4 *CMZ :- -29/01/93 11.11.55 by Bryan Webber
6 *-- Author : Giovanni Abbiendi & Luca Stanco
8 C---------------------------------------------------------------------
10 FUNCTION HWUECM (S,M1QUAD,M2QUAD)
12 C-----------------------------------------------------------------------
14 C C.M. ENERGY OF A PARTICLE IN 1-->2 BRANCH, MAY BE SPACELIKE
16 C---------------------------------------------------------------------
18 DOUBLE PRECISION HWUECM,S,M1QUAD,M2QUAD
20 HWUECM = (S+M1QUAD-M2QUAD)/(2.D0*SQRT(S))