Comments from Anna • Comment 1. Triggers: as discussed during meeting – consider move to higher offline lepton pT cut or check data/MC agreement for slope of the turn on curve of used triggers Answer: Our signal region is at pretty high lepton pt so the trigger we used has little effect for our search; for background control region(Mll’<200), this is a common issue, and we followed the SMEW recommendation. For the discrepancy between data and MC, we used a correction with a standard tool ” TrigMuonEfficiency-00-02-42” which is provided by the trigger performance group • Comment 2. Did you consider to use tight tau ID? Or it reduces too much acceptance of your signal? Answer: Our signal is a sharp peak, so when we do signal search, we focus on a mass window at high mass region, the background is small, so we are not concern about the backgrounds. Medium tau ID is the recommended one from tau performance group, if we change to tight tau, we loose >30% signals.
Comments from Anna • Comment 3. Triggers: I understand you donotdo overlap removal between e/tau and mu/tau? Answer: We the dphi between good elec(or mu) and good tau >2.7, and we veto events with a 2nd loose elec/muon/tau, we didn’t perform further e/tau or mu/tau overlap removal since Zll background is negligible at high mass(signal) region • Comment 4. >100% error on estimation of W+jet background looks bad.Like this this background is consistent with 0 Answer: Jet fake bkgd is high correlated with other background components, and also their uncertainties. Since the overall fraction of jet fake bkgd is only ~ 3%, so we leave it as it was, but we will try to see whether we can improve the uncertainties. • Comment 5. Just for my curiosity as it should not have any impact on your analysis. Does used Z' model predict its polarization? If yes, is it modeled by the generator you use for Z' sample? Answer: We don’t think the polarization is considered in our generator Pythia, will further confirm that.
Comments from George • Comment 1. Definitions of signal, control, and validation regions were causing some confusion among the EB; would be good to clarify this in thenext version of the note Answer: will try to make it more clear in the coming version • Comment 2. Is it possible to validate the MC at high mass, for example bylooking at ee and mumu events, perhaps with a mild MET cut to removeDrell-Yan? Answer: will add this part in the coming version • Comment 3. Multijetbkg comes from OS/SS method, relying on results from H->tautau for validation of the technique. An independent validationmight be useful, given that the lepton pt range in this analysis is probably rather different Answer: since multi-jet(di-jet) process is highly dominated by gluon-gluon process, OS/SS = 1 is supposed. Theoretically, the deviation of OS/SS from 1 in multi-jet(di-jet) process depends on the ratio of gluon-jet and quark jet, should be less correlated with lepton pt range.
Comments from George • Comment 4. Some discussion about trigger efficiencies, why some triggers are Ored(e.g. e60 with e24vhi) but others are not (e.g. no muontrigger for emu channel). a general comment is that there is currently no documentation in the note about trigger efficiencies Answer: will add muon trigger in for emu channel. For trigger efficiencies, it’s calculated with packages from trigger performance group, we will add a part of trigger efficiency in our next version • Comment 5. In the emu channel the main bkg is ttbar. Would applying a bjet veto help? Yes, but this introduces some signal model dependence.Or have two signal regions, with and without bjet veto? Answer: will try with and without bjet veto in emu channel in the following version
Suggestions from exotic group last week • 1. why only 1 prong tau ? • 2. better to use Drell-Yan samples for high mass region to make sure enough statistics PowhegPythia8_AU2CT10_DYee_120M180 …….. • 3. Why have different selections for muon at bkgd control region and signal region ? May potentially cause all kinds of problems if the selection is different in the CR and in the SR recommend to only use one selection, which is the MCP recommended high-pt muon selection • 4. the uncertainty for ttbar x-section is not correct ?https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/Top2012MCCrossSectionReference • 5. The validation of the W+jets shape by comparing sherpa and alpgen is not very convincing, as statistics stops at 200 GeV in lepton pT, but you need to compare at even higher values Use Sherpa samples that are binned in boson pT if possible also a different MC in addition. There are pt-binned Powheg samples
Task • Txt update of our note according to the comments • Update section 5, the signal plots • Emu channel • try b tagging • add muon stream in (prepare skimmed samples) • Remove jet mu overlap removal in jet selection and re-plot jet multiplicity figures • Update plots for mutau channel(add points >100GeV for lepton pT plots) • Calculate backgrounds for signal region and expect limits • MC validation at high mass region • ttbar • WW • Validate contributions from drell-yan process at high mass region
Need discussion? • Whether to add e/tau, mu/tau overlap removal to further suppress Zee/Zmmbkgd ? • How to suppress signal leakage in jet fake background estimation for signal region • Wjet validation with new samples suggested by exotic group Tasks to be finished in 2~3 weeks