Bonn 2010 – wissenschaftliches Programm
HK 16.2: Gruppenbericht
Dienstag, 16. März 2010, 14:30–15:00, HG III
New results of transverse target spin asymmetries on a proton target at COMPASS — •Andreas Richter — Physikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
COMPASS is a fixed target experiment at the CERN M2 external beamline using a 160 GeV/c polarized µ+ beam. After the data taking in 2002-04 with a transversely polarized deuterium target, in 2007 COMPASS has taken data with a transversely polarized proton (NH3) target. For having a full description of the spin structure of the nucleon at quark level at leading twist it is necessary to know all three quark distribution functions, namely the unpolarized distribution function q(x), the helicity distribution function Δ q(x) and the transverse spin distribution function ΔT q(x), the so-called Transversity. One possibility to extract the transverse spin distribution function is the measurement of the Collins effect in semi-inclusive DIS on a transversely polarized target, describing the fragmentation of transversely polarized quarks into spinless hadrons. Furthermore the Sivers effect was studied at COMPASS, which measures the correlation of the transverse momentum of an unpolarized quark in a transversely polarized nucleon and the transverse polarization of the nucleon. New results on those asymmetries will be presented and will be compared to COMPASS deuteron data. The work is supported by the BMBF.