main_2d_2tau_NLO.F

00001       program main_DownDown_TauTau_NLO
00002       implicit none!
00003 !#include "s2n_declare.h"
00004 
00005       integer*4  l1,l2,l3,l4,iz
00006       integer*4 iqed,iew,iborn,gfscheme,ifgg
00007       real*8     sum,sig(2),har,hai,nc,fc,tlmu2,cosf
00008       real*8     s,t,u,betaf,sigma,mta,conhc,pi
00009       complex*16 DownDown_TauTau_HA_NLO,ha
00010 C      external   DownDown_TauTau_HA_NLO
00011 
00012 **********************************************************
00013 *   iqed     = 0   without QED corrections
00014 *              1   with QED corrections
00015 *              2   ISR
00016 *              3   IFI
00017 *              4   FSR
00018 *              5   [IFI+FSR]
00019 *
00020 *   iew      = 0   without Weak corrections
00021 *              1   with Weak corrections
00022 *
00023 *   iborn    = 0   Born + 1-loop
00024 *              1   Born
00025 *
00026 *   gfscheme = 0   alpha(0) calculation scheme
00027 *              1   GF
00028 *              2   GF prime
00029 *                
00030 *   ifgg    = -1   ffgg = 0
00031 *              0          zoro
00032 *              1          [zoro+coeff*ff_gg]
00033 *              2          [zoro/(1d0 - coeff*ff_gg)]
00034 *
00035 ********************************************************
00036 
00037 *///////////////////////
00038 *-- Flag settings 
00039       iqed     = 0
00040       iew      = 1
00041       iborn    = 0
00042       gfscheme = 0
00043       ifgg     = 1
00044 *///////////////////////
00045 *///////////////////////
00046 
00047 
00048 *///////////////////////
00049 * 'tlmu2' is IR singularity regulator
00050 *(photon mass sqared). Affects NLO
00051 * amlitude in case QED is on(iqed=1)
00052       nc = 1d0
00053       fc = 3d0
00054       tlmu2 = 1d-5
00055       call flagset(iqed,iew,iborn,gfscheme,ifgg,nc,fc,tlmu2)
00056 *///////////////////////
00057       call paraget(mta,conhc,pi)
00058 
00059       call PrintConsts(0)
00060 
00061 *///////////////////////
00062 * Mandelstam  variables
00063       s = 4900.d0
00064 *- banchmark values for sigma
00065       cosf = 0.850441873760279d0  ! sigma = 0.858063448047948
00066       cosf = 0.597827578699185d0  ! sigma = 0.769763514142223
00067       cosf = 0.101415698761118d0  ! sigma = 1.02286831492221
00068       cosf = 7.010634195128589d-3 ! sigma = 1.13490153765726
00069       cosf =-0.242846676312558d0  ! sigma = 1.52987537366104
00070 *-
00071       betaf = sqrt(1d0-4d0*mta**2/s)
00072       t = mta**2 - s/2*(1d0-betaf*cosf)
00073       u = mta**2 - s/2*(1d0+betaf*cosf)
00074 *//////////////////////
00075       
00076       do iz = 0,1
00077          sum = 0d0
00078          do l1 = 1,2
00079             do l2 = 1,2
00080                do l3 = 1,2
00081                   do l4 = 1,2
00082                      call DownDown(l1,l2,l3,l4,s,t,u,iz,har,hai);
00083                      sum = sum + har*har+hai*hai ! ha*dconjg(ha)
00084                   enddo
00085                enddo
00086             enddo
00087          enddo
00088          sig(iz+1) = sum
00089       enddo
00090       sigma = conhc*                  ! to pbarn
00091      &         nc/fc*1d0/2/s * 
00092      &         1d0/4 *                ! spin sum
00093      &         (sig(2) - sig(1)) *    ! |Amp|^2 - linearized
00094      &         betaf/16/pi            ! phase_space/dcos{theta}
00095       print*,''
00096       print*, "d_sigma/d_cos{theta} = ",sigma
00097       print*,''
00098 
00099       stop
00100       end