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Unified Search for Associated Production of Chargino-Neutralino using Leptons
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We present a search for the associated production of chargino and neutralino supersymmetric
particles using data collected by the CDF II experiment at the Tevatron. We analyze events
with three charged leptons and momentum imbalance, in five exclusive channels. We observe no
excess over standard model expectation. We present upper limits on the production cross section
in the mSUGRA model.
Blessed Plots and Tables
(Click on images for Full Size)
Jump to Final Tables, Limit Plot, Final Selections,
Event Displays, Dilepton control regions, Trilepton control regions
Definitions of Exclusive Channels
Table shows the definitions of the exclusive channels.
`Tight' refers to a restrictive selection of lepton to keep high purity,
`Loose' is with some requirements relaxed to keep high acceptance.
Final Tables
Table shows the final expected signal and background events along
with the observed candidate events in the five channels. Signal point considered here is mSUGRA point
with following parameters -- m0=60, m½=190, tan(beta)=3, A0=0, sign(mu)>0
Table shows the list of systematic uncertainties in percentage
broken down by channels. The systematic uncertainties are
ID : Lepton identification Trig : Trigger efficiency
JES : Jet energy scale X-sec : Process cross-section, NLO corrections to X-sec
PDF : Parton distribution functions ISR/FSR: Initial/Final State Radiation
Conv: Photon conversion removal
ITR(nom) : Isolated Track Rate with nominal parametrization
ITR(alt) : Isolated Track Rate with alternate parametrization
Fake: Misidentification of hadrons as leptons.
Table shows some properties of the candidate events broken down by channels.
FINAL LIMIT PLOT for mSUGRA
Plot shows the final limit for the
mSUGRA model with parameters indicated on the plot. m½ is varied to get the chargino mass along X-axis.
The red curve shows the theory cross section (PROSPINO 2.0). The dashed and solid black lines show the
expected and observed limits. We exclude charginos with Mass < 140 GeV/c². The signal is generated with
Pythia v6.216 and Isajet v7.51.
The uncertainty on the theory cross section is folded into the limit calculation for expected
and observed limits. Additional information about the limit.
FINAL SELECTIONS
We show distributions of final selection variables after all other selections except the one being plotted
are made. We also indicate the value of the cut we make by an arrow on the plot.
Selection: 3tight
Plot shows the missing energy, we keep events with missing transverse energy > 20 GeV.
Plot shows the number of jets (jet ET>15 GeV), we reject events with more than one jet.
Plot shows the highest invariant mass of opposite-charge lepton pairs.
We reject events if 76<Mass<106 GeV/c²
Selection: 2tight,1Track
Plot shows the missing energy, we keep events with missing transverse energy > 20 GeV.
Plot shows the number of jets (jet ET>15 GeV), we reject events with more than one jet.
Plot shows the highest invariant mass of opposite-charge lepton pairs.
We reject events if 76<Mass<106 GeV/c²
Plot shows the azimuthal separation between opposite-sign lepton pairs.
We keep events with DeltaPhi < 2.8 radians.
Selection: 1tight,1loose,1Track
Plot shows the missing energy, we keep events with missing transverse energy > 20 GeV.
Plot shows the azimuthal separation between opposite-sign lepton pairs.
We keep events with DeltaPhi < 2.8 radians.
EVENT DISPLAYS
Event 1 : Three tight electrons: ET = 24, 17, 5.8 GeV - COT, Lego, CAL3D
Event 2 : Two tight muons, One Track: PT = 34, 6.2, 9.2 GeV - COT, Lego, CAL3D
Control Regions (DILEPTON)
The figure illustrates our control regions for dilepton selection.
Control regions are defined according to the dilepton invariant mass and momentum imbalance
(missing energy or MET) in the detector. The control region names are defined as follows
Z : Zee, dilepton invariant mass is 76<Mll<106 GeV/c²
!Z : not Zee (Z-veto), dilepton invariant mass is Mll<76 OR Mll>106 GeV/c²
lo : low refers to MET<10 GeV
hi : high refers to MET>15 GeV
Combinations of these names give other control regions, for example !Zlo is !Z with low MET,
Zhi is Z with high MET.
Plot shows the agreement in dilepton control regions.
The uncertainties are statistical, along with systematic uncertainties due to lepton identification,
trigger efficiencies and NLO corrections to the cross section of background process.
Plot shows the invariant mass distribution of lepton
pairs for dilepton events with missing transverse energy < 10 GeV.
Same as above, linear scale.
Plot shows the missing transverse energy for dilepton events
with lepton pair invariant mass in the 'Z' window : 76<Mll<106 GeV/c²
Same as above, linear scale.
Control Regions (TRILEPTON)
The figure illustrates our control regions for trilepton selection.
The !Zhi region, with Z-veto and high MET is now our signal region. We test the regions Zlo,Zhi,
and !Zhi.
Plot shows the agreement in trilepton control regions.
The uncertainties are statistical, along with systematic uncertainties due to lepton identification,
trigger efficiencies and NLO corrections to the cross section of background process.
Plot shows the highest invariant mass distribution of
opposite-charge lepton pairs for dilepton+track(2tight,1Track) events with missing transverse
energy(MET) < 10 GeV.
Plot shows the missing transverse energy distribution for
dilepton+track(2tight,1Track) events with highest opposite-charge lepton pair mass in 'Z'
window : 76<Mll<106 GeV/c²
Plot shows the track PT distribution for
dilepton+track(2tight,1Track) events with highest opposite-charge lepton pair mass in 'Z'
window : 76<Mll<106 GeV/c²
Plot shows the highest invariant mass distribution of
opposite-charge lepton pairs for trilepton events(3tight) with missing transverse energy < 10 GeV.
Plot shows the softest lepton ET distribution for
opposite-charge lepton pairs for trilepton events(3tight) with highest opposite-charge
lepton pair mass in 'Z' window : 76<Mll<106 GeV/c²
Sourabh Dube
Last modified: Wed Jan 30 09:01:24 CST 2008
