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pwhgreweight.f
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pwhgreweight.f
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subroutine pwhgnewweight(iunin,iunrwgt)
implicit none
integer iunin,iunrwgt
character * 500 stringin
integer iret
include 'nlegborn.h'
include 'pwhg_flst.h'
include 'pwhg_rad.h'
include 'pwhg_flg.h'
include 'pwhg_st.h'
include 'pwhg_pdf.h'
include 'LesHouches.h'
integer maxev
integer k
integer gen_seed,gen_n1,gen_n2
common/cgenrand/gen_seed,gen_n1,gen_n2
real * 8 newweight
logical pwhg_isfinite
external pwhg_isfinite
character * 3 whichpdfpk
character * 200 string
real * 8 powheginput
external powheginput
call lhefreadevnew(iunin,iunrwgt,iret,stringin)
if(iret.lt.0) then
write(*,*) ' End of event file! Aborting ...'
call exit(-1)
endif
call setrandom(gen_seed,gen_n1,gen_n2)
if(rad_type.eq.1) then
call gen_btilderw
newweight=rad_btilde_arr(rad_ubornidx)*
1 rad_btilde_sign(rad_ubornidx)
if(flg_fullrwgt) then
call fullrwgt(newweight)
endif
elseif(rad_type.eq.2) then
call gen_sigremnantrw
newweight=rad_damp_rem_arr(rad_realalr)
elseif(rad_type.eq.3) then
call gen_sigremnantrw
newweight=rad_reg_arr(rad_realreg)
else
write(*,*) 'Error in pwhgnewweight, invalid rad_type: ',
$ rad_type
call exit(-1)
endif
if(.not.pwhg_isfinite(newweight)) newweight=0d0
write(string,*) '#new weight,renfact,facfact,pdf1,pdf2',
1 xwgtup*newweight/rad_currentweight,st_renfact,
2 st_facfact,pdf_ndns1,pdf_ndns2,' ',whichpdfpk()
write(iunrwgt,'(a)') trim(adjustl(string))
if(adjustl(stringin).eq.'<rwgt>') then
write(iunrwgt,'(a)') trim(stringin)
do k=1,1000000
read(unit=iunin,fmt='(a)',end=999,err=999) stringin
if(stringin.ne.'</rwgt>') then
write(iunrwgt,'(a)') trim(stringin)
else
call lhrwgt_writeweight
1 (iunrwgt,xwgtup*newweight/rad_currentweight)
write(iunrwgt,'(a)') trim(stringin)
return
endif
enddo
else
write(iunrwgt,'(a)') trim(stringin)
endif
return
999 continue
write(*,*) 'Did not find </rwgt> after <rwgt>'
write(*,*) 'in Les Houches file. Exiting ...'
call exit(-1)
end
subroutine gen_btilderw
implicit none
include 'nlegborn.h'
include 'pwhg_flst.h'
integer mcalls,icalls
include 'cgengrids.h'
real * 8 xx(ndiminteg)
real * 8 btilde
external btilde
mcalls=0
icalls=0
call gen(btilde,ndiminteg,xgrid,ymax,ymaxrat,xmmm,ifold,2,
# mcalls,icalls,xx)
end
subroutine gen_sigremnantrw
implicit none
include 'nlegborn.h'
include 'pwhg_flst.h'
include 'cgengrids.h'
real * 8 xx(ndiminteg)
integer mcalls,icalls
real * 8 sigremnant
external sigremnant
mcalls=0
icalls=0
call gen(sigremnant,ndiminteg,xgridrm,ymaxrm,ymaxratrm,
1 xmmmrm,ifoldrm,2,mcalls,icalls,xx)
end
subroutine openoutputrw(iunrwgt)
implicit none
integer iunrwgt
character * 20 pwgprefix
integer lprefix
common/cpwgprefix/pwgprefix,lprefix
include 'pwhg_rnd.h'
call newunit(iunrwgt)
if(rnd_cwhichseed.ne.'none') then
open(unit=iunrwgt,file=pwgprefix(1:lprefix)//'events-rwgt-'
1 //rnd_cwhichseed//'.lhe'
2 ,status='unknown')
else
open(unit=iunrwgt,file=pwgprefix(1:lprefix)//'events-rwgt.lhe'
1 ,status='unknown')
endif
end
c...reads event information from a les houches events file on unit nlf.
