München 2006 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 15: Elektromagnetische und Hadronische Sonden
HK 15.1: Gruppenbericht
Dienstag, 21. März 2006, 14:00–14:30, F
The Determination of the Gluon Polarisation at COMPASS — •Martin von Hodenberg, H. Fischer, J. Franz, S. Hedicke, F.H. Heinsius, F. Hermann, D. Kang, K. Königsmann, F. Nerling, C. Schill, D. Setter, A. Vossen, E. Weise, and H. Wollny — Physikalisches Institut, Albert-Ludwigs-Universität Freiburg
COMPASS is an experiment at the SPS at CERN, which is aiming at a better understanding of the spin structure of the nucleon, by performing a measurement of the gluon polarisation Δ G/G. In order to achieve this goal, polarised muons with a momentum of 160 GeV/c are scattered from a polarised fixed LiD-target and events are studied where the underlying process is the fusion of a virtual photon with a gluon from the nucleon.
Two approaches are used in COMPASS in order to tag these photon-gluon fusion (PGF) events, which give then access to the gluon polarisation via double spin asymmetries.
The so-called open-charm method requires the production of a cc-pair, which results in charmed mesons in the final state. These mesons are detected in the COMPASS spectrometer via their decay products.
In the second approach the fraction of PGF events is enhanced by requiring two hadrons with high transverse momentum pt. Monte Carlo simulations are used in this case to estimate the relative contributions from PGF and background processes.
The presentation will inform about the current status of the analyses and present their results for the gluon polarisation.
This project is supported by BMBF.