1 #include "isajet/pilot.h"
2 SUBROUTINE IPRTNS(NPRTNS,PRTNS,IDQ)
3 C----------------------------------------------------------------------
5 C- Purpose and Methods :
6 C- Fill PINITS common block
8 C- IDQ(2)= id's of partons starting reaction
10 C- Created 10-OCT-1991 Serban D. Protopopescu
11 C- Renamed from IPINIT to avoid name clash with Cern Library
13 C----------------------------------------------------------------------
14 #if defined(CERNLIB_IMPNONE)
19 #include "isajet/jetpar.inc"
20 #include "isajet/pinits.inc"
21 REAL AMASS, AM1SQ,AM2SQ,ROOT,QPL,QMN,P1PL,P1MN,P2PL,P2MN
23 C----------------------------------------------------------------------
25 C assumes sum of transverse momenta is zero
29 QPL=QPL+PRTNS(4,I)+PRTNS(3,I)
30 QMN=QMN+PRTNS(4,I)-PRTNS(3,I)
37 PINITS(5,I)=AMASS(IDQ(I))
41 C and solve initial kinematics
44 ROOT=SQRT((QPL*QMN-AM1SQ-AM2SQ)**2-4.*AM1SQ*AM2SQ)
45 P1PL=(QPL*QMN+AM1SQ-AM2SQ+ROOT)/(2.*QMN)
47 P2MN=(QPL*QMN+AM2SQ-AM1SQ+ROOT)/(2.*QPL)
49 PINITS(3,1)=.5*(P1PL-P1MN)
50 PINITS(4,1)=.5*(P1PL+P1MN)
51 PINITS(3,2)=.5*(P2PL-P2MN)
52 PINITS(4,2)=.5*(P2PL+P2MN)