pymass.f

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C*********************************************************************
 
C...PYMASS
C...Gives the mass of a particle/parton.
 
      FUNCTION pymass(KF)
 
C...Double precision and integer declarations.
      IMPLICIT DOUBLE PRECISION(a-h, o-z)
      IMPLICIT INTEGER(i-n)
      INTEGER pyk,pychge,pycomp
C...Commonblocks.
      common/pydat1/mstu(200),paru(200),mstj(200),parj(200)
      common/pydat2/kchg(500,4),pmas(500,4),parf(2000),vckm(4,4)
      SAVE /pydat1/,/pydat2/
 
C...Reset variables. Compressed code. Special case for popcorn diquarks.
      pymass=0d0
      kfa=iabs(kf)
      kc=pycomp(kf)
      IF(kc.EQ.0) THEN
        mstj(93)=0
        RETURN
      ENDIF
 
C...Guarantee use of constituent masses for internal checks.
      IF((mstj(93).EQ.1.OR.mstj(93).EQ.2).AND.
     &(kfa.LE.10.OR.mod(kfa/10,10).EQ.0)) THEN
        IF(kfa.LE.5) THEN
          pymass=parf(100+kfa)
          IF(mstj(93).EQ.2) pymass=max(0d0,pymass-parf(121))
        ELSEIF(kfa.LE.10) THEN
          pymass=pmas(kfa,1)
        ELSEIF(mstj(93).EQ.1) THEN
          pymass=parf(100+mod(kfa/1000,10))+parf(100+mod(kfa/100,10))
        ELSE
          pymass=max(0d0,pmas(kc,1)-parf(122)-2d0*parf(112)/3d0)
        ENDIF
 
C...Other masses can be read directly off table.
      ELSE
        pymass=pmas(kc,1)
      ENDIF
 
C...Optional mass broadening according to truncated Breit-Wigner
C...(either in m or in m^2).
      IF(mstj(24).GE.1.AND.pmas(kc,2).GT.1d-4) THEN
        IF(mstj(24).EQ.1.OR.(mstj(24).EQ.2.AND.kfa.GT.100)) THEN
          pymass=pymass+0.5d0*pmas(kc,2)*tan((2d0*pyr(0)-1d0)*
     &    atan(2d0*pmas(kc,3)/pmas(kc,2)))
        ELSE
          pm0=pymass
          pmlow=atan((max(0d0,pm0-pmas(kc,3))**2-pm0**2)/
     &    (pm0*pmas(kc,2)))
          pmupp=atan(((pm0+pmas(kc,3))**2-pm0**2)/(pm0*pmas(kc,2)))
          pymass=sqrt(max(0d0,pm0**2+pm0*pmas(kc,2)*tan(pmlow+
     &    (pmupp-pmlow)*pyr(0))))
        ENDIF
      ENDIF
      mstj(93)=0
 
      RETURN
      END