TrackMET and ATLAS Run2 xAOD Trigger for Muhammad Firdaus Mohd - - PowerPoint PPT Presentation

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TrackMET and ATLAS Run2 xAOD Trigger for Muhammad Firdaus Mohd Soberi University of Michigan-CERN University of Washington Seattle Winter REU 2015 Mentor: Dr. Song-Ming Wang 4/9/2015 Document reference 1

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SLIDE 1

TrackMET and ATLAS Run2 xAOD Trigger for π‘ŽπΌ β†’ πœ‰πœ‰π‘π‘

4/9/2015 Document reference 1

Muhammad Firdaus Mohd Soberi University of Washington Seattle University of Michigan-CERN Winter REU 2015 Mentor: Dr. Song-Ming Wang

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SLIDE 2

Overview

4/9/2015 Document reference 2

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SLIDE 3

4/9/2015 Document reference 3

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What have I done?

οƒΌ Performance study of the TrackMET vs

CaloMET in Run2

οƒΌ Selection cut study to reject QCD

background events

οƒΌ Look at different trigger configuration

specific for Hbb analysis (eg. π‘ŽπΌ β†’ πœ‰πœ‰π‘π‘)

οƒΌ Look at the efficiency curves as a function of

  • ffline MET

οƒΌ Estimate MET threshold for event selection

for 100% efficiency

4/9/2015 Document reference 4

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SLIDE 5

What Remains (If feasible)

  • Continue the trigger MET study to help

performance for the π‘ŽπΌ β†’ πœ‰πœ‰π‘π‘ analysis

  • Learn trigger detailed implementation for

future analysis

  • Help the development of Run2 TrackMET
  • Validate trigger menu from samples

4/9/2015 Document reference 5

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SLIDE 6

TrackMET

4/9/2015 Document reference 6

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SLIDE 7

TrackMET

  • Tool developed as alternative for

calorimeter-based MET

  • Tracker and calorimeter are independent

measurement, different systematic effect

  • Currently being migrated for xAOD
  • Useful to reject QCD backgrounds

4/9/2015 Document reference 7

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SLIDE 8

TrackMET?

  • Can associate tracks to primary vertex,
  • Calculate MET and SumPt based on primary vertex of the event ,thus more

correlated to true MET of the main physics process– important in pileup case

  • Will deteriorate less than calorimeter based variables as

instantaneous luminosity increase

  • Has less effect due to cosmic muon and beam background
  • Some analysis it is used:
  • BSM: H->ZZ->vvqq
  • SM: ZH->vvbb, H->WW->lvlv
  • ZH->bbxx(invisible)
  • Disadvantages :
  • See only charged particles
  • Smaller geometrical coverage (|eta|<2.5 Compared to calorimeter

πœƒ <4.5)

  • Momentum resolution get worse in higher Pt (expected in Run2, need

a way to fix that)

4/9/2015 Document reference 8

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SLIDE 9

METphi_vs_MPTphi

4/9/2015 Document reference 9

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SLIDE 10

METvsMPT (nonPV)

4/9/2015 Document reference 10

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SLIDE 11

METphivsMPTphi

4/9/2015 Document reference 11

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SLIDE 12

Trigger Side

4/9/2015 Document reference 12

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SLIDE 13

Trigger Side

  • L1 triggers:

L1_XE50, L1_XE70, …

  • L1 topo trigger:

L1_J40_DPI-J20s2XE50

  • HLT triggers:

HLT_xe100 HLT topo triggers: HLT_j80_xe80_dphi1_L1J40_DPHI-J20s2XE50

  • Inclusive: L1_XE50, L1_XE70, HLT_xe100
  • Meant to complement the TrackMET study

by identifying which MET threshold gives maximum discrepancy power

4/9/2015 Document reference 13

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SLIDE 14

ATLAS Trigger System (Run2)

4/9/2015 Document reference 14

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SLIDE 15

ATLAS Trigger System

What is a trigger sytem?

System that uses simple criteria to quickly decide events in particle detector to keep when small fraction of total can be recorded

Real-world limitations

Data Storage, CPU Capacity (time) and collision rates

How?

Searches for β€œinteresting events” (decay of rare particles) which occur at relatively low rates, and identify events that should be saved for further analysis Trigger has large number (hundreds) of hypothesis independently: trigger chains

Why?

It is often the case that people check the trigger objects to match the offline reconstruction

Offline vs Online Trigger reconstruction (online) happens during data-taking, once data taken the trigger information is fixed for all times

4/9/2015 Document reference 15

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SLIDE 16

ATLAS Trigger System

The Technicality

Job: Select few hundred events of interest/second for permanent storage

  • Run 1: 20MHzοƒ  700Hz => rejection factor of 30 000

First level trigger (L1)

  • Synchronous at 40MHz with fixed latency 2.5πœˆπ‘‘
  • Identifies Region-of-Interest (RoI) in muon spectrometer and/or

calorimeter with coarse resolution High Level Trigger (HLT)

  • Handles complexity with custom fast software on commercial

CPUs

  • Access full resolution of ALL detectors
  • Access both partial events (L2 RoIs (Run1)) and full event (Event

