We have to explain using quark model why there are no known mesons with and or with and .

Solution:             Click For PDF Version

Properties of the fundamental quarks are as given in the following table:

Quark	Symbol	Charge (e)	Spin	Baryon Number	Strangeness
Up	u				0
Down	d				0
Strange	s				-1

The charge, baryon number, and strangeness of , , and are opposite of u, d, and s, respectively.

Mesons have baryon number 0, therefore they comprise of one quark and one anti-quark. A meson with charge can either be the combination u, or u. The strangeness of u is 0 and that of u is . Therefore, there is no known meson with and .

Meson with has to be the quark combination d or s. The strangeness of d is zero and that of s is . Therefore, there is no known meson with and .