lecture 4

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4. Muons in data
analysis
Piet Verwilligen
INFN Sezione di Bari
Capita Selecta in HEP
Vrije Universiteit Brussel
April 9-10, 2014
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Muon Identification
I
I
Intro
Why Muon
identification?
I
Tools in hand &
Identification
definitions
I
Performance
I
Isolation
3 / 62
Why Muon identification?
Riccardo Bellan — https://indico.cern.ch/event/210563/
4 / 62
Why Muon identification?
Global Muons at 100 GeV/c
I Pion Fake rate: 3% (total) 1% (decay)
I Kaon Fake rate: 5% (total) 1% (decay)
Riccardo Bellan — https://indico.cern.ch/event/210563/
Tracker Muons at 100 GeV/c
I Pion Fake rate: 3% (total) 0.75% (decay)
I Kaon Fake rate: 3% (total) 0.75% (decay)
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Tools available for identification
Handles for Global Muon ID fake rejection
I
Inner track information:
I
I
I
I
I
I
Calorimeter based information:
I
I
energy deposition in ECAL and HCAL (compatible with MIP?)
Muon system information:
I
I
I
I
hits in pixel tracker
hits in strip tracker
quality of the track fit (χ2 /ndof)
kink in track?
impact parameters
hits and segments in muon system
penetration depth in muon system
Stand-Alone muon quality
Global Fit information: fit quality (χ2 /ndof)
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Why Muon identification?
Kaons vs Muons
I
Quality of Global Muon fit ::
χ2 /ndof < 10
. . . but long tails . . .
I
Inner track :: dxy < 0.2 cm
. . . room for optimization
I
Inner track :: nhits > 11
. . . could be made as function of η
Riccardo Bellan — https://indico.cern.ch/event/210563/
7 / 62
Why Muon identification?
I
Cuts used:
I
Global Muon fit: χ2 /ndof < 10
I
Inner track :: dxy < 0.2 cm
I
Inner track :: nhits > 11
I
Results:
Muon ID efficiency high
I
I
Kaon Fake Rate reduced
with factor 10
0.3% vs 3% (before) at 100 GeV/c
Riccardo Bellan — https://indico.cern.ch/event/210563/
8 / 62
Why Muon identification?
Riccardo Bellan — https://indico.cern.ch/event/210563/
9 / 62
Muon Identification :: 4 definitions
Soft Muon ID ::
[muons from b-decays]
I Tracker Muon Arbitrated (TMA)
I TMOneStationTight: Tracker track
matched with at least one muon segment
in both X and Y coordinates (< 3σ)
I number of strip tracker hits > 5
I number of pixel tracker hits > 1
I χ2 /ndof of inner track Fit < 1.8
I inner track transverse impact parameter
dxy < 3 cm
I inner track longitudinal impact parameter
|dz | < 30 cm
Tight Muon ID ::
[muons from W ,Z ]
I muon reconstructed as Global Muon
I muon identified as Particle Flow Muon
I χ2 /ndof of Global Muon Fit < 10
I at least 1 muon chamber hit included in
the Global Fit
I muon segments in at least 2 stations
I inner track transverse impact parameter
dxy < 0.2 cm
I inner track longitudinal impact parameter
|dz | < 0.5 cm
I number of pixel tracker hits > 0
I number of strip tracker hits > 5
High Pt Muon ID ::
[high pT muons]
I pT and inner track defined by TuneP
I Tight ID without PF ID & χ2 /ndof < 10
I ∆pT /pT < 0.3
Loose Muon ID ::
[multiple muons]
I PF Muon
I TMA OR Global Muon
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Particle Flow Muon Identification
Slava Valuev — https://indico.cern.ch/event/110072/
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Particle Flow Muon Identification
Slava Valuev — https://indico.cern.ch/event/110072/
12 / 62
Particle Flow Muon Identification
Cristina Botta — https://indico.cern.ch/event/185274/
13 / 62
Muon Identification :: Overview
Alicia Calderon — 14th ICATPP Conference Como 2013
14 / 62
Muon Identification :: Kinematics
Alicia Calderon — 14th ICATPP Conference Como 2013
15 / 62
Muon Identification :: Kinematics :: Soft Muon
Alicia Calderon — 14th ICATPP Conference Como 2013
16 / 62
Muon Identification :: Kinematics :: Tight Muon
Alicia Calderon — 14th ICATPP Conference Como 2013
17 / 62
Muon Identification :: Kinematics :: Tight Muon
