STATUS OF Hee ANALYSIS
Genova team - December 5, 2000

 


1- TEST OF POSSIBLE IMPROVEMENTS

    a- looser bhabha rejection
       from:     reject if one electron > 65 GeV below 250 (above1550)
                      reject if acoplanarity< 30 and both electr. > 40 GeV

       to:         reject if one electron > 70 GeV below 250 (above1550) and ch. mult. <13
                      reject if acoplanarity< 30 and both electr. > 40 GeV and ch. mult. <13
         
    b- more accurate selection of H--> tau tau decays
        from:     multiplicities of the tau "jets" < 4 and masses < 2 GeV

        to:        in addition, ask at least 1 odd multiplicity

    c- alternative to b: give up to H--> tau decay (a good reason for it: the second
        discriminating variable, i.e. btag)

Tested on 206.7C MC samples at the final cut for 2-d input production
 
 

Sample
standard
a
b
c
a+c
eeqq
1.999
2.092
1.999
1.999
2.092
q qbar
0.1300
0.1300
0.1300
0.1300
0.1300
WW-like
0.2348
0.2348
0.2348
0.2348
0.2348
e e tau tau *
0.0248
0.0248
0.0232
0.0031
0.0031
e e e e *
0.0828
0.0828
0.0828
0
0
q q tau tau *
0.0171
0.0172
0.0171
0.0171
0.0172
q q mu mu *
0.0003
0.0003
0.0003
0.0003
0.0003
gamma gamma *
0.1125
0.1500
0.1125
0.1125
0.1500
background *
0.2375
0.2751
0.2359
0.1330
0.1706
tot. bkg.
2.6013
2.7319
2.5997
2.4968
2.6274
eff. M_H=114 GeV
54.22 %
57.60 %
54.22 %
53.36 %
56.73 %
eff. M_H=115 GeV
55.01 %
58.51 %
55.01 %
54.34 %
57.84 %

Our proposal: apply both a and c changes (b does not really help)
This choice gets rid of the btag problem for H--> tau tau decays
              better efficiency and similar bkg compared to the standard analysis
 
 

2- ARE WE MISSING EVENTS? CHECK WITH GUENNADI eeqq ANALYSIS

111223/3356 : in theta crack; E/p below 0.3 and dE/dx < 1.4

111851/1811: killed by anti-Bhabha cut (fwd electr. > 65 GeV) -
                     recovered by new selection

 112579/20089: one electron killed by isolation cut

 112708/1581: sum of jets and electron  masses below 150 GeV

 115072/5758: killed by anti-Bhabha cut (acoplanarity) -
                     recovered by new selection

 115947/1106: one electron killed by isolation cut

 116590/7648: one electron rejected because  impact par. (z) above 1 cm

 116629/16405: one "electron" rejected because  forward shower without
                      charged track
 

Conclusion: the events are not "lost" for mysterious reasons but for features of
the analysis applied to MC as well as to real data. The MC/data discrepancy may
be due to a fluctuation or to a very special kind of incorrect MC description
affecting only a selected category of events.