C++ Interface to Tauola
main_2d_2tau_NLO.F
1 program main_downdown_tautau_nlo
2 implicit none!
3!#include "s2n_declare.h"
4
5 integer*4 l1,l2,l3,l4,iz
6 integer*4 iqed,iew,iborn,gfscheme,ifgg
7 real*8 sum,sig(2),har,hai,nc,fc,tlmu2,cosf
8 real*8 s,t,u,betaf,sigma,mta,conhc,pi
9 complex*16 DownDown_TauTau_HA_NLO,ha
10C external DownDown_TauTau_HA_NLO
11
12**********************************************************
13* iqed = 0 without QED corrections
14* 1 with QED corrections
15* 2 ISR
16* 3 IFI
17* 4 FSR
18* 5 [IFI+FSR]
19*
20* iew = 0 without Weak corrections
21* 1 with Weak corrections
22*
23* iborn = 0 Born + 1-loop
24* 1 Born
25*
26* gfscheme = 0 alpha(0) calculation scheme
27* 1 GF
28* 2 GF prime
29*
30* ifgg = -1 ffgg = 0
31* 0 zoro
32* 1 [zoro+coeff*ff_gg]
33* 2 [zoro/(1d0 - coeff*ff_gg)]
34*
35********************************************************
36
37*///////////////////////
38*-- Flag settings
39 iqed = 0
40 iew = 1
41 iborn = 0
42 gfscheme = 0
43 ifgg = 1
44*///////////////////////
45*///////////////////////
46
47
48*///////////////////////
49* 'tlmu2' is IR singularity regulator
50*(photon mass sqared). Affects NLO
51* amlitude in case QED is on(iqed=1)
52 nc = 1d0
53 fc = 3d0
54 tlmu2 = 1d-5
55 call flagset(iqed,iew,iborn,gfscheme,ifgg,nc,fc,tlmu2)
56*///////////////////////
57 call paraget(mta,conhc,pi)
58
59 call printconsts(0)
60
61*///////////////////////
62* Mandelstam variables
63 s = 4900.d0
64*- banchmark values for sigma
65 cosf = 0.850441873760279d0 ! sigma = 0.858063448047948
66 cosf = 0.597827578699185d0 ! sigma = 0.769763514142223
67 cosf = 0.101415698761118d0 ! sigma = 1.02286831492221
68 cosf = 7.010634195128589d-3 ! sigma = 1.13490153765726
69 cosf =-0.242846676312558d0 ! sigma = 1.52987537366104
70*-
71 betaf = sqrt(1d0-4d0*mta**2/s)
72 t = mta**2 - s/2*(1d0-betaf*cosf)
73 u = mta**2 - s/2*(1d0+betaf*cosf)
74*//////////////////////
75
76 do iz = 0,1
77 sum = 0d0
78 do l1 = 1,2
79 do l2 = 1,2
80 do l3 = 1,2
81 do l4 = 1,2
82 call downdown(l1,l2,l3,l4,s,t,u,iz,har,hai);
83 sum = sum + har*har+hai*hai ! ha*dconjg(ha)
84 enddo
85 enddo
86 enddo
87 enddo
88 sig(iz+1) = sum
89 enddo
90 sigma = conhc* ! to pbarn
91 & nc/fc*1d0/2/s *
92 & 1d0/4 * ! spin sum
93 & (sig(2) - sig(1)) * ! |Amp|^2 - linearized
94 & betaf/16/pi ! phase_space/dcos{theta}
95 print*,''
96 print*, "d_sigma/d_cos{theta} = ",sigma
97 print*,''
98
99 stop
100 end