Alicia Calderon — 14th ICATPP Conference Como 2013
17 / 62
Muon Identification :: Kinematics :: Tight Muon
Alicia Calderon — 14th ICATPP Conference Como 2013
18 / 62
Muon Isolation :: Intro
Alicia Calderon — 14th ICATPP Conference Como 2013
19 / 62
Particle Flow Muon Identification
Slava Valuev — https://indico.cern.ch/event/110072/
20 / 62
Particle Flow Muon Identification
Slava Valuev — https://indico.cern.ch/event/110072/
21 / 62
PU-corrections :: Effective Area correction
Effective Area correction
Pch had
PFRelIso =
no PU
pT +
Pneutr had
ET +
Pγ
ET
pTlepton
I Estimate mean PU contribution in isolation cone of the
lepton:
I Calculate FastJet energy density for each jet: ρ
I Median of ρ for each event is chosen
I Effective area Aeff is ratio of slopes ρ/uncorrected iso


neutrX
had+γ
neutrX
had+γ

ET = max
ET − ρ · Aeff , 0
corr
uncorr
I cumbersome computations
I Aeff calculated for different η intervals
I Aeff not determined event-by-event, but averaged over
data taking period
22 / 62
PU-corrections :: ∆β correction
∆β correction
Pneutr had
Pγ
I Estimate:
ET + PU ET
PU
I Open same cone in PU-vertex and collect
Pch had
charged energy from PU:
PU
PF energy fraction
Charged particles can be identified to originate from a PU vertex, but
this cannot be done for γ and neutral hadrons
CMS preliminary, L = 1.6 fb-1
s = 8 TeV
0.9
0.8
0.7
0.6
0.5
49 GeV < pT < 114 GeV
Tag & Probe method
0.4
Charged pile-up:
Charged hadrons:
Photons:
Neutral hadrons:
Electrons & Muons:
Forward hadrons:
Forward photons:
0.3
0.2
MC DATA
0.1
I Neutral energy ≈ half of charged energy
Pch had
I This estimate is ∆β ≈ 1
pT
PU
2
Pch had
PFRelIso =
no PU
pT + max
0
-5 -4 -3 -2 -1 0
1
2
3
4
5
η
P
neutr had
lepton
pT
ET +
Pγ
ET − ∆β, 0
23 / 62
PU-corrections :: the future
Nahn Viet Tran & Phillip Coleman Harris — work in progress
24 / 62
PU-corrections :: the future
Nahn Viet Tran & Phillip Coleman Harris — work in progress
25 / 62
PU-corrections :: the future
Nahn Viet Tran & Phillip Coleman Harris — work in progress
26 / 62
Cosmic Ray Muon Rejection
Cosmic Muons
I generally not passing
through the vertex region
I hence not reconstructed
I generally not in synch with
LHC collisions
I ∠(2 legs) α ≈ π
Variables
I Impact parameter
I log10 (π − α)
I muon time at vtx
I ∆t muon legs
Cosmic muons pointing to the vertex can be identified by searching for a tracker track
back-to-back with the Reco muon: (α − π) 1
Remaining contribution of in-time Cosmic muons could be estimated from out-of-time cosmics
27 / 62
Muon Performance
Measurements
I
How to measure
properties of the
Muon object in an
unbiassed way?
I
Reco & Selection
Efficiency
I
Fake Rates
I
Momentum Scale and
Resolution
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Events / GeV
Resonances used as a source of pure muons
6
10
η
ρ,ω
φ
J/ψ
5
10
ψ'
Υ
104
Z
103
102
10
1
CMS
s = 7 TeV
Lint = 40 pb -1
1
10
102
Dimuon mass (GeV/c2 )
29 / 62
Resonances used as a source of pure muons
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Measuring Muon Efficiencies
I Resonances reconstructed as pairs with:
I
I
a tightly identified leg: tag-muon
a loosely identified leg: probe-muon
I Tightly identified tag and the constraints
on tag-and-probe pair ensure origin of the
probe to be a real muon
I Efficiency to pass certain selection criteria
is measured on probe-muons:
I
I
pass critera ⇒ passing probes
fail criteria ⇒ failing probes
I Same (signal + background) lineshape is fit
separately to passing and failing probes
I Efficiency is calculated as the ratio of the
signal yields in above fits
I Efficiency is relative to the loose
probe-identification:
I
ε(X ) = ε(X |Tracking)
I Procedure is repeated in bins of
probe-variables (pT , η, nvtx , . . . )
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Tracking Efficiency
Efficiency factorization for Muons
ε = ε(Tracking)·ε(RECO+ID|Tracking)·ε(ISO|RECO+ID)·ε(TRIG|ISO)
I How well can the tracker
reconstruct tracks?
