A new gamma*-p / pbar-p factorization test in diffraction, valid below Q² about 6 GeV²

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One of the key experimental issues in high energy hadron physics is the extent to which data from the diffractive interaction mechanism may be described by a factorized formula which is the product of a universal term describing the probability of finding a Pomeron in a proton (loosely referred to as the "Pomeron flux-factor") and a term decribing the Pomeron's interaction with the other incident proton. In the present paper, after demonstrating that existing data on diffractive gamma*-p and pbar-p interactions show that the Pomeron flux-factor is not universal, we present the results of a new test of factorization in these interactions which does not rely on universality of the flux-factor. The test is satisfied to within 20% for 1 < Q² 6 GeV² and beta < 0.2 in the gamma*-p interactions, suggesting that the resons for non-universality of the flux-factor have a limited effect on the factorization itself. However, a clear breakdown of this test is observed at larger Q². Kharzeev and Levin suggest that this can be attributed to the onset of QCD evolution effects in the Pomeron's structure. The breakdown occurs in a Q² region which agrees with their estimates of a small Pomeron size.