lu1ent.f

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C
C
C
C     Modified for HIJING program
c
c    modification July 22, 1997  In pyremnn put an upper limit
c     on the total pt kick the parton can accumulate via multiple
C     scattering. Set the upper limit to be the sqrt(s)/2,
c     this is fix cronin bug for Pb+Pb events at SPS energy.
c
C
C Last modification Oct. 1993 to comply with non-vax
C machines' compiler 
C
C
      SUBROUTINE lu1ent(IP,KF,PE,THE,PHI)   
    
C...Purpose: to store one parton/particle in commonblock LUJETS.    
      common/lujets/n,k(9000,5),p(9000,5),v(9000,5) 
      SAVE /lujets/ 
      common/ludat1/mstu(200),paru(200),mstj(200),parj(200) 
      SAVE /ludat1/ 
      common/ludat2/kchg(500,3),pmas(500,4),parf(2000),vckm(4,4)    
      SAVE /ludat2/ 
    
C...Standard checks.    
      mstu(28)=0    
      IF(mstu(12).GE.1) CALL lulist(0)  
      ipa=max(1,iabs(ip))   
      IF(ipa.GT.mstu(4)) CALL luerrm(21,    
     &'(LU1ENT:) writing outside LUJETS memory')    
      kc=lucomp(kf) 
      IF(kc.EQ.0) CALL luerrm(12,'(LU1ENT:) unknown flavour code')  
    
C...Find mass. Reset K, P and V vectors.    
      pm=0. 
      IF(mstu(10).EQ.1) pm=p(ipa,5) 
      IF(mstu(10).GE.2) pm=ulmass(kf)   
      DO 100 j=1,5  
      k(ipa,j)=0    
      p(ipa,j)=0.   
  100 v(ipa,j)=0.   
    
C...Store parton/particle in K and P vectors.   
      k(ipa,1)=1    
      IF(ip.LT.0) k(ipa,1)=2    
      k(ipa,2)=kf   
      p(ipa,5)=pm   
      p(ipa,4)=max(pe,pm)   
      pa=sqrt(p(ipa,4)**2-p(ipa,5)**2)  
      p(ipa,1)=pa*sin(the)*cos(phi) 
      p(ipa,2)=pa*sin(the)*sin(phi) 
      p(ipa,3)=pa*cos(the)  
    
C...Set N. Optionally fragment/decay.   
      n=ipa 
      IF(ip.EQ.0) CALL luexec   
    
      RETURN    
      END