Transcript Diapositiva 1

09-03-2009
PDCMSSW - Luca Perrozzi
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Summary
• Searching for K0s→p+p- and F→K+K- punch
through rates as a function of:
• Pt
• Eta
• Impact parameter
Framework used:
• CMSSW_2_2_3
• V0 producer module
• Phi
• 240K events analysis (BCtoMu sample from LNL)
– 8 files: QCD_BCtoMu_Pt30to50_PAT_30000ev_Xover8.V0.g4.root (X=1..8)
• available on /raid4/perrozzi/PAT_production/
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K0s selection
• Invariant mass fit (m= 498 MeV, σ= 6.5 MeV)
Counts
– 2.8s window for signal & background
background
signal
(GeV)
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Strategy
Reco K0s
Pi tracks from
K0s Background
Pi tracks from
K0s Signal
Sig - Bkg
Reco Mu
DR<0.01
DPt<0.01
Pi Rate
DR<0.01
DPt<0.01
Mu/Pi
Mu Rate
Mu associated to
Pi track from
K0s Signal
Mu associated to
Pi track from
K0s Background
Pi (from K0s)
punch through
(as function of
Pt, Eta, Phi,dxy,
decay length)
Sig - Bkg
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K0s RecoPi-RecoMu track association
DR<0.01
|DPt/Pt|<0.01
R = D 2 + D 2
m
Counts
Counts
m
DR(cm)
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DPt/Pt
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K0s Pi Punch through vs. Pt
•Increases with Pt
•As aspected!
•Meaningless after 10 GeV
•More statistics needed!
Distributions before ratio
Red: Muon
Black: Pi
Log scale!
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PDCMSSW - Luca Perrozzi
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K0s Pi Punch through vs. Eta
•Shows hadronic calorimeter
“holes”at ~2
•More statistics needed!
Distributions before ratio
Red: Muon
Black: Pi
Log scale!
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K0s Pi Punch through vs. dxy
•Decreases with dxy
•To be well understood
•Meaningless after 0.4 cm
•More statistics needed!
Distributions before ratio
Red: Muon
Black: Pi
Log scale!
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PDCMSSW - Luca Perrozzi
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K0s Pi Punch through vs. Phi
•Reasonably flat
•Can be used as reference plot
•More statistics needed!
Distributions before ratio
Red: Muon
Black: Pi
Pi punch through probability
~ 0.6%
Log scale!
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PDCMSSW - Luca Perrozzi
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 selection (part I)
• Invariant mass best cut selection with significance
maximization:
N
– c2track<2
– Pt>1.0 GeV
– dxy< 0.045
(less important)
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Significance =
PDCMSSW - Luca Perrozzi
Sig
N Sig + 2 N Bkg
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 selection (part II)
• Invariant mass fit (m= 1.02 GeV, σ= 3.7 MeV)
Counts
– 2.8s window for signal & background
signal
background
Mass (GeV)
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PDCMSSW - Luca Perrozzi
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Strategy
Reco K0s
K tracks from
 Background
K tracks from
 Signal
Sig - Bkg
Reco Mu
DR<0.01
DPt<0.01
K Rate
DR<0.01
DPt<0.01
Mu/K
Mu Rate
Mu associated to
K track from
 Signal
Mu associated to
K track from
 Background
K (from )
punch through
(as function of
Pt, Eta, Phi,dxy,
decay length)
Sig - Bkg
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 RecoK-RecoMu track association
DR<0.01
|DPt/Pt|<0.01
R = D 2 + D 2
m
Counts
Counts
m
DR(cm)
DPt/Pt
LOG SCALE!
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’s K Punch through vs. Pt
•Increases with Pt
•What happens after 10 GeV?
•Meaningless after 20 GeV
•More statistics needed!
Distributions before ratio
Red: Muon
Black: K
Log scale!
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PDCMSSW - Luca Perrozzi
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’s K Punch through vs. Eta
•Shows hadronic calorimeter
“holes”at ~2
•More statistics needed!
Distributions before ratio
Red: Muon
Black: K
Log scale!
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PDCMSSW - Luca Perrozzi
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’s K Punch through vs. dxy
•Increases with dxy
•To be well understood
•Cut at 4.5 cm to select 
•More statistics needed!
Distributions before ratio
Red: Muon
Black: Pi
Log scale!
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’s K Punch through vs. phi
•Reasonably flat
•Can be used as reference plot
•More statistics needed!
Distributions before ratio
Red: Muon
Black: K
Pi punch through probability
~ 3.6%
Factor 10 more than Pi!
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Log scale!
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Summary
• Punch through probability:
– From Pi seems to be around 0.6%
– From K seems to be around 3.6%
• A factor 10 between the two particles
• Distribution behaviors:
– Some as aspected
• Phi
• Eta
– Some to be understood
• dxy
• Pt
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Next steps
• Include lambda particles
• Automatize Phi particle reconstrction in V0
producer module
• Increase statistics (at least 1M events)
• Better understand distribution behaviors
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On demand slides
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Significance
F = Ns + Nb – Nc
 F
 N S
 2  F  2  F
 s NS + 
s NB + 
 N B 

 NC
= N S + N B + NC
s F2 = 
S+B
 2
 s NC =

Se NB =NC
C
F
sF
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=
PDCMSSW - Luca Perrozzi
NS
N S + N B + NC
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