pythiaeRHIC/pythia/pytbhq.f

0001 C---------------------------------------------------------
0002 C 2)  Q QBAR ->TBH^+
0003        SUBROUTINE PYTBHQ(Q1,Q2,P1,P2,P3,MT,MB,RMB,MHP,AMP2)
0004 C
0005 C AMP2(OUTPUT) =MATRIX ELEMENT (AMPLITUDE**2) FOR Q QBAR->TB H^+
0006 C (NB SAME STRUCTURE AS FOR PYTBHG ROUTINE ABOVE)
0007       IMPLICIT DOUBLE PRECISION(A-H, O-Z)
0008       IMPLICIT INTEGER(I-N)
0009       DOUBLE PRECISION MW2,MT,MB,MHP,MW
0010       DIMENSION Q1(4),Q2(4),P1(4),P2(4),P3(4)
0011       COMMON/PYDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
0012       COMMON/PYDAT2/KCHG(500,4),PMAS(500,4),PARF(2000),VCKM(4,4)
0013       COMMON/PYMSSM/IMSS(0:99),RMSS(0:99)
0014       COMMON/PYCTBH/ ALPHA,ALPHAS,SW2,MW2,TANB,VTB,V,A
0015       SAVE /PYDAT1/,/PYDAT2/,/PYMSSM/,/PYCTBH/
0016 C !THE RELEVANT INPUT PARAMETERS ABOVE ARE NEEDED FOR CALCULATION
0017 C BUT ARE NOT DEFINED HERE SO THAT ONE MAY CHOOSE/VARY THEIR VALUES:
0018 C ACCORDINGLY, WHEN CALLING THESE SUBROUTINES, PLEASE SUPPLY VIA
0019 C THIS COMMON/PARAM/ YOUR PREFERRED ALPHA, ALPHAS,..AND TANB VALUES
0020 C
0021 C THE NORMALIZED V,A COUPLINGS ARE DEFINED BELOW AND USED BOTH
0022 C IN THIS ROUTINE AND IN THE TOP WIDTH CALCULATION PYTBHB(..).
0023 C
0024       DIMENSION YY(2,2)
0025
0026       PI = 4*DATAN(1.D0)
0027       MW = DSQRT(MW2)
0028
0029 C COLLECTING THE RELEVANT OVERALL FACTORS:
0030 C 3X3 INITIAL QUARK COLOR AVERAGE, 2X2 QUARK SPIN AVERAGE
0031       PS=1.D0/(3.D0*3.D0 *2.D0*2.D0)
0032 C COUPLING CONSTANT (OVERALL NORMALIZATION)
0033       FACT=(4.D0*PI*ALPHA)*(4.D0*PI*ALPHAS)**2/SW2/2.D0
0034 C NB ALPHA IS E^2/4/PI, BUT BETTER DEFINED IN TERMS OF G_FERMI:
0035 C ALPHA= DSQRT(2.D0)*GF*SW2*MW**2/PI
0036 C ALPHAS IS ALPHA_STRONG;
0037 C SW2 IS SIN(THETA_W)**2.
0038 C
0039 C      VTB=.998D0
0040 C VTB IS TOP-BOTTOM CKM MATRIX ELEMENT (APPROXIMATE VALUE HERE)
0041 C
0042       V = ( MT/MW/TANB +RMB/MW*TANB)/2.D0
0043       A = (-MT/MW/TANB +RMB/MW*TANB)/2.D0
0044 C V AND A ARE (NORMALIZED) VECTOR AND AXIAL TBH^+ COUPLINGS
0045 C
0046 C REDEFINING P2 INGOING FROM OVERALL MOMENTUM CONSERVATION
0047 C (BECAUSE P2 INGOING WAS USED IN OUR GRAPH CALCULATION CONVENTIONS)
0048       DO 100 KK=1,4
0049         P2(KK)=P3(KK)-Q1(KK)-Q2(KK)+P1(KK)
0050   100 CONTINUE
0051 C DEFINING VARIOUS RELEVANT 4-SCALAR PRODUCTS:
0052       S = 2*PYTBHS(Q1,Q2)
0053       P1Q1=PYTBHS(Q1,P1)
0054       P1Q2=PYTBHS(P1,Q2)
0055       P2Q1=PYTBHS(P2,Q1)
0056       P2Q2=PYTBHS(P2,Q2)
0057       P1P2=PYTBHS(P1,P2)
0058 C
