Measurement of single-spin azimuthal asymmetries in semi-inclusive electroproduction of pions and kaons on a longitudinally polarised deuterium target

Abstract

Single-spin asymmetries have been measured for semi-inclusive electroproduction of pi(+), pi(-), pi(0) and K+ mesons in deep-inelastic scattering off a longitudinally polarised deuterium target. The asymmetries appear in the distribution of the hadrons in the azimuthal angle phi around the virtual photon direction, relative to the lepton scattering plane. The corresponding analysing powers in the sinphi moment of the cross section are 0.012 +/- 0.002(stat.) +/- 0.002(syst.) for pi(+), 0.006 +/- 0.003(stat.) +/- 0.002(syst.) for pi(-), 0.021 +/- 0.005(stat.) +/- 0.003(syst.) for pi(0) and 0.013 +/- 0.006(stat.) +/- 0.003(syst.) for K The sin 20 moments are compatible with zero for all particles. (C) 2003 Elsevier Science B.V All rights reserved

Transversity distribution in spin asymmetries in semi-inclusive DIS and in the Drell-Yan process

“…In the HERMES experiments [20,21,22] the x-and z-dependence of asymmetries (6) for pions and kaons with W = sin φ or sin 2φ from longitudinally (relative to the non-polarized lepton beam) polarized proton and deuterium target were measured. As it is seen from (4) only the second term of dσ 0L and the first (Collins) and the third (Sivers) ones 6 ) of dσ 0T with factor (3) do contribute to the numerator of (6) for W = sin φ with negative sign (φ S = π) and only the third one of the dσ 0L contributes for W = sin 2φ.…”

Collins effect and single spin azimuthal asymmetriesin the HERMES and COMPASS experiments

“…Noticeable single spin azimuthal asymmetries 1 A sin φ UL have been observed by the HERMES collaboration in pion and kaon electro-production in semi-inclusive deep-inelastic scattering (SIDIS) of an unpolarized lepton beam off a longitudinally polarized proton or deuteron target [1][2][3][4]. Recently the CLAS collaboration reported the measurement of the azimuthal asymmetry A sin φ LU from SIDIS of a polarized beam off an unpolarized target [5].…”

Twist-4 contributions to the azimuthal asymmetry in semi-inclusive deeply inelastic scattering

“…There exist experimental measurements of the azimuthal asymmetries in both unpolarized and polarized DIS [14][15][16][17][18][19][20][21][22][23][24][25]. More results are expected from CLAS at JLab and COMPASS at CERN.…”

“…The azimuthal asymmetries and their spin and/or nuclear dependences of the SIDIS cross sections are directly related to the parton distribution and polarization inside nucleon or nuclei and therefore are the subjects of intense studies both theoretically [1][2][3][4][5][6][7][8][9][10][11][12][13] and experimentally [14][15][16][17][18][19][20][21][22][23][24][25]. They provide us with a glimpse into the dynamics of strong interaction within nucleons or nuclei and a baseline for the study of parton dynamics in other extreme conditions at high temperature and baryon density.…”