crsjet.f

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C
C
C       THIS PROGRAM IS TO CALCULATE THE JET CROSS SECTION
C       THE INTEGRATION IS DONE BY USING VEGAS
C
        SUBROUTINE crsjet
        IMPLICIT REAL*8(a-h,o-z)
        REAL hipr1(100),hint1(100)
        common/hiparnt/hipr1,ihpr2(50),hint1,ihnt2(50)
        SAVE  /hiparnt/
        common/njet/n,ip_crs
        SAVE  /njet/
        common/bveg1/xl(10),xu(10),acc,ndim,ncall,itmx,nprn
        SAVE  /bveg1/
        common/bveg2/xi(50,10),si,si2,swgt,schi,ndo,it
        SAVE  /bveg2/
        common/bveg3/f,ti,tsi
        SAVE  /bveg3/
        common/seedvax/num1
        SAVE  /seedvax/
        EXTERNAL fjet,fjetrig
C
c************************
c       NCALL give the number of inner-iteration, ITMX 
C       gives the limit of out-iteration. Nprn is an option
C       ( 1: print the integration process. 0: do not print)
C

C       print *, 'ncall = ', ncall
C       print *, 'itmx = ', itmx
C       print *, 'nprn = ', nprn
C       print *, 'acc = ', acc
C       print *, 'xl(1), xu(1) = ', XL(1), XU(1)
C       print *, 'xl(2), xu(2) = ', XL(2), XU(2)
C       print *, 'xl(3), xu(3) = ', XL(3), XU(3)

C +++BAC
C
C  The following line inserted to improve the accuracy of the jet cross-section
C    integration for LHC purposes where integration region runs out to XT=1 where the
C    contribution is infinitesimal. Found to be necessary because large jet cross-section
C    errors were affecting total and inelastic cross-sections.
C
        ncall = 4000

C ---BAC

        ndim=3
        ip_crs=0
        CALL vegas(fjet,avgi,sd,chi2a)
        hint1(14)=avgi/2.5682
        IF(ihpr2(6).EQ.1 .AND. ihnt2(1).GT.1) THEN
                ip_crs=1
                CALL vegas(fjet,avgi,sd,chi2a)
                hint1(15)=avgi/2.5682
        ENDIF
        IF(ihpr2(6).EQ.1 .AND. ihnt2(3).GT.1) THEN
                ip_crs=2
                CALL vegas(fjet,avgi,sd,chi2a)
                hint1(16)=avgi/2.5682
        ENDIF
        IF(ihpr2(6).EQ.1.AND.ihnt2(1).GT.1.AND.ihnt2(3).GT.1) THEN
                ip_crs=3
                CALL vegas(fjet,avgi,sd,chi2a)
                hint1(17)=avgi/2.5682
        ENDIF
C               ********Total inclusive jet cross section(Pt>P0) 
C
        IF(ihpr2(3).NE.0) THEN
           ip_crs=0
           CALL vegas(fjetrig,avgi,sd,chi2a)
           hint1(61)=avgi/2.5682
           IF(ihpr2(6).EQ.1 .AND. ihnt2(1).GT.1) THEN
              ip_crs=1
              CALL vegas(fjetrig,avgi,sd,chi2a)
              hint1(62)=avgi/2.5682
           ENDIF
           IF(ihpr2(6).EQ.1 .AND. ihnt2(3).GT.1) THEN
              ip_crs=2
              CALL vegas(fjetrig,avgi,sd,chi2a)
              hint1(63)=avgi/2.5682
           ENDIF
           IF(ihpr2(6).EQ.1.AND.ihnt2(1).GT.1.AND.ihnt2(3).GT.1) THEN
              ip_crs=3
              CALL vegas(fjetrig,avgi,sd,chi2a)
              hint1(64)=avgi/2.5682
           ENDIF
        ENDIF
C                       ********cross section of trigger jet
C
        RETURN
        END