The dissociation of virtual photons, $\gamma^{\star} p \to X p$, in events with a large rapidity gap between $X$ and the outgoing proton, as well as in events in which the leading proton was directly measured, has been studied with the ZEUS detector at HERA. The data cover photon virtualities $Q^2>2$ GeV$^2$ and $\gamma^{\star} p$ centre-of-mass energies $40<W<240$ GeV, with $M_X>2$ GeV, where $M_X$ is the mass of the hadronic final state, $X$. Leading protons were detected in the ZEUS leading proton spectrometer. The cross section is presented as a function of $t$, the squared four-momentum transfer at the proton vertex and $\Phi$, the azimuthal angle between the positron scattering plane and the proton scattering plane. It is also shown as a function of $Q^2$ and $\xpom$, the fraction of the proton's momentum carried by the diffractive exchange, as well as $\beta$, the Bjorken variable defined with respect to the diffractive exchange.
The differential cross section DSIG/DT for the LRG and the LPS data samples.
The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).
The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).
Virtual photoproduction of J/ ψ mesons has been measured for 280 GeV muon iron interactions in an iron/scintillator calorimeter target. The J/ψ's were identified by their decay into muon pairs. 315 events were observed, about half of which were elastic. The t , Q 2 and v distributions of these elastic events are presented. The v dependence is measured between 40 and 180 Mev and compared with lower energy photoproduction results. The Q 2 dependence is compared with the predictions of the vector dominance model.
TPRIME DISTRIBUTION OF ELASTIC J/PSI EVENTS FOR ALL Q2 AND NU WITH 280 GEV MUON BEAM.
NORMALIZED Q**2 DISTRIBUTION OF ELASTIC J/PSI EVENTS FOR ALL NU AND T WITH 280 GEV MUON BEAM.
EXTRAPOLATION OF Q**2 AND T DEPENDENCE TO CALCULATE D(SIG)/DT AT Q**2=0 AND T=0 FOR ELASTIC J/PSI PHOTOPRODUCTION PER NUCLEON.
The differential cross section for π−−p elastic scattering has been measured at 13.8 and 22.6 GeV/c up to −t=5 (GeV/c)2. The dips in the angular distribution at −t≈0.8 and 2.8 (GeV/c)2 previously observed at lower momenta become less prominent at higher momentum. The −t=2.8 (GeV/c)2 dip is still observed at 13.8 GeV/c, but at 22.6 GeV/c it has become a sharp kink in the angular distribution. At large momentum transfers, dσdt at fixed t is still decreasing with increasing s, but at a slower rate in the 14- to 23-GeV/c region than at lower momenta.
No description provided.
No description provided.
The differential cross section for π+p elastic scattering has been measured at 13.8 GeVc for 0.7<|t|<3.8(GeVc)2. The cross section is found to be equal to that previously obtained for π−p elastic scattering, except in the region |t|=2.8 (GeVc)2, where the π+p data do not show the prominent dip observed in π−p scattering. Data have also been obtained for 13.8−GeVc K+p elastic scattering for 0.8<|t|<2.2 (GeVc)2.
No description provided.
No description provided.
We have measured the production and decay angular distributions of the reaction π + p→ π O Δ ++ at 13.1 GeV/ c incident momentum. For − t > 0.1 (GeV/ c ) 2 the data is well described by M1 ϱ-exchange models, the best results being obtained from a weak cut model with a wrong signature nonsense zero. For − t < 0.1 (GeV/c) 2 there is evidence for the existence of other exchange mechanisms.
No description provided.
No description provided.
No description provided.
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