Search for Heavy Majorana Neutrino and W R Boson on CMS Sergei Gninenko (INR), Anton Karneyeu (INP, LAPP), Mikhail Kirsanov (INR), Nikolai Krasnikov (INR), Ivan Mologin (INR), Alexander Toropin (INR), Viacheslav Duk (INR), Lyubov Menshikh (INR) CERN 12 March 2009
Search for Heavy Majorana Neutrino and W R Boson on CMS Sergei Gninenko (INR), Anton Karneyeu (INP, LAPP), Mikhail Kirsanov (INR), Nikolai Krasnikov (INR), Ivan Mologin (INR), Alexander Toropin (INR), Viacheslav Duk (INR), Lyubov Menshikh (INR) CERN 12 March 2009. Analysis status. - PowerPoint PPT Presentation
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Search for Heavy Majorana Neutrino and WR Boson on CMS
Sergei Gninenko (INR), Anton Karneyeu (INP, LAPP), Mikhail Kirsanov (INR), Nikolai Krasnikov (INR), Ivan Mologin (INR), Alexander Toropin (INR),Viacheslav Duk (INR), Lyubov Menshikh (INR)
• Analysis approved on 22 of October• Presented at PANIC08 by M. Kirsanov (CMS CR
2009/018)• CMS discovery potential in terms of WR – heavy
neutrino masses at the LHC collision energies of 6 and 10 TeV have been studied on request of the CMS Exotica group (CMS AN 2009/007). The results were shown at the Les Houches LHC performance Workshop in February
The dependence of the maximum MWR 5σ discovery reach in left-right symmetric models with 100 pb-1 integrated luminosity (CMS AN 2009/007).
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Summary
• CMS potential for discovery of heavy right-handed neutrino and WR boson is studied
• Good separation of the signal from SM background processes can be achieved due to resonance nature of signal
• For the integrated luminosity of 100 pb-1 particles can be observed with masses up to MWR = 2100 GeV and MN = 1200 GeV
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Plans
• Study e-mu channel• Process CSA08 backgrounds (thus moving to 10 TeV
collision energy) and new signal samples• Move to CMSSW_2_2_6• Start to use PAT• Improve significance and limits calculations:
- Estimate the effect of systematics on the limits- Breit-Wigner for signal in Nl projection too narrow?- Move to median values in the discovery plot
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Backup slides
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Triggers
• Trigger menu for luminosity L = 1032 cm-2 sec-1
• Electron channel:HLT1EMHighEt, HLT1EMVeryHighEtSignal efficiency 99%, rate 0.6 Hz
• Muon channel:HLT1MuonIsoSignal efficiency 93%, rate 18 Hz (very high, would like to select events with trigger candidate Pt cut 80 GeV: no efficiency drop)
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Backgrouns. Studied on CSA07 and private samples Main one tt + jets, then Z + jets
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Remarks about same sign background
Composition of background, 1500 GeV, wide W mass window:
all: 1.892
chowder: 0.7685
gumbo Gamma+jets: 0.675
Stew bbe e-enriched: 0.195
diboson WZ 0.111 (physical)
diboson WW 0.136
The measurements will not be based on the same sign signature because
we lose half of signal events and significance drops. This is only a
cross-check if we see a signal. So, just absolute data correction from the
same sign events in the Z peak could be sufficient.
• We should not be sensitive to the wrong prediction of the total number of BG events
• But still it would be good to find some signal-free region and look at it
• One of them – W masses from 500 to 800 GeV: signal excluded. Will be automatically taken into account in the fits.
• At the first stage can consider electron – muon channel as signal-free (assuming that the probability of strong mixing between heavy neutrinos is small)
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BG control (2)Most important BG components:
• tt events: electron – muon sample to controle-mu: 45 eventse-mu same-sign: 9 events
• Z+jets events: sample with relaxed Mll cut (80 GeV) to control: > 200 events with MW > 500 GeV. The shape can be different!
• Events with fake leptons (W+jets, gamma+jets, QCD): electron – muon sample with same sign to control
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BG control procedure
• tt distribution shape: we compare 1D projections of the electron – muon sample with MC (40 events: rather big errors) and can use directly these corrections
• Z+jets distribution shape: we compare the sample with relaxed Mll cut (80 GeV) with MC. The shape can be different, so probably we cannot use directly the corrections.
• Events with fake leptons (W+jets, gamma+jets, QCD): check electron – muon sample with same sign and compare the number with all signs. If the factor is much different from 5, we introduce weight and eventually try to tighten the lepton selection cuts
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Fit results(μμ channel, MWR = 1500 GeV/c2)
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Pseudo-experiments (toy MC)
• Based on parameter from fit• Only nsig and nbkg parameters are free• 2000 pseudo-experiments per Reference Point