Related papers: The energy behaviour of real and virtual photon--p…
Measurements of the total cross section for real and virtual photons on protons at center-of-mass energies in the range from 20 GeV to 270 GeV with photon virtualities up to 5000 GeV^2 are presented. For real photons this cross section can…
The photon-proton total cross section has been measured in the process e+ p -> e+ gamma p -> e+ X with the ZEUS detector at HERA. Events were collected with photon virtuality Q^2 < 0.02 GeV^2 and average gamma-p center-of-mass energy…
A small electromagnetic sampling calorimeter, installed in the ZEUS experiment in 1995, significantly enhanced the acceptance for very low x and low Q^2 inelastic neutral current scattering, e^{+}p \to e^{+}X, at HERA. A measurement of the…
The results of a measurement of the proton structure function F_2(x,Q^2)and the virtual photon-proton cross section are reported for momentum transfers squared Q^2 between 0.35 GeV^2 and 3.5 GeV^2 and for Bjorken-x values down to 6 10^{-6}…
The electron-proton collider HERA at DESY opened the door for the study of diffraction in real and virtual photon-proton scattering at center-of-mass energies W up to 250 GeV and for large negative mass squared -Q^2 of the virtual photon up…
The dependence of the photon structure on the photon virtuality, Q^2, is studied by measuring the reaction e^+p\to e^+ + {\rm jet} + {\rm jet} + {\rm X} at photon-proton centre-of-mass energies 134 < W < 223 GeV. Events have been selected…
The structure of real and virtual photons has been studied in ep collisions at HERA using dijet production. Measurements of differential dijet cross sections as function of the fraction of photon's momentum invested in the dijet system are…
A recent H1 measurement of triple differential dijet cross sections in electron-proton interactions in the region of photon virtualities 2<Q2<80 GeV is presented and compared to LO and NLO QCD predictions. Effects that go beyond the…
The scale dependence of the evolution of photoproduction cross sections with the photon-proton centre of mass energy W is studied using low Q^2 < 0.01 GeV^2 e^+p interactions collected by the H1 experiment at HERA. The value of the largest…
Measurements of proton structure functions made in neutral and charged current interactions at HERA are discussed, covering four-momentum transfers Q^2 from about 0.5 GeV^2 to 30000 GeV^2. The results include the rise of the structure…
We present a new measurement of the total photoproduction cross section performed with the H1 detector at HERA. For an average centre of mass energy of 200~GeV a value of $\sigma_{tot}^{\gamma{p}}= 165\pm2\pm11\mu$b has been obtained. A…
The elastic electroproduction of phi mesons is studied at HERA with the H1 detector for photon virtualities 1 < Q^2 < 15 GeV^2 and hadronic centre of mass energies 40 < W < 130 GeV. The Q^2 and t dependences of the cross section are…
Cross sections for the reactions gamma^(*) gamma^(*) --> hadrons and gamma^(*) gamma^(*) --> 2 vector mesons are calculated as functions of energy (sqrt(s) > 20 GeV) and photon virtualities. Good agreement with experiment is obtained for…
A first measurement is reported of the longitudinal proton structure function F_L(x,Q^2) at the ep collider HERA. It is based on inclusive deep inelastic e^+p scattering cross section measurements with a positron beam energy of 27.5 GeV and…
The measurement and QCD analysis of neutral and charged current cross sections at HERA are presented. For the kinematic range of four-momentum transfer Q^2 between approx. 1 GeV^2 and 30000 GeV^2 and Bjorken x between 0.0013 and 0.65 the…
The energy dependence of the photon-proton total cross section was determined from positron-proton scattering data collected with the ZEUS detector at HERA at three values of the center-of-mass energy, W, of the \gamma p system in the range…
A measurement is presented of elastic Deeply Virtual Compton Scattering e^+ + p -> e^+ + photon + p at HERA using data taken with the H1 detector. The cross section is measured as a function of the photon virtuality, Q^2, and the invariant…
The energy dependence of cross sections is discussed as a way to learn about the dynamics of photon induced interactions at HERA. The question of determining the scale of exclusive electroproduction of vector mesons is addressed.
We report on a measurement of the proton structure function $F_2$ in the range $3.5\times10^{-5}\leq x \leq 4\times10^{-3}$ and 1.5 ${\rm GeV^2} \leq Q^2 \leq15$ ${\rm GeV^2}$ at the $ep$ collider HERA operating at a centre-of-mass energy…
Deeply virtual Compton scattering has been measured in e^+p collisions at HERA with the ZEUS detector using an integrated luminosity of 61.1 pb^-1. Cross sections are presented as a function of the photon virtuality, Q^2, and photon-proton…