subroutine lhefreadevnew(nlf,nuo,iret,string)
implicit none
integer nlf,nuo,iret
character * 500 string
include 'LesHouches.h'
integer i,j
iret=0
1 continue
string=' '
read(nlf,fmt='(a)',err=777,end=666) string
write(nuo,'(a)') trim(string)
if(string.eq.'</LesHouchesEvents>') then
goto 998
endif
if(string(1:6).eq.'<event') then
c on error try next event. The error may be cause by merging
c truncated event files. On EOF return with no event found
read(nlf,fmt='(a)',err=777,end=666) string
write(nuo,'(a)') trim(string)
read(string,fmt=*,end=998,err=1)
1 nup,idprup,xwgtup,scalup,aqedup,aqcdup
do i=1,nup
read(nlf,'(a)',err=777,end=666) string
write(nuo,'(a)') trim(string)
read(string,fmt=*,end=998,err=1)
1 idup(i),istup(i),mothup(1,i),
& mothup(2,i),icolup(1,i),icolup(2,i),(pup(j,i),j=1,5),
& vtimup(i),spinup(i)
enddo
call lhefreadextrarw(nlf,nuo,iret,string)
c Go on reading, find the end of the weights section
goto 999
else
goto 1
endif
c no event found:
777 continue
write(*,*) "Error in reading"
write(*,*) string
call exit(-1)
666 continue
iret=-1
return
998 continue
print *,"read </LesHouchesEvents>"
iret=-1
nup=0
999 end
subroutine lhefwritetrailernw(iunin,iunout)
implicit none
integer iunin,iunout
character * 500 string
1 continue
string=' '
read(iunin,fmt='(a)',err=998,end=998) string
write(iunout,'(a)') trim(string)
if(string.eq.'</LesHouchesEvents>') then
goto 998
endif
goto 1
998 continue
end
subroutine lhefreadextrarw(nlf,nou,iret,string)
implicit none
include 'LesHouches.h'
include 'nlegborn.h'
include 'pwhg_flst.h'
include 'pwhg_rad.h'
include 'pwhg_st.h'
include 'pwhg_kn.h'
include 'pwhg_flg.h'
character * 500 string
integer nlf,nou,iret
logical readrw
integer gen_seed,gen_n1,gen_n2
common/cgenrand/gen_seed,gen_n1,gen_n2
readrw = .false.
1 continue
read(unit=nlf,fmt='(a)',end=998) string
if(string.eq.'<rwgt>'.or.
1 string.eq.'</event>') then
c Don't write the end event record; first we must output the new weight
return
endif
if(string.eq.'<event>') then
if(.not.readrw) then
write(*,*)
$ 'Error in lhefreadextra, while reading rwg informations'
write(*,*)'Abort run'
call exit(-1)
endif
backspace nlf
return
endif
if(string.eq.'# Start extra-info-previous-event') then
write(nou,'(a)') trim(string)
read(nlf,'(a)') string
write(nou,'(a)') trim(string)
read(string(3:),*) rad_kinreg
read(nlf,'(a)') string
read(string(3:),*) rad_type
endif
write(nou,'(a)') trim(string)
if(flg_newweight) then
c read a string; if it starts with #rwgt, read first rad_type from the
c string, then all other information, depending upon rad_type.
c set readrw to true
string=adjustl(string)
if(string(1:5).eq.'#rwgt') then
string(1:5)=' '
c do things
c print*, 'FOUND'
read(string,*) rad_type
if(rad_type.eq.1) then
c btilde
read(string,*)rad_type,
$ rad_ubornidx,rad_currentweight,
$ gen_seed,gen_n1,gen_n2
elseif(rad_type.eq.2) then
c remnant
read(string,*)rad_type,
$ rad_realalr,rad_currentweight,
$ gen_seed,gen_n1,gen_n2
elseif(rad_type.eq.3) then
c regular
read(string,*)rad_type,
$ rad_realreg,rad_currentweight,
$ gen_seed,gen_n1,gen_n2
else
write(*,*) 'Invalid rad_type in lhefwriteevrw: ',rad_type
call exit(-1)
endif
c if all went ok, set readrw to true
readrw=.true.
endif
endif
goto 1
998 continue
iret=-1
end
c The following are routines for the implementation of the
c Les Houches standard for reweighting
subroutine lhrwgt_writeweight(iun,weight)
implicit none
integer iun
include 'pwhg_lhrwgt.h'
double precision weight
write(iun,'(a,e16.9,a)')
1 "<wgt id='"//trim(adjustl(lhrwgt_id))//"'> ",
2 weight,' </wgt>'
end
subroutine lhrwgt_writeheader(iun)
implicit none
integer iun
include 'pwhg_lhrwgt.h'
character * 200 tmpstring
integer j,iret
logical written,in_group
c This flag is set to true when the current weight has
c been written out
written = .false.
