Measurement of the diffractive structure function F_2^D(3)

Reference P Newman, talk presented at EPS 2001, July 2001
Document Conference paper
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Contact Paul Newman
Abstract A new high precision inclusive measurement of the diffractive deep inelastic scattering (DIS) process ep -> eXY is presented, where Y is a proton or a low mass proton excitation carrying a fraction 1 - xpom > 0.95 of the beam longitudinal momentum and the squared 4-momentum transfer at the proton vertex t > -1 GeV^2. The measurement is presented in the form of a diffractive structure function F_2^D(3)(beta, Q^2, xpom), which is measured in the kinematic range 6.5 < Q^2 < 120 GeV^2, 0.01 < beta< 0.9 and 10^-4 <= xpom < 0.05. The xpom dependence of the data is interpreted in terms of a measurement of the effective pomeron intercept alphapom(0), which is compared with the same quantity extracted from inclusive DIS. The beta and Q^2 dependences of F_2^D are studied at fixed xpom. Scaling violations resulting in a rising dependence on ln(Q^2) are observed up to large values of beta. The Q^2 dependence of F_2^D is compared with the Q^2 dependence of F_2(x,Q^2) at the same value of x. The data can be described by the DGLAP evolution equations assuming QCD hard scattering factorisation for semi-inclusive processes and an xpom dependence motivated by Regge theory. The measured F_2^D is compared with models for diffractive DIS.
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