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semi_dilution.f
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real*8 function semi_dilution(vertex,main)
* Sept. 2003 D. Gaskell
* Purpose:
* This routine calculates p(e,e'pi+)X semi-inclusive cross sections from
* the CTEQ5M parton distribution functions and a simple parameterization
* of the favored and unfavored fragmentation functions.
* output:
* sigma_eepiX !d3sigma/dEe'dOmegae'Omegapi (microbarn/MeV/sr^2)
*
* For now, just does PI+ !!!!!!!!!!!!!!!!!!
*
* October 3 2003 D. Gaskell
* Replace simple fragmentation function paramterization with a slightly
* more sophisticated treatment from Binnewies et. al.,PRD 52, p.4947 (1995).
* This parameterization gives: D_u^(pi+ + pi-) = D_d^(pi+ + pi-) = D+ + D-
* The separate favored and unfavored fragmentation functions are given by
* the ratio D-/D+ from HERMES data (my fit to P. Geiger's results).
* The D-/D+ fit is valid from z=0.25 to 0.9 or so, but behaves pretty well
* at lower z (approaches simple form of Field and Feynman (1-z)/(1+z)).
*
*
* October 4 2003 D. Gaskell
* Add PI- functionality
*
* October 9 2003 D. Gaskell
* Add deuterium functionality. Assume just an incoherent sum of parton
* distributions from proton and neutron. Assume isospin symmetry so
* d_neutron(x) = u_proton(x)
* dbar_neutron(x) = ubar_proton(x)
* u_neutron(x) = d_proton(x)
* ubar_neutron(x) = dbar_proton(x)
*
*
* October 14 - Now adapted to get the dilution factor.
USE structureModule
implicit none
include 'simulate.inc'
type(event_main):: main
type(event):: vertex
* PDFs
integer iset !which set (1=cteq5m)
integer ipart !particle u=1, ubar=-1, d=2, dbar=-2
real*8 u,d,ubar,dbar
real*8 qu,qd ! u and d quark charges
real*8 D_fav, D_unfav, D_sum, R_D !favored,unfavored,sum,ratio of FFs
real*8 lambda, Q2zero ! scales for FF param
real*8 sv !scaling variable for FF param
real*8 N,a1,a2 !parameters for FF param
real*8 xbj,y,s, Q2gev, Qgev, pt2gev
real*8 b ! pt2 parameter for FFs
real*8 sum_sq, dsigdz, sigsemi, jacobian, sigma_eepiX
real*8 sighad, sige
real*8 sum_sq_prot,sum_sq_neut,dsigdz_prot,dsigdz_neut
real*8 sighad_prot,sighad_neut, sige_prot, sige_neut
real*8 sigsemi_prot,sigsemi_neut,dilution
real*8 N15,He4,Al,Ni,Cu
real*8 Ctq5Pdf
c external Ctq5Pdf
logical first,kfirst
parameter (iset=1)
parameter (qu=2./3.)
parameter (qd=-1./3.)
parameter (b=3.76) !GeV^-2
parameter (lambda=0.227) !0.227 GeV for NLO
parameter (Q2zero=2.0) !Gev^2 for u,d,s,g
data first /.TRUE./
data kfirst /.TRUE./
if(first) then
call SetCtq5(iset) ! initialize Cteq5 (we're using cteq5m)
first=.FALSE.
endif
s = (2.*vertex%Ein*mp + mp**2)/1.e6 !convert to GeV2
xbj = vertex%Q2/2./mp/vertex%nu
if(xbj.gt.1.0) then
write(6,*) 'XBj is too large!', xbj
xbj=1.0
endif
y = vertex%nu/vertex%Ein
C DJG convert some stuff to GeV
Q2gev = vertex%q2/1.e6
Qgev = sqrt(Q2gev)
pt2gev = vertex%pt2/1.e6
C Get the PDFs
ipart=1
u = Ctq5pdf (ipart , xbj, Qgev)
ipart=-1
ubar = Ctq5pdf (ipart , xbj, Qgev)
ipart=2
d = Ctq5pdf (ipart , xbj, Qgev)
ipart=-2
dbar = Ctq5pdf (ipart , xbj, Qgev)
C Simple paramaterization from Kretzer et al (EPJC 22 p. 269)
C for Q2=2.5.
c D_fav = 0.689*vertex.zhad**(-1.039)*(1.0-vertex.zhad)**1.241
c D_unfav = 0.217*vertex.zhad**(-1.805)*(1.0-vertex.zhad)**2.037
C
C Paramaterization from Binneweis et al
sv = log( log(Q2gev/lambda**2)/log(Q2zero/lambda**2) )
C Form of parameterization is D = N z^a1 (1-z)^a2
if(doing_semipi) then
N = 1.150 - 1.522*sv + 1.378*sv**2 - 0.527*sv**3
a1 = -0.740 - 1.680*sv + 1.546*sv**2 - 0.596*sv**3
a2 = 1.430 + 0.543*sv - 0.023*sv**2
elseif(doing_semika) then
if (kfirst) then
write(6,*) 'Kaon FF in semi_dilution not iomplemented yet -using pion values'
kfirst=.false.
