Study of low energy ^^-KN interaction

我们一直在研究核子和K介子(Kaon)之间的强相互作用，方法是用具有奇怪夸克的Kaon取代氢原子中的一个电子。当Kaon停在气态氢靶中时，就会产生Kaon氢原子。连续灭磁产生的X射线能量使能量漂移和线宽从电磁场值变宽，特别是对于向地面的过渡。因此，对这一X射线的精确测量给出了低能极限下^^-kN相互作用的最基本信息。我们在KEK PS-E228(KpX)上成功地观测到了高能氢2p到1s的跃迁，并开始了DAΦNE-DELE实验，通过对K-d和K-p原子X射线观测的详细研究，推导出相互作用的同位旋依赖关系，但研究的道路并不一定是平坦的。最大的问题是，加速器的运行被大大推迟了，远远超出了预期。此外，我们还遭受了巨大的背景，超出预期100倍以上。另一方面，这一困难推动了与Akaishi等人的理论联合研究。结果表明，K介子可以在核内形成一个稳定的态，这是基于以下结果：1)我们的GSI实验S218表明，π介子可以存在于核内；2)我们的KpX结果表明，K介子和质子之间具有很强的吸引力。如果原子核内部存在深度束缚的高子态，则可以更直接、更有效地实现这一研究计划的目的。通过目前的资助，我们能够开始在KEK(PS-E471)上寻找深度束缚的高子态。

We have been studying the strong interaction between nucleon and K meson (kaon) by replacing an electron in the hydrogen atom with kaon, which has a strange quark. When, kaon stops in the gaseous hydrogen target, kaonic hydrogen atom is generated. The energy of the emitted x ray from the successive deexcitation gives energy shift and line width broadening from the electromagnetic value, especially for the transition to the ground. Therefore, the precise measurement of this X rays gives the most basic information of the ^^-KN interaction at the low energy limit. We have succeeded to observe the kaonic hydrogen 2p to 1s transition at KEK PS-E228 (KpX), and began the DAΦNE-DEAR experiment to deduce the isospin dependence of the interaction by detailed study both on K-d and K-p atom X rays observations.However, the way of the research is not necessarily smooth. The biggest problem is that the accelerator operation had been delayed substantially from the schedule away beyond the expectation. Moreover, we had been suffered by the huge background, which exceeded the expectation by 100 times more. On the other hand, this difficulty promoted a joint research with the theory with Akaishi et al. It is shown that the kaon may form a stable state inside the nuclei, based on the results i) our GSI experiment S218 revealed that the pi meson can exist inside the nuclei, and ii) our KpX result indicated strongly attractive nature between kaon and proton. If there exist deeply bound kaonic state inside nuclei, the purpose of this research program can be achieved more directly in more efficient way. By the present grant, we were able to start the search for the deeply-bound kaonic state at KEK (PS-E471).