Egamma TriggersEgamma Triggers

Alessandro Tricoli (CERN)Alessandro Tricoli (CERN)

On behalf of the egamma

and trigger groups

20th October 2011Level-1 Calorimeter Trigger Joint Meeting

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Overview

20th October 2011

Major E/Gamma trigger developments in 2011 and physics implications

Effort to maintain low thresholds at L1 and HLT and keep high performance L1 adjustemnts HLT selection tightening

Electron and Photon Trigger Performance

Outlook for 2012 dead-material corrections at L1 HLT isolation

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Overall Trigger conditions

New Trigger menu, Physics_pp_v3, already deployed since data-period L covering lumi range ≥ 3x1033 cm-1s-1

this year we will not reach 5x1033, but this menu is good preparation for 2012

Run at 400 Hz total average EF output rate for the rest of this year p-p running Total Rates within limits

• L1: 50 kHz• L2: 4 kHz• EF: 500 Hz at peak 3x1033 cm-1s-1, average 400 Hz• Egamma stream: 110 Hz

Run 190256: peak lumi 3.3e33 107 pb-1 collected

L1 L2EF

Egamma stream

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Latest Primary Electron Triggers

Primaries

List of primary Electron triggers for remain of 2011 data-taking(rest of presentation will clarify their definitions and illustrate their performance)

V3 menu L1 rate [Hz] at 3x1033

EF rate [Hz] at 3x1033

Justification

e22vh_medium1 10 k (EM16VH) 60 SM, top, Higgs, Susy, exotics

e45_medium1 2.5 k (EM30) 8 Susy, exotics

2e12Tvh_medium 2k (2EM10VH) 3 DY, H4l

e15vh_loose1_e12Tvh_loose1_Zee 2 k (2EM10VH) 0.6 H4l

e12Tvh_medium_2e6T_medium 3.2k (3EM5_EM10VH)

0.1 Susy

e10_medium_mu6 4k (EM5_MU6) 15 H4l, HWWll, A

e10_medium_mu6_topo_medium 4k (EM5_MU6) 2 A

e15vh_medium_xe40_noMu 1.8 k (EM10VH_XE30)

5 He

Medium1 = medium++ offlineLoose1 = loose++ offlineSee backup slides

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Latest Primary Photon Triggers

List of primary Photon triggers for remain of 2011 data-taking

V3 menu L1 rate [Hz] at 3x1033

EF rate [Hz] at 3x1033

Justification

g80_loose 2.5 k (EM30) 10 Direct photons

g60_loose 2.5 k (EM30) 2 Hz prescaled Direct photons

g40_loose 2.5 k (EM30) 2 Hz prescaled Direct photons

g20_loose 50 (EM12) prescaled 2 Hz prescaled Direct photons

2g20_loose 4 k (2EM12) 6 Di-photons, H

g150_etcut 2.5 k (EM30) 6 Exotics

g40_loose_xe45_medium_noMu 2.5 k (EM30) 5 Susy

g40_tight_b10_medium 2.5 k (EM30) 3 Higgs(+Z→+bb)

Primaries

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2011 rate constraints

20th October 2011

During 2011 pp data-taking L1, L2 and EF rates had to be adjusted a few times to remain within budget

in winter menu was originally prepared for two lumi points: 5x1032 and 1x1033

then adjusted for 3x1033 and planned for 5x1033 (never reached)

Limitations encountered at all trigger levels: o L1: raise thresholds

o EM14->EM16; 2EM7->2EM10o EM16->EM16VH; 2EM10->2EM10VH; add EM18VH as backupo low-pt triggers (i.e. J/Psi) still L1 limited

L2: a few times L2 selection of primary triggers had been tightenedo low-pt tight triggers, e.g. J/Psi triggerso medium-pt tight triggers for tau studies, e.g. e15_tight o medium triggers, e.g. L2_e20_mediumo medium1 triggers, e.g. L2_e22vh_medium1

EF: raise of thresholds and tightening of identification selectiono e20->e22, raise thresholds of combined triggers, e.g. e+met, e+muo medium->medium1 (corresponding to medium++ offline selection, see backup slides)

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L1 threshold evolution

Change of L1 thresholds since period L to reduce L1 rate without raising HLT thresholds

Current L1 HLT

EM3 e5

EM5 e10

EM7 e13

EM10VH e15,e12T

EM12 g20

EM16VH e22

EM18VH e22 - e25

EM30 High pt

For detail description of ‘VH’ triggers refer to Monika Wielers’ talk on 26 th July ATLAS Weeklyhttps://indico.cern.ch/materialDisplay.py?contribId=1&materialId=slides&confId=119648

