L2Offline MET

1
L2/Offline MET
PRS Physics Reconstruction and
Selection HCAL/JetsMET group

• Pal Hidas
• (Shuichi Kunori)
• 08-Feb-2002

2
SUSY Probing Points
(S.Abdullin)
3
Complex SUSY Channel- an example -
40 60
m 0 m 1/2 (1425,312)
Mh 116GeV Mgluino 804GeV Msquark
1500GeV
( a SUSY point from hep-ph/0105204)
4
qqH(120), H?invisible

• Event selection
• 2 FWD tag jets
• Et gt 40GeV
• Dhgt4.4, h1h2lt0.0
• M(jj) gt 1200GeV
• Between 2 FWD jets
• no jet
• Etgt20GeV
• no lepton
• pt(m) gt 5 GeV
• pt(e) gt 10GeV
• METgt100GeV
• DF(jj) lt 1.0

• q
• Invisible
• (neutralinos)
• (gravitinos)
• q

Signal (sBR) 4300fb (BR1) Background
QCD Zjj QCD Wjj EW Zjj EW Wjj
NB tt is no more major background.
5
Reconstruction and Selection

• MET Reconstruction
• Vector sum of ET in ECALHCAL towers
• Threshold ET(tower)gt0.5GeV
• Energy scale correction (not applied in this
  analysis)
• Jet energy correction for found jets and
  min-bias correction for outside of the jets
  (cone).
• Event Selection
• Filter to remove abnormal events and/or channels
• CMSIM120 large energy deposit in single readout
• Due to 1) wrong choice of a GEANT parameter for
  energy loss and 2) memory collapse(?) in CMSIM
• ET(1x1)/ET(3x3) gt 0.9
• Real detector
• Due to hot/noisy channel (for example)
• Topological cuts
• Back to back jet veto for 1st 2nd highest ET
  jets
• 1) no cut, 2) df gt p - 0.5

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MET resolution
reconstructed
h lt 5
n, m excluded
QCD Bins (PT-hat)
7
MET Distributions
Invisible Higgs
SUSY
8
QCD jets MET RatesGenerated Particle Level
n, m excluded
h lt 5 (n, m excluded)
1Hz
9
QCD JetsHeavy Flavor Contribution
heavy flavor fraction
MET
Generated MET
PT hat
10
Df for MET gt 50 GeV
Jet1 vs Jet2
MET vs Jet2
80 lt PT lt 120 GeV
380 lt PT lt 470 GeV
11
DFJJ cuts and results
- this - - DZ - Higgs
74.7 (96.7) fb QCD Zjj
48.0 (71.8)QCD Wjj job
running EW Zjj 12.8 (14.8) EW
Wjj 8.9 (9.9) (very
preliminary)
Set upper limit on sBR(H?inv)
(A.Nikitenko K.Mazumdar)
12
L2 without/with Df(1,2) cut
No Df(1,2) cut
Df(1,2) cut
90 GeV
120 GeV
1Hz
MET Threshold
MET Threshold
10 reduction in rate with Df(1,2) cut
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L2 (no Df(1,2) cut) vs L1
L2
L1
1Hz
MET HLT Threshold
MET L1 Threshold
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mSUGRA1
Trigger rates with 95 efficiency as a fucc
of generated MET
1kHz
1Hz
Generated MET
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Invisible Higgs
Trigger rates with 95 efficiency as a
function of generated MET
Generated MET
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Alternative HLT for Invisible Higgs
(A.Nikitenko)
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Summary

• L2 MET Thresholds for 1Hz are
• 120GeV without Df(1,2) cut
• 90GeV with Df(1,2) cut
• Need to implement MET energy scale correction
  with jet correction
• Need to understand source of difference in L2 and
  L1 MET resolution.
• Continue to look for algorithm to lower the MET
  threshold by
• Additional topological cuts
• Improving MET resolution

18
Additional Slides
19
MET
Multi-jets and MET will provide discovery of
SUSY. How to measure SUSY parameters? ?
need a lot of work. By the way
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Jets
Et of 1st 2nd highest Et jets
Jet Multiplicity (Etgt40GeV)
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Dijet Mass Resolution
With pileup
No pileup
W(jj)
Top(jjj)
Before correction
M(bb) in WH
15
21
After correction
Jet energy correction without 19
with 14 CMSJET 15
16
22
(V.Drollinger)
(R.Kinunnen)
22
.
A.Nikitenko (Talk on Wednesday)
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MET
Out of cone corr. uses weights for jet(30GeV)
corr.
Corrections Type 1 Jet corr. Type
2 Jet corr. out of cone corr.
(Nikitenko)
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Corrected MET for mSUGURA JetsMET at low lumi
s
Mean offset
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Higgs mass in bbA, A?2t?2j
(A.Nikitenko)
before correction
after correction
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Jet Cone Size
particle-jets vs. reco-jets
Resolution of Mass(Z?jj) - 1994 study -
No min-bias overlap
ISAJET 6.36 Parameterized Simu.
h0.0-0.3

30 min-bias overlap
40
20
No bin-bias overlap
0
h1.8-2.1
.2 .4 .6 .8 1.0 1.2
Cone Size
(Fermilab-FN-626)

• Larger R is better for di-jets _at_ low luminosity.
• Need to test with multi jets.
• _at_ high luminosity

(Vardanian/Kodolova)
27
Effect of Thresholdon low ET jet and MET
20GeV parton jet _at_ 10E34
MET
(I.Vardanian)
(S.Nikitenko)
Lower threshold is better!
Electronics noise and occupancy define the
threshold. gtgt aim at 0.5GeV/tower _at_ 10E34