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73 lines
2.0 KiB
73 lines
2.0 KiB
!
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! SPDX-License-Identifier: GPL-3.0-or-later
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! Copyright (C) 2019-2022, respective authors of MCFM.
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!
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subroutine qqb_Hg_v(p,msq)
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implicit none
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include 'types.f'
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c---Matrix element squared averaged over initial colors and spins
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c parton(-p1)+parton(-p2) --> H(p)+parton(p5)
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c |
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c --> b(p3)+bb(p4)
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c--all momenta incoming
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include 'constants.f'
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include 'nf.f'
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include 'mxpart.f'
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include 'masses.f'
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include 'msbarmasses.f'
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include 'ewcouple.f'
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include 'susycoup.f'
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include 'scheme.f'
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include 'scale.f'
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include 'couple.f'
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integer:: j,k
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real(dp):: msq(-nf:nf,-nf:nf),p(mxpart,4),s
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real(dp):: coupsq_eff,ghbb_eff
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real(dp):: mb_eff,massfrun
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real(dp):: fac,propsq,hdecay,bbghvirt
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c--susycoup is the deviation of Higgs coupling
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c-- from the standard model value
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c--statement function
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s(j,k)=2._dp*(p(j,4)*p(k,4)-p(j,1)*p(k,1)
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& -p(j,2)*p(k,2)-p(j,3)*p(k,3))
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c---ur-amplitude is b(p1)+bbar(p2)+g(p3)+H(q)
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c amp(j1,j2,j3)=4._dp*(s(j1,j2)**2+s(3,4)**2)/(s(j1,j3)*s(j2,j3))
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scheme='dred'
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msq(:,:)=0._dp
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if (s(3,4) < 4._dp*mbsq) return
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c--- run mb to appropriate scale
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mb_eff=massfrun(mb_msbar,scale,amz,2)
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c mb_eff=mb_msbar
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call hbbdecay(p,3,4,hdecay)
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hdecay=hdecay*susycoup**2
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propsq=1._dp/((s(3,4)-hmass**2)**2+(hmass*hwidth)**2)
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c--- The _eff couplings include the running mass
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c--- We need to separate these from the factors associated with the
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c--- Higgs decay, because the Br. Ratio does not include running mb
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ghbb_eff=sqrt(esq/xw)*mb_eff/2._dp/wmass
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coupsq_eff=susycoup**2*ghbb_eff**2
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fac=coupsq_eff*propsq*hdecay
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c fac=CF*xn*gsq*coupsq*propsq*hdecay
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msq(0,+5)=+fac*aveqg*bbghvirt(2,5,1)
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msq(0,-5)=+fac*aveqg*bbghvirt(5,2,1)
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msq(+5,0)=+fac*aveqg*bbghvirt(1,5,2)
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msq(-5,0)=+fac*aveqg*bbghvirt(5,1,2)
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return
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end
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