Measurement of $A_{LL}(pT)$ for single hadron photoproduction at high $p_T$ at COMPASS

In order to understand the gluon contribution to the nucleon spin, some experiments can study the production of hadrons at high transverse momemtum from lepton-nucleon or nucleon-nucleon scattering. RHIC has recently measured such double spin asymmetries A LL ( p T ) for pion production at high center of mass energies [ 1 ] [ 2 ], and inclusion of its data to global fits based on NLO collinear pQCD calculations gives some constraints on the gluon polarization in the range 0 : 05 < x g < 0 : 2. [ 3 ] To completement these results at COMPASS range, we will present preliminary COMPASS re- sults on double longitudinal spin asymmetries A LL ( p T ) for single hadron production measured on deuteron and proton target at Q 2 < 1 ( GeV = c ) 2 , p T > 1 GeV = c and center of mass energy p s 18 GeV . All COMPASS data taken from 2002 to 2011 by scattering 160 GeV polarized muons on longitudinally polarized 6 LiD and NH 3 targets have been used, and the number of hadrons collected with p T > 1 GeV = c for this analysis amounts to about 10 millions. The obtained asymmetries will be compared to theoretical predictions of at NLO without gluon resummation calculation