Dileptonic Top Analysis and Data Quality …...Overview & Introduction Dileptonic Top Analysis and...

Dileptonic Top Analysis and

Data Quality Monitoring with the

CMS experiment

Markus Marienfeld

Deutsches Elektronen-Synchrotron (DESY)

28.01.2010

Overview & Introduction

Dileptonic Top Analysis and Data Quality Monitoring with the CMS experiment 28.01.2010

1Markus Marienfeld (DESY)

I. Top quark physics at the LHC

The Large Hadron Collider (LHC)

The Compact Muon Solenoid (CMS)

II. The data quality monitoring system of CMS

DQM workflow

Online/offline DQM

III. DQM for physics: Top quark

Top-specific data validation

Status of top-dilepton DQM

Overview & Introduction1

Markus Marienfeld (DESY)





DQM workflow

Online/offline DQM





The Large Hadron Collider

➢ Proton-proton collider with √s = Ecms = 14 TeV possible.

➢ Four experiments: Atlas, CMS, Alice & LHCb.

➢ First collisions at Ecms = 2.36 TeV in December 2009!



Top

Higgs

7 10 14 TeV

Top Quark Pair Production

➢ Heaviest known elementary particle (171 GeV).

➢ Production of top quark pairs: g g → t t .

➢ Ca. one top pair per second (“top factory”) at 14 TeV.


ca. 90% @ √s = 14 TeV


Dileptonic Decay of Top Quark Pairs

➢ Clean event signature: t t → W+ b W- b → ℓ+ ℓ- + 2 jets

Two (oppositely charged) isolated leptons.

Two b-jets + Missing Transverse Energy (MET).

✗ Small branching ratio: ~2,5%.

✗ No use of b-tagging or MET for first data analysis.



The Compact Muon Solenoid

➢ Total weight of 12'500 t.

➢ Lenght: 22 m, Diameter: 15 m.

➢ Magnetic field strenght: 3.8 T.



Data Acquisition (DAQ) at CMS6


(1) Collision rate: 40 MHz

(2) Level-1-Trigger (L1T): 100 KHz

(3) High-Level-Trigger (HLT): 100 Hz

➢ Worldwide data processing:

Tier-0 & CAF at CERN

Tier-1 (7 computing centres)

Tier-2 (ca. 40 analysis centres)

25nsp p

Storagemanager(100 Hz)

L1T

HLT


Contents7






DQM workflow

Online/offline DQM





The DQM Workflow8


➢ Online: Real time detector control.

➢ Offline: Monitoring and certification of reconstruction and calibration.

➢ Playback: Environment for testing and software integration.O

NLIN

EO

FFLI

NE


DQM Shift Overview9


➢ Online Shifts at P5 (3/day for 24 hours coverage)

23:007:00 | 7:0015:00 | 15:0023:00

➢ Offline Shifts (CRAFT09: 2/day)

9:3017:30 | 13:3021:30● Run at Meyrin CC with a delay of ~24 hours.

➢ Remote Shifts (3/day for 24 hours coverage)

● Run at FNAL and DESY ROC's in parallel with P5 shifts.


CMS Remote Center at DESY

Online DQM10


➢ Event data is processed in parallel by independent DQM applications.

➢ Creation of ROOT histograms in real time with monitor elements.

➢ Visualization by one centralized, web-based Graphical User Interface (GUI).


The Graphical User Interface (GUI)11


Good: ≥ 95%

Warning: < 95%

ERROR: < 85%

No DAQ: not in readout

Global summary valuesby subsystems:

➢ Online monitoring of detector status & offline object validation.

➢ Summary page: Compact overview about all subsystems status.

➢ Monitoring of live histograms as well as archived runs.


Data Reconstruction & Offline DQM12


➢ Monitoring of reconstructed physics objects: muons, photons, jets...

➢ New evaluation of detector components with full event statistics.

➢ Real data validation for fast feedback.

(1) Reconstruction & Harvesting

(2) DQM Offline shift

(3) Certification


Contents13






DQM workflow

Online/offline DQM





DQM for Physics (PAG): Top Quark14


✗ Not sufficient event statistics for top-dilepton monitoring in early data.

➢ Monitoring of double muon events at RECO (Offline) and HLT (Online &

Offline) level using signal muons for physics oriented monitoring.

➢ Need O (0.1-1 pb-1) for visible J/-peak (900 GeV) or Z-peak (≳ 7 TeV).

➢ Top-specific event topology: single/double leptons + multiple jets.