0059 C   TOP WIDTH CALCULATION
0060       CALL PYTBHB(MT,MB,MHP,BR,GAMT)
0061 C   GAMT IS THE TOP WIDTH: T->BH^+ AND/OR T->B W^+
0062 C THEN DEFINE TOP (RESONANT) PROPAGATOR:
0063       A1INV= S -2*P1Q1 -2*P1Q2
0064       A1 =A1INV/(A1INV**2+ (GAMT*MT)**2)
0065 C (I.E. INTRODUCE THE TOP WIDTH IN A1 TO REGULARISE THE POLE)
0066 C  NB  A12 = A1*A1 BUT WITH CORRECT WIDTH TREATMENT
0067       A12 = 1.D0/(A1INV**2+ (GAMT*MT)**2)
0068       A2 =1.D0/(S +2*P2Q1 +2*P2Q2)
0069 C NOTE A2 IS B PROPAGATOR, DOES NOT NEED A WIDTH
0070 C  NOW COMES THE AMP**2:
0071 C NB COLOR FACTOR (COMING FORM GRAPHS) ALREADY INCLUDED IN
0072 C THE EXPRESSIONS BELOW
0073       YY(1, 1) = -16*A**2*A2**2*MB*MT+
0074      &64*A**2*A2**2*P1Q2*P2Q1**2/S**2+
0075      &128*A**2*A2**2*MB*MT*P2Q1*P2Q2/S**2-
0076      &128*A**2*A2**2*P1P2*P2Q1*P2Q2/S**2-
0077      &64*A**2*A2**2*P1Q1*P2Q1*P2Q2/S**2-
0078      &64*A**2*A2**2*P1Q2*P2Q1*P2Q2/S**2+
0079      &64*A**2*A2**2*P1Q1*P2Q2**2/S**2-
0080      &32*A**2*A2**2*MB**3*MT/S+32*A**2*A2**2*MB**2*P1P2/S+
0081      &32*A**2*A2**2*MB**2*P1Q1/S+32*A**2*A2**2*MB**2*P1Q2/S-
0082      &32*A**2*A2**2*P1P2*P2Q1/S-32*A**2*A2**2*P1Q1*P2Q1/S-
0083      &32*A**2*A2**2*P1P2*P2Q2/S-32*A**2*A2**2*P1Q2*P2Q2/S+
0084      &16*A2**2*MB*MT*V**2+64*A2**2*P1Q2*P2Q1**2*V**2/S**2-
0085      &128*A2**2*MB*MT*P2Q1*P2Q2*V**2/S**2-
0086      &128*A2**2*P1P2*P2Q1*P2Q2*V**2/S**2-
0087      &64*A2**2*P1Q1*P2Q1*P2Q2*V**2/S**2-
0088      &64*A2**2*P1Q2*P2Q1*P2Q2*V**2/S**2+
0089      &64*A2**2*P1Q1*P2Q2**2*V**2/S**2
0090       YY(1, 1)=YY(1, 1)+32*A2**2*MB**3*MT*V**2/S+
0091      &32*A2**2*MB**2*P1P2*V**2/S+
0092      &32*A2**2*MB**2*P1Q1*V**2/S+32*A2**2*MB**2*P1Q2*V**2/S-
0093      &32*A2**2*P1P2*P2Q1*V**2/S-32*A2**2*P1Q1*P2Q1*V**2/S-
0094      &32*A2**2*P1P2*P2Q2*V**2/S-32*A2**2*P1Q2*P2Q2*V**2/S
0095       YY(1, 1)=2*YY(1, 1)
0096
0097       YY(1, 2) = -32*A**2*A1*A2*MB*MT+
0098      &128*A**2*A1*A2*MB*MT*P1Q2*P2Q1/S**2-
0099      &128*A**2*A1*A2*P1P2*P1Q2*P2Q1/S**2+
0100      &64*A**2*A1*A2*P1Q1*P1Q2*P2Q1/S**2-
0101      &64*A**2*A1*A2*P1Q2**2*P2Q1/S**2+
0102      &64*A**2*A1*A2*P1Q2*P2Q1**2/S**2+
0103      &128*A**2*A1*A2*MB*MT*P1Q1*P2Q2/S**2-
0104      &128*A**2*A1*A2*P1P2*P1Q1*P2Q2/S**2-
0105      &64*A**2*A1*A2*P1Q1**2*P2Q2/S**2+
0106      &64*A**2*A1*A2*P1Q1*P1Q2*P2Q2/S**2-
0107      &64*A**2*A1*A2*P1Q1*P2Q1*P2Q2/S**2-
0108      &64*A**2*A1*A2*P1Q2*P2Q1*P2Q2/S**2+
0109      &64*A**2*A1*A2*P1Q1*P2Q2**2/S**2-
0110      &64*A**2*A1*A2*MB*MT*P1P2/S+
0111      &64*A**2*A1*A2*P1P2**2/S+32*A**2*A1*A2*MB**2*P1Q1/S+
