Heidelberg 2015 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 1: Invited Talks 1

HK 1.3: Hauptvortrag

Montag, 23. März 2015, 12:30–13:00, T/HS1

Exploring the transverse structure of the nucleon at COMPASS — •Rainer Joosten — HISKP, Universität Bonn

In recent years, considerable theoretical and experimental progress has been made to study the partonic structure of nucleons beyond the standard collinear approach, accounting for transverse degrees of freedom. In the present theoretical framework, eight transverse momentum dependent parton distribution functions (TMDs) are required at leading twist for each quark flavor. They describe all possible correlations between the transverse momentum and spin of the quarks, and the spin of the nucleon. When integrating over the quark transverse momentum five of these functions vanish, while three of them give the known collinear density, helicity and transversity distribution functions.

Experimentally, Semi-Inclusive Deep Inelastic Scattering (SIDIS) is the main source of information. Requiring the detection of at least one final state hadron in coincidence with the scattered lepton, the chiral-odd transversity distribution as well as a variety of new TMDs could be accessed. In addition, the use of different targets and hadron identification allows for a flavor separation of the involved TMDs.

COMPASS is a fixed target experiment at the CERN SPS taking data since 2002. SIDIS data have been collected using a 160 GeV longitudinally polarized muon beam and longitudinally or transversely polarized proton and deuteron targets.

In this talk, selected results related to the transverse structure of the nucleon will be presented and the prospects of future COMPASS measurements accessing TMDs and GPDs will be assessed.