ISAJET/isasusy/sualfe.F

   1 #include "isajet/pilot.h"
   2 C----------------------------------------------------------------------
   3       FUNCTION SUALFE(QS)
   4 C----------------------------------------------------------------------
   5 C
   6 C     Returns the running EM coupling alpha_em(q**2)
   7 C
   8 C-----SEE BARGER/PHILLIPS, P. 202 ---------------------------
   9 #if defined(CERNLIB_IMPNONE)
  10       IMPLICIT NONE
  11 #endif
  12 #include "isajet/sslun.inc"
  13       REAL SUALFE
  14       REAL PI,MB,SUM,A0,QD,QU,MS,ME,QS,MM,MD,MU,MTAU,MC
  15       DATA ME/.0005/,MM/.105/,MTAU/1.784/,MU/.01/,MD/.01/
  16       DATA MS/.5/,MC/1.6/,MB/5.0/,PI/3.1415926/
  17 C
  18       SUM=0.
  19       QU=2./3.
  20       QD=-1./3.
  21       IF (QS.GT.4*ME**2) SUM=SUM+LOG(QS/4./ME**2)
  22       IF (QS.GT.4*MM**2) SUM=SUM+LOG(QS/4./MM**2)
  23       IF (QS.GT.4*MTAU**2) SUM=SUM+LOG(QS/4./MTAU**2)
  24       IF (QS.GT.4*MU**2) SUM=SUM+3*QU**2*LOG(QS/4./MU**2)
  25       IF (QS.GT.4*MD**2) SUM=SUM+3*QD**2*LOG(QS/4./MD**2)
  26       IF (QS.GT.4*MS**2) SUM=SUM+3*QD**2*LOG(QS/4./MS**2)
  27       IF (QS.GT.4*MC**2) SUM=SUM+3*QU**2*LOG(QS/4./MC**2)
  28       IF (QS.GT.4*MB**2) SUM=SUM+3*QD**2*LOG(QS/4./MB**2)
  29       A0=1./137.
  30       SUALFE=A0/(1.-A0/3./PI*SUM)
  31       RETURN
  32       END