QWHICH_EN: to know how the LEP energy QELEP was found

The output argument ISTAT may be used to know how the center-of-mass LEP energy QELEP was found. For most LEP2 events, this energy is defined in 15 minutes time slices by the LEP Energy Working group. It is available only for high energy runs of 1996 and after. See the note of P.Bright-Thomas ALEPH 97-029 (PHYSIC 97-024) for more details.

ISTAT

Output argument: flag telling how QELEP was obtained.

• = 0 No QELEP energy found! This should NEVER happen !

• = 1 QELEP is obtained from the 'RLEP' bank. This is always the case for Monte Carlo events. For real data, this should be very rare, and only if all other methods described below have failed.

• = 2 QELEP is an averaged value over the current LEP fill. This is the case for 1989 to 1992 real data (from database bank LFIL), or for events in some very short runs taken in 1993 and after (from database bank RNF2).

• = 3 QELEP is an average value over the current run, taken from the database bank RNR2. This is the case for LEP 2 data if no time slice value was available for the event (mostly events taken before or after the official start/stop time of a LEP fill, as recorded in the LEP Energy working group tables).

  For LEP 1 data from 1993 to 1995 included, the values are run averages computed from the LEP Working Group values.

• = 4 QELEP was obtained from the 15 minutes time-slice energy determinations for ALEPH, from the LEP energy working group, stored in the database bank RNL2. These time-slices exist only for LEP2 High Energy data for 1996 and after.