New commit of Z_ew-BMNNPV

git-svn-id: svn://powhegbox.mib.infn.it/trunk/POWHEG-BOX@2200 9e129b38-c2c0-4eec-9301-dc54fda404de

Author: nason

Z_ew-BMNNPV/Born.f

@@ -0,0 +1,220 @@
+      subroutine born_phsp(xborn)
+      implicit none
+      include 'nlegborn.h'
+      include 'pwhg_flst.h'
+      include 'pwhg_kn.h'
+      include 'pwhg_math.h'
+      include 'PhysPars.h'
+      real * 8 xborn(ndiminteg-3)
+      real * 8 xjac,tau,y,beta,vec(3),cth,cthdec,phidec,s,
+     # z,zhigh,zlow
+      integer mu,k
+      logical ini
+      data ini/.true./
+      save ini
+      real*8 random
+      external random
+      real *8 decmass
+      common/clepmass/decmass
+      real*8 lambda,dotp
+      external lambda,dotp
+      real*8 pmod
+
+      real*8 anorm,anbw,anlog,pbw,csi
+
+      if(ini) then
+c     set initial- and final-state masses for Born and real
+         do k=1,2
+            kn_masses(k)=0
+         enddo
+         kn_masses(3)=decmass
+         kn_masses(4)=decmass
+         kn_masses(nlegreal)=0
+         ini=.false.
+      endif
+c Phase space:
+c 1 /(16 pi S) d m^2 d cth d y
+      xjac=1d0/kn_sbeams/(16*pi)
+
+
+      pbw=0.5d0
+
+      zlow=atan((ph_Zmass2low  - ph_Zmass2)/ph_ZmZw)
+      zhigh=atan((ph_Zmass2high  - ph_Zmass2)/ph_ZmZw)
+
+      anbw = (zhigh - zlow)/ph_ZmZw
+
+      anlog = log(ph_Zmass2high/ph_Zmass2low)
+
+      anorm = pbw*anbw + (1d0-pbw)*anlog
+
+c      z=zlow+(zhigh-zlow)*xborn(1)
+c      m2=ph_ZmZw*tan(z)+ph_Zmass2
+
+      if (xborn(1).lt.pbw) then
+          s = ph_Zmass2 + ph_ZmZw*tan(ph_ZmZw*anbw*xborn(2)+zlow)
+      else
+          s = exp(anlog*xborn(2)) * ph_Zmass2low
+      endif
+
+      xjac = xjac /
+     &        ( pbw/((s-ph_Zmass2)**2+ph_ZmZw**2)/anbw
+     &         + (1.d0-pbw)/s/anlog)
+c d m^2 jacobian
+c      xjac=xjac*(zhigh-zlow)
+c      xjac=xjac*ph_ZmZw/cos(z)**2
+c d x1 d x2 = d tau d y;
+      tau=s/kn_sbeams
+      kn_sborn=s
+c ymax=|log(tau)|/2
+      y=-(1-2*xborn(3))*log(tau)/2
+      xjac=-xjac*log(tau)
+      z=1-2*xborn(4)
+      xjac=xjac*2
+      cth=1.5d0*(z-z**3/3)
+      xjac=xjac*1.5d0*(1-z**2)
+      kn_born_pt2=0d0
+      
+      xjac = xjac * sqrt(lambda(s,kn_masses(3)**2,kn_masses(3)**2))/s
+c
+      cthdec=cth
+      phidec=0d0
+      kn_cthdec=cthdec
+      kn_jacborn=xjac
+c Build kinematics
+      kn_xb1=sqrt(tau)*exp(y)
+      kn_xb2=tau/kn_xb1
+c initial state particles
+      kn_cmpborn(0,1)=sqrt(s)/2
+      kn_cmpborn(1,1)=0
+      kn_cmpborn(2,1)=0
+      kn_cmpborn(3,1)=kn_cmpborn(0,1)
+
+      kn_cmpborn(0,2)=kn_cmpborn(0,1)
+      kn_cmpborn(1,2)=0
+      kn_cmpborn(2,2)=0      
+      kn_cmpborn(3,2)=-kn_cmpborn(0,2)
+
+c decay products in their rest frame
+      pmod = sqrt(lambda(s,decmass**2,decmass**2))
+     +            /2d0/sqrt(s)
+
+      kn_cmpborn(0,3) = sqrt(pmod**2 + decmass**2)
+      kn_cmpborn(1,3) = pmod*sqrt(1-kn_cthdec**2)*cos(phidec)
+      kn_cmpborn(2,3) = pmod*sqrt(1-kn_cthdec**2)*sin(phidec)
+      kn_cmpborn(3,3) = pmod*kn_cthdec
+     
+      kn_cmpborn(0,4) = sqrt(s) - kn_cmpborn(0,3)
+      kn_cmpborn(1,4) = - kn_cmpborn(1,3)
+      kn_cmpborn(2,4) = - kn_cmpborn(2,3)
+      kn_cmpborn(3,4) = - kn_cmpborn(3,3)
