Speaker
Andrea Bressan
(TS)
Description
The spin-dependent structure function g_2 of the proton has been exacted
by the COMPASS experiment (SPS, CERN) from DIS data collected in 2010
using 160 GeV/c muon beam and transversely polarized NH_3 target. Within
the so-called Wandzura-Wilczek approximation, g2 can be related to the
spin-dependent structure function g_1 while from the constraints imposed
by Lorentz invariance relations, it is expected to be linked to the
first k_T-moment of the g_{1T} TMD PDF.
The extraction of g_2 virtual photon-absorption asymmetry A_2 was based
on the measurement of A_{T}^{cos(\phi_S)} asymmetry and on the available
global fit results on g_1 and ratio of longitudinal and transverse
photoabsorption cross sections R.
Compared to the previous measurements performed by SLAC and HERMES
experiments, COMPASS covers larger kinematic range (0.003 < x < 0.9),
providing access to the previously unexplored low-x domain.
In this talk COMPASS preliminary results on g_2 will be presented along
with relevant details of the analysis and comparison with previous
measurements.
Primary author
Andrea Bressan
(TS)