➢ High-pT leptons (muons & electrons) → Dileptonic top-like selection cuts.

➢ Run-by-run monitoring of quality and stability of signal rates.

Trigger monitoring

Prompt data validation

( ONLINE & OFFLINE DQM )

RECO level

HLT level

( OFFLINE DQM )✓ DONE

→ TESTED


Offline Prompt Data Monitoring

➢ Status of prompt data validation:

➢ Monitoring of dilepton reconstruction & trigger efficiencies at RECO level

and HLT level for simple physics feedback (→ dilepton mass spectrum).

➢ Running within Offline DQM sequence since October 2009!

First collisionat 2.36 TeV!!


✔ Successfully working in Offline DQM sequence.

✔ First update submitted.

➢ 'Real' tag & probe approach

has to be implemented!


Physics / Top / DiLepton

Offline Prompt Trigger Validation

Invariant mass (Z → µ µ) [GeV]

Invariant mass (J/ψ → µ µ) [GeV]

Z → µ

µ M

C

Eve

nts

J/ψ →

µ µ

MC

Eve

nts


► Input: RECO::Muons ⊕ RECO::GsfElectrons

➊ ∑ Leptons ≥ 2

➋ Isolation cut ⊕ control trigger (µ)

► Monitoring: p⊥(µ,e), η(µ,e), ... ∆η(ℓ,ℓ'), ...

► Trigger validation:

➌ Inv. mass cut ⊕ charge cut (RC)

εsig = [signal] && [control]

[control]

Effi

cien

cy


High-level Trigger Monitoring

➢ Plans for prompt trigger monitoring:

➢ Online/Offline monitoring and checks of lepton trigger efficiencies from

dileptonic top-like events at HLT level.


Effi

cien

cy

RelValZmumuJets_CMSSW_3_2_7-MC_31X_V8

Test implementation

Effi

cien

cy

Z → µ

µ M

C

Z → µ

µ M

C


Online/offline Trigger Monitoring18


► Input: L1/L3 muon collection (≥ 2 muons)

➊ Control triggers:

900 Gev (J/ψ) ≥ 7 TeV (Z)

HLT_Mu3 HLT_Mu9 / HLT_Mu15

➋ Muon isolation cut

► Monitoring plots:minv(µ,µ), p⊥, η, φ, ... ∆η, ∆φ, ...

► Trigger validation:

Signal triggers: Mu9, Mu15, DoubleMu3

Control triggers: Mu3, Mu9, Mu15

➌ Inv. mass cut ⊕ charge cut (RC)

εsig = [signal] && [control]

[control]

Invariant mass (Z → µ µ) [GeV]

Number of muons Z → µ

µ M

CZ → µ

µ M

C

Effi

cien

cy


First Collisions at 2.36 TeV19



Run: 124120

Event: 11016632

( Only a cosmic muon... )

First Collisions at 2.36 TeV20



Run: 124120

Event: 5686693

( ... and a J/ candidate )

PT(1) = 3.6 GeV

PT(2) = 2.6 GeV

Minv() = 3.03 GeV

Top Physics-related DQM for Analysis21


➢ Make sure, that events with a top-like event

signature are triggered and recorded.

➢ Run-by-run monitoring of quality and stability of

signal rates.

➢ Assess the quality of data taken and provide

feedback to detector experts in case of problems

as soon as possible.


➢ Understand lepton trigger efficiencies and reconstruction quality

at the earliest possible stage.

➢ Detailed studies of trigger efficiencies and quality need to follow

in the offline analysis.

Simulated dileptonic e- top pair decay

e

Trigger monitoring

Prompt data validation

( ONLINE & OFFLINE DQM )

RECO level

HLT level

( OFFLINE DQM )

Summary22


➢ Rediscovery of the top quark with first data of the LHC in the dileptonic

decay channel.

➢ The DQM system provides real time detector control during data taking.

➢ Monitoring of lepton trigger rates with a top-like event signature at

online & offline level.


Top physics

The DQM system

DQM for top physics

Conclusions & Outlook

➢ First version of offline dilepton monitoring successfully implemented!

➢ Need a realistic background estimation for 0.1-1 pb-1.

➢ Measurement of the cross section of dileptonically decaying top

quark pairs in the first year of data taking.



Eve

nts

Invariant µ µ mass [GeV]

L = 1 pb-1 @ 10 TeV

QCD inclusive

Z →

RelValZmumuJets/CMSSW_3_3_6-MC_3XY_V9A_LowLumiPileUp

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