ISAJET/isasusy/ssmqcd.F

   1 #include "isajet/pilot.h"
   2       DOUBLE PRECISION FUNCTION SSMQCD(DM,DQ)
   3 C-----------------------------------------------------------------------
   4 C     Calculate leading-log running mass for quark with mass DM at
   5 C     scale Q, using alpha_s which is continuous across thresholds.
   6 C     See Drees and Hikasa, Phys. Lett. B240: 455-464, Eq. 4.5.
   7 C
   8 C     Note the threshold is at Q = 2 m, not at Q = m as in MSbar.
   9 C
  10 C     Bisset's QCDRAD, WDHFFC
  11 C-----------------------------------------------------------------------
  12 #if defined(CERNLIB_IMPNONE)
  13       IMPLICIT NONE
  14 #endif
  15 #include "isajet/sssm.inc"
  16 C
  17       DOUBLE PRECISION DM,DQ,DLAM4,DLAM5,DLAM6,DNEFF,POW,RENORM
  18      $,DQBT,DQTP
  19 C
  20 C         Do nothing for light quarks
  21 C
  22       IF(DM.LT.1.0) THEN
  23         SSMQCD=DM
  24         RETURN
  25       ENDIF
  26 C
  27 C          Calculate running mass
  28 C
  29       DLAM4=DBLE(ALQCD4)
  30       DQBT=2*DBLE(AMBT)
  31       DQTP=2*DBLE(AMTP)
  32       SSMQCD=0
  33 C          Q < 2 m(b)
  34       DNEFF=4
  35       POW=12.D0/(33.D0-2.*DNEFF)
  36       IF(DQ.LT.DQBT) THEN
  37         RENORM=(LOG(2*DM/DLAM4)/LOG(DQ/DLAM4))**POW
  38         SSMQCD=RENORM*DM
  39         RETURN
  40       ELSE
  41         RENORM=(LOG(2*DM/DLAM4)/LOG(DQBT/DLAM4))**POW
  42       ENDIF
  43 C          2 m(b) < Q < 2 m(t)
  44       DNEFF=5
  45       POW=12.D0/(33.D0-2.*DNEFF)
  46       DLAM5=DEXP((25.D0*LOG(DLAM4)-LOG(DQBT**2))/23.D0)
  47       IF(DQ.GE.DQBT.AND.DQ.LT.DQTP) THEN
  48         RENORM=RENORM
  49      $  *(LOG(DQBT/DLAM5)/LOG(DQ/DLAM5))**POW
  50         SSMQCD=RENORM*DM
  51         RETURN
  52       ELSE
  53         RENORM=RENORM
  54      $  *(LOG(DQBT/DLAM5)/LOG(DQTP/DLAM5))**POW
  55       ENDIF
  56 C          2 m(t) < Q
  57       DNEFF=6
  58       POW=12.D0/(33.D0-2.*DNEFF)
  59       DLAM6=DEXP((25.D0*LOG(DLAM4)-LOG(DQBT**2)
  60      $-LOG(4*AMTP**2))/21.D0)
  61       RENORM=RENORM
  62      $*(LOG(DQTP/DLAM6)/LOG(DQ/DLAM6))**POW
  63       SSMQCD=RENORM*DM
  64       RETURN
  65       END