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Strategy for single top analysis in the e + jets channel

Strategy for single top analysis in the e + jets channel. B.Andrieu, E. Busato (LPNHE, Paris) + special thanks to M. Kado (LAL, Orsay). General remarks. Signal vs background Low cross section signal (handful of events)  Maximize selection efficiency

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Strategy for single top analysis in the e + jets channel

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  1. Strategy for single top analysisin the e + jets channel B.Andrieu, E. Busato (LPNHE, Paris) + special thanks to M. Kado (LAL, Orsay)

  2. General remarks • Signal vs background • Low cross section signal (handful of events) Maximize selection efficiency • High cross section background After e + jets preselection, first use most efficient selection criteria (b-quark jet tagging) before topological cuts • Background not precisely predicted by theory and Monte Carlo simulation Avoid restricting phase space too early in order to keep handle on background • Selection of b-quark jets • No 100 % efficient, background-free, b-quark jet tagging method Use (as many as possible) different subchannels (tagging methods, number of tags, …) • But these different subchannels are based on the same sample Use exclusive samples to be able to combine independent limits in the most efficient and simple way B.Andrieu (LPNHE, Paris) Strategy for single top e + jets analysis -

  3. Strategy for b-quark jet tagging • FIRST use Soft Muon Tagging Select events with >= 1 SMT jet • Well-established, simple and robust b-quark tagging method • Experience from first-pass p13 analysis • Possible gain on trigger efficiency using e-mu trigger jointly withe + jets trigger • If possible, separate again according to 2nd jet tagging: • >= 2 SMT jets • Exactly 1 SMT jet + >= 1 JLIP-tagged jet • Exactly 1 SMT jet + 0 JLIP-tagged jet • THEN use a second tagger (JLIP) Select events with >= 1 JLIP jet + SMT veto • Use only e + jets trigger for this channel • If possible, separate again according to 2nd jet tagging (JLIP) B.Andrieu (LPNHE, Paris) Strategy for single top e + jets analysis -

  4. Final selection? • Topological cuts? • Optimize cuts to obtain the best limit: in each channel separately or use the same cuts for all channels? • Combine statistically independent limits from different channels • Knowing the efficiencies of topological cuts on signal and background,is it possible to use a “Matrix Method” to estimate the contribution of signal and background for each channel? • OR Combine the variables with the highest signal vs background separating power into a likelihood ratio? • Estimate a limit for each channel and combine these statisticallyindependent limits? • OR combine all channels using the likelihood-ratio distribution andderive a single limit for the e + jets channel? B.Andrieu (LPNHE, Paris) Strategy for single top e + jets analysis -

  5. Summary • First attempt to define a strategy for e + jets analysis • Combination of different tagging methods relatively clear • Strategy for final selection and result still to be discussed • Eventually, plans with evolve as analysis progresses and time schedule becomes tighter! B.Andrieu (LPNHE, Paris) Strategy for single top e + jets analysis -

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