fWSN->Eval(0.001) to avoid fpe.

[u/mrichter/AliRoot.git] / HIJING / hipyset1_35 / ulmass_hijing.F

* $Id$
    
C*********************************************************************  
    
      FUNCTION ULMASS_HIJING(KF)   
    
C...Purpose: to give the mass of a particle/parton. 
#include "ludat1_hijing.inc"
#include "ludat2_hijing.inc"
    
C...Reset variables. Compressed code.   
      ULMASS_HIJING=0. 
      KFA=IABS(KF)  
      KC=LUCOMP_HIJING(KF) 
      IF(KC.EQ.0) RETURN    
      PARF(106)=PMAS(6,1)   
      PARF(107)=PMAS(7,1)   
      PARF(108)=PMAS(8,1)   
    
C...Guarantee use of constituent masses for internal checks.    
      IF((MSTJ(93).EQ.1.OR.MSTJ(93).EQ.2).AND.KFA.LE.10) THEN   
        ULMASS_HIJING=PARF(100+KFA)    
        IF(MSTJ(93).EQ.2) ULMASS_HIJING=MAX(0.,ULMASS_HIJING-PARF(121))   
    
C...Masses that can be read directly off table. 
      ELSEIF(KFA.LE.100.OR.KC.LE.80.OR.KC.GT.100) THEN  
        ULMASS_HIJING=PMAS(KC,1)   
    
C...Find constituent partons and their masses.  
      ELSE  
        KFLA=MOD(KFA/1000,10)   
        KFLB=MOD(KFA/100,10)    
        KFLC=MOD(KFA/10,10) 
        KFLS=MOD(KFA,10)    
        KFLR=MOD(KFA/10000,10)  
        PMA=PARF(100+KFLA)  
        PMB=PARF(100+KFLB)  
        PMC=PARF(100+KFLC)  
    
C...Construct masses for various meson, diquark and baryon cases.   
        IF(KFLA.EQ.0.AND.KFLR.EQ.0.AND.KFLS.LE.3) THEN  
          IF(KFLS.EQ.1) PMSPL=-3./(PMB*PMC) 
          IF(KFLS.GE.3) PMSPL=1./(PMB*PMC)  
          ULMASS_HIJING=PARF(111)+PMB+PMC+PARF(113)*PARF(101)**2*PMSPL 
        ELSEIF(KFLA.EQ.0) THEN  
          KMUL=2    
          IF(KFLS.EQ.1) KMUL=3  
          IF(KFLR.EQ.2) KMUL=4  
          IF(KFLS.EQ.5) KMUL=5  
          ULMASS_HIJING=PARF(113+KMUL)+PMB+PMC 
        ELSEIF(KFLC.EQ.0) THEN  
          IF(KFLS.EQ.1) PMSPL=-3./(PMA*PMB) 
          IF(KFLS.EQ.3) PMSPL=1./(PMA*PMB)  
          ULMASS_HIJING=2.*PARF(112)/3.+PMA+PMB+PARF(114)*PARF(101)**2
     $         *PMSPL   
          IF(MSTJ(93).EQ.1) ULMASS_HIJING=PMA+PMB  
          IF(MSTJ(93).EQ.2) ULMASS_HIJING=MAX(0.,ULMASS_HIJING-PARF(122)
     $         -2.*PARF(112)/3.)  
        ELSE    
          IF(KFLS.EQ.2.AND.KFLA.EQ.KFLB) THEN   
            PMSPL=1./(PMA*PMB)-2./(PMA*PMC)-2./(PMB*PMC)    
          ELSEIF(KFLS.EQ.2.AND.KFLB.GE.KFLC) THEN   
            PMSPL=-2./(PMA*PMB)-2./(PMA*PMC)+1./(PMB*PMC)   
          ELSEIF(KFLS.EQ.2) THEN    
            PMSPL=-3./(PMB*PMC) 
          ELSE  
            PMSPL=1./(PMA*PMB)+1./(PMA*PMC)+1./(PMB*PMC)    
          ENDIF 
          ULMASS_HIJING=PARF(112)+PMA+PMB+PMC+PARF(114)*PARF(101)**2
     $         *PMSPL 
        ENDIF   
      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.1E-4) THEN 
        IF(MSTJ(24).EQ.1.OR.(MSTJ(24).EQ.2.AND.KFA.GT.100)) THEN    
           ULMASS_HIJING=ULMASS_HIJING+0.5*PMAS(KC,2)*TAN((2.
     $          *RLU_HIJING(0)-1.)*ATAN(2.*PMAS(KC,3)/PMAS(KC,2)))   
        ELSE    
          PM0=ULMASS_HIJING    
          PMLOW=ATAN((MAX(0.,PM0-PMAS(KC,3))**2-PM0**2)/    
     &    (PM0*PMAS(KC,2))) 
          PMUPP=ATAN((PM0+PMAS(KC,3))**2-PM0**2)/(PM0*PMAS(KC,2))   
          ULMASS_HIJING=SQRT(MAX(0.,PM0**2+PM0*PMAS(KC,2)*TAN(PMLOW+   
     &    (PMUPP-PMLOW)*RLU_HIJING(0))))   
        ENDIF   
      ENDIF 
      MSTJ(93)=0    
    
      RETURN    
      END