4 *CMZ :- -26/04/91 11.11.56 by Bryan Webber
6 *-- Author : Bryan Webber
8 C-----------------------------------------------------------------------
12 C-----------------------------------------------------------------------
14 C PUTS INVARIANT MASS IN 5TH COMPONENT OF VECTOR
16 C (NEGATIVE SIGN IF SPACELIKE)
18 C-----------------------------------------------------------------------
20 DOUBLE PRECISION HWUSQR,P(5)
24 P(5)=HWUSQR((P(4)+P(3))*(P(4)-P(3))-P(1)**2-P(2)**2)