I Use Tag & Probe technique
to estimate how often an
inner track of a muon is not
reconstructed
I Tag :: Tight Muon
I Probe :: Stand-Alone Muon
I Check whether an inner
track is associated to the
Stand-Alone Muon (Probe)
I Fortunately very high
Tracking efficiency
Tracking Efficiency (2011)
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Muon ID Efficiency :: 7 TeV
Alicia Calderon — 14th ICATPP Conference Como 2013
33 / 62
Muon ID Efficiency :: 8 TeV
Alicia Calderon — 14th ICATPP Conference Como 2013
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Muon ISO Efficiency
Alicia Calderon — 14th ICATPP Conference Como 2013
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Muon TRG Efficiency
Alicia Calderon — 14th ICATPP Conference Como 2013
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Double Muon Trigger :: Problem
2011
I A Double Muon Trigger selects two muons independently
I MUO-10-04 studies show uncorrelated Leg efficiencies for dR > 0.5 (on J/Ψ)
2012
I Double Muon Trigger contaminated by two muons
coming from different PV (increasing with PU)
I Trigger Rate reduction obtained by requiring the
z-coordinate of the Point of Closest Approach
(PCA) of the two Muons: dz < 0.2 cm
I Rate Red. of 40% at a price of ∼ 1 − 3% Eff. loss
dZ filter applied to HLT Mu17 Mu8 and HLT Mu17 TkMu8
I Suboptimal dZ filter due to suboptimal (muon) tracking in HLT, causing worse
tails in dz resolution and thus a lower efficiency of the dz filter
(∼ 10% for
HLT Mu17 Mu8, ∼ 5% for HLT Mu17 TkMu8)
I runs 190456 - 199608 :: dZ filter suboptimal, then fixed during 2012C and good
for runs 199698 – 208357 → overall Scale Factor provided
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Double Muon Trigger :: Method
Component Method
I Efficiency of (H L OR S):
ε(H L||S) = s1 + s2 − s1 s2
[Y+G]
+z12 (h1 l2 + l1 h2 − h1 h2 )
[B+G]
−z12 (s1 l2 + l1 s2 − s1 s2 )
[G]
I Efficiency of (H L):
I L = Double Mu: lower th
I H = Double Mu: higher th
I S = Single Mu
ε(H L) = z12 (h1 l2 + l1 h2 − h1 h2 )
Muon Leg Efficiencies (best Z mass)
[B+G]
dZ Filter Efficiency
CMS Preliminary, s = 8 TeV, 11.22 fb-1
0.6
0.4
0.2
20 < pT < ∞ GeV/c
Data 2012
CMS Preliminary, s = 8 TeV
Simulation
CMSSW 53X Run C,D: 199698 --- 207898 [11.22 fb-1]
MC Truth
1.045
0
0.2
0.4
0.6
0.8
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
1.2
1.4
1.6
1.8
2
2.2
2.4
1.015
0.985
0.955
0
1
2
2.2 2.4
Muon |η| [-]
1
10 < pT(µ 1) < 20 GeV/c
2.4
2.2
+1.00
± +0.02
+0.86
± +0.09
+1.00
± +0.10
-nan
± +0.00
+1.00
± +0.00
+1.00
± +0.02
+0.95
± +0.02
+1.00
± +0.23
+1.00
± +0.08
+1.00
± +0.12
+0.96
± +0.04
+1.00
± +0.07
1
2
µ |η| [-]
HLT_Mu17TkMu8_TkMu8Leg Efficiency
Data/MC
HLT_Mu17TkMu8_Mu17Leg Efficiency