endif
N = 1.150 - 1.522*sv + 1.378*sv**2 - 0.527*sv**3
a1 = -0.740 - 1.680*sv + 1.546*sv**2 - 0.596*sv**3
a2 = 1.430 + 0.543*sv - 0.023*sv**2
endif
D_sum = N*vertex%zhad**a1*(1.0-vertex%zhad)**a2
C Ratio of D-/D+ from P. Geiger's thesis (HERMES)
R_D = (1.0-vertex%zhad)**0.083583/(1.0+vertex%zhad)**1.9838
D_fav = D_sum/(1.0+R_D)
D_unfav = D_sum/(1.0+1.0/R_D)
sum_sq = qu**2*(u+ubar) + qd**2*(d+dbar)
sum_sq_prot = sum_sq
sum_sq_neut = qu**2*(d+dbar) + qd**2*(u+ubar)
if (doing_deutsemi) then
sum_sq = sum_sq + qu**2*(d+dbar) + qd**2*(u+ubar)
endif
if(sum_sq.gt.0.) then
if(doing_hplus) then
dsigdz = (qu**2*u*D_fav + qu**2*ubar*D_unfav +
> qd**2*d*D_unfav + qd**2*dbar*D_fav)/sum_sq
else
dsigdz = (qu**2*u*D_unfav + qu**2*ubar*D_fav +
> qd**2*d*D_fav + qd**2*dbar*D_unfav)/sum_sq
endif
if(doing_deutsemi) then
if(doing_hplus) then
dsigdz = dsigdz + (qu**2*d*D_fav + qu**2*dbar*D_unfav +
> qd**2*u*D_unfav + qd**2*ubar*D_fav)/sum_sq
else
dsigdz = dsigdz + (qu**2*d*D_unfav + qu**2*dbar*D_fav +
> qd**2*u*D_fav + qd**2*ubar*D_unfav)/sum_sq
endif
endif
else
dsigdz = 0.0
endif
if(sum_sq_prot.gt.0.) then
if(doing_hplus) then
dsigdz_prot = (qu**2*u*D_fav + qu**2*ubar*D_unfav +
> qd**2*d*D_unfav + qd**2*dbar*D_fav)/sum_sq_prot
dsigdz_neut = (qu**2*d*D_fav + qu**2*dbar*D_unfav +
> qd**2*u*D_unfav + qd**2*ubar*D_fav)/sum_sq_neut
else
dsigdz_prot = (qu**2*u*D_unfav + qu**2*ubar*D_fav +
> qd**2*d*D_fav + qd**2*dbar*D_unfav)/sum_sq_prot
dsigdz_neut = (qu**2*d*D_unfav + qu**2*dbar*D_fav +
> qd**2*u*D_fav + qd**2*ubar*D_unfav)/sum_sq_neut
endif
else
dsigdz_prot = 0.0
dsigdz_neut = 0.0
endif
sighad = dsigdz*b*exp(-b*pt2gev)/2./pi
sige = alpha**2*(1.+(1.-y)**2)*(vertex%e%E/1000.)/
> (s*xbj*y**2*(mp/1000.)*(vertex%nu/1000.))
> * sum_sq
C DJG This dsig/(dOmega_e dE_e dz dpt**2 dPhi_had) in microbarn/GeV**3/sr
sigsemi = sige*sighad*(hbarc/1000.)**2*10000.0
sighad_prot = dsigdz_prot*b*exp(-b*pt2gev)/2./pi
sige_prot = alpha**2*(1.+(1.-y)**2)*(vertex%e%E/1000.)/
> (s*xbj*y**2*(mp/1000.)*(vertex%nu/1000.))
> * sum_sq_prot
C DJG This dsig/(dOmega_e dE_e dz dpt**2 dPhi_had) in microbarn/GeV**3/sr
sigsemi_prot = sige_prot*sighad_prot*(hbarc/1000.)**2*10000.0
sighad_neut = dsigdz_neut*b*exp(-b*pt2gev)/2./pi
sige_neut = alpha**2*(1.+(1.-y)**2)*(vertex%e%E/1000.)/
> (s*xbj*y**2*(mp/1000.)*(vertex%nu/1000.))
> * sum_sq_neut
C DJG This dsig/(dOmega_e dE_e dz dpt**2 dPhi_had) in microbarn/GeV**3/sr
sigsemi_neut = sige_neut*sighad_neut*(hbarc/1000.)**2*10000.0
N15 = 8.0*sigsemi_neut + 7.0*sigsemi_prot
He4 = 2.0*sigsemi_neut + 2.0*sigsemi_prot
Al = 14.0*sigsemi_neut + 13.0*sigsemi_prot
Cu = 35.*sigsemi_neut + 29.0*sigsemi_prot
Ni = 31.0*sigsemi_neut + 28.0*sigsemi_prot
if(sigsemi_prot.gt.0.0.and.sigsemi_neut.gt.0.0) then
dilution = sigsemi/(sigsemi+0.3333*N15+0.3165*He4+
> 0.0144*Al + 0.0031*Cu + 0.0013*Ni)
else
dilution = 999
endif
C Need to convert to dsig/ (dOmega_e dE_e dE_h dCos(theta) dPhi_had
C This is just given by 1/omega * 2*p_h**2*cos(theta)
c jacobian = 1./(vertex.nu/1000.)*2.*(vertex.p.P/1000.)**2
c 1 *cos(vertex.theta_pq)
c sigma_eepiX = sigsemi*jacobian/1.e6
c main.davejac = jacobian
c ntup.sigcm = sighad
c peepiX = sigma_eepiX
semi_dilution = dilution
return
end