标题： $e^+e^-$源在$pN$和$pd$碰撞中的衰减各向异性 显示英文标题

标题： Decay Anisotropy of $e^+e^-$ Sources from $pN$ and $pd$ collisions

摘要： 对在中间能量下由$e^+e^-$对在$pp$、$pn$和$pd$碰撞中产生时的轻子对角度特性进行了完整计算。 证明了所提出的新的可观测量——二轻子衰变各向异性——对于不同的来源会非常敏感，可能有助于它们的区分。 在 BEVALAC 观测到的$pd$反应与$pp$反应的轻子产率比值的令人困惑的能量行为背景下，展示了二轻子衰变各向异性的相关性。 显示英文摘要

摘要： A full calculation of lepton-pair angular characteristics is carried out for $e^+e^-$ pairs created in $pp$, $pn$ and $pd$ collisions at intermediate energies. It is demonstrated that the proposed new observable, the dilepton decay anisotropy, quite sensitively changes for different sources and may be useful for their disentangling. The relevance of the dilepton decay anisotropy is shown in the context of a puzzling energy behavior for the ratio of the lepton yield from $pd$ to $pp$ reactions as observed at the BEVALAC.