JADE Algorithm with E scheme:

A loop runs over all pairs of tracks and finds the pair which has the smallest invariant mass M. If (M/EVIS)² < YCUT, these 2 tracks are merged (i.e., 4-momenta added).

The loop is then rerun over the new list of tracks which has lost 2 particles and gained the merged pair. When no remaining pair has a low enough mass, the track list contains a set of merged tracks called jets.

Input arguments:

ICLASS

described in 10.3.

YCUT

Cut on the scaled invariant mass of 2 tracks. Pairs of tracks are merged if their scaled invariant mass is smaller than YCUT.

EVIS

The visible energy of the event. If EVIS equals 0, the visible energy is computed as the sum of the input particle energies.

Results:

NJETS

is the number of ``jets'' .

• > 0 = number of jets found
• - 1 = input error with EVIS , or no particles
• - 2 = error in one of the particles
• - 3 = too many jets found
• - 4 = unknown combination scheme requested
• - 5 = unknown algorithm requested
• - 99 = Not enough BOS workspace to do jet finding
'name'
Vectors containing 4-momenta of the jets.

EXAMPLE:

      DIMENSION LISTEJ(300)
      CHARACTER*13 CNAM
C---Select option: charged tracks
      CALL QJOPTR('CH',' ')
C---calculate visible energy from input tracks:
      EVISRE = 0.
      YCUT  = 0.02
      CALL QJMMCL(NJT,'MMCLUS_RE_vis',KRECO,YCUT,EVISRE)
      CNAM = 'MMCLUS_RE_vis'
      WRITE(KUPRNT,*)' # of jets reconstructed ', CNAM, ':', NJT
      IF(NJT.GT.0) THEN
C--- get ALPHA number for first jet found:
        JJ = KPDIR(CNAM,KRECO)
  20    IF(JJ .NE. 0) THEN
C--- get the list of tracks merged into this jet:
          LL = 0
          DO 211 L  = KFCHT, KLCHT
C--- check if this track belongs to this jet:
            IF(.NOT.XSAME(JJ,L)) GOTO 211
            LL = LL + 1
            LISTEJ(LL) = L
  211     CONTINUE
          WRITE(KUPRNT,*) 'Jet # ', J
          WRITE(KUPRNT,*) QX(JJ),QY(JJ),QZ(JJ),QE(JJ)
          WRITE(KUPRNT,*) 'List of tracks merged into this jet:'
          WRITE(KUPRNT,*) (LISTEJ(L),L=1,LL)
C--- get ALPHA number for next jet found:
          JJ = KFOLLO(JJ)
          GOTO 20
        ENDIF
      ENDIF