write(iun,'(a)') '<initrwgt>'
if(lhrwgt_group_name.eq.' ') then
c Write all lines firs
do j=1,lhrwgt_nheader
write(iun,'(a)') trim(lhrwgt_header(j))
enddo
else
c this flag is set to true when we are writing out weights in
c the current group
in_group = .false.
do j=1,lhrwgt_nheader
if(.not.written.and.in_group
1 .and.adjustl(lhrwgt_header(j)).eq.'</weightgroup>')
2 then
write(iun,'(a)') "<weight id='"//
1 trim(adjustl(lhrwgt_id))//
2 "'>"//' '//trim(adjustl(lhrwgt_descr))
3 //' </weight>'
in_group = .false.
written = .true.
endif
write(iun,'(a)') trim(lhrwgt_header(j))
tmpstring = adjustl(lhrwgt_header(j))
if(tmpstring(1:18).eq.'<weightgroup name=') then
tmpstring = tmpstring(19:)
call getquotedstring(tmpstring,tmpstring,iret)
if(tmpstring.eq.lhrwgt_group_name) in_group = .true.
endif
enddo
endif
if(.not.written) then
if(lhrwgt_group_name.ne.' ') then
if(lhrwgt_group_combine.ne.' ') then
write(iun,'(a)') "<weightgroup name='"
1 //trim(lhrwgt_group_name)//"' combine='"
1 //trim(lhrwgt_group_combine)//"'>"
else
write(iun,'(a)') "<weightgroup name='"
1 //trim(lhrwgt_group_name)//"'>"
endif
endif
write(iun,'(a)') "<weight id='"//
1 trim(adjustl(lhrwgt_id))//
1 "'>"//' '//trim(adjustl(lhrwgt_descr))//' </weight>'
if(lhrwgt_group_name.ne.' ') then
write(iun,'(a)') '</weightgroup>'
endif
endif
write(iun,'(a)') '</initrwgt>'
end
subroutine lhrwgt_checkheader
implicit none
include 'pwhg_lhrwgt.h'
character * (lhrwgt_max_header_columns) string
integer j,iret
do j=1,lhrwgt_nheader
string = adjustl(lhrwgt_header(j))
if(string(1:11).eq.'<weight id=') then
call getquotedstring(string(12:),string,iret)
if(string.eq.lhrwgt_id) then
write(*,*) ' lhrwgt_checkheader: ERROR'
write(*,*) ' lhrwgt_id ',trim(string),' already in use'
call exit(-1)
endif
endif
enddo
end
subroutine lhrwgt_readheader(iun)
implicit none
include 'pwhg_lhrwgt.h'
integer iun
character * (lhrwgt_max_header_columns+200) string,string0
integer j,k
do j=1,1000000
read(iun,'(a)') string0
string=adjustl(string0)
if(string.eq.'<initrwgt>') then
lhrwgt_nheader = 0
do k=1,1000000
read(iun,'(a)') string0
string=adjustl(string0)
if(string.ne.'</initrwgt>') then
lhrwgt_nheader = lhrwgt_nheader + 1
if(lhrwgt_nheader.gt.lhrwgt_maxnheader) then
write(*,*) '******** ERROR ******'
write(*,*) ' lhrwgt_readheader: '
write(*,*)
1 ' found too many strings in header'
write(*,*) ' increase lhrwgt_maxnheader'
1 //' in include/pwg_lhrwgt.h'
call exit(-1)
endif
c check that the string fits
if(len(trim(string0)).gt.
