Date of Award
Doctor of Philosophy (PhD)
A measurement of the effective diffractive structure function Ffi of the antiproton obtained from a study of single diffractive dijet events produced in association with a leading antiproton in pp collisions at the center-of-mass energy y/s = 1800 and 630 GeV is presented. Inclusive samples of single diffractive events were collected during the Tevatron collider run of 1995—1996 using the Collider Detector at Fermilab (CDF) by triggering on a leading antiproton detected in a forward Roman Pot spectrometer. From these samples, single diffractive dijet subsamples were selected by requiring two or more jets with transverse energy ET > 7 GeV in an event. From the dijet data samples, an effective leading order diffractive structure function Ffi of the antiproton is extracted. In the kinematic region of antiproton fractional momentum loss 0.035 < £ < 0.095, four-momentum transfer squared \t\ < 1.0 GeV2 and (3 = xp/£, < 0.5, where xp is the Bjorken scaling variable of the struck parton the antiproton, Ffi(/?,£) is found to have the form Fg (/?,£) oc /r 10±01£-0 9±01 yfs = 1800 GeV. To address the question of QCD factorization in diffraction processes, i.e. universality of the diffractive structure function, several comparisons are made on the measured Ffi. In comparisons with expectations based on results obtained in diffractive deep inelastic scattering experiments at HERA, Ffi measured in this analysis is found to be smaller by approximately an order of magnitude, indicating a breakdown of QCD factorization in diffraction processes. In comparisons with results obtained in pp collisions at y/s = 630 GeV, the ratio in normalization of the measured Ffi at the two energies is found to be R_mo_ = 1.3 ± 0.2(stat)^o3(syst). This is compatible with the factorization expectation of unity, but is also in agreement within errors with predictions in the range 1.6—1.8 from phenomenological models that explain the suppression of the diffractive structure function in pp collisions relative to that collisions. Comparisons with results from a study of dijet events by double pomeron exchange and single diffractive events containing a J/ip meson by the CDF collaboration, and with results from a study of single diffractive dijet events obtained by the UA8 collaboration in pp collisions at y/s = 630 GeV are also presented.
Hatakeyama, Kenichi, "Measurement of the Diffractive Structure Function of the Antiproton in Proton-Antiproton Collisions at √ s = 1800 and 630 GeV" (2003). Student Theses and Dissertations. 328.