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vendor/IREGI/src/qcdloop/ql/qlI4.f

 

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      double complex function qlI4(p1,p2,p3,p4,s12,s23,

 

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     . m1,m2,m3,m4,mu2,ep)

 

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      implicit none

 

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      double precision p1,p2,p3,p4,s12,s23,m1,m2,m3,m4,mu2,newmu2

 

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      integer ep,j

 

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C     pi=p(i)^2, i=1,2,3,4 are momentum squared of the external lines

 

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C     mi=m(i)^2  i=1,2,3,4 are masses squared of the internal lines

 

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C     sij=(pi+pj)^2 are external invariants

 

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C     mu2 is the square of the scale mu

 

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C     ep=-2,-1,0 chooses the coefficient in the Laurent series.

 

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      double precision xpi(13),scalefac

 

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      double complex qlI4array

 

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C     Uses the ordering for the routine xpi wanted by FF

 

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C     psq(1) lies between msq(1) and msq(2) and so on

 

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C     xpi(1-4) = msq(1),msq(2),msq(3),msq(4)

 

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C     xpi(5-8) = psq(1),psq(2),psq(3),psq(4)

 

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C     xpi(9-10) = s12,s23

 

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C     xpi(11) = +xpi(5)+xpi(6)+xpi(7)+xpi(8)-xpi(9)-xpi(10)

 

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C     xpi(12) = -xpi(5)+xpi(6)-xpi(7)+xpi(8)+xpi(9)+xpi(10)

 

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C     xpi(13) = +xpi(5)-xpi(6)+xpi(7)-xpi(8)+xpi(9)+xpi(10)

 

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      xpi(1)=m1

 

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      xpi(2)=m2

 

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      xpi(3)=m3

 

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      xpi(4)=m4

 

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      xpi(5)=p1

 

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      xpi(6)=p2

 

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      xpi(7)=p3

 

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      xpi(8)=p4

 

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      xpi(9)=s12

 

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      xpi(10)=s23

 

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      xpi(11)=+xpi(5)+xpi(6)+xpi(7)+xpi(8)-xpi(9)-xpi(10)

 

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      xpi(12)=-xpi(5)+xpi(6)-xpi(7)+xpi(8)+xpi(9)+xpi(10)

 

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      xpi(13)=+xpi(5)-xpi(6)+xpi(7)-xpi(8)+xpi(9)+xpi(10)

 

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      scalefac=max(abs(s12),abs(s23),abs(p1),abs(p2),abs(p3),abs(p4))

 

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      do j=1,13

 

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      xpi(j)=xpi(j)/scalefac

 

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      enddo

 

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      newmu2=mu2/scalefac

 

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      qlI4=qlI4array(xpi,newmu2,ep)/scalefac**2

 

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      return

 

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      end

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