Search for 1st and 2nd Generation Scalar Leptoquarks at CDF with ~200pb : Combined Limits
CDF Collaboration

Contacts: Simona Rolli
Abstract
We report on the combination procedure to obtain the final mass limit as a function of = Br (LQ -> l q).

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.

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/c)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/c)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/c)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/c)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/c)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

Results


References
(1) Kramar, M. et al, "Pair Production of Scalar Leptoquarks at the TeVatron", Phys. Rev. Lett. 79 (1997), 341

Last modified: Sat Jan 15 2005