Suggested Results for Moriond

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Suggested Results for Moriond
DØ New Phenomena Group March 1, 2002
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Z(ee) Candidate w/ Two 3D-tracks
D? Run 2 Preliminary
Impressive performance ofthe tracker! pT/ET is
still offdue to a crudealignment
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Tracking in the diEM events

• Tracking also helps to fight misidentification
  backgrounds
• Top plot diEM mass spectrum with standard EM ID
  cuts
• Background shape is taken from data (EM objects
  failing standard ID cuts)
• Bottom plot the same, with an additional
  requirement of at least one matching track with
  pT gt 10 GeV

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diEMMET Channel

• ggMET is an important channel for new physics
  searches (GMSB SUSY, radiative neutralino decays,
  extra dimensions, etc.)
• The key is a good MET resolution and small
  non-Gaussian tails
• Top plot MET in the inclusive diEM sample
• Bottom plot MET in the diEM sample w/ at least
  one matching track
• Red line shows the fit to a resolution function

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MET Significance

• One can use a likelihood quantity, the MET
  significance to improve S/B by taking into
  account event topology, found vertices, and
  resolutions
• Low significance correspond to no physics source
  of MET
• Ligh significance means that MET is likely not
  due to mismeasurement

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Highest-MET diEMMET Candidate
An interesting event, as itcannot be explained
witha vertex mismeasurement.Can be explained by
theresolution effects.
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em Candidate Event
Top, SUSY, b-physics, Z(tt)give rise to em X
events
D? Run 2 Preliminary
Electron
MET
Muon
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J/? ? ?? Reconstruction
D? Run 2 Preliminary
Minimal kinematic cuts
pT(mm)
M(mm)
opposite sign
same sign
J/???? events from muon triggers, as
reconstructed in the forward muon system. Low pT
dimuon events are characteristic of the trilepton
SUSY signature.
M(mm) for pT(mm) gt 5 GeV
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eee Candidate Event
D? Run 2 Preliminary
Trilepton eventsare classical SUSY signature
Electron
Electrons
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e?? Candidate Event
D? Run 2 Preliminary
Muon system
Electron
Muon
Muon
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e?? Cosmic Background Event
D? Run 2 Preliminary
muon system
MIP Trace of the muon
Electron
Muon
Muon
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Leptoquark Search in eejj Channel

• Leptoquarks hypothetical particles with
  properties of both quarks and leptons restore
  symmetry between the two
• Search strategy motivated by the well-optimized
  Run 1 analysis
• Kinematic cuts 2 EM objects w/ ET gt 25 GeV and
  at 2 jets w/ ET gt 20 GeV
• Use ST scalar sum of transverse energies of
  electrons and jets to separate signal and
  background
• Additional variable two pair masses M(ej) for
  the combination that gives the closest match
  between the two
• Five events survive these cuts (in 6 pb-1) one
  has a track match
• The most energetic event has ST 315 GeV (Run 1
  cut was at 350 GeV) and no track match

LQ(200 GeV) signal shape
ST
Background shape
5 candidate events,one with a track match
Mej
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Highest ST eejj Candidate Event
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Search for Extra Dimensions
diEM channel tooptimize sensitivity ET(EM) gt 25
GeV Good fiducial Standard ID
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The Most Massive Candidate Event
Mass, cost 212.9 GeV, 0.85 MET 22.9 GeV
nvtx/Zvtx 1/-10.5465 EM1 Et, phi, eta
92.1989 3.97754 0.795084 EM2 Et, phi, eta
72.671 1.046 -0.736977 CFT track match