Soft-photon contribution into two-photon exchange corrections for azimuthal asymmetries of SIDIS

It is demonstrated that two-photon exchange (TPE) corrections to the cross-section of unpolarized semi-inclusive deep-inelastic scattering generate azimuthal-dependent terms and the corresponding <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mo stretchy="false">⟨</a:mo><a:mrow><a:mi>cos</a:mi><a:mrow><a:mo stretchy="false">(</a:mo><a:mi>n</a:mi><a:mi>ϕ</a:mi><a:mo stretchy="false">)</a:mo></a:mrow></a:mrow><a:mo stretchy="false">⟩</a:mo></a:math> moments. A quark-diquark model of a nucleon was used in the calculations along with a soft-photon approximation. The infrared divergences in the intermediate steps of calculation are regularized with the fictitious photon mass that cancels out in the final result when the soft-photon bremsstrahlung process and interference terms are added. The calculations employ the oopools package to evaluate the loop integrals. TPE corrections are analyzed in the kinematics of planned experiments at Jefferson Lab.