Available on CMS information server CMS DP -2015/067

CMS Performance Note

19 December 2015 (v2)

Electron and Photon performance using datacollected by CMS at

√s = 13 TeV and 25ns

EGamma POG

Abstract

This note describes preliminary performances of the electron and photon reconstruction with the CMSexperiment using data collected at

√s = 13 TeV and with a LHC bunch spacing of 25ns. Electron and

photon key discriminating variables and their data to simulation agreement are shown. The identifica-tion and reconstruction efficiencies are also computed and compared to the ones from the simulation.Performances and data to simulation agreement are expected to improve with future calibrations andreprocessing.

Outline

Dielectron mass plot

Electron ID and Isolation Variables (using Z→ee)

Electron Reconstruction and Identification Efficiency

Photon ID and Isolation Variables (using Z→μμγ)

Photon Identification and Electron Veto Efficiency

1

Electrons data / MC agreement, event selection

Data: recorded with single electron trigger, 2.1 fb-1

Simulation: only Drell Yan simulated using madgraph generator

Data/MC agreement shown for probe electrons selected using a tag and probe methods with the following criteria

2

pT(e) > 30 GeV

|η(e)| < 2.1

Tight identification criteria

Trigger matched

Tag electron selectionpT(e) > 10 GeV

|η(e)| < 2.5

Loose identification criteria

Relative isolation (PU corrected) < 0.1

Probe electron selection

Event selection80 < m(ee) < 100 GeV

Leading Electron pT

3

Electron transverse momentum spectrum for the leading electron. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right).

Trailing Electron pT

4

Electron transverse momentum spectrum for the trailing electron. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right).

5

Electron pseudorapidity (left) and phi (right) distributions for the leading electron.

Leading Electron η & φ

6

Electron pseudorapidity (left) and phi (right) distributions for the trailing electron.

Trailing Electron η & φ

7

ECAL-crystal-based shower covariance in the η direction. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right).

σiηiη

barrel endcap

8

The sum of transverse energies of neutral electromagnetic candidates in a ΔR = 0.3 cone around the electron, divided by the electron transverse momentum. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right), isolation cut removed.

Relative Electromagnetic Isolation

barrel endcap

9

The sum of transverse energies of charged hadron candidates in a ΔR = 0.3 cone around the electron, divided by the electron transverse momentum. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right), isolation cut removed.

Relative Charged Hadron Isolation

barrel endcap

10

The sum of transverse energies of neutral hadron candidates in a ΔR = 0.3 cone around the electron, divided by the electron transverse momentum. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right), isolation cut removed.

Relative Neutral Hadron Isolation

barrel endcap

11

The ratio of energy measured in the hadronic calorimeter (HCAL), in a ΔR = 0.15 cone behind the electron seed, over the energy measured in the ECAL. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right).

H / E

barrel endcap

12

The difference in η between the energy-weighted supercluster position in the electromagnetic calorimeter (ECAL) and the track direction at the innermost tracker position. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right). Disagreement in the EE due to Tracker/ECAL misalignment not corrected yet.

Δηin

barrel endcap

13

Δɸin

The difference in ɸ between the energy-weighted supercluster position in the electromagnetic calorimeter (ECAL) and the track direction at the innermost tracker position. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right).

barrel endcap

14

The fraction of momentum lost to bremsstrahlung measured in the tracker, defined as fBrem. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right).

Bremsstrahlung Fraction

barrel endcap

15

Absolute difference between the inverse electron energy measured in the electromagnetic calorimeter (ECAL) and the inverse momentum measured in the tracker. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right).

| 1/E - 1/p |

barrel endcap

16

The number of missing inner layer hits in the electron track. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right).

Missing Inner Layer Hits

barrel endcap

17

The output of the electron identification MVA, which uses track and supercluster variables as input. Shown for electrons in the ECAL barrel (left) and ECAL endcap (right). The data/MC discrepancy on the left tail is due to background contamination.

MVA

barrel endcap

Data: recorded with single electron trigger, 2.5 fb-1

Efficiency measured in data with the tag and probe method using Z→eenumber of probe electrons obtained from a fit to the dielectron invariant mass

signal modeled by (Z/γ*→ee) simulation

background modeled with ad hoc analytical function

Three different types of efficiency are measured:electron reconstruction criteria

electron cut-based identification criteria

electron mva-based identification criteria (for triggering and non-triggering electrons)

Sources of systematic uncertainties consideredModeling: signal and background modeling

Simulation: kinematics, pile-up

Event selection: tag electron selection

Electron efficiency measurement

18

Electron Reconstruction Efficiency

19

Electron reconstruction efficiency in data (top) and data to MC efficiency ratios (bottom).

The efficiency is measured with the tag and probe method and shown in five pseudorapidity ranges as a function of the electron transverse momentum.

Blue points correspond to the Barrel-Endcap transition region.

[GeV]T

p20 30 40 50 60 70 80 90 100 200

Dat

a / M

C

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2 210D

ata

effic

ienc

y0.8

0.85

0.9

0.95

1

1.05

1.1

1.15 0.800≤ | η | ≤0.000 1.444≤ | η | ≤0.800 1.566≤ | η | ≤1.444 2.000≤ | η | ≤1.566 2.500≤ | η | ≤2.000

(13 TeV)-12.5 fb

CMSPreliminary

20

Electron cut-based ID

Electron identification efficiency in data (top) and data to MC efficiency ratios (bottom) measured for the tight cut-based work points.

The efficiency is measured with the tag and probe method and shown in five pseudorapidity ranges as a function of the electron transverse momentum.

