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eps_n_theta.f
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eps_n_theta.f
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subroutine eps_n_theta(npol,Eb,w,q2,tm,um,u_min,thetacm,eps)
c To calculate model theta_pq in CM and epsilon. This subroutine is largely
c based on theta_cm.f function, which in turn is based Jochen's script.
implicit none
integer npol
real Eb,w,q2,tm,um,thetacm,eps
real thetacm1, thetacm2, thetacm3
real thetacm_t, thetacm_u
REAL s,omega,q,tmin,umin,u_min
REAL p1cm,p3cm,e1cm,e3cm,p1lab
REAL p4cm,e4cm
REAL m2,m3,m4
REAL m12,m22,m32,m42
real mp,mp2,mpi,mpi2,mn,mn2
real mw, mw2, pi
parameter (mp=.93827231) !mp
parameter (mp2=.88035493) !mp^2
parameter (mpi=.13956995) !mpi
parameter (mpi2=.01947977) !mpi^2
parameter (mn=.93956563) !mn
parameter (mn2=.88278357) !mn^2
parameter (pi=3.14159265) !mn^2
ccc/*--------------------------------------------------*/
ccc Modification for omega
ccc WL
ccc Date: 31/March/2016
parameter (mw=.78265) !mw
parameter (mw2=.61254) !mw2
ccc
ccc/*--------------------------------------------------*/
parameter (m3=mw)
parameter (m32=mw2)
c if(npol.gt.0) then
c m2=mp
c m22=mp2
c m4=mn
c m42=mn2
c else
c m2=mn
c m22=mn2
c m4=mp
c m42=mp2
c end if
c W = 2.48
c q2 = 1.75
c W=2.47
c q2=1.6
c q2=2.35
m2=mp
m22=mp2
m4=mp
m42=mp2
s=w*w
omega=(s+q2-m22)/(2*m2)
q=sqrt(q2+omega**2)
print*, q2
* m12=q2 !error?
m12=-q2 !mass squared of virtual photon.
e1cm=(s+m12-m22)/(2*w)
e3cm=(s+m32-m42)/(2*w)
e4cm=(s+m42-m32)/(2*w)
p1lab=q
p1cm=p1lab*m2/w
p3cm=sqrt(e3cm*e3cm-m32)
p4cm=sqrt(e4cm*e4cm-m42)
tmin=-((e1cm-e3cm)**2-(p1cm-p3cm)**2)
umin=-((e1cm-e4cm)**2-(p1cm-p4cm)**2)
c print*, 't mininum check in eps n theta check (eps_n_theta.f): ', tm, tmin
c
c if (tm.ge.tmin .AND. (tm-tmin)/(4*p1cm*p3cm) .lt. 1) then
c thetacm_t=2*asin(sqrt((tm-tmin)/(4*p1cm*p3cm)))
c else
c thetacm_t= 3.1415926
c print*, 'eps_n_theta: *** tm=',tm,' < tmin=',tmin,' ! ***'
c endif
c thetacm2 = acos((m32 - m12 - 2*m22 + 2*(e1cm + m2) * e4cm - 2*e1cm * m2)/(2 * p1cm * p4cm))
c thetacm2 = acos((m32 - m12 - 2*m22 + 2*(e1cm + m2) * e4cm - 2*e1cm * m2)/(2 * p1cm * p4cm))
thetacm2 = acos((2*e1cm*e4cm - m12 - m42 - um)/(2 * p1cm * p4cm))
thetacm3 = acos((2*e1cm*e3cm - m12 - m32 - tm)/(2 * p1cm * p3cm))
thetacm1 = 2*asin(sqrt((um-umin)/(4* p1cm * p4cm)))
print*, "Momentum Check: ", p1cm, p3cm, p4cm
print*, "t and u Check ", tm, um
print*, "Min Check and x: ", tmin, umin, q2/(w**2 + q2 -mp2)
print*, "Angle Check: ", thetacm, thetacm1, thetacm + thetacm1
print*, "Angle Check other: ", thetacm3, thetacm2, thetacm2+thetacm3
c stop
if (um.ge.umin .AND. (um-umin)/(4*p1cm*p4cm) .lt. 1) then
thetacm_u=2*asin(sqrt((um-umin)/(4*p1cm*p4cm)))
else
thetacm_u= 0.0
print*, 'eps_n_theta: *** tm=',tm,' < tmin=',tmin,' ! ***'
print*, 'eps_n_theta: *** um=',um,' < umin=',umin,' ! ***'
endif
u_min = umin
thetacm = pi - thetacm_u
print*, Eb, omega, q2, 2*(q2+omega**2), 4.*Eb*(Eb-omega)-q2
c print*,1.+2.*(q2+omega**2)/(4.*Eb*(Eb-omega)-q2)
eps=1.+2.*(q2+omega**2)/(4.*Eb*(Eb-omega)-q2)
eps=1./eps
c print*,"asdasdasda ", q2, w, Eb, eps, thetacm, (tm-tmin)/(4*p1cm*p3cm),
c * um/(4*p1cm*p3cm)
c
c
c print*, w, q2, umin
c
c stop
c print*, thetacm, eps
c write(*,'(a13,7(F8.5,1x))')
c * 'eps_n_theta: ',w,q2,t,tmin,thetacm,eps,omega
end