1 lhrwgt_max_header_columns) then
write(*,*) '******** ERROR ******'
write(*,*) ' lhrwgt_readheader: '
write(*,*)
1 ' found too long a string in the header'
write(*,*)
1 ' increase lhrwgt_max_header_columns'
1 //' in include/pwg_lhrwgt.h'
call exit(-1)
endif
lhrwgt_header(lhrwgt_nheader) = trim(string0)
else
return
endif
enddo
write(*,*) '******** ERROR ******'
write(*,*) ' lhrwgt_readheader: '
write(*,*) ' didn;t find the end of the header'
call exit(-1)
endif
enddo
write(*,*) '******** ERROR ******'
write(*,*) ' lhrwgt_readheader: '
write(*,*) ' didn;t find the header'
call exit(-1)
end
subroutine lhrwgt_copyheader(iunin,iunout)
implicit none
include 'pwhg_lhrwgt.h'
integer iunin,iunout
character * (400) string,string0
integer j,k
logical written,in_group
do j=1,1000000
read(unit=iunin,fmt='(a)',end=999,err=999) string0
string=adjustl(string0)
if(string.eq.'<initrwgt>') then
backspace(iunin)
call lhrwgt_readheader(iunin)
call lhrwgt_checkheader
call lhrwgt_writeheader(iunout)
return
else
write(iunout,'(a)') trim(string0)
endif
enddo
999 continue
write(*,*) ' ERROR: did not find <initrwgt> in lhe file'
write(*,*) ' Most likely, the initial run did not specify'
write(*,*) ' a rwgt_id line'
call exit(-1)
end
subroutine getreweightinput
implicit none
include 'pwhg_lhrwgt.h'
call powheginputstring("#lhrwgt_group_name",lhrwgt_group_name)
call powheginputstring("#lhrwgt_group_combine",
1 lhrwgt_group_combine)
call powheginputstring("#lhrwgt_id",lhrwgt_id)
call powheginputstring("#lhrwgt_descr",lhrwgt_descr)
end
subroutine printrwghthdr(iun)
implicit none
include 'pwhg_lhrwgt.h'
INTEGER IUN
if(lhrwgt_id.ne.' ') then
write(iun,'(a)') '<initrwgt>'
if(lhrwgt_group_name.ne.' ') then
if(lhrwgt_group_combine.ne.' ') then
write(iun,'(a)') "<weightgroup name='"
1 //trim(lhrwgt_group_name)//"' combine='"
1 //trim(lhrwgt_group_combine)//"'>"
else
write(iun,'(a)') "<weightgroup name='"
1 //trim(lhrwgt_group_name)//"'>"
endif
endif
write(iun,'(a)') "<weight id='"//trim(lhrwgt_id)
1 //"'> "//trim(lhrwgt_descr)//" </weight>"
if(lhrwgt_group_name.ne.' ') then
write(iun,'(a)') "</weightgroup>"
endif
write(iun,'(a)') "</initrwgt>"
endif
end
subroutine printrwgtev(nlf,weight)
implicit none
integer nlf
double precision weight
include 'pwhg_lhrwgt.h'
write(nlf,'(a,e16.9,a)')"<wgt id='"//trim(lhrwgt_id)//"'> ",
1 weight,' </wgt>'
end
c From here to the end of file are the subroutines needed for full reweighting,
c that also includes the effect of the change in pdf's in the hardest radiation
subroutine readpowheginputinfo(nlf)
c If any information from the current lhe file is desired, get it here.
c In this case, we set the pdf's used for generating the file, that may
c be needed for reweighting.
implicit none
integer nlf
character * 100 string
character * 3 whichpdf
include 'pwhg_pdf.h'
integer j,ndns1,ndns2,lhans1,lhans2
rewind(nlf)
do j=1,1000000
read(unit=nlf,fmt='(a)',end=999,err=999) string
if(string(1:5) .eq. 'ndns1') then
read(string(6:),*) ndns1
elseif(string(1:5) .eq. 'ndns2') then
read(string(6:),*) ndns2
elseif(string(1:6) .eq. 'lhans1') then
read(string(7:),*) lhans1
elseif(string(1:6) .eq. 'lhans2') then
read(string(7:),*) lhans2
elseif(string(1:12) .eq. 'PDF package:') then
if(adjustl(string(13:)) .eq. 'lha') then
pdf_ndns1lhe = lhans1
pdf_ndns2lhe = lhans1
whichpdf = 'lha'
elseif(adjustl(string(13:)) .eq. 'mlm') then
pdf_ndns1lhe = ndns1
pdf_ndns2lhe = ndns2
whichpdf = 'mlm'
else
write(*,*) ' readpowheginputinfo: cannot identify'
write(*,*) ' psf package ',trim(adjustl(string))
call exit(-1)
endif
rewind(nlf)
if(pdf_ndns1lhe .ne. pdf_ndns2lhe) then
write(*,*)
1 ' readpowheginputinfo: got two different pdf sets',
2 ' for the two imcoming hadrons: ',
3 pdf_ndns1lhe, pdf_ndns2lhe
write(*,*) ' cannot handle that! exiting ...'
