Azimuthal asymmetries of charged hadrons produced by high-energy muons scattered off longitudinally polarised deuterons

Understand

Azimuthal asymmetries in semi-inclusive production of positive (h^+) and negative hadrons (h^-) have been measured by scattering 160 GeV muons off longitudinally polarised deuterons at CERN.

• The asymmetries were decomposed in several terms according to their expected modulation in the azimuthal angle phi of the outgoing hadron.
• Each term receives contributions from one or several spin and transverse-momentum-dependent parton distribution and fragmentation functions.
• The amplitudes of all phi-modulation terms of the hadron asymmetries integrated over the kinematic variables are found to be consistent with zero within statistical errors, while the constant terms are nonzero and equal for h^+ and h^- within the statistical errors.