Author/Authors :
Brِmmel، نويسنده , , D. and Diehl، نويسنده , , M. and Gِckeler، نويسنده , , M. and Hنgler، نويسنده , , Ph. and Horsley، نويسنده , , R. and Nakamura، نويسنده , , Y. and Pleiter، نويسنده , , D. and Rakow، نويسنده , , P.E.L. and Schنfer، نويسنده , , A. and Schierholz، نويسنده , , G. and Stüben، نويسنده , , H. and Zanotti، نويسنده , , J.M.، نويسنده ,
Abstract :
This paper presents recent lattice QCD calculations of transverse spin densities of quarks in hadrons.22This contribution is based on Refs. [M. Göckeler, et al., Phys. Rev. Lett. 98 (2007) 222001; D. Brömmel, et al., [QCDSF Collaboration]. arXiv:hep-lat/0708.2249].
on our simulation results for the tensor generalized form factors, we find substantial correlations between spin and coordinate degrees of freedom in the nucleon and the pion. They lead to strongly distorted transverse spin densities of quarks in the nucleon and a surprisingly non-trivial transverse spin structure of the pion. Following recent arguments by Burkardt [M. Burkardt, Phys. Rev. D 72 (2005) 094020], our results imply that the Boer–Mulders function h 1 ⊥ , describing correlations of the transverse spin and intrinsic transverse momentum of quarks, is large and negative for up-quarks in the proton and the π + . This supports the recent hypothesis that all Boer–Mulders functions are alike [arXiv:0705.1573], and also provides additional motivation for future studies of azimuthal asymmetries in π p Drell-Yan production at, e.g., COMPASS.