0112      &32*A**2*A1*A2*P1P2*P1Q1/S+32*A**2*A1*A2*MB**2*P1Q2/S+
0113      &32*A**2*A1*A2*P1P2*P1Q2/S-32*A**2*A1*A2*MT**2*P2Q1/S
0114       YY(1, 2)=YY(1, 2)-32*A**2*A1*A2*P1P2*P2Q1/S-
0115      &64*A**2*A1*A2*P1Q1*P2Q1/S-
0116      &32*A**2*A1*A2*MT**2*P2Q2/S-32*A**2*A1*A2*P1P2*P2Q2/S-
0117      &64*A**2*A1*A2*P1Q2*P2Q2/S+32*A1*A2*MB*MT*V**2-
0118      &128*A1*A2*MB*MT*P1Q2*P2Q1*V**2/S**2 -
0119      &128*A1*A2*P1P2*P1Q2*P2Q1*V**2/S**2+
0120      &64*A1*A2*P1Q1*P1Q2*P2Q1*V**2/S**2-
0121      &64*A1*A2*P1Q2**2*P2Q1*V**2/S**2+
0122      &64*A1*A2*P1Q2*P2Q1**2*V**2/S**2-
0123      &128*A1*A2*MB*MT*P1Q1*P2Q2*V**2/S**2-
0124      &128*A1*A2*P1P2*P1Q1*P2Q2*V**2/S**2-
0125      &64*A1*A2*P1Q1**2*P2Q2*V**2/S**2+
0126      &64*A1*A2*P1Q1*P1Q2*P2Q2*V**2/S**2-
0127      &64*A1*A2*P1Q1*P2Q1*P2Q2*V**2/S**2-
0128      &64*A1*A2*P1Q2*P2Q1*P2Q2*V**2/S**2+
0129      &64*A1*A2*P1Q1*P2Q2**2*V**2/S**2+
0130      &64*A1*A2*MB*MT*P1P2*V**2/S+64*A1*A2*P1P2**2*V**2/S
0131       YY(1, 2)=YY(1, 2)+32*A1*A2*MB**2*P1Q1*V**2/S+
0132      &32*A1*A2*P1P2*P1Q1*V**2/S+
0133      &32*A1*A2*MB**2*P1Q2*V**2/S+32*A1*A2*P1P2*P1Q2*V**2/S-
0134      &32*A1*A2*MT**2*P2Q1*V**2/S-32*A1*A2*P1P2*P2Q1*V**2/S-
0135      &64*A1*A2*P1Q1*P2Q1*V**2/S-32*A1*A2*MT**2*P2Q2*V**2/S-
0136      &32*A1*A2*P1P2*P2Q2*V**2/S-64*A1*A2*P1Q2*P2Q2*V**2/S
0137
0138
0139       YY(2, 2) =-16*A**2*A12*MB*MT+
0140      &128*A**2*A12*MB*MT*P1Q1*P1Q2/S**2-
0141      &128*A**2*A12*P1P2*P1Q1*P1Q2/S**2+
0142      &64*A**2*A12*P1Q1*P1Q2*P2Q1/S**2-
0143      &64*A**2*A12*P1Q2**2*P2Q1/S**2-64*A**2*A12*P1Q1**2*P2Q2/S**2+
0144      &64*A**2*A12*P1Q1*P1Q2*P2Q2/S**2-32*A**2*A12*MB*MT**3/S+
0145      &32*A**2*A12*MT**2*P1P2/S+32*A**2*A12*P1P2*P1Q1/S+
0146      &32*A**2*A12*P1P2*P1Q2/S-32*A**2*A12*MT**2*P2Q1/S-
0147      &32*A**2*A12*P1Q1*P2Q1/S-32*A**2*A12*MT**2*P2Q2/S-
0148      &32*A**2*A12*P1Q2*P2Q2/S+16*A12*MB*MT*V**2-
0149      &128*A12*MB*MT*P1Q1*P1Q2*V**2/S**2-
0150      &128*A12*P1P2*P1Q1*P1Q2*V**2/S**2+
0151      &64*A12*P1Q1*P1Q2*P2Q1*V**2/S**2-
0152      &64*A12*P1Q2**2*P2Q1*V**2/S**2-64*A12*P1Q1**2*P2Q2*V**2/S**2+
0153      &64*A12*P1Q1*P1Q2*P2Q2*V**2/S**2+32*A12*MB*MT**3*V**2/S+
0154      &32*A12*MT**2*P1P2*V**2/S+32*A12*P1P2*P1Q1*V**2/S+
0155      &32*A12*P1P2*P1Q2*V**2/S-32*A12*MT**2*P2Q1*V**2/S
0156       YY(2, 2)=YY(2, 2)-32*A12*P1Q1*P2Q1*V**2/S-
0157      &32*A12*MT**2*P2Q2*V**2/S-
0158      &32*A12*P1Q2*P2Q2*V**2/S
0159       YY(2, 2)=2*YY(2, 2)
0160
0161       RES=YY(1,1)+2*YY(1,2)+YY(2,2)
0162       AMP2=  FACT*PS*VTB**2*RES
0163
0164       END