call exit(-1)
endif
write(*,*)
1 ' readpowheginputinfo: got ',whichpdf,' set ',
1 pdf_ndns1lhe,' from input lhe file: '
return
endif
enddo
999 continue
write(*,*) ' readpowheginputinfo: something wrong reading'
call exit(-1)
end
subroutine fullrwgt(weight)
c This subroutines reweights also the R/B exp[-int R/B] term in the
c Sudakov form factor.
c It needs to now the pdf's used in the original .lhe
c file. These are provided in a powheg.input "pdforig" entry.
c it computes all reweighting factors needed to update the R/B
c and Sudakov form factor (the last one in an approximate way).
implicit none
real * 8 weight
include 'nlegborn.h'
include 'pwhg_kn.h'
include 'pwhg_flst.h'
include 'pwhg_rad.h'
include 'pwhg_flg.h'
include 'pwhg_st.h'
include 'pwhg_pdf.h'
include 'LesHouches.h'
c These are needed to call generipdfpar.
integer iord,ih,iret
real * 8 lam5l
character * 2 scheme
c
real * 8 mu2
integer fl1b,fl2b,fl1r,fl2r
real * 8 pdf(-pdf_nparton:pdf_nparton)
real * 8 lumorig,lum,as,asorig,exponent,exponentorig,
1 lumbornorig,lumborn,lumreal,lumrealorig,q2l,
2 save_st_lambda5MSB,save_st_mufact2,x1r,x2r,fact
real * 8 powheginput,dotp
integer npdforig,npdf
logical ini
data ini/.true./
integer mode
save ini,npdforig,npdf,mode
logical pwhg_isfinite
external pwhg_isfinite
c These variables are the only ones accessed by the contained subroutines
double precision mm,mm2,ym,ptm,q,ptm2,q2,mtm,mtm2,
1 logtaumin,logtaumax,taumin,taumax,taubmin
integer ngauss
parameter (ngauss=16)
double precision xgauss(ngauss),wgauss(ngauss)
double precision shat,z,em,kmom,aslim,ycmmin,ycmmax,
1 alphads
double precision lam5,q2low,q2high
c end variables accessed by the contained subroutines
c two possibilities:
c A) HERWIG style Sudakov
c Radiation factor = Real(kt2)/Born(kt2) * Lumborn(kt2)/Lumborn(q2l) * Delta_Herwig
c The correction factor is
c alpha(kt2)/alpha_old(kt2) * (Lumreal(kt2)/Lumrealold(kt2))/(Lumborn(kt2)/Lumborn_old(kt2))
c Times (Lumborn(kt2)/Lumborn(q2l))/(Lumborn_old(kt2)/Lumborn_old(q2l)) Delta_Herwig/Delta_Herwig_old
c Equals to
c alpha(kt2)/alpha_old(kt2) * (Lumreal(kt2)/Lumreal_old(kt2)) Lumborn_old(q2l)/Lumborn(q2l)
c times Delta_Herwig/Delta_Herwig_old;
c B) Sjostrand style Sudakov
c Radiation factor = Real(kt2)/Born(kt2) * Delta_Sjostrand
c Correction factor:
c alpha(kt2)/alpha_old(kt2) * (Lumreal(kt2)/Lumreal_old(kt2))/(Lumborn(kt2)/Lumborn_old(kt2))
c Times Delta_Sjostrand/Delta_Sjostrand_old
c Equals to
c alpha(kt2)/alpha_old(kt2) * (Lumreal(kt2)/Lumreal_old(kt2)) * (Lumborn_old(kt2)/Lumborn(kt2))
c
if(ini) then
npdforig = pdf_ndns1lhe
mode = powheginput("#fullrwgtmode")
if(mode.lt.0) mode = 4
if(pdf_ndns1.ne.pdf_ndns2) then
write(*,*) " fullpdfrwgt now works only for identical pdf's"
write(*,*) " for the two beams ! exiting ..."
call exit(-1)
endif
npdf = pdf_ndns1
ini = .false.
endif
x1r = pup(4,1)/ebmup(1)
x2r = pup(4,2)/ebmup(2)
fl1b = flst_born(1,rad_ubornidx)
fl2b = flst_born(2,rad_ubornidx)
fl1r = idup(1)
if(fl1r.eq.21) fl1r = 0
fl2r = idup(2)
if(fl2r.eq.21) fl2r = 0
c If it has Born kinematics, it is already reweighted by the standard POWHEG reweighter.
c However, it must be reweighted with the Sudakov form factor for not emitting below the cutoff scale
c Check that it has Born kinematics by requiring the same flavours and same x_1/2 for real and born.
c Reals are written to the LH file with a precision of 1d-9
if(fl1r .eq. fl1b .and. fl2r .eq. fl2b .and.
