the CC cross section, the mass term in the CC propagator is determined to be M(W) = 76 +/- 16 +/- 13 GeV

Bestimmung der Ereigniszeit von ep-Wechselwirkungen durch Kalorimetrie am ZEUS-Detektor

Available from TIB Hannover: RN 2821(94-01) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Calibration of the forward and rear ZEUS calorimeter using cosmic ray muons

The forward and rear calorimeter of the ZEUS experiment consists of 48 modules. Before their installation into the ZEUS detector they were calibrated at DESY using cosmic ray muons in order to check their performance and to compare the response to cosmic muons to the response, obtained for some modules, to 100 GeV beam muons. The setup, the test procedure and the analysis of the data are described in this paper. The relative calibration of the different modules, as well as of the different cells within a module can be obtained with cosmic ray muons with an accuracy of about one percent for a measurement time of 3–5 days/module

Calibration of the forward and rear ZEUS calorimeter using cosmic ray muons

The forward and rear calorimeter of the ZEUS experiment consists of 48 modules. Before their installation into the ZEUS detector they were calibrated at DESY using cosmic ray muons in order to check their performance and to compare the response to cosmic muons to the response, obtained for some modules, to 100 GeV beam muons. The setup, the test procedure and the analysis of the data are described in this paper. The relative calibration of the different modules, as well as of the different cells within a module can be obtained with cosmic ray muons with an accuracy of about one percent for a measurement time of 3–5 days/module