C++ Interface to Tauola
disth.f
1 C this is variant SM-only. We need it inside TauSpinner `always' but may be
2 C it is not an appropriate place for it.
3 
4  REAL*8 FUNCTION disth(S,T,H1,H2)
5 C***************************************************************************
6 C* CALCULATES DSIGMA/DT FOR GluonGluon -> TAU+TAU- VIA:
7 C s-channel SM Higgs if KEY=0
8 C s-channel spin2 object if KEY=1
9 C S -- CM gluon-gluon ENERGY^2
10 C T -- cosTheta (scattering angle of tau- with respect to gluon
11 C H1 - HELICITY OF TAU-: 1=R, -1=L
12 C H2 - HELICITY OF TAU+
13 C KEY=0 SM, KEY=1 SPIN2
14 C***************************************************************************
15 
16 C***************************************************************************
17 C* *
18 C***************************************************************************
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 
38 C* ========== 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 
77 C Br/2 because of FB symmetry
78  return
79  ENDIF
80 
81 
82 
83 
84 
85  return
86  END
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