Unitarity bounds for 4-fermion contact interactions

Abstract

In this paper the authors consider the effect of unitarity bounds s[sub b] [ge] s is defined (E[sub 1] + E[sub 2])[sup 2][sub cms] for the recently proposed types of nonderivative 4-fermion contact interactions. To this purpose the authors decompose the helicity amplitudes at c.m.s. into partial waves. The bounds are defined to hold for all reaction channels due to the same type of contact interaction. It is found that s[sub b] = [tau]4[pi]/[kappa] where [kappa] is the coupling constant. The factor [tau] depends on the type of coupling and on the different cases to identify the fermions. It ranges from 1/3 to 4. 12 refs., 2 tabs.