1 abs((kn_xb1-x1r)/x1r) .lt. 2d-9 .and.
2 abs((kn_xb2-x2r)/x2r) .lt. 2d-9) then
if(mode.eq.4) then
c we must compute the Sudakov form factor at the current scale with current pdf's
mu2=rad_ptsqmin
save_st_lambda5MSB = st_lambda5MSB
save_st_mufact2 = st_mufact2
c Sudakov, Sjostrand kind, exact phase space
call sudakovxxx(mu2,exponent)
c Compute the same for original pdf's
pdf_ndns1 = npdforig
pdf_ndns2 = npdforig
call genericpdfpar(npdforig,ih,lam5l,scheme,iord,iret)
st_lambda5MSB = lam5l
c Sudakov, Sjostrand kind, exact phase space
call sudakovxxx(mu2,exponentorig)
fact = exp(exponent-exponentorig)
if(pwhg_isfinite(fact)) then
weight = weight * fact
endif
c Set parameters affecting pdf's as in the current settings
st_lambda5MSB = save_st_lambda5MSB
st_mufact2 = save_st_mufact2
pdf_ndns1 = npdf
pdf_ndns2 = npdf
call genericpdfpar(npdf,ih,lam5l,scheme,iord,iret)
endif
return
endif
c Set scale equal to boson pt; take real kinematics from LH event;
c the kn_*real variables are undefined during reweighting.
mu2 = pup(1,nup)**2 + pup(2,nup)**2
q2l = dotp(kn_cmpborn(:,3)+kn_cmpborn(:,4),
1 kn_cmpborn(:,3)+kn_cmpborn(:,4))
save_st_mufact2 = st_mufact2
c Compute Born lum for current pdf's
call genericpdfpar(npdf,ih,lam5l,scheme,iord,iret)
if(mode.ne.3.and.mode.ne.4) then
c in these mode, it is assumed that HERWIG style Sudakovs is a good approximation
st_mufact2 = max(pdf_q2min,q2l)
else
c Sjostrand style Sudakov; must supply the ratio of born luminosities computed at kt2
st_mufact2 = max(pdf_q2min,mu2)
call pdfcall(1,kn_xb1,pdf)
lumborn = pdf(fl1b)
call pdfcall(2,kn_xb2,pdf)
lumborn = lumborn * pdf(fl2b)
endif
c Compute Real lum for current pdf's
st_mufact2 = max(pdf_q2min,mu2)
call pdfcall(1,x1r,pdf)
lumreal = pdf(fl1r)
call pdfcall(2,x2r,pdf)
lumreal = lumreal * pdf(fl2r)
c Get as to compute radiation for current pdf's
as = mcalphas(mu2,lam5l)
save_st_lambda5MSB = st_lambda5MSB
st_lambda5MSB = lam5l
if(q2l.gt.mu2) then
if(mode.eq.1) then
c Sudakov MiNLO style (HERWIG kind)
call sudakov_exponent(mu2,q2l,q2l,exponent,.true.,
1 2,.false.)
elseif(mode.eq.2) then
c Sudakov sikmplified (HERWIG kind)
exponent = simplesudakov(lam5l,mu2,q2l)
elseif(mode.eq.3) then
c Sudakov sikmplified (Sjostrand kind)
exponent =
1 simplesudakovx(lam5l,mu2,q2l,kn_xb1,kn_xb2,fl1b,fl2b)
endif
else
exponent = 0
endif
if(mode.eq.4) then
c Sudakov, Sjostrand kind, exact phase space
call sudakovxxx(mu2,exponent)
exponent = exponent/2
endif
c Compute the same for original pdf's
pdf_ndns1 = npdforig
pdf_ndns2 = npdforig
call genericpdfpar(npdforig,ih,lam5l,scheme,iord,iret)
if(mode.ne.3.and.mode.ne.4) then
st_mufact2 = max(pdf_q2min,q2l)
call pdfcall(1,kn_xb1,pdf)
lumbornorig = pdf(fl1b)
call pdfcall(2,kn_xb2,pdf)
lumbornorig = lumbornorig * pdf(fl2b)
else
c Sjostrand style Sudakov; must supply the ratio of luminosities computed at kt2
st_mufact2 = max(pdf_q2min,mu2)
call pdfcall(1,kn_xb1,pdf)
lumbornorig = pdf(fl1b)
call pdfcall(2,kn_xb2,pdf)
lumbornorig = lumbornorig * pdf(fl2b)
endif
st_mufact2 = max(pdf_q2min,mu2)
call pdfcall(1,x1r,pdf)
lumrealorig = pdf(fl1r)
call pdfcall(2,x2r,pdf)
lumrealorig = lumrealorig * pdf(fl2r)
c Get as to compute radiation for original pdf's
asorig = mcalphas(mu2,lam5l)
st_lambda5MSB = lam5l
if(q2l.gt.mu2) then
if(mode.eq.1) then
c Sudakov MiNLO style (HERWIG kind)
call sudakov_exponent(mu2,q2l,q2l,exponentorig,.true.,
1 2,.false.)
