Speaker
Prof.
Eva-Maria Kabuss
(Mainz university)
Description
The COMPASS experiment is a fixed target experiment at the CERN SPS using muon and hadron beams for the investigation of the spin structure of the nucleon and hadron spectroscopy. The main objective of the muon physics programme is the study of the nucleon spin. COMPASS has accumulated data during 6 years scattering polarised muons off a longitudinally or a transversely polarised
deuteron ($^6$LiD) or proton (NH$_3$) target.
Results for the gluon polarisation are obtained from double spin cross section asymmetries using two different channels, open charm production and high transverse momentum hadron pairs, both proceeding through the photon-gluon fusion process. Also, the longitudinal spin structure functions of the proton
and the deuteron were measured in parallel as well as the helicities for the three lightest quark flavours.
On the transversity side, results were obtained with proton and deuteron targetsfor the Collins and Sivers asymmetries for charged hadrons as well as for identified kaons and pions.
The Collins asymmetry is sensitive to the transverse spin structure, while the Sivers asymmetry reflects correlations between the quark transverse momentum and the nucleon spin.
Recently, a new proposal for the COMPASS II experiment was accepted by the CERN SPS which includes two new topics: Exclusive reactions like DVCS and DVMP using the muon beam and a hydrogen target to study generalized parton distributions and Drell-Yan measurements using a pion beam and a polarised NH_3 targetto study transverse momentum dependent distributions.
Primary author
Prof.
Eva-Maria Kabuss
(Mainz university)
