Production of exclusive dijets in diffractive deep inelastic scattering at HERA
Production of exclusive dijets in diffractive deep inelastic $e^\pm p$ scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 372 pb$^{-1}$. The measurement was performed for $γ^*-p$ centre-of-mass energies in the range $90 < W < 250$ GeV and for photon virtualities $Q^2 > 25$ GeV$^2$. Energy and transverse-energy flows around the jet axis are presented. The cross section is presented as a function of $β$ and $ϕ$, where $β=x/x_{\rm I\!P}$, $x$ is the Bjorken variable and $x_{\rm I\!P}$ is the proton fractional longitudinal momentum loss. The angle $ϕ$ is defined by the $γ^*-$dijet plane and the $γ^*-e^\pm$ plane in the rest frame of the diffractive final state. The $ϕ$ cross section is measured in bins of $β$. The results are compared to predictions from models based on different assumptions about the nature of the diffractive exchange.