1 / 24

Egamma Triggers

Egamma Triggers. Alessandro Tricoli (CERN) On behalf of the egamma and trigger groups. 20 th October 2011. Level-1 Calorimeter Trigger Joint Meeting. Overview. Major E/Gamma trigger developments in 2011 and physics implications

chelsa
Download Presentation

Egamma Triggers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Egamma Triggers Alessandro Tricoli (CERN) On behalf of the egamma and trigger groups 20th October 2011 Level-1 Calorimeter Trigger Joint Meeting

  2. Overview • 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 A. Tricoli

  3. 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 L1 L2 EF Egamma stream • Run 190256: • peak lumi 3.3e33 • 107 pb-1 collected A. Tricoli

  4. Latest Primary Electron Triggers List of primary Electron triggers for remain of 2011 data-taking (rest of presentation will clarify their definitions and illustrate their performance) Primaries • Medium1 = medium++ offline • Loose1 = loose++ offline • See backup slides A. Tricoli

  5. Latest Primary Photon Triggers List of primary Photon triggers for remain of 2011 data-taking Primaries A. Tricoli

  6. 2011 rate constraints • 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: • L1: raise thresholds • EM14->EM16; 2EM7->2EM10 • EM16->EM16VH; 2EM10->2EM10VH; add EM18VH as backup • low-pt triggers (i.e. J/Psi) still L1 limited • L2: a few times L2 selection of primary triggers had been tightened • low-pt tight triggers, e.g. J/Psi triggers • medium-pt tight triggers for tau studies, e.g. e15_tight • medium triggers, e.g. L2_e20_medium • medium1 triggers, e.g. L2_e22vh_medium1 • EF: raise of thresholds and tightening of identification selection • e20->e22, raise thresholds of combined triggers, e.g. e+met, e+mu • medium->medium1 (corresponding to medium++ offline selection, see backup slides) A. Tricoli

  7. L1 threshold evolution Change of L1 thresholds since period L to reduce L1 rate without raising HLT thresholds • EM14 threshold removed to make space for other thresholds • Many more L1 items available from combinations of these 8 thresholds 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 For detail description of ‘VH’ triggers refer to Monika Wielers’ talk on 26th July ATLAS Weekly https://indico.cern.ch/materialDisplay.py?contribId=1&materialId=slides&confId=119648 HLT triggers seeded of L1 ‘VH’ triggers have ‘vh’ added to the name, e.g. e22vh_medium1 • Under discussion the implementation of proper dead-material corrections next year A. Tricoli

  8. L1 VH trigger definitions • For lumi ≥ 3x1033, L1 rate beyond safety margin, the choice was • raise L1 thresholds for trigger with high pT electrons and for H • apply different thresholds as a function of the coarse granularity of the cluster processor (=0.40.4) => V • Apply hadronic core isolation (= longitudial isolation in 22 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 A. Tricoli

  9. L1 EM VH trigger performance Efficiencies of L1_EM16 and L1_EM16VH wrt offline medium++ electron identification by Z->ee tag-and-probe analysis • 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 • 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“ A. Tricoli

  10. ‘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 • Efficiency ratio 2e12T/2e12 shows • lower efficiency up to 20 GeV for 2e12T • at 15 GeV ~ 5% extra inefficiency for 2e12T Offline electron ET>15 GeV A. Tricoli

  11. 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 Dh 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% • 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 A. Tricoli

  12. e22vh_medium1 performance efficiency Z→ee tag-and-probe Z→ee tag-and-probe Z→ee tag-and-probe • efficiencies of e20_medium and e22_medium comparable on plateau • drop by ~2% in transition medium→medium1 • most losses due to tracking at high h • detail investigation on-going • e22vh_medium1 efficiency in period L5, measured by Z→ee tag-and-probe for ET> 25 GeV L1: 99.83±0.02 L2: 97.61±0.06 EF: 95.51±0.09 A. Tricoli

  13. e22vh_medium1 performance pileup dependence 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) • L1 shows no pileup dependence • L2 and EF efficiency show pileup dependence • on-going investigation A. Tricoli

  14. 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 EF_g20_loose efficiency Bootstrapped from L1_EM12 Wrt offline tight photons Periods L2-L3 • L1 Pass-through triggers (no HLT selection): • EM3 - 1 Hz • EM12 - 1 Hz • 2EM12 - 1 Hz (to be disabled) • EM30 - 1 Hz ET [GeV] A. Tricoli

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

  16. 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 • Df(MET, jet) > 0.7 or > 2.0, with jet pt>10 GeV • Run 190256: • peak lumi 3.3e33 • 107 pb-1 collected • 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 A. Tricoli

  17. Prospects for dead-material corr. Preparation for 2012 data-taking • 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 A. Tricoli

  18. 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 • 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 A. Tricoli

  19. 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 A. Tricoli

  20. Backup A. Tricoli

  21. Medium++ and loose++ • Medium1 at trigger is equivalent to medium++ offline • Loose1 at trigger is equivalent to loose++ offline • medium++ • medium selection requirements with the addition of: • tighter shower shapes for |h| > 2.01 • tighter Dh track-cluster matching ( | Dh |<0.005) • stricter bLayer and Pixel hit requirements • bL + bLOutlier > 0 for |h| < 2.01 and nPix+nPixOutliers > 0; • nPix + nPixOutliers > 1 for |h| > 2.01 • loose TRT HT Fraction cuts • loose++ • looser shower shape cuts than loose • additional tracking cuts as in medium • nPix+nPixOutliers >=1 and nSi+nSiOutliers >= 7 • loose Dh track-cluster matching ( | Dh | < 0.015) For more details see Egamma Twiki page https://twiki.cern.ch/twiki/bin/view/AtlasProtected/TechnicalitiesForMedium1 A. Tricoli

  22. e12_medium performance Efficiencies of combined triggers, e.g. 2e12(Tvh)_medium, obtained from efficiency of single e12_medium trigger • 2011 Data: 1.5 fb-1, period B-J • MC10b: 5 fb-1, 106046 Zee • Zee tag-and-probe analysis • Tag electron: tight and isolated electron that trigger e20_medium, exclude crack • Probe electron: ET > 12 GeV, |η| < 2.47 data mc data mc e12_medium wrt tight e12_medium wrt tight Scale factors for e12_medium wrt offline tight(medium) electrons available https://indico.cern.ch/getFile.py/access?contribId=1&resId=0&materialId=slides&confId=116220 A. Tricoli

  23. 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 A. Tricoli

  24. 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 • Plan to run isolated electron triggers soon, for validation studies only, but NOT for event selection until next year 1) pt >25, bLayer cut added also in |h|>2, ptCone20/pt < 0.100 OR’ed with pt >30, bLayer added also in |h|>2 2) pt>22, bLayer also in |h|>2, ptCone20/pt > 0.050, etCone20/et < 0.175, OR’ed with pt >30, bLayer added also in |h|>2 e25i5vh_medium2 [30 Hz at 5e33] e30vh_medium2 [+5 Hz unique rate] • 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 e22i6vh_medium2 [35 Hz at 5e33] e30vh_medium2 [+9 Hz unique rate] For more details see, egamma talk at Trigger General Meeting: https://indico.cern.ch/getFile.py/access?contribId=4&resId=0&materialId=slides&confId=129126 Studies on Z->ee show good performance of track and calo isolation at EF wrt offline variables A. Tricoli

More Related