Data/MC
Run2012C,D: 199698 ≤ runs ≤ 207898
1
0.8
0.8
2
1.8
0.6
1.6
1.4
0.4
1.2
0.2
Data 2012
CMSSW 53X Run C,D: 199698 --- 207898 [11.22 fb-1]
MC Truth
0
0.8
CMS Preliminary, s = 8 TeV
Simulation
1.045
1
10 < pT < 20 GeV/c
0.2
0.4
0.6
0.8
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
1.2
1.4
1.6
1.8
2
2.2
0.6
0.4
0
+1.00
± +0.09
+0.97
± +0.03
+1.00
± +0.00
0.2
0.985
0.955
+1.00
± +0.07
2.4
1.015
1
2
2.2 2.4
Muon |η| [-]
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2 2.4
µ |η| [-]
1
10-1
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Run2012ABCD
:: Mu17Mu8 Eff ::
[DATA][Loose ID][±STAT]
∆R < 0.1
∆R < 0.3
CMS Preliminary, s = 8 TeV, 18.774 fb-1
Run2012ABCD: 190456 ≤ runs ≤ 208357
20 < p (µ ) < ∞ GeV/c
T 2
10 < pT(µ 1) < 20 GeV/c
2.4
Mu17_Mu8 Eff ± STAT
Loose Muon ID
2
2.2
1
2
0.826
± 0.011
1.8
0.9
0.731
± 0.023
20 < pT(µ 2) < ∞ GeV/c
10 < pT(µ 1) < 20 GeV/c
2.2
0.8
0.9
0.736
± 0.024
0.833
± 0.012
0.8
1.6
1.4
0.7 1.4
0.7
1.2
0.6 1.2
0.6
1
0.5
0.8
0.4
0.811
± 0.009
0.884
± 0.016
0.6
1
0.5
0.8
0.840
± 0.025
0.6
0.3
0.4
0.4
0.830
± 0.011
0.3
0.4
0.2 0.2
0.2
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2 2.4
µ |η|
0.1
0
0
0.2
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
1
0.774
± 0.020
2.2
2
Mu17_Mu8 Eff ± STAT
Loose Muon ID
1
0.9
0.1
20 < pT(µ 2) < ∞ GeV/c
20 < pT(µ 1) < ∞ GeV/c
0.780
± 0.024
2.2
2
1.1
1
0.9
1.8
1.8
0.763
± 0.008
0.754
± 0.007
1.6
0.8
0.776
± 0.004
0.790
± 0.008
0.833
± 0.015
0.805
± 0.007
0.807
± 0.015
0.863
± 0.005
0.846
± 0.003
0.862
± 0.005
1.6
0.6
0.6 1.2
1.2
1
0.782
± 0.014
0.779
± 0.004
0.816
± 0.012
0.8
0.5
0.4
0.8
0.7
0.7 1.4
1.4
1
0.8
0.5
0.4
0.6
0.6
0.843
± 0.005
0.902
± 0.002
0.4
0.826
± 0.003
0.845
± 0.005
0.3
0.914
± 0.003
0.4
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2 2.4
µ |η| [-]
1
0.1
0
0
0.3
0.2
0.2 0.2
0.2
0
0
CMS Preliminary, s = 8 TeV, 18.774 fb-1
Run2012ABCD: 190456 ≤ runs ≤ 208357
1.1 2.4
2
20 < p (µ ) < ∞ GeV/c
T 2
20 < pT(µ 1) < ∞ GeV/c
2.2 2.4
µ |η|
1
µ |η| [-]
CMS Preliminary, s = 8 TeV, 18.774 fb-1
Run2012ABCD: 190456 ≤ runs ≤ 208357
2.4
2
µ |η| [-]
Mu17_Mu8 Eff ± STAT
Loose Muon ID
20 < pT (µ1 ) < ∞ GeV/c
1.1
1
2
1.8
1.6
CMS Preliminary, s = 8 TeV, 18.774 fb-1
Run2012ABCD: 190456 ≤ runs ≤ 208357
1.1 2.4
µ |η|
2
µ |η|
10 < pT (µ1 ) < 20 GeV/c
Mu17_Mu8 Eff ± STAT
Loose Muon ID
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2 2.4
µ |η| [-]
1
0.1
39 / 62
Run2012ABCD
:: Mu17TkMu8 Eff ::
[DATA][Loose ID][±STAT]
∆R < 0.1
∆R < 0.3
CMS Preliminary, s = 8 TeV, 18.774 fb-1
Run2012ABCD: 190456 ≤ runs ≤ 208357
20 < p (µ ) < ∞ GeV/c
T 2
10 < pT(µ 1) < 20 GeV/c
2.4
Mu17_TkMu8 Eff ± STAT
Loose Muon ID
2
2.2
1
2
0.9
0.822
± 0.023
0.854
± 0.017
1.8