elseif(mode.eq.2) then
c Sudakov sikmplified (HERWIG kind)
exponentorig = simplesudakov(lam5l,mu2,q2l)
elseif(mode.eq.3) then
c Sudakov sikmplified (Sjostrand kind)
exponentorig =
1 simplesudakovx(lam5l,mu2,q2l,kn_xb1,kn_xb2,fl1b,fl2b)
endif
else
exponentorig = 0
endif
if(mode.eq.4) then
c Sudakov, Sjostrand kind, exact phase space
call sudakovxxx(mu2,exponentorig)
exponentorig = exponentorig/2
endif
c Set parameters affecting pdf's as in the current settings
st_lambda5MSB = save_st_lambda5MSB
st_mufact2 = save_st_mufact2
pdf_ndns1 = npdf
pdf_ndns2 = npdf
call genericpdfpar(npdf,ih,lam5l,scheme,iord,iret)
c Compute reweighting factor:
fact = as/asorig ! as for radiation updated
if(mode.ne.3.and.mode.ne.4) then
fact = fact * lumbornorig/lumborn ! pdf ratio arising
! from Sudakov form factors
else
fact = fact * lumbornorig/lumborn ! Factor due to R/B in radiation
! this time evaluated at kt2
endif
fact = fact * lumreal/lumrealorig ! new pdf's in radiation
fact = fact * exp(2*(exponent-exponentorig)) ! Sudakov form factors
if(pwhg_isfinite(fact)) then
weight = weight * fact
endif
contains
double precision function
1 simplesudakovx(lam5,q2low,q2high,x1,x2,fl1,fl2)
implicit none
double precision lam5,q2low,q2high,x1,x2
integer fl1,fl2
integer ngauss
parameter (ngauss=16)
double precision xgauss(ngauss),wgauss(ngauss),xxx(2)
integer j,k
c double precision simplesudakovx0,
double precision res
logical ini
data ini/.true./
save ini,xgauss,wgauss
c Setup gaussian weights and points
if(ini) then
call dgset(0d0,1d0,ngauss,xgauss,wgauss)
ini = .false.
endif
res = 0
do j=1,ngauss
xxx(1) = xgauss(j)
do k=1,ngauss
xxx(2) = xgauss(k)
res = res + wgauss(j)*wgauss(k)*
1 simplesudakovx0(lam5,q2low,q2high,x1,x2,fl1,fl2,xxx)
enddo
enddo
simplesudakovx = res
end function simplesudakovx
double precision function
1 simplesudakovx0(lam5,q2low,q2high,x1,x2,fl1,fl2,xxx)
implicit none
double precision lam5,q2low,q2high,x1,x2,xxx(2)
integer fl1,fl2,fl,j
include 'pwhg_math.h'
include 'pwhg_pdf.h'
include 'pwhg_st.h'
real * 8 kt2,x,xjac,lq2,as,eta,xi,ximax,ximin,y,ymax,z,xx
real * 8 fxr(-pdf_nparton:pdf_nparton),
1 fxb(-pdf_nparton:pdf_nparton)
c real * 8 mcalphas
c external mcalphas
xjac = 1
lq2 = log(q2high/q2low)
kt2 = exp(xxx(1)*lq2)*q2low
xjac = xjac * kt2 * lq2
eta = 4*kt2/q2high
simplesudakovx0 = 0
do j=1,2
if(j.eq.1) then
xx = x1
fl = fl1
else
xx = x2
fl = fl2
endif
if((1-xx)**2.gt.eta) then
c define y=sqrt((1-x)^2-eta);
c y d y = (1-x) dx, dx = y dy /(1-x)
c y goes from 0 to sqrt((1-x1)**2-eta). Needs importance sampling
c near the upper bound, and also near the lower bound if x1 is small.