V = varied threshold, i.e. coarse dead-material corrections - effective ‘V’ threshold implements different thresholds in different eta regions with the coarse 0.4 granularity of the L1Calo cluster processor (e.g. EM16VH uses EM16,EM17,EM18)

H = hadronic leakage requirement, i.e. absolute hadronic core requirement

HLT triggers seeded of L1 ‘VH’ triggers have ‘vh’ added to the name, e.g. e22vh_medium1

Old L1 HLT

EM3 e5

EM5 e10

EM7 e12

EM10 e15

EM12 -

EM14 e20

EM16 e22

EM30 High pt

EM14 threshold removed to make space for other thresholds

Many more L1 items available from combinations of these 8 thresholds

Under discussion the implementation of proper dead-material corrections next year

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L1 VH trigger definitions

20th October 2011

For lumi ≥ 3x1033, L1 rate beyond safety margin, the choice was 1.raise L1 thresholds for trigger with high pT electrons and for H2.apply different thresholds as a function of the coarse granularity of the cluster processor (=0.40.4) => V3.Apply hadronic core isolation (= longitudial isolation in 22 towers behind EM cluster core)

very similar to hadronic leakage cuts applies in the HLT and offline

• we wanted to avoid raise threshold (loss in physics acceptance)• we wanted to avoid EM isolation (unsafe due to pileup dependence)• dead-material corrections needed longer investigation=> Deployment of 2. and 3., i.e. VH, since August technical Stop

EM16VH Hadcore ≤1 GeV (cts), ET thresh. cut between 16 and 18 GeV rate reduction 45, rates at 3x1033 : EM16=18 kHz , EM16VH = 10 kHz performance studied on Z events

EM10VH (to keep 2TAU8_EM10 within acceptable rate limits) Hadcore ≤1 GeV (cts), ET thresh. cut between 10 and 11 GeV rate reduction 40% on 2TAU8_EM10, factor 3 on 2EM10VH performances studied on W and cross-checked on Z events

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L1 EM VH trigger performance

EM16VH turn-on curve steeper than EM16 and starting at slightly higher ET, due to tighter thresholds in some eta bins, reach same values around ET=27GeV

details of turn-on profile under investigation eta region by eta region only 0.1% efficiency loss of EM16VH wrt EM16 for Z→ee electrons with ET>25 GeV

Losses due to this hadronic leakage cut seen for electrons with ET>300-400GeV

Efficiencies of L1_EM16 and L1_EM16VH wrt offline medium++ electron identificationby Z->ee tag-and-probe analysis

EM30 [-> e45_medium1] does NOT apply hadronic leakage cut at L1 High PT Electron analysis must use OR of triggers:

“e22vh_medium1 OR e45_medium1“

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‘T’ di-electron triggers

To reduce L1 rate with no increase of HLT thresholds on di-electron triggers replace 2EM7 (18 kHz at 3e33) with 2EM10 (6.5 kHz at 3e33) then 2EM10VH (2 kHz at 3e33) (VH introduced to cut rate of combined TAU+EM10 triggers) bring L1 threshold closer to HLT threshold

Period A-J: 2EM7 seeding 2e12_medium Period: K: 2EM10 seeding 2e12T_medium Period L: 2EM10VH seeding 2e12Tvh_medium(where ‘T’ indicates smaller gap between L1 and HLT thresholds)

Implications for physics analysis for offline electron cut of ET>15 GeV the trigger is not fully efficient

=> work on efficiency turn-on curve

Offline electron ET>15 GeV

Efficiency ratio 2e12T/2e12 shows lower efficiency up to 20 GeV for 2e12T at 15 GeV ~ 5% extra inefficiency for 2e12T

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Evolution L2 and EF selections

L2 selection of lowest unprescaled single electron trigger tightened a few times this year mostly with negligible impact on total trigger efficiency (sub-% effect)

In period L5, rate reduced by factor 2 in preparation for luminosities ≥ 4 x 1033 cm-2 s-1 tighter shower shape cuts and tighter cut between cluster and track L2_e22vh_medium1 rate from 800 Hz to 400 Hz at 3e33, and efficiency wrt offline medium++ decreased by 1%

20th October 2011

Evolution of lowest unprescaled single electron trigger (to accommodate rate within allocated bandwidth)

periods A-J: e20_medium (projected rate at 3x1033 ~170 Hz) period K: e22_medium (projected rate at 3x1033 ~130 Hz) period L: e22vh_medium1 (rate at 3x1033 ~60 Hz)– medium1 same identification selection as medium++ offline (see backup slide)

Implication on physics analysis: slightly lower efficiency offline electron that fired trigger must be selected with medium++ identification

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e22vh_medium1 performance efficiency

