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Contacts: Simona Rolli
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Abstract
We report on the combination procedure to obtain the final mass limit as a function of
ß = Br (LQ -> l q).
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Introduction
We combined the results from the following three decay channels:
- dileptons + jets
- lepton + MET + jets
- MET + jets
A Bayesian approach has been used. A joint likelihood has been formed from the product of
the individual channels likelihood. For each mass we simulated 10K pseudo-experiments,
smearing the calculated number of background events and the estimated number of signal
events by their respective total uncertainties. The searches in the lljj and lnujj channel
use common criteria and sometime apply the same kind of requirements (for example on the
lepton identification) so the uncertainties in the acceptances have been considered
completely correlated. When calculating the limit
combination including also the nunujj channel the uncertainties in the acceptances have been
considered uncorrelated.
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Efficiencies
When calculating the combined limit the following expression for the combined efficiency has been used:
Here we report on the individual channels acceptances, errors and background expectation
vs data observed.
- Dielectron :
| Mass (GeV/c²) | Acceptance (%) | Relative Error (%) |
| 100 | 0.027 | 0.07 |
| 140 | 0.12 | 0.047 |
| 160 | 0.32 | 0.042 |
| 200 | 0.35 | 0.054 |
| 220 | 0.38 | 0.046 |
| 240 | 0.404 | 0.042 |
| 260 | 0.42 | 0.041 |
| Expected Background | 6.24 pm 2.16 |
| Data | 4 |
- Electron + MET :
| Mass (GeV/c²) | Acceptance (%) | Relative Error (%) |
| 100 | 0.017 | 0.13 |
| 140 | 0.085 | 0.089 |
| 160 | 0.088 | 0.088 |
| 200 | 0.165 | 0.081 |
| 220 | 0.19 | 0.08 |
| 240 | 0.204 | 0.079 |
| 260 | 0.22 | 0.079 |
| Expected Background |
- Dimuons :
| Mass (GeV/c²) | Acceptance (%) | Relative Error (%) |
| 100 | 0.0189 | 0.17 |
| 120 | 0.04 | 0.09 |
| 160 | 0.13 | 0.08 |
| 180 | 0.16 | 0.08 |
| 200 | 0.19 | 0.08 |
| 220 | 0.22 | 0.08 |
| 240 | 0.23 | 0.08 |
| Expected Background | 2.87 pm 1.0 |
| Data | 2 |
- Muon + MET + jets :
| Mass (GeV/c²) | Acceptance (%) | Relative Error (%) |
| 100 | 0.0051 | 0.47 |
| 120 | 0.073 | 0.07 |
| 160 | 0.051 | 0.08 |
| 180 | 0.073 | 0.08 |
| 200 | 0.094 | 0.07 |
| 220 | 0.109 | 0.07 |
| 240 | 0.125 | 0.07 |
| Background |
- nunu jj :
| Mass (GeV/c²) | Acceptance (%) | Relative Error (%) |
| 75 | 0.0073 | 0.29 |
| 80 | 0.0113 | 0.26 |
| 90 | 0.0187 | 0.23 |
| 100 | 0.0300 | 0.20 |
| 110 | 0.0431 | 0.16 |
| 115 | 0.0482 | 0.15 |
| 125 | 0.0590 | 0.15 |
| 150 | 0.0828 | 0.13 |
| 175 | 0.1010 | 0.12 |
| Expected Background | 118.5 pm 14.5 |
| Data | 124 |
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Results
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