1.Basic Information


First Observation of the Decay Ds+ -> pn bar


Liu Kai      Su Yumo    Ryuta Kiuchi     Lu Xiaoxu


Question A:  What's the main purpose & conclusion of studying this Feynman diagram?

Answer:  W annihilation diagram is short-distance process. There's also long-distance process. These two processes are competitors, hence measuring this could help understand the contribution proportion. Besides, this paper introduces work about 10 years ago, therefore some physical mechanisms are not that clear.  Recent study shows that long-distance process contributes more that W annihilation.

Question B:  Could we study similar physical mechanisms in B meson energy region?

Answer: Charm sector is more special. B meson is heavier, and therefore could get more final processes. However, in charm sector, pn bar process is the only one that could happen.