Related papers: An Experimenter's Highlights
A survey is presented of the various processes measurable at HERA in which two photons are involved. Their current experimental status and future prospects are discussed.
The highlights of the Working Group 5B, Theory, are summarised. There has been reported impressive progresses in the study of BFKL Pomeron and Odderon dynamics. It turns out that the leading log approximation is not still a good one in the…
Recent results on searches for new particles at the electron-proton collider HERA are reported. Based on roughly 100pb-1 of e^+p data and 16pb-1 of e^-p data per experiment, taken in the years 1994-2000, the H1 and ZEUS collaborations have…
Photoproduction data collected with the H1 detector at HERA in 1994 are used to study the cross-sections for inclusive charged particle production and the structure of the photon. The differential cross-sections dsigma/dpT2, for |eta| < 1…
Glueballs and other resonances with large gluonic components are predicted as bound states by Quantum Chromodynamics (QCD). The lightest (scalar) glueball is estimated to have a mass in the range from 1 to 2 GeV/c**2; a pseudoscalar and…
Measures taken to extend the acceptance of the H1 detector at HERA for photoproduction events are described. These will enable the measurement of electrons scattered in events in the high y range 0.85 < y < 0.95 in the 1998 and 1999 HERA…
Photoproduction at HERA is studied in $ep$ collisions, with the ZEUS detector, for $\gamma p$ centre-of-mass energies ranging from 130-270 GeV. A sample of events with two high-$p_T$ jets ($p_T > 6$ GeV, $\eta <1.6$) and a third cluster in…
Two-dimensional electronic spectroscopy provides information on coupling and energy transfer between excited states on ultrafast timescales. Only recently, incoherent fluorescence detection has made it possible to combine this method with…
The objectives of my talk are to provide a very brief introduction to diffractive photoprocesses in general and the colour dipole model in particular; and to comment on possible gluon saturation effects at HERA and beyond.
We have performed a dynamical analysis of the mixing in the pseudoscalar channel with the goal of understanding the existence and behavior of the pseudoscalar glueball. Our philosophy has not been to predict precise values of the glueball…
Positivity constraints have proved to be important for spin observables of exclusive reactions involving polarized initial and final particles. Attention is focused in this note on the photoproduction of pseudoscalar mesons from spin 1/2…
Many new results on hadron spectra have been appearing in the past few years thanks to improved experimental techniques and searches in new channels. New theoretical techniques including refined methods of lattice QCD have kept pace with…
I present a concise review of the possible evidence for new physics at HERA and of the recent work towards a theoretical interpretation of the signal. It is not clear yet if the excess observed at large Q^2 is a resonance or a continuum…
A selection of theoretical and experimental results are presented in the broader context of understanding QCD and its relation to photon physics. A phenomenological analysis of HERA data to constrain the gluon content of the proton and…
A brief survey is given of recent HERA results in jet production and prompt photon production, together with the evaluation of the QCD coupling constant alpha_s.
Recent results on searches for physics beyond the Standard Model obtained by the H1 and ZEUS experiments are reported here. After a brief introduction to the HERA collider, indirect searches for contact interactions and extra-dimensions are…
Recent results from the ep (electron-proton) collider HERA are presented. Jet production and diffraction type reactions allow tests of predictions of Quantum Chromodynamics (QCD). Jet measurements are used to improve the combined H1-ZEUS…
We study the associated production of $ J/\psi\ + \gamma $ in fixed-target experiments with nuclear targets as well as at the relativistic heavy-ion collider (RHIC). We find that this process affords a very clean probe of $\rho_g$, the…
Heavy flavour production and spectroscopy are key components of the HERA physics programme. I will summarise a selection of the recent results obtained by the H1 and ZEUS collaborations. The production of excited charm mesons and J/psi will…
A search for excited electrons is performed using the full $e^{\pm}p$ data sample collected by the H1 experiment at HERA, corresponding to a total luminosity of 475 pb$^{-1}$. The electroweak decays of excited electrons…