Production of exclusive dijets in diffractive deep inelastic scattering at HERA

Abstract

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 $$\gamma ^{*}$$ –p centre-of-mass energies in the range $$90< W < {250}\,{\mathrm{GeV}}$$ and for photon virtualities $$Q^2 > {25}\,{\mathrm{GeV}^{2}}$$ . Energy flows around the jet axis are presented. The cross section is presented as a function of $$\beta $$ and $$\phi $$ , where $$\beta =x/x_\mathrm{I\!P}$$ , x is the Bjorken variable and $$x_\mathrm{I\!P}$$ is the proton fractional longitudinal momentum loss. The angle $$\phi $$ is defined by the $$\gamma ^{*}$$ –dijet plane and the $$\gamma ^{*}$$ – $$e^\pm $$ plane in the rest frame of the diffractive final state. The $$\phi $$ cross section is measured in bins of $$\beta $$ . The results are compared to predictions from models based on different assumptions about the nature of the diffractive exchange.