Filter(Run1))

4/9/2015 Document reference 16

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SLIDE 17

ATLAS xAOD

Software

  • Trigger Decision Tool (TDT)
  • xAODTrigConf
  • xAODTrigger (EmTauRoI, Jet, etc)
  • xAODTrigEgamma
  • xAODTrigMissingET

4/9/2015 Document reference 17

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SLIDE 18

Efficiency Curves

  • Reconstructed events at offline level do not

perfectly match the real data (online)

  • Measure of β€˜goodness’ of trigger

𝐹𝑔𝑔. ~ πΉπ‘€π‘“π‘œπ‘’π‘‘ π‘žπ‘π‘‘π‘‘ 𝑒𝑠𝑗𝑕𝑕𝑓𝑠

π‘ˆπ‘π‘’π‘π‘š π‘“π‘€π‘“π‘œπ‘’π‘‘

  • Nomenclature:
  • XE, xe, J, dphi, …
  • L1_XE70, HLT_xe100, L1_...

4/9/2015 Document reference 18

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SLIDE 19

𝑒𝑒 (online MET trig)

4/9/2015 Document reference 19

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SLIDE 20

𝑒𝑒 (offline MET trig)

4/9/2015 Document reference 20

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SLIDE 21

𝑒𝑒 Efficiency (HLTtopo w/o offline cut)

4/9/2015 Document reference 21

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SLIDE 22

Trigger offline cut

  • At least two jets
  • π‘„π‘ˆ>20GeV
  • πœƒ < 2.5
  • Leading jet with π‘„π‘ˆ > 45π»π‘“π‘Š
  • Minβˆ†βˆ… π‘πΉπ‘ˆ, π‘˜π‘“π‘’ > 1.5

4/9/2015 Document reference 22

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SLIDE 23

𝑒𝑒 Efficiency (after offline cut)

4/9/2015 Document reference 23

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SLIDE 24

𝑒𝑒 Efficiency (L1topo trigger)

4/9/2015 Document reference 24

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Monohiggs sample (π‘žπ‘ž β†’ β„Žπ‘¦π‘¦ β†’ 𝑐𝑐𝑦𝑦)

4/9/2015 Document reference 25

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SLIDE 26

Conclusion

  • TrackMet could help in rejecting processes

which are source of fake MET, such as QCD

  • It can be a powerful tool in W/Z analysis,

and any other processes with real MET.

  • Trigger study in Run2 useful for looking at

the efficiency of MET signature trigger

  • Study of trigger efficiency plots could help

analysis in getting the optimum event selection by finding MET threshold

4/9/2015 Document reference 26

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SLIDE 27

4/9/2015 Document reference 27

Special thanks… And Lounsbery Foundation…

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SLIDE 28

Questions???

4/9/2015 Document reference 28

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Fun Time

4/9/2015 Document reference 29

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Backup

4/9/2015 Document reference 30

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SLIDE 31

ATLAS Trigger System

Trigger is your first step of analysis

For analysis, understanding which trigger chain(s) to work with is

  • important. (First selection step of signal and background data)

Can use tools provided by trigger group to check outcome of hypothesis and analyze trigger objects Important for analysis: Matching offline reconstruction to trigger objects

4/9/2015 Document reference 31

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SLIDE 32

ATLAS Trigger System

Online vs Offline

Trigger reconstruction (online) happens during data-taking, once data taken the trigger information is fixed for all times.

Expectation vs Reality

Expectation: In ideal-world we want trigger to reconstruct events same way as it is done Offline Reality: In real-world limitations make it impossible (there would always be mismatch between online and offline reconstruction) Trigger decision and reconstructed event objects is stored as part of ATLAS Raw Data (produced during Online data taking)

4/9/2015 Document reference 32

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SLIDE 33

Missing Transverse Energy

  • In p-p collision at the LHC, a significant, unmeasured amount of energy

escapes in z-direction.

  • Total initial and final momentum is zero in transverse direction
  • Imbalance of energy in transverse direction signals presence of weakly/non-

interacting particles such as neutrinos

πΉπ‘ˆ = (π‘žπ‘¦

𝑛𝑗𝑑𝑑)2 + (π‘žπ‘§ 𝑛𝑗𝑑𝑑)2

π‘žπ‘¦

𝑛𝑗𝑑𝑑 = βˆ’

π‘žπ‘¦,𝑗

π‘‚π‘‘π‘π‘œπ‘’π‘ π‘—π‘ 𝑗=1

π‘žπ‘§

𝑛𝑗𝑑𝑑 = βˆ’

π‘žπ‘§,𝑗

π‘‚π‘‘π‘π‘œπ‘’π‘ π‘—π‘ 𝑗=1

  • xAOD Missing ET

4/9/2015 Document reference 33

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SLIDE 34

METJEt_dphi_min

4/9/2015 Document reference 34

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SLIDE 35

RoIs

  • RoI=Region of Interest
  • LVL1EmTauContainer

4/9/2015 Document reference 35

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SLIDE 36

Trigger emulation vs flag

(EM18VH vs L1_EM18VH)

4/9/2015 Document reference 36

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SLIDE 37
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SLIDE 38