Why is mass^2 "proportional" to total angular momentum in mesons (Regge theory)?


Regge theory states that mass m and angular momentum J
are related by
m^2 ~ c+d*J
for mesons of similar properties. It s also states that this
has to do with the elongated shape of mesons.
Can somebody explain this in simple physics?

I do not seem to find a simple explanation on the
internet - only research papers.

Thanks in advance!

Frank
.