The dependence of the photon structure on the photon virtuality, Q(2), is s
tudied by measuring the reaction e(+) p --> e(+) + jet + jet + X at photon-
proton centre-of-mass energies 134 < W < 223 GeV. Events have been selected
in the Q(2) ranges approximate to 0 GeV2, 0.1-0.55 GeV2, and 1.5-4.5 GeV2,
having two jets with transverse energy E-f(jet) > 5.5 GeV in Ihe Final sta
te. The dijet cross section has been measured as a Function of the fraction
al momentum of the photon participating in the hard process, x(gamma)(OBS).
The ratio of the dijet cross section with x(gamma)(OBS) < 0.75 to that wit
h x(gamma)(OBS) > 0.75 decreases as Q(2) increases. The data are compared w
ith the predictions of NLO pQCD and leading-order Monte Carlo programs usin
g various parton distribution functions of the photon. The measurements can
be interpreted in terms of a resolved photon component that falls with Q(2
) but remains present at values of Q(2) up to 4.5 GeV2. However, none of th
e models considered gives a good description of the data. (C) 2000 Elsevier
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