c Take xi = log((y+eta)/(1-y)) as sampling variable xi
ymax = sqrt((1-xx)**2-eta)
ximax = log((ymax+eta)/(1-ymax))
ximin = log(eta)
xi = (ximax-ximin)*xxx(2) + ximin
xjac = xjac*(ximax-ximin)
z=exp(xi)
xjac = xjac * z
y = (z-eta)/(1+z)
xjac = xjac * (1+eta) / (1+z)**2
x = 1 - sqrt( y**2 + eta )
xjac = xjac * y/(1-x)
st_mufact2 = max(pdf_q2min,kt2)
as = mcalphas(kt2,lam5)
call pdfcall(1,xx,fxb)
call pdfcall(1,xx/x,fxr)
simplesudakovx0 = simplesudakovx0 + (
1 ( cf * (1+x**2)/(1-x) * fxr(fl) +
2 tf * (x**2+(1-x)**2) * fxr(0) )/fxb(fl) )
3 * as/(2*pi) /kt2/x *xjac
4 / sqrt(1-eta/(1-x)**2)
endif
enddo
c we divide by two simply because we multiply by 2 in the main program
simplesudakovx0 = - simplesudakovx0 / 2
end function simplesudakovx0
double precision function simplesudakov(lam50,q2low0,q2high0)
implicit none
double precision lam50,q2low0,q2high0
double precision dgauss
lam5 = lam50
q2low = q2low0
q2high = q2high0
simplesudakov = dgauss(simplesudakov0,0d0,1d0,1d-4)
end function simplesudakov
double precision function simplesudakov0(x)
implicit none
include 'nlegborn.h'
include 'pwhg_math.h'
include 'pwhg_st.h'
include 'pwhg_rad.h'
double precision x
double precision dgauss
real * 8 as,lqlow,l,q2
integer nf
lqlow = log(q2high/q2low)
l = x*lqlow
q2 = q2low*exp(l)
as = mcalphas(q2,lam5)
c Sudakov exponent is (for each leg)
c d q2 C_f [ Q2 ]
c \int ----- ---- as(q) [ log --- + B1 ], B1 = -3/2 = -1.5
c q2 2 pi [ q2 ]
c lqlow is the jacobian
simplesudakov0 = - cf/(2*pi)*as*(l-1.5d0) * lqlow
end function simplesudakov0
double precision function mcalphas(q2,lam5)
implicit none
include 'nlegborn.h'
include 'pwhg_math.h'
include 'pwhg_rad.h'
include 'pwhg_st.h'
real * 8 q2
real * 8 lam5
integer nf
real * 8 as,pwhg_alphas
external pwhg_alphas
if(q2.lt.rad_charmthr2) then
nf=3
elseif(st_muren2.lt.rad_bottomthr2) then
nf=4
else
nf=5
endif
as = pwhg_alphas(q2,lam5,-1)
as = as * (1+as/(2*pi)*((67d0/18-pi**2/6)*ca-5d0/9*nf))
mcalphas = as
end function mcalphas
subroutine sudakovxxx(kt2max,result)
implicit none
real * 8 result,kt2max
include 'nlegborn.h'
include 'pwhg_kn.h'
include 'pwhg_st.h'
include 'pwhg_pdf.h'
real * 8 pdf1(-pdf_nparton:pdf_nparton),
1 pdf2(-pdf_nparton:pdf_nparton)
double precision deltasud,tau0,tau1,eta,pm(0:3)
real * 8 dotp
logical ini
data ini/.true./
save ini
c Setup gaussian weights and points
if(ini) then
call dgset(0d0,1d0,ngauss,xgauss,wgauss)
ini = .false.
endif
c the vector meson rapidity and virtuality is the same in the Born and Real kinematics
pm = kn_pborn(:,3)+kn_pborn(:,4)
mm2 = dotp(pm,pm)
mm=sqrt(mm2)
ym = 0.5d0*log((pm(0)+pm(3))/(pm(0)-pm(3)))
ptm2 = kt2max
ptm = sqrt(kt2max)
q2 = kn_sbeams
q = sqrt(q2)
taubmin=mm2/q2
mtm2 = mm2+ptm2
mtm = sqrt(mtm2)
eta=exp(-2*abs(ym))
tau0 = (ptm+mtm)**2/q2
tau1 = ((eta*q2-mm2)*sqrt(eta*q2*mtm2)+eta*q2*ptm2)
1 /(q2*(eta*q2-mtm2))
if(tau0.lt.eta) then
if(tau1.lt.eta) then
taumin=tau0