Transcript Jet+MET Topology Group Anwar A Bhatti The Rockefeller University LPC Jterm-III January 16, 2009 Conveners: Teruki Kamon kamon@physics,tamu.edu Anwar Bhatti [email protected] Meetings: bi-weekly (alternate week dijet) Tuesdays 13:00-15:00 (CST) EVO/Round Table.

Jet+MET Topology Group
Anwar A Bhatti
The Rockefeller University
LPC Jterm-III
January 16, 2009
Conveners:
Teruki Kamon kamon@physics,tamu.edu
Anwar Bhatti [email protected]
Meetings:
bi-weekly (alternate week dijet)
Tuesdays 13:00-15:00 (CST)
EVO/Round Table (WH11 SE)
Jan 16, 2009
Anwar Bhatti LPC JTerm-III
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Supersymmetry
LM1
60,250
GeV
Final state typically has multiple jets and large missing transverse energy.
Cross sections depend on the SUSY parameters, specially masses of
squarks and gluinos.
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Benchmark Point LM1
m0=60 GeV, m½=250 GeV, tan()=10,A0=0,sign(µ)>0
Gluino mass = 600 GeV, squark mass =320 GeV
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Inclusive Jet+MET Analysis
Standrad Model Processes
1010 pb
QCD
W+jet (leptons)
7x104 pb
Z+jets (leptons)
7x103 pb
tt
800 pb
SUSY LM1 ~50 pb
• Require large MET and multi-jets to suppress
the SM backgrounds.
• Use data-driven techniques to estimate
backgrounds.
Event Selection: (PTDR2)
• Cleanup
• No leptons (no e,µ, isolated tracks, EM rich jets)
• Three leading jets with Pt>180, 110, 30 GeV
• HT = PtJet2+PtJet3+PtJet4+MET >500 GeV
• MET> 200 GeV
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Significant Backgrounds
QCD
mis-measured jet, b/c quarks
Top
semi-leptonic τ-lepton or lost lepton
W,Z diboson τ-leptons, lost leptons
Z→νν
irreducible
Estimated based on Monte Carlo PTDR-II (fb-1 @14 TeV
Signal
QCD
Top pair
Z(νν)
W/Z
Single top
6319
107
54
48
33
3
Major effort over last year has been to develop methods to extract
these background from data.
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QCD background Elif Albayrak (Iowa)
Other Efforts at CMS:
C. Auterman et el (Hamburg)
ABCD Method
Jess Reidel (UCSB)
Smearing Technique
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This method over (under) estimated the low
(high) ET miss region.
Under study.
Need to understand the tails in the
response function.
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tt background
Jan 16, 2009
Duong Nguyen (Brown)
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tt background
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tt
The procedure works reasonable well in absence of SUSY.
SUSY contaminates (template , data) → over estimate
Investigating various techniques to separate tt and SUSY.
MT = mass of lepton and missing transverse energy
•
Δφ between the hemisphere containing lepton and
•
Top and W mass constraints
LM1
Events/30 GeV
•
Events/30 GeV
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background
Missing ET (GeV)
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MET
LM6
Missing ET (GeV)
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Invisible Z bosons
ν_
ν
Z
pTZ  200 GeV  MET> 200 GeV
σ(Z→νν) = 20% × σ(Z)
What processes are similar?
Z/γ*
remove
remove
μ-
μ+
W-
μ_νμ
– Lower statistics
(than γ, a bit > Z→νν)
– Simpler theory corrections
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remove
γ
– Higher statistics
(no branching ratio)
– More theory corrections
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Photon+jets
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Sue Ann Koay (UCSB)
For large pT > 200 GeV, Pt and η spectrum are similar.
Hadronic activity within 20%.
Detailed studies to determine fake rate, photon efficiency from data
Z→νν background estimate (100 pb-1)
Jan 16, 2009
MC-truth
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From γ+jet
29±3(stat)±5(sys)
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Invisible Z background from Zµµ
• Similar production mode but
σ(Z→µµ) = σ(Zνν)/6
Gheorghe Lungu (Rockefeller)
• Statistically limited .
→
Loosen the cuts and extrapolate.
•Signal Region MET>200 GeV
•Control Region 100-200 GeV
• Fit exponential
• Events @100 pb-1
• Fit 15, true 19.4
•Features of the method
• relies minimally on Monte Carlo
• biased by shape of function
•At high luminosity (>600 pb-1 )
•Enough statics to direct measurement.
