Roberto Chierici, convener of the LEP 4f WG, asked the LEP collaborations to provide distributions of the MC event weights used to implement in the WW 4f generators the DPA NL O(alpha) correction. The details of Roberto's request can be found in this e-mail.
ALEPH distributions have been produced by using the Common Ntuples made with 2M 4f events at 189 GeV (Kww984fM0G0-xx xx=1,40 ; total cross section 17.708 pb) and with 1M 4f events at 205 GeV (Kww2k14fM0G0-xx xx=1,20 ; total cross section 18.9324 pb) by selecting evud events (156364 and 81276 selected events at 189 and 205 GeV respectively).
The weight distributions have been filled by using the MCEWEIGHT array according to the following table:
| 4f full DPA / 4f | 1-(1-MCEWEIGHT(5)/MCEWEIGHT(4)*MCEWEIGHT(3))/ (1+MCEWEIGHT(5)/MCEWEIGHT(4)*(MCEWEIGHT(6)/MCEWEIGHT(7)-1)) |
| YFSWW | MCEWEIGHT(3) |
| CC3 /4f | 1/(1+MCEWEIGHT(5)/MCEWEIGHT(4)*(MCEWEIGHT(6)/MCEWEIGHT(7)-1)) |
| CC3_KC/CC3 | MCEWEIGHT(5)/MCEWEIGHT(4) |
In addition, since the events used to fill the distributions have to be with unscreened Coulomb correction, while ALEPH events are generated with screened Coulomb correction (KC), the distributions have been filled by weighting each event with the following weights:
4f : (1+MCEWEIGHT(7)/MCEWEIGHT(6)*(MCEWEIGHT(4)/MCEWEIGHT(5)-1))
CC3 : MCEWEIGHT(7)/MCEWEIGHT(6)*MCEWEIGHT(4)/MCEWEIGHT(5)
Using this weights the generated cross sections of the uvud channel are: 4f = 1.383±0.003 pb, CC03 = 1.152±0.003 pb at 189 GeV and 4f = 1.537±0.005 pb, CC03 = 1.218±0.004 pb at 205 GeV.
The plots of the distributions can be found here.
03/04/02
Andrea Venturi