+
+c now boost everything along 3
+      beta=(kn_xb1-kn_xb2)/(kn_xb1+kn_xb2)
+      vec(1)=0
+      vec(2)=0
+      vec(3)=1
+      call mboost(nlegborn-2,vec,beta,kn_cmpborn(0,3),kn_pborn(0,3))
+      do mu=0,3
+         kn_pborn(mu,1)=kn_xb1*kn_beams(mu,1)
+         kn_pborn(mu,2)=kn_xb2*kn_beams(mu,2)
+      enddo
+c      call checkmomzero(nlegborn,kn_pborn)
+c      call checkmass(2,kn_pborn(0,3))
+
+c minimal final state mass 
+      kn_minmass=sqrt(ph_Zmass2low)
+
+      end
+
+
+      subroutine born_suppression(fact)
+      implicit none
+      include 'nlegborn.h'
+      include 'pwhg_flst.h'
+      include 'pwhg_kn.h'
+      logical ini
+      data ini/.true./
+      real * 8 fact,pt
+      real * 8 powheginput
+      external powheginput
+      if (ini) then
+         pt = powheginput("#ptsupp")         
+         if(pt.gt.0) then
+            write(*,*) ' ******** WARNING: ptsupp is deprecated'
+            write(*,*) ' ******** Replace it with bornsuppfact'
+         else
+            pt = powheginput("#bornsuppfact")
+         endif
+         if(pt.ge.0) then
+            write(*,*) '**************************'
+            write(*,*) 'No Born suppression factor'
+            write(*,*) '**************************'
+         endif
+         ini=.false.
+      endif
+      fact=1d0
+      end
+
+
+      subroutine set_fac_ren_scales(muf,mur)
+      implicit none
+      include 'PhysPars.h'
+      include 'nlegborn.h'
+      include 'pwhg_flst.h'
+      include 'pwhg_kn.h'
+      include 'mathx.h'
+      real * 8 muf,mur
+      logical ini
+      data ini/.true./
+      real *8 muref
+      real *8 dotp
+      external dotp
+      logical runningscales
+      save runningscales
+      real * 8 pt2
+      real * 8 powheginput
+      external powheginput
+      if(ini) then
+         if(powheginput('#runningscale').ge.1) then
+            runningscales=.true.
+         else
+            runningscales=.false.
+         endif
+      endif
+      if (runningscales) then
+         if (ini) then
+            write(*,*) '*************************************'
+            write(*,*) '    Factorization and renormalization '
+            if (powheginput('#runningscale').eq.1) then
+               write(*,*) '    scales set to the Z virtuality ' 
+            else 
+               write(*,*) "runningscale value not allowed"
+               call exit(1)
+            endif
+            write(*,*) '*************************************'
+            ini=.false.
+         endif
+         muref=sqrt(2d0*dotp(kn_pborn(0,3),kn_pborn(0,4)))
+      else
+         if (ini) then
+            write(*,*) '*************************************'
+            write(*,*) '    Factorization and renormalization '
+            write(*,*) '    scales set to the Z mass '
+            write(*,*) '*************************************'
+            ini=.false.
+         endif
+         muref=ph_Zmass
+      endif
+      muf=muref
+      mur=muref
+      mudim2=1d0
+      end
+      
+
+      function lambda(x,y,z)
+      real*8 lambda
+      real*8 x,y,z
+      lambda = x**2+y**2+z**2 - 2.d0*x*y - 2.d0*x*z - 2.d0*y*z
+      return
+      end