20 < pT(µ 2) < ∞ GeV/c
10 < pT(µ 1) < 20 GeV/c
2.2
0.8
0.9
0.826
± 0.022
0.851
± 0.016
0.8
1.6
1.4
0.7 1.4
0.7
1.2
0.6 1.2
0.6
1
0.5
0.8
0.4
0.854
± 0.012
0.912
± 0.016
0.6
1
0.5
0.8
0.913
± 0.001
0.6
0.3
0.4
0.4
0.857
± 0.012
0.3
0.4
0.2 0.2
0.2
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2 2.4
µ |η|
0.1
0
0
0.2
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
1
0.830
± 0.030
2.2
2
Mu17_TkMu8 Eff ± STAT
Loose Muon ID
1
0.9
0.1
20 < pT(µ 2) < ∞ GeV/c
20 < pT(µ 1) < ∞ GeV/c
0.829
± 0.029
2.2
2
1.1
1
0.9
1.8
1.8
0.835
± 0.009
0.866
± 0.008
1.6
0.8
0.860
± 0.008
0.830
± 0.009
0.929
± 0.012
0.901
± 0.006
0.869
± 0.017
0.925
± 0.004
0.893
± 0.003
0.882
± 0.007
1.6
0.6
0.6 1.2
1.2
1
0.871
± 0.017
0.904
± 0.003
0.945
± 0.009
0.8
0.5
0.4
0.8
0.7
0.7 1.4
1.4
1
0.8
0.5
0.4
0.6
0.6
0.929
± 0.004
0.927
± 0.003
0.4
0.895
± 0.003
0.886
± 0.004
0.3
0.923
± 0.003
0.4
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2 2.4
µ |η| [-]
1
0.1
0
0
0.3
0.2
0.2 0.2
0.2
0
0
CMS Preliminary, s = 8 TeV, 18.774 fb-1
Run2012ABCD: 190456 ≤ runs ≤ 208357
1.1 2.4
2
20 < p (µ ) < ∞ GeV/c
T 2
20 < pT(µ 1) < ∞ GeV/c
2.2 2.4
µ |η|
1
µ |η| [-]
CMS Preliminary, s = 8 TeV, 18.774 fb-1
Run2012ABCD: 190456 ≤ runs ≤ 208357
2.4
2
µ |η| [-]
Mu17_TkMu8 Eff ± STAT
Loose Muon ID
20 < pT (µ1 ) < ∞ GeV/c
1.1
1
2
1.8
1.6
CMS Preliminary, s = 8 TeV, 18.774 fb-1
Run2012ABCD: 190456 ≤ runs ≤ 208357
1.1 2.4
µ |η|
2
µ |η|
10 < pT (µ1 ) < 20 GeV/c
Mu17_TkMu8 Eff ± STAT
Loose Muon ID
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2 2.4
µ |η| [-]
1
0.1
40 / 62
Fake Rate Measurement
Alicia Calderon — 14th ICATPP Conference Como 2013
Pion misidentification from Ks0 → π + π − selection
Alicia Calderon — 14th ICATPP Conference Como 2013
41 / 62
Pion misidentification from Ks0 → π + π − selection
42 / 62
B → J/ΨK selection
43 / 62
Kaon misidentification from B → J/ΨK selection
44 / 62
45 / 62
Muon Momentum Scale
Alicia Calderon — 14th ICATPP Conference Como 2013
46 / 62
Muon Momentum Scale
Alicia Calderon — 14th ICATPP Conference Como 2013
47 / 62
Analysis Examples
I
W (µν) & Z (µµ)
I
I
Bs (µµ)
W 0 (µν) & Z 0 (µµ)
I
H(ZZ → 4µ)
48 / 62
Alicia Calderon — 14th ICATPP Conference Como 2013
49 / 62
Alicia Calderon — 14th ICATPP Conference Como 2013
50 / 62
Alicia Calderon — 14th ICATPP Conference Como 2013
51 / 62
Alicia Calderon — 14th ICATPP Conference Como 2013
52 / 62
Alicia Calderon — 14th ICATPP Conference Como 2013
H(ZZ → 4`) :: Event Selection
53 / 62
leptons
I
pT (µ) > 5 GeV/c, η µ < 2.4
pT (e) > 7 GeV/c, η e < 2.5
I
| σIPIP | < 4.0
PF
Irel
< 0.4
signal
Narrow resonance
O(2 − 4 GeV/c 2 )
background
I
Z + X (reducible)
I
I
I
I
Z + jets
Z + bb
estimated from data
ZZ (ireducible)
I