L1: 99.83±0.02 L2: 97.61±0.06 EF: 95.51±0.09

e22vh_medium1 efficiency in period L5, measured by Z→ee tag-and-probe for ET> 25 GeV

efficiencies of e20_medium and e22_medium comparable on plateau drop by ~2% in transition medium→medium1

most losses due to tracking at high detail investigation on-going

Z→ee tag-and-probe Z→ee tag-and-probe

Z→ee tag-and-probe

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e22vh_medium1 performance pileup dependence

L1 shows no pileup dependence L2 and EF efficiency show pileup dependence

on-going investigation

Integrated efficiency of e22(vh)_medium1 wrt offline medium++ for electron ET>25 GeV in period F-L, as function of no. of primary vertices

N.B.: trigger efficiency measured relative to same offline selection

pileup dependence may largely cancel here shown additional pileup dependence of trigger relative to offline (due to resolution effects)

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Photon trigger performance

Single photon triggers in 2011: unprescaled: g60_loose-> g80_loose prescaled: g20_loose, g40_loose, then g60_loose

di-photon trigger: unprescaled: 2g20_loose – to be kept unprescaled for the rest of the year

EM14 threshold removed from period L => (2)g20 triggers re-seeded of (2)EM12 photon trigger performance very stable throughout the year

g20_loose efficiency close to 100% efficiency measured by bootstraping from low threshold L1-pass-through triggers

20th October 2011

EF_g20_loose efficiencyBootstrapped from L1_EM12Wrt offline tight photons Periods L2-L3

ET [GeV]

L1 Pass-through triggers (no HLT selection): EM3 - 1 Hz EM12 - 1 Hz 2EM12 - 1 Hz (to be disabled) EM30 - 1 Hz

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Jpsi triggers

J/Psi triggers effort to maintain J/Psi tag-and-probe triggers at 3x1033 luminosity. crucial to understand low-pT electrons for e.g. H → 4e J/Psi -> ee events are also important for the understanding of the EM calorimeter performance (extraction of resolution, intercalibration, etc)

Tag electron is tight; no identification selection on Probe electron leg (only ET cut) Invariant mass cut 1-5 GeV at HLT to improve purity Jpsi triggers are all prescaled => statistics is a concern Limitation from L1 rate

=>L1 rate increased progressively during a fill when lumi and total L1 rate drop

Electron efficiency calculated from J/ψ ll, W lν, Z ll data samples: use J/Psi and W triggers(see following talk by Lydia)

20th October 2011

Example where L1 topological triggers would be very useful(e.g. inv mass cut at L1 as done at HLT)

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W tag-and-probe triggers

Electron efficiency calculated from J/ψ ll, W lν, Z ll data samples: use J/Psi and W triggers(see following talk by Lydia)

W tag-and-probe triggers Tag the event via missing ET significance XS~MET/sqrt(SumET) apply minimal requirements Probe electron: only ET threshold and basic track quality cuts to further reduce rate and allow trigger to run unprescaled, MET isolation applied

o (MET, jet) > 0.7 or > 2.0, with jet pt>10 GeV

Rates show clear dependence on pileup => rate increase during a fill as pileup decreases missing ET significance inefficient at high pileup bias on offline efficiency measurement in different pileup conditions under investigation

Run 190256: peak lumi 3.3e33 107 pb-1 collected

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Prospects for dead-material corr.

20th October 2011

dead-material correction could replace ‘V’ thresholds provide sharper turn-on curve efficiency vs eta is flatter efficiency plateau reached at lower ET

results with Zee tag-and-probe so far are encouraging need to adjust thresholds seeding HLT chains to control rates

list of L1_EM threshold would need to be revisited need to cross check results on lower-ET physics signals, e.g. J/Psi other trigger signature groups need to validate the results obtained within egamma

Preparation for 2012 data-taking

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HLT Isolation Preparation for 2012 data-taking

EF_e22vh_medium1 projected rate at 5x1033 is ~96 Hz rate reduction by factor 3 by tightening medium1 selection and add EF isolation

Egamma proposal for EF isolation – two options both are OR between one isolated and one higher threshold non-isolated trigger

opt. 1: raise threshold from e22 to e25, tighter identification selection, loose relative track isolation OR non-isolated higher threshold trigger opt. 2: keep e22 threshold, tighter identification selection, tight relative track isolation and loose relative calo isolation OR non-isolated higher threshold trigger(see backup slide)

Studies on Z->ee show good performance of track and calo isolation at EF wrt offline variables

