Author/Authors :
ZEUS Collaboration، نويسنده , , J. Breitweg، نويسنده , , Valeri S. Chekanov، نويسنده , , M. Derrick، نويسنده , , D. Krakauer، نويسنده , , S. Magill، نويسنده , , B. Musgrave، نويسنده , , A. Pellegrino، نويسنده , , J. Repond، نويسنده , , Christopher R. Stanek، نويسنده , , R. Yoshida، نويسنده , , M.C.K. Mattingly، نويسنده , , G. Abbiendi، نويسنده , , F. Anselmo، نويسنده , , P. Antonioli، نويسنده , , G. Bari، نويسنده , , M. Basile، نويسنده , , L. Bellagamba، نويسنده , , D. Boscherini، نويسنده , , C. B. Vicentini and A. Bruni، نويسنده , , et al.، نويسنده ,
Abstract :
The dependence of the photon structure on the photon virtuality, Q2, is studied by measuring the reaction e+p→e++jet+jet+X at photon-proton centre-of-mass energies 1345.5 GeV in the final state. The dijet cross section has been measured as a function of the fractional momentum of the photon participating in the hard process, xγOBS. The ratio of the dijet cross section with xγOBS<0.75 to that with xγOBS>0.75 decreases as Q2 increases. The data are compared with the predictions of NLO pQCD and leading-order Monte Carlo programs using various parton distribution functions of the photon. The measurements can be interpreted in terms of a resolved photon component that falls with Q2 but remains present at values of Q2 up to 4.5 GeV2. However, none of the models considered gives a good description of the data.
