Transcript Invariant mass distribution of jet pairs produced in

Invariant mass distribution of jet pairs
produced in association with a W boson
in pp collisions at √s=1.96 TeV
CDF
•
•
•
•
•
•
•
Layer 1: Beam Pipe
Layer 2: Silicon Detector
Layer 3: Central Outer Tracker
Layer 4: Solenoid Magnet
Layer 5: Electromagnetic Calorimeters
Layer 6: Hadronic Calorimeters
Layer 7: Muon Detectors
Electron (muon):
pT>20 GeV/c
|η|<1.0
Missing transverse energy ET>25 GeV
The transverse mass of the lepton +ET system
must be greater than 30 GeV/c2.
Two jets:
ET > 30 GeV
|η|< 2.4
Dijet system pT>40 GeV/c
The two jets must be separated by |η|<2.5.
Direction of pT and of the most energetic jet
are separated azimuthally by |Δφ|>0.4.
The dijet invariant mass distribution. The sum of electron and muon events
is plotted. The band in the subtracted plots represents the sum of all
background shape systematic uncertainties described in the text. The
distributions are shown with a 8GeV/c2 binning, while the actual fit is
performed by using a 4GeV/c2 bin size.
The dijet invariant mass distribution for the sum of electron and muon
events. The fit χ²/ndf is 62.0/81. Rjj distribution for events with Mjj< 115
and Mjj > 175 GeV/c2 of the data compared to the background estimation
that corresponds to the same systematic combination of. The uncertainty
band corresponds to background statistical uncertainty.
Variation with ET threshold
Increasing the jet ET threshold in steps of 5 GeV. The result is compatible with the
expectation from a Monte Carlo simulation of a W boson plus a particle with a
mass of 150 GeV/c2 and decaying into two jets.
If the ET threshold is reduced to 20 GeV the significance of the excess is reduced
and becomes 1.1 sigma.
High pT sample. The significance of the excess for the
subsample of events selected with pT> 60 GeV is 2.2 σ.
"Inclusive" distributions without Njets=2 cut
The MJJ and background subtracted MJJ distributions are
shown below when the Njets=2 cut is relaxed.
Resonant production
Distribution of the total mass of the event and Q = Ml ν+ JJ - MJJ -MW distribution.
The pZ of the neutrino is obtained by constraining the W mass to the PDG
value and extracting the two solutions. The plots thus have two entries per
event. The distributions are compatible with the background-only hypothesis.