Deeply Virtual Compton Scattering off unpolarised deuterium at HERMES

[摘要] The HERMES experiment was a forward angle spectrometer on the HERA storage ring at DESY, Hamburg, Germany. HERMES successfully increased understanding of the “spin puzzle”, the spin structure of the nucleon, by providing high precision measurements of ∆Σ in the Quark Parton Model, the fraction of the spin carried by the current quarks.Following the link of another piece of the puzzle, the orbital angular momentum of quarks and gluons, to the Generalised Parton Distribution (GPD) theoretical framework, HERMES focused on measurements of the Deeply Virtual Compton Scattering (DVCS) process. These measurements are sensitive to GPDs, allowing further experimental constraints to be made on the components of nucleon spin. In the Winter shutdown period 2005-2006 HERMES was upgraded with a Recoil Detector in the target region. This allowed the experiment to make exclusive measurements of the DVCS process for the first time, reducing background and increasing the resolution of various kinematic variables. The method for reconstructing particle tracks in the inhomogeneous magnetic field is investigated here. DVCS off a deuterium target is measured with all available data prior to the installation of the Recoil Detector. A comparison is made to currently available models of spin-1/2 GPDs. This analysis has been approved for publication by the HERMES collaboration. The data is further employed in an investigation of a model dependent constraint of the total angular momentum of up and down quarks in the nucleon.

[发布机构] University:University of Glasgow;Department:School of Physics and Astronomy

[关键词] Deeply Virtual Compton Scattering, Deuterium, HERMES, DVCS, GPDs