C++ Interface to Tauola
disth.f
1C this is variant SM-only. We need it inside TauSpinner `always' but may be
2C it is not an appropriate place for it.
3
4 REAL*8 FUNCTION disth(S,T,H1,H2)
5C***************************************************************************
6C* CALCULATES DSIGMA/DT FOR GluonGluon -> TAU+TAU- VIA:
7C s-channel SM Higgs if KEY=0
8C s-channel spin2 object if KEY=1
9C S -- CM gluon-gluon ENERGY^2
10C T -- cosTheta (scattering angle of tau- with respect to gluon
11C H1 - HELICITY OF TAU-: 1=R, -1=L
12C H2 - HELICITY OF TAU+
13C KEY=0 SM, KEY=1 SPIN2
14C***************************************************************************
15
16C***************************************************************************
17C* *
18C***************************************************************************
19
20 IMPLICIT REAL*8(a-h,m,o-z)
21 INTEGER H1,H2
22
23
24! IF(KEY.EQ.0) THEN
25! WRITE(*,*) 'SM Higgs'
26! ELSE IF(KEY.EQ.1) THEN
27! WRITE(*,*) 'nonSM not ready'
28! STOP
29! ELSE
30! WRITE(*,*) 'WRONG KEY'
31! STOP
32! ENDIF
33
34
35
36 cost=t
37
38C* ========== Standard Model Parameters ==========
39 alphaem=1.d0/128.d0 ! at mZ
40 alphas=0.112d0 ! at mZ
41 gf=1.1667d-5 ! Fermi constant
42 s2w = .2315d0 ! sin^2(theta_W)
43 c2w = 1.d0-s2w
44 cw = dsqrt(1.d0-s2w)
45 sw = dsqrt(s2w)
46 f=1000.d0 ! scale of spin-2 physics ????
47
48 mz = 91.187d0 ! Z mass
49 wz = 2.d0 ! Z width
50 mh = 125.d0 ! SM Higgs mass
51 mt=173.d0 ! top quark mass
52 mx=125.d0 ! spin-2 mass choose your own
53 wx=10.d0 ! spin-2 width choose your own
54 mw = mz*cw
55 pi=4.d0*datan(1.d0)
56 e=dsqrt(4.d0*pi*alphaem)
57 br= 0.065d0 ! Br(H->tautau)
58
59
60
61
62 ! SM Higgs via top quark loop
63
64 IF(h1.EQ.-h2) THEN
65 disth=0.d0 ! for spin 0 Higgs
66 return
67 ELSE
68 taut=mh**2/4/mt**2
69 tauq=taut
70 stauq=dsqrt(tauq)
71
72
73 disth=gf*alphas**2/288.d0/dsqrt(2.d0)/pi*dabs(3.d0/2d0*
74 . (tauq+(tauq-1.0)*(dasin(stauq))**2)/tauq**2)**2
75 . *br/2.d0
76
77C Br/2 because of FB symmetry
78 return
79 ENDIF
80
81
82
83
84
85 return
86 END