20th October 2011

some analyses want to and can avoid trigger isolation by using combined triggers defining combined triggers to reduce rate and avoid isolation on electron trigger thriving discussion on what triggers to implement compatibly with rate budget

electron+jets, electron+MET, di-electron, electron+muon full scan possibly more…

More supporting triggers to be introduced

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Conclusions Excellent performance of L1 EM thresholds in 2011 (thanks!) Continuing effort to keep egamma triggers with the lowest possible threshold and highest performance with ever increasing LHC luminosity

adjustments at L1 (V, H and T triggers) tightening of selection at HLT

Continuing studies of trigger performance Preparatory work for 2012

positive studies of dead-material corrections proposal for electron trigger isolation to keep single electron trigger at lowest possible threshold

egamma workshop 24-28 October 2011, includes triggers session summarise 2011 operations and performance, and plan 2012 https://indico.cern.ch/conferenceDisplay.py?confId=148154

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Backup

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Medium++ and loose++ Medium1 at trigger is equivalent to medium++ offline Loose1 at trigger is equivalent to loose++ offline

For more details see Egamma Twiki pagehttps://twiki.cern.ch/twiki/bin/view/AtlasProtected/TechnicalitiesForMedium1

medium++ medium selection requirements with the addition of:

o tighter shower shapes for || > 2.01 o tighter track-cluster matching ( ||<0.005) o stricter bLayer and Pixel hit requirements

• bL + bLOutlier > 0 for || < 2.01 and nPix+nPixOutliers > 0; • nPix + nPixOutliers > 1 for || > 2.01

o loose TRT HT Fraction cuts

loose++ looser shower shape cuts than loose additional tracking cuts as in medium

o nPix+nPixOutliers >=1 and nSi+nSiOutliers >= 7 o loose track-cluster matching ( || < 0.015)

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e12_medium performance

2011 Data: 1.5 fb-1, period B-J MC10b: 5 fb-1, 106046 Zee Zee tag-and-probe analysis

o Tag electron: tight and isolated electron that trigger e20_medium, exclude crack o Probe electron: ET > 12 GeV, |η| < 2.47

Efficiencies of combined triggers, e.g. 2e12(Tvh)_medium, obtained from efficiency of single e12_medium trigger

e12_medium wrt tight e12_medium wrt tight

Scale factors for e12_medium wrt offline tight(medium) electrons availablehttps://indico.cern.ch/getFile.py/access?contribId=1&resId=0&materialId=slides&confId=116220

datamc data

mc

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Current Supporting Triggers

Supporting Triggers for electron background measurements: e11_etcut – 0.5 Hz g20_etcut – 1.5 Hz e22vh_loose – 1.5 Hz e22vh_loose1 – 1.0 Hz (loose1 = loose++ offline selection) e22vh_looseTrk – 1.0 Hz (looseTrk=loose + tack quality cuts) e22vh_loose_3j20_a4tc_EFFS – 0.5 Hz e22vh_loose_4j15_a4tc_EFFS – 1.0 Hz

Jpsi and W tag-and-probe triggers (see next slides)

Supporting triggers for tracking studies: e22vh_medium_SiTrk, e22vh_medium_TRT, e22vh_medium_IDTrkNoCut – 0.5 Hz

L1 Pass-through triggers (no HLT selection): EM3 - 1 Hz EM12 - 1 Hz 2EM12 - 1 Hz (to be disabled) EM30 - 1 Hz

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HLT Isolation Preparation for 2012 data-taking

1) pt >25, bLayer cut added also in ||>2, ptCone20/pt < 0.100OR’ed with

pt >30, bLayer added also in ||>2

2) pt>22, bLayer also in ||>2, ptCone20/pt > 0.050, etCone20/et < 0.175, OR’ed with

pt >30, bLayer added also in ||>2

e30vh_medium2 [+5 Hz unique rate]

e25i5vh_medium2 [30 Hz at 5e33]

e22i6vh_medium2 [35 Hz at 5e33]e30vh_medium2 [+9 Hz unique rate]

https://indico.cern.ch/getFile.py/access?contribId=4&resId=0&materialId=slides&confId=129126For more details see, egamma talk at Trigger General Meeting:

EF_e22vh_medium1 projected rate at 5x1033 is ~96 Hz rate reduction by factor 3 by tightening medium1 selection and add EF isolation Plan to run isolated electron triggers soon, for validation studies only, but NOT for event selection until next year

Egamma proposal for EF isolation – two options both are OR between one isolated and one higher threshold non-isolated trigger

opt. 1: raise threshold from e22 to e25, tighter identification selection, loose relative track isolation OR non-isolated higher threshold trigger opt. 2: keep e22 threshold, tighter identification selection, tight relative track isolation and loose relative calo isolation OR non-isolated higher threshold trigger

Studies on Z->ee show good performance of track and calo isolation at EF wrt offline variables

20th October 2011