The exclusive diffractive production of vector mesons and real photons in ep collisions has been studied at HERA in a wide kinematic range. Here the most recent experimental results are presented together with a Regge-type model and projects for new diffractive studies at LHC.
An increased precision of HERA data allows studies of exclusive processes in their transition from soft to hard interactions as well as in the pQCD domain. The recent measurements of vector meson production and Deeply Virtual Compton Scattering (DVCS) performed by the H1 and ZEUS experiments are reported and compared to pQCD expectations.
Recent results obtained at HERA on deeply virtual Compton scattering and exclusive vector meson production are reviewed, with the emphasis on the transition from soft to hard diffraction and on spin dynamics.
In this article, recent measurements of diffraction in deep inelastic scattering are presented along with QCD fits to extract the partonic structure of the exchange. These so-called diffractive parton density functions can then be used in predictions for other processes to test factorisation in diffraction. This is an important verification of QCD and has significance for predicting exotic signals such as diffractive Higgs production at the LHC.
In this report, we describe the most recent results on exclusive diffraction from the ATLAS, CMS, LHCb, TOTEM experiments at the LHC concerning exclusive pions, $J/Psi$, $Psi(2S)$, dilepton, diphoton, $WW$ productions and prospects concerning the search for anomalous couplings and axion-like particle production.
The exclusive electroproduction of two pions in the mass range 0.4 < M{pi}{pi} < 2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb-1. The analysis was carried out in the kinematic range of 2 < Q2 < 80 GeV2, 32 < W < 180 GeV and |t| < 0.6 GeV2, where Q2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, |F(M{pi}{pi})|, assuming that the studied mass range includes the contributions of the {rho}, {rho} and {rho} vector-meson states. The masses and widths of the resonances were obtained and the Q2 dependence of the cross-section ratios {sigma}({rho} rightarrow {pi}{pi})/{sigma}({rho}) and {sigma}({rho} rightarrow {pi}{pi})/{sigma}({rho}) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e+e- rightarrow {pi}+{pi}-.