# XX International Workshop on Deep-Inelastic Scattering and Related Subjects

26-30 March 2012
University of Bonn
Europe/Berlin timezone

## Measurement of the Diffractive Longitudinal Structure Function F_L^D at HERA

27 Mar 2012, 09:20
20m
Lecture Hall, Institute for Applied Physics (University of Bonn)

### Lecture Hall, Institute for Applied Physics

#### University of Bonn

Diffraction and vector mesons

### 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))

 Slides