Diffractive Dijet Production

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Contact(s) M. Gallinaro, K. Goulianos and K. Terashi
Abstract Results are presented from a study of diffractive dijet production in p-pbar collisions at a center-of-mass energy of 1.96 TeV. The data sample consists of events collected by triggering on a high transverse energy jet in coincidence with a recoil antiproton detected in a Roman Pot Spectrometer (RPS). Approximately, the average jet transverse energy in an event is 12 GeV, and the fractional momentum loss of the recoil antiproton, ξ, and 4-momentun transfer squared, |t|, are in the range 0.03 < ξ < 0.1 and |t| < 0.1 GeV^2. We measure the ratio of single-diffractive (SD) to non-diffractive (ND) dijet event rates as a function of x-Bjorken and Q^2 in the range 10^-3 < x_Bj < 10^-1 and 10^2 < Q^2 < 100^2 GeV^2. We also measure the |t|-distribution of diffractive events as a function of Q^2 in the range |t| < 1 GeV^2 and Q^2 < 100^2 GeV^2. Our results confirm our Run I result on x_Bj dependence of the ratio of SD/ND event rates, show small Q^2 dependence in the SD/ND event ratio, and no observable Q^2 dependence in the diffractive |t|-distributions. These results reinforce the picture emerged from our Run I results for the diffractive exchange, the Pomeron, as evolving similarly to the proton. This picture is consistent with a composite Pomeron made up from a combination of proton PDFs, one on the hard scale that produces the jets and another (or others) on a soft scale responsible for neutralizing the color being exchanged and producing the rapidity gap.
Comments Last Update: February 2006       Dataset: 128 pb-1