Hadron leptoproduction in Semi-Inclusive measurements of Deep-Inelastic Scattering (SIDIS) on unpolarised nucleons allows one to get information on the intrinsic transverse momentum of quarks in a nucleon and on the Boer-Mulders function through the measurement of azimuthal modulations in the cross section. These modulations were recently measured by the HERMES experiment at DESY on proton and deuteron targets, and by the COMPASS experiment using the CERN SPS muon beam and a ⁶LiD target. In both cases, the amplitudes of the $\cos {\varphi }_h$ and $\cos 2{\varphi }_h$ modulations show strong kinematic dependences for both positive and negative hadrons. It has been known since some time that the measured final-state hadrons in those SIDIS experiments receive a contribution from exclusive diffractive production of vector mesons, particularly important at large values of z, the fraction of the virtual photon energy carried by the hadron. In previous measurements of azimuthal asymmetries this contribution was not taken into account, because it was not known that it could distort the azimuthal modulations. Presently, a method to evaluate the contribution of the exclusive reactions to the azimuthal asymmetries measured by COMPASS has been developed. The subtraction of this contribution results in a better understanding of the kinematic effects, and the remaining non-zero $\cos 2{\varphi }_h$ modulation gives indication for a non-zero Boer-Mulders effect.

非极化核子的深非弹性散射（SIDIS）半包容性测量中的强子造血术使人们能够通过测量横截面的方位角调制来获得关于核子中夸克的固有横向动量和布尔-莫尔德函数的信息。这些调制最近通过在DESY上的HERMES实验在质子和氘核靶上进行了测量，并通过使用CERN SPS介子束和⁶ LiD靶的COMPASS实验进行了测量。在这两种情况下，$\cos {\varphi }_H$ 和 $\cos 2{\varphi }_H$调制对正和负强子都显示出强烈的运动学依赖性。一段时间以来，人们已经知道，在那些SIDIS实验中，测得的最终态强子受到矢量介子独家衍射产生的贡献，这在大z值（强子携带的虚拟光子能量的分数）大时尤为重要。在先前的方位角非对称性测量中，未考虑此影响，因为不知道它会扭曲方位角调制。目前，已经开发出一种方法来评估专用反应对COMPASS测量的方位不对称性的贡献。减去此贡献有助于更好地理解运动学效果，而剩下的非零值$\cos 2{\varphi }_H$ 调制给出了非零Boer-Mulders效应的指示。