estimated from MC
At the time of Discovery
I
54 / 62
450
CMS Simulation, s=8 TeV
FSR applied
300
250
s = 7 (8) TeV, L = 5.1 (19.6) fb-1
CMS preliminary
FSR not applied
80
Events affected by FSR
MH = 126 GeV
40
35
100
400
350
120
/
4e: 8TeV / 7 TeV
/
4µ: 8TeV / 7 TeV
/
2e2µ: 8TeV / 7 TeV
30
25
20
60
200
15
150
40
10
100
5
50
20
0
80 90 100 110 120 130 140 150 160
40
50
60
70
80
90
I
Z candidates formed from
`+ `− pair of same flavour
100
110
120
0
mZ1 (GeV)
m4l+γ [GeV]
I
40 < mZ1 < 120 GeV/c 2
I
FSR recovery:
|m``γ − mZ | < |m`` − mZ |
I
Z1 closest to PDG mass Z
I
∃`a with pT (`a ) > 20 GeV/c
I
12 < mZ2 < 120 GeV/c 2
I
∃`b with pT (`b ) > 10 GeV/c
I
Z2 with highest pT
m4` > 100 GeV/c 2 & ∀` : m2` > 4 GeV/c 2
121.5 < m4` < 130.5 GeV/c 2
500
mZ2 (GeV)
events
H(ZZ → 4`) :: Building 4` candidates
55 / 62
H(ZZ → 4`) :: Lepton Selection
one on-shell Z ⇒ hard `
one off-shell Z ⇒ soft `:
I
50% below 10 GeV/c
I
background rate
I
selection efficiency
My Work!
this is a big Challenge
H(ZZ → 4`) :: Loose Muon ID & ISO Efficiency
56 / 62
57 / 62
H(ZZ → 4`) :: ISO & SIP
I Loose Muon ID has high and uniform
efficiency
I PF-Isolation at low pT is challenging
I PU-corrections to PF-Isolation give flat
curve
I Significance of Impact parameter:
SIP =
IP
σIP
I uniform behaviour (while tracker resolution
is worse in endcap)
I SIP used to discover sudden pixel
misalignment in 2012 data
H(ZZ → 4`) :: Lepton Resolution and Scale
I
e :: Momentum Regression in ECAL
I
BDT trained on DY MC leads to 10% improvement
I
e :: Momentum Scale: using Z , J/Ψ → ee
I
µ :: Resolution & Scale: improved by correction of
Tracker Misalignment (h1/pT i)
I
µ :: Validation on J/Ψ, Y and Z decays
58 / 62
59 / 62
H(ZZ → 4`) :: Precise Measurement of Z → 4`
I First observation at CMS
I JHEP 12 (2012) 034
I Same Fit procedure as
for m4`
I Good Data/MC
agreement on width
I MZ = 91.1876 ± 0.0021 GeV/c 2
I ΓZ = 2.4952 ± 0.0023 GeV/c 2
[PDG]
Animation!
Fast Animation
Slow Animation
m4` distribution
60 / 62
61 / 62
Alicia Calderon — 14th ICATPP Conference Como 2013
62 / 62
Sources
I Riccardo Bellan — Muon intro at Quarkonia Workshop —
https://indico.cern.ch/event/60388/
I Slava Valuev — Muon Object in Particle Flow —
https://indico.cern.ch/event/110072/
I Cristina Botta — Muon Object developments — https://indico.cern.ch/event/185274/
I CMS-MUO-10-004
— Performance of CMS muon reconstruction in pp collision events at
√
7 TeV — http://cds.cern.ch/record/1456510
I CMS-Note-2008-097 — Muon Reconstruction in CMS
I CMS-Note-2008-098 — Muon Identification in CMS
I Alicia Calderon — 14th ICATPP Conference Como 2013 —
http://cds.cern.ch/record/1609525

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