AOD analysis for DC2 SUSY sample'

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AOD analysis for DC2 SUSY sample.
Pavel Zarzhitsky SMU
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Introduction.

• DC2 has a new SUSY point in the coannihilation
  region. The parameters of the point are
• m070 m1/2350 A00 tanß10.0 sgn(µ)
  mtop175.
• The coannihilation point is in a region that is
  favored if SUSY is to explain dark matter. LSP is
  almost degenerate with sleptons. It is close to
  point 5 in TDR, but there are some mass
  differences that need to be taken into account.
• I performed some standard analysis using AODs,
  produced using full simulated data. The data
  contain no noise.

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Data production.

• 400,000 events were produced and digitized. The
  digitized data files located at
  /usatlas/magdacache001/ common/doyen/A9_digi/
• All events are made without noise.
• AOD analysis job takes 20 min for 100000 events
  on 1.5 GHz CPU.
• To analyze AOD use a sample Athena packages
  PhysicsAnalysis/SUSYPhys/SUSYPhysAlgs,
  PhysicsAnalysis/SUSYPhys/SUSYPhysUtils,
  PhysicsAnalysis/SUSYPhys/SUSYPhysUser.

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Physics process.
The leading processes in coannihilation region
give squark that can decay through producing slow
leptons
The similar process for taus is given by
Slow leptons are produced from following sources
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Leptons pT distribution.
pT distribution for all electrons.
pT distribution for all muons.
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Leptons pT distribution.
pT for leading and soft electrons
pT for leading and soft muons
leading e second e
leading muon second muon
pT distribution for leading and soft electrons
that are used to calculate dilepton invariant
mass.
pT distribution for leading and soft muons that
are used to calculate dilepton invariant mass.
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Invariant mass of e-e and µ-µ pairs.
Invariant mass for electron pair.
Invariant mass for muon pair.
opposite sign same sign
These are invariant mass plots for electrons and
muons separately. As you can see there is an
excess of electrons with low invariant mass.
Almost all of these low mass events have two soft
electrons. Used cuts are on the next slide.
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Electrons with low inv mass.

• As you could see on the previous slide there is
  an excess of electrons with low invariant mass.
  These events have following properties
• We have low mass events for the same charge and
  opposite charge electrons.
• Almost all of these low mass events have two
  soft electrons.
• Both electrons in the pair are very close to
  each other in space. Plots with eta and phi
  differences for electron pairs with low invariant
  mass are on the next slide.
• We believe that these low mass events are caused
  by fake electrons from e-gamma conversion and
  photon emission. Both these processes will
  produce two adjacent clusters in the calorimeter
  and one track associated with them. And this is
  the case.

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Electrons with low inv mass.
These 2 plots show difference in eta and phi
between electrons in pair with invariant mass lt
5GeV. As you see, they are very close to each
other.
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Electrons ? distribution.
Invariant mass for electron pair.
eta for all electrons passed ET and jet cuts eta
for all electrons used for inv mass
calculation eta for electrons with inv mass lt 5GeV
Electrons have a strange behavior in a transition
region. There are two peaks at eta -1.5,
especially for electrons with low invariant mass.
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Invariant mass of e-e pair.
Invariant mass for electron pair.
The electron sample was clean by requirement that
distance between any two electrons must be gt0.2
in eta and gt0.2 in phi. From two adjacent
electrons the one with highest pT was left in the
sample. On the plot you can see a comparison of
e-e invariant mass with and without cleaning.
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Dilepton endpoint.
Invariant mass for lepton pair.

• xETgt300 GeV
• 2 SF/OS leptons Ptgt10 GeV
• gt1 jets with Ptgt150 GeV
• Opposite sign/ Opposite flavor subtraction
  applied
• events with invariant mass lt 5GeV are eliminated
  to remove electrons with low invariant mass
• Two endpoints are expected. One from

at 67 GeV. The
Compare with TDR plots 20-9 and 20-10.
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Pt for taus.
pT for leading and soft taus
leading tau second tau
pT distribution for leading and soft taus that
are used to calculate tau-tau invariant mass.
pT distribution for all taus.
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Tau inv mass.
Invariant mass for tau pair.

• This is the same lepton pair invariant mass for
  two opposite sign taus.
• xETgt300 GeV
• 1 tau pT gt 40 GeV,
• 1 tau pT gt 25 GeV
• gt 1 jet with pT gt 100 GeV, gt 1 jets with
• pT gt 40 GeV

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Jet ll inv mass.

• Using two leptons and a jet we can form invariant
  mass of a squark. This is for
• at least four jets with pT1gt100 GeV, pT2,3,4 gt
  50 GeV
• Meff gt 400 GeV
• Etmiss gt max(100 GeV, 0.2 Meff )
• Two opposite sign leptons with pT gt 10 GeV.
• The lepton pair was combined with two hardest
  jets. The smaller invariant mass is on the plot.
  It must be smaller then the four body endpoint
  for squark. Mllqmax 609 GeV. Compare to TDR
  Fig. 20-20. The larger invariant mass should give
  the same endpoint on the left edge.

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Jet ll inv mass.
Smaller of the two e e- q masses. Only
electrons are included.
Smaller of the two µ µ q masses. Only muons are
included.
cut1 means Mll lt 67 GeV cut2 means Mll lt 100 GeV.
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Jet ll inv mass.
OF/OS leptons subtracted. It is not clear that
the endpoint is at 609 GeV.
Smaller of the two l l- q masses.
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Summary.

• AOD production for DC2 is working.
• For coannihilation point two endpoints in l-l
  invariant mass can be clearly seen.
• There is a problem with excess of soft electrons
  with low invariant mass that is correlated with
  two peaks in eta.
• More work is needed to understand endpoints in
  jet-l-l invariant mass.

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Effective mass.

• This is so called effective mass plot.
• MeffpT1pT2pT3pT4Etmiss
• where pTi are for 4 hardest jets in the event.
• xETgt100 GeV
• 4 hard jets (pT1,2gt100 GeV pT3,4 gt50 GeV)
• No isolated electrons or muons (pTgt20 GeV)

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Missing energy
Missing energy plot.
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Tau likelihood.
This is a plot of a tau selection likelihood. It
should be more then 0 for the candidate to be a
tau jet. Shape must be much more smooth, no
peaks. Compare to DC1 results.