dlower.F

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C **********************************************************************

      FUNCTION dlower(V1)

C...Lower limit on second variable (y, Q**2 or W**2) depending on first
C...variable x=V1. Used for integrating differential cross-section.


*
* to avoid variable conflictions, a second keep element is necessary
* with the same common block name (see LPTOU2)
*
      COMMON /leptou/ cut(14),lst(40),parl(30),
     &                x,y,w2,q2,u
      REAL cut,parl,x,y,w2,q2,u
      INTEGER lst
      SAVE /leptou/

      COMMON /lintrl/ psave(3,4,5),ksave(4),xmin,xmax,ymin,ymax,
     &q2min,q2max,w2min,w2max,ilep,inu,ig,iz
      REAL psave,xmin,xmax,ymin,ymax,q2min,q2max,w2min,w2max
      INTEGER ksave,ilep,inu,ig,iz
      SAVE /lintrl/

      REAL dlower,v1,s,pm2

C...CMS energy squared and target nucleon mass.
      s=parl(21)
      pm2=psave(3,2,5)**2
      IF(lst(31).EQ.1) THEN
        dlower=max(q2min,v1*ymin*s,(w2min-pm2)*v1/max(1.-v1,1.e-22))
      ELSEIF(lst(31).EQ.2) THEN
        dlower=max(ymin,q2min/(s*v1),(w2min-pm2)/max(s*(1.-v1),1.e-22))
      ELSEIF(lst(31).EQ.3) THEN
        dlower=max(w2min,(1.-v1)*ymin*s+pm2,
     &  q2min*(1.-v1)/max(v1,1.e-22)+pm2)
      ENDIF
      RETURN
      END