TEST OF KINEMATICAL FIT INCLUDING ISR

Hee Genova team






Recall the standard procedure adopted in the Hee analysis:


New scheme tested in order to account for events with hard ISR:


The new scheme has been applied to the event 111886/551 (Hee candidate with mass ~110 GeV in the usual scheme and |miss. Pz| > 20 GeV).
 
 
 

 
Z mass constraint (5/4 C)
No Z mass constraint (4/3 C)
Mjet
Mee 
fit prob.
Mjet 
Mee 
fit prob.
Standard fit
110.257
91.19
0.046
107.802
93.4643
0.025
New fit (ISR)
90.6322 
91.19
0.051
89.209 
93.0382 
0.874

 
 

So the new fit scheme brings this event to "canonical" ZZ masses in fair agreement with G. Borissov evaluation [M(ee) = 90.9 GeV; M(qq) = 94.0 - the differences may be attributed to a different evaluation of the electron energy and different error tuning].
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

BUTa hard ISR is not likely in high mass Higgs production. Test the procedure on a sample of MC Hee events (E=206 GeV, M=110 GeV).
The jet mass plots show a broadening of the mass peak. The effect is more clear (see plots) selecting ISR like events (theta and |Pz miss| selection).
So this method does not improve the mass resolution for high mass higgs although occasionally it provides more sensible results on backround events.

Test the method on the main background source (MC eeqq at 206 GeV).
The plots, produced selecting ISR-like events after the last cut of the Hee analysis (i.e. esssentially on shell ZZ), show comparisons for

No significant improvement observed with the new fit.

TENTATIVE CONCLUSION: