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qlbox3.f
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qlbox3.f
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subroutine qlbox3(Y,musq,Ires)
implicit none
c I_4^{D=4-2 \epsilon}(0,\pd^2,0,\pq^2;s_{12},s_{23};0,0,0,0)
C ----%\cite{Bern:1993kr}
c----\bibitem{Bern:1993kr}
c---- Z.~Bern, L.~J.~Dixon and D.~A.~Kosower,
c---- %``Dimensionally regulated pentagon integrals,''
c---- Nucl.\ Phys.\ B {\bf 412}, 751 (1994)
c---- [arXiv:hep-ph/9306240].
c---- %%CITATION = HEP-PH 9306240;%%
c---- Eqs. (I.13)
c [ s12 p4sq ]
c [ 0 0 - --- - ---- ]
c [ 2 2 ]
c [ ]
c [ p2sq s23 ]
c [ 0 0 - ---- - --- ]
c [ 2 2 ]
c Y3 = [ ]
c [ s12 p2sq ]
c [ - --- - ---- 0 0 ]
c [ 2 2 ]
c [ ]
c [ p4sq s23 ]
c [ - ---- - --- 0 0 ]
c [ 2 2 ]
include 'qlconstants.f'
double precision si,ta,mp2sq,mp4sq,musq,r,Y(4,4)
double complex Ires(-2:0),qlLsm1_2me,qlL0,qlL1,qllnrat,fac
logical landau
si=2d0*Y(1,3)
ta=2d0*Y(2,4)
mp4sq=2d0*Y(1,4)
mp2sq=2d0*Y(2,3)
r=1d0-mp2sq*mp4sq/(si*ta)
C Use expansion only in cases where signs (si,ta,mp2sq,mp4sq) are not
C ++-- or --++
landau=((sign(1d0,si) .eq. sign(1d0,ta))
. .and. (sign(1d0,mp2sq) .eq. sign(1d0,mp4sq))
. .and. (sign(1d0,si) .ne. sign(1d0,mp2sq)))
if ((abs(r) .lt. 1d-6) .and. (landau .eqv. .false.)) then
C---expanded case
fac=dcmplx(1d0/(si*ta))
Ires(-2)=czip
Ires(-1)=-dcmplx(2d0+r)*fac
Ires( 0)=fac*(dcmplx(2d0-0.5d0*r)
. +dcmplx(2d0+r)*(qllnrat(si,musq)+qllnrat(ta,mp4sq))
. +dcmplx(2d0)*(qlL0(mp4sq,ta)+qlL0(mp4sq,si))
. +dcmplx(r)*(qlL1(mp4sq,ta)+qlL1(mp4sq,si)))
else
C---general case
fac=dcmplx(1d0/(si*ta-mp2sq*mp4sq))
Ires(-2)=czip
Ires(-1)=fac*2d0*(qllnrat(mp2sq,si)
. +qllnrat(mp4sq,ta))
Ires( 0)=fac*(+qllnrat(si,musq)**2+qllnrat(ta,musq)**2
. -qllnrat(mp2sq,musq)**2-qllnrat(mp4sq,musq)**2
. +2d0*qlLsm1_2me(-si,-ta,-mp2sq,-mp4sq))
endif
return
end

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