Blue points correspond to the Barrel-endcap transition region, hence have a much lower efficiency.

[GeV]T

p20 30 40 50 60 70 80 90 100 200

Dat

a / M

C

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2 210D

ata

effic

ienc

y0.3

0.4

0.5

0.6

0.7

0.8

0.9

1 0.800≤ | η | ≤0.000 1.444≤ | η | ≤0.800 1.566≤ | η | ≤1.444 2.000≤ | η | ≤1.566 2.500≤ | η | ≤2.000

(13 TeV)-12.5 fb

CMSPreliminary

21

Electron triggering MVA ID

Electron identification efficiency in data (top) and data to MC efficiency ratios (bottom) measured for the identification criteria based on a MVA discr iminant wi th an average efficiency of 80%.

The efficiency is measured with the tag and probe method and shown in three pseudorapidity ranges as a function of the electron transverse momentum.

[GeV]T

p20 30 40 50 60 70 80 90 100 200

Dat

a / M

C

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2 210D

ata

effic

ienc

y0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05 1.000≤ | η | ≤0.000 1.500≤ | η | ≤1.000 2.500≤ | η | ≤1.500

(13 TeV)-12.5 fb

CMSPreliminary

Photon data/MC agreement, event selection

Data: recorded with double muon trigger, 2.2 fb-1

Simulation: only Drell Yan simulated using MC@NLO generator

Photon sample from Z → μμγ decay selected with

22

pT(μ) > 20, 10 GeV

Tight identification criteria

Muon selectionpT(γ) > 10 GeV

H/E < 0.05

σiηiη < 0.011 (0.031) for EB (EE)

charged isolation (corrected from PU) < 3.0 GeV

Photon selection

Event selection∆R(μ,γ)min < 0.8

m(μμγ) + m(μμ) < 180 GeV

70 < m(μμγ) < 110 GeV

23

Pseudorapidity (left) and φ (right) distributions of the SuperCluster of selected photons.

Photon SuperCluster η and φ

24

SuperCluster energy (left) and transverse momentum (right) distributions of the SuperCluster of selected photons.

Photon SuperCluster Energy and ET

25

ECAL-crystal-based shower width in the η direction for barrel (left) and endcap (right) photons.

σiηiη

26

ECAL-crystal-based coviariance for barrel (left) and endcap (right) photons.

Covarianceiφiη

27

Ratio of energy in the HCAL to the energy of the ECAL SuperCluster for barrel (left) and endcap (right) photons.

H/E

28

η (left) and φ width of the SuperCluster of the selected photons.

Width of the Photon SuperCluster in η and φ

29

Sum of transverse energy of the charged hadrons around the selected photons. This is shown in the barrel (left) and endcap (right).

Relative Charged Hadron Isolation

30

Sum of transverse energy of the photons around the selected photons. This is shown in the barrel (left) and endcap (right).

Relative Electromagnetic Isolation

barrel endcap

31

Sum of transverse energy of the neutral hadrons around the selected photons. This is shown in the barrel (left) and endcap (right).

Relative Neutral Hadron Isolation

barrel endcap

32

The output of the photon identification MVA. Shown for photons in the barrel (left) and endcap (right)

MVA

barrel endcap

Data: recorded with single electron trigger, 2.5 fb-1

Efficiency measured in data with the tag and probe method using Z→eeprobe candidates are electrons reconstructed as photons

number of probe photons obtained from a fit to the dielectron invariant mass

signal modeled by (Z/γ*→ee) simulation

background modeled with ad hoc analytical function

Two different types of efficiency are measured:photon cut-based identification criteria

photon mva-based identification criteria

Sources of systematic uncertainties consideredModeling: signal and background modeling

Simulation: kinematics, pile-up

Event selection: tag electron selection

Photon efficiency measurement

33

[GeV]T

p20 30 40 50 60 70 80 90 100 200

Dat

a / M

C

0.8

0.85

0.9

0.95

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1.05

1.1

1.15

1.2 210

Dat

a ef

ficie

ncy

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15 1.000≤ | η | ≤0.000 1.444≤ | η | ≤1.000 2.500≤ | η | ≤1.566

(13 TeV)-12.5 fb

CMSPreliminary

34

Photon ID efficiency

Photon identification efficiency in data and data to MC efficiency ratios measured for the tight cut-based work point (left) and for the identification based on a MVA discriminant (right). The efficiency is measured with the tag and probe method and shown in three pseudorapidity ranges as a function of the photon transverse momentum.

[GeV]T

p20 30 40 50 60 70 80 90 100 200

Dat

a / M

C

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2 210

Dat

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0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85 1.000≤ | η | ≤0.000 1.444≤ | η | ≤1.000 2.500≤ | η | ≤1.566

(13 TeV)-12.5 fb

CMSPreliminary

Photon conversion safe electron Veto (CSEV) efficiency

35

P u r e s a m p l e o f p h o t o n s selected from Z→ μμγ decay (see page 23)

Efficiency measured counting numbers of photon passing and failing the CSEV criteria

|ηSuperCluster |0 0.5 1 1.5 2 2.5

Dat

a / M

C

0.94

0.96

0.98

1

1.02

1.04

1.060 0.5 1 1.5 2 2.5

Dat

a ef

ficie

ncy

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15 < 0.949R 0.94≥ 9R

(13 TeV)-12.5 fb

CMSPreliminary

CSEV identification efficiency in data (top) and corresponding data to MC efficiency ratios (bottom).

Statistical uncertainties only