•116 events with MET>200 in Zµµ+3jets
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Working Point LM5
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Hemisphere Algorithm
Harold Nguyen
 Determine two axes that approximate the direction of primary partons
by using all objects (jets, leptons, photons) in an event
Axis 1
Axes are computed by:
Axis 2
Starting with two initial seeds –
two objects which form the highest objectobject invariant mass
Objects are then associated to the nearest
hemisphere axis based on relative transverse
momentum.
Group1
Sum connected momenta → new axes
Keep iterating until no objects switch
Reduce QCD background by
Δφ(h1,h2)>2.7
Jan 16, 2009
Group2
(rejection of ~5)
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Invariant Mass
Harold Nguyen
All events with number of b-jets
≥2
Normalized to 1 fb^-1
14-January-2009
JTerm III, H. Nguyen
PTDR Results (Filip et.
al)
Similar shape to PTDR
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Searching for SUSY in Co-annihilation Region
Astronomical observation indicates that we live
in a universe that is made of a type of heavy
weakly interacting matter that we call Dark Matter
Supersymmetry models with
R-Parity Conservation give rise
to a dark matter candidate particle
Co-Annihilation Region
Co-Annihilation
Diagram
Important in the
early universe
11/7/2015
Minimal Super Gravity (mSUGRA) type models with
a near mass degeneracy between the stau and the
lightest neutralino give rise to dark matter density
predictions that agree with observation
SUSY Low Mass Point 2
Jonathan Asaadi Texas A&M
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Low Mass Point 2 (LM2)
Jonthan Assadi (TAMU)
Large tan → large number of τs
Branching ratio ~95% at LM2
PTDR
• Using PF-Taus, a lot of technical issues
• Optimizing selection cuts
• Plan to move to 2_2_x
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Trigger Studies HT+MHT Trigger Jim Lungu
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Missing Et Rates
Jan 16, 2009
Gheorge Lungu
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Zττ,tool for SUSY/Higgs Search
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Zττ is good place to study τ identificarion.
Alfredo Gurrola (TAMU)
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Detailed study tau reconstruction and isolation variables
Background
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Data driven techniques to determine BG
QCD BG:
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
W+jet
QCD
ABCD method using using
muon and tau isolation variables
W+jet
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τ isolation and Δφ(µ,τ)
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Estimated # of Events at 100 pb-1 Alfredo G.
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Define all the selections:
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≥ 1 global muon w/ PT > 20 and |h| < 2.1
≥ 1 jet with PT > 10 GeV and |h| < 2.5
Seed track (DR<0.2 from jet axis) with PT
>6
Exactly 1 jet with PT > 10 GeV (jet veto)
Muon-Jet seperation cut : DRm-jet ≥ 0.7
Muon PT < 50
Muon Isolation < 1 (both tracks &
gammas)
Muon IP < 0.01 cm
cos Df(m-t) < -0.95
m track & t seed track opposite charge
t isolation (both tracks & gammas)
# of events at 100 pb-1
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•
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Z → mt :
218.86 ± 9.82
W+jets :
13.40 ± 2.76
QCD (pp → m+X) : 4.60 ± 2.30
Alfredo Gurrola
Jets + MET Topology Meeting
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Other Studies
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Extension of αT to three jets (Taylan Yektin, Mehmet Vergili)
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So far main effort by CERN, Imperial College Groups.
Global run analysis
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Missing Et clean-up (Ming Yan, Alfredo Gurola)
Jet trigger Studies (Mehmet Deliomeroglu LPC/Bogazici)
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Missing Transverse Energy
Cosmic Ray Muon
Air Shower
Cosmic Muon
Energy: 250 GeV (ECAL)
Event Cleanup
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
≥ 1 primary vertex
Activity in Ecal, Hcal and tracker
Halo Muons in CSCs and HB
>0.175
> 0.1
Not a big issue as long as such events do not
overlap with real pp collision.
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
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Studies of CRAFT and CRUZET data shows that the rate of very high
missing Et rate (from detector (HCAL) and cosmic rays) is a few
Hertz. The overlap rate is expected to be small.
We will able to understand MET quickly (months!!) to make a
statement about SUSY at LM1 i.e. exclude/discover.
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600 events for 100 pb-1 @14 TeV.
Come and join us to be part of the excitement.
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Trigger
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Missing transverse Energy
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HT/MHT trigger studies
Studies of Jet trigger in CRAFT
Analysis of CRUZET and CRAFT data
Clean-up and filters
Hadronic SUSY analysis
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QCD background
Top background
Invisible Z boson background
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αT analysis
h  bb
t -lepton final states
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