LEP c.m.s. energy QELEP

The ALPHA variable QELEP gives the best available value of the LEP c.m.s. energy, in GeV.

This is intermediate between a Run information and an event-by-event information.

Since ALPHA 123.08 (October 1998) this value is obtained as follows:

• For Monte Carlo events, QELEP is the generated LEP energy.

• For about 99% of LEP2 events QELEP is obtained from the 15 minutes time-chunk determinations of the LEP c.m.s energy in ALEPH, as given by the LEP Energy Group (values stored in the database bank RNL2). See the note ALEPH 97-029 (PHYSIC 97-24) for more details.

• For LEP1 events, or for a tiny fraction of LEP2 events without time-chunk, QELEP is obtained from run-averaged energies (values stored in the database bank RNR2).

• If none of the above values is available (in general because the run is too short), QELEP is taken as the average LEP energy over the corresponding LEP fill (values stored in the database bank RNF2).

For a given event, to know how the LEP energy was obtained, please use the subroutine QWHICH_EN described in 12.16 on p. .

Important: Please DO NOT call any more the subroutines QELEP2 or QELEP1.