The general spin structure of the matrix element, taking into account the two--photon exchange contribution, for the elastic electron (positron) --deuteron scattering has been derived using general symmetry properties of the hadron electromagnetic interaction, such as P--, C-- and T--invariances as well as lepton helicity conservation in QED at high energy. Taking into account also crossing symmetry, the amplitudes of $e^{\mp}d-$scattering can be parametrized in terms of fifteen real functions. The expressions for the differential cross section and for all polarization observables are given in terms of these functions. We consider the case of an arbitrary polarized deuteron target and polarized electron beam (both longitudinal and transverse). The transverse polarization of the electron beam induces a single--spin asymmetry which is non--zero in presence of two--photon exchange. It is shown that elastic deuteron electromagnetic form factors can still be extracted in presence of two photon exchange, from the measurements of the differential cross section and of one polarization observable (for example, the tensor asymmetry) for electron and positron deuteron elastic scattering, in the same kinematical conditions.
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机译:考虑到弹性电子(正电子)-氘核散射的两个光子交换贡献,矩阵元素的一般自旋结构是使用强子电磁相互作用的一般对称性(例如P--)推导出来的,高能态QED中的C和T不变性以及轻子螺旋性守恒还考虑到交叉对称性,可以根据十五个实函数对$ e ^ {\ mp} d- $散射的幅度进行参数化。根据这些函数给出了微分横截面和所有偏振可观测值的表达式。我们考虑任意极化氘核靶和极化电子束(纵向和横向)的情况。电子束的横向极化引起单旋不对称,在存在两个光子交换的情况下该非旋不对称。结果表明,在存在两个光子交换的情况下,仍然可以从微分截面的测量结果以及电子和正电子氘核弹性散射的可观察到的一个极化(例如张量不对称)的测量结果中提取弹性氘电磁形状因数。相同的运动条件。
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