Speaker
Markus Diefenthaler
(Physikalisches Institut II, Friedrich-Alexander-Universität)
Description
In 2005 the HERMES collaboration published first evidence for azimuthal
single-spin asymmetries in semi-inclusive production of charged pions on
a transversely polarised hydrogen target.
The measured asymmetries are caused by both the Collins and the Sivers
mechanisms. Their distinctive Fourier components provide signals to
previously unmeasured quantities: the transversity quark distribution in
conjunction with the Collins fragmentation function (Collins
mechanism/asymmetry) and the Sivers parton distribution (Sivers
mechanism/asymmetry). The transversity distribution will provide a
detailed insight into the relativistic nature of the quarks inside the
nucleon. Continuous theoretical work could relate the Sivers function to
the contribution of the orbital angular momentum of both quarks and
gluons to the spin of the nucleon.
The presented results for charged pions have a much higher statistical
significance than the published data, and are accompanied by the
measurement of the Collins and Sivers asymmetries for charged kaons.
Author
Markus Diefenthaler
(Physikalisches Institut II, Friedrich-Alexander-Universität)
