Is the Regge Trajectory Quasi-linear or Square-root Form?

A review of the open charm and open bottom systems

“…In reality, the linear property is just the leading order phenomenon in the Regge theory. Various studies have shown that the Regge trajectories can be nonlinear [194,198,199,200,201,202,203]. Although the string-like models or semirelativistic potential models may give a linear relation between the hadron mass squared and its quantum numbers, the universal behavior for both light and heavy quark systems is difficult to obtain in a natural way [204,205].…”