Speaker
David Salek
(CERN)
Description
First measurements are presented of the diffractive cross section
$\sigma_{ep \rightarrow eXY}$ at centre-of-mass energies $\sqrt{s}$ of
225 and 252 GeV, together with a precise new measurement at $\sqrt{s}$ of
319 GeV, using data taken with the H1 detector in the years 2006 and 2007.
Together with previous H1 data at $\sqrt{s}$ of 301 GeV, the measurements
are used to extract the diffractive longitudinal structure function F_L^D
in the range of photon virtualities 4.0 <= Q^2 <= 44.0 GeV^2 and fractional
proton longitudinal momentum loss 5 10^{-4} <= x_{IP} <= 3 10^{-3}. The
measured F_L^D is compared with leading twist predictions based on
diffractive parton densities extracted in NLO QCD fits to previous
measurements of diffractive Deep-Inelastic Scattering and with a model
which additionally includes a higher twist contribution derived from a
colour dipole approach. The ratio of the diffractive cross section induced
by longitudinally polarised photons to that for transversely polarised
photons is extracted and compared with the analogous quantity for inclusive
Deep-Inelastic Scattering.
Primary author
Richard Polifka
(University of Toronto (CA))
