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Level-1 Trigger

Level-1 Trigger. CMS Week, Brussels 14 Sep. 2011 C .-E. Wulz Deputy Trigger Project Manager Institute of High Energy Physics, Vienna Prepared with slides/material from: L. Guiducci , M. Jeitler , P. Klabbers , M.  Konecki , A. Kropivnitskaya , E. Perez, A. Tapper.

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Level-1 Trigger

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  1. Level-1 Trigger CMS Week, Brussels 14 Sep. 2011 C.-E. Wulz Deputy Trigger Project Manager Institute of High Energy Physics, Vienna Prepared with slides/material from: L. Guiducci, M. Jeitler, P. Klabbers, M. Konecki, A. Kropivnitskaya, E. Perez, A. Tapper

  2. Trigger menu development • currently running with “3e33 menu” • menu designed for instantaneous luminosity of 3×1033 cm-2 s-1 • small updates applied last week • one more menu planned for 2011 proton run

  3. Recent L1 trigger developments • new muon combination scheme proposed in GMT • instead of taking minimum PTof two systems take the one with the higher rank • will lead to a few percent better efficiency • influence on rates has to be tested • new LUTs and configuration key made • currently being analyzed • new CSC PT assignment • based on CLCT in ME1 • new features in RPC PACT • changed algorithm, to increase efficiency • HSCP trigger: 2 BX wide and 1 BX delayed wrt DT and CSC

  4. CSCTF PT assignment Golden eta region: 1.2 < η < 2.1 2 or 3 station tracks with ME1 ImprovedME1 CLCT patterns for 2 station tracks: - curves PT ≥ 5 GeV the same for PTLUT2010 and PTLUT2011 as expected; CLCT pattern starts to work from PT> 5 GeV - Efficiency below threshold drops from 5-10% (2010) to ~2% (2011) for PTthresholds ≥ 7 GeV and up - Significant improvement in 2011 compared to the 2010 PTassignment, especially for PT ≥ 7 GeV, lowering the trigger rate

  5. RPC PAC trigger improvements in 2011 • In 2011 the RPC PAC trigger algorithm was changed: in the barrel it requires at least 3 layers fired (out of 6 available) to generate a muoncandidate. 4 layers were required in 2010. It was possible since the chamber noise is lower than expected. efficiency in the barrel increased • The optical links were arranged to obtain better geometrical coverage in the region between wheels 0 and +/- 1  additional increase of the efficiency in|| ~0.3 Offline muon pT >8GeV/c Offline muon pT > 7GeV/c • The PAC is now able to trigger on “slow” particles, which reach the muon system in the next BX: it looks for the coincidence of hits in two consecutive BXs, the candidate BX is determined by the BPTX trigger veto. L1 RPC Trigger Efficiency including detector geometrical acceptance and hit efficiency vs L1 CSC or DT trigger CMS Week, Sep. 2011

  6. Stability of L1RPC after automatic HVversus pressure correction HV(p) corrections no corrections from pressure changes at the beginning of each fill • Variation of chamber efficiency affects the absolute trigger efficiency (difficult to follow) and pTspectrum • check fraction of L1RPC candidates with givenpTCodevs all. • after applied modifications RPC trigger pTspectrum stable vs pressure • stability better in barrel than in endcaps

  7. RPC data synchronisation • Only small modification of timing settings done in 2011

  8. Recent L1 trigger developments (continued) • new jet energy corrections have been developed • had only been applied up to 92 GeV • 1-hour test run with new corrections has been taken • modifications to be applied for next menu (“2011, version 7”)

  9. Uncorr UNCORRECTED 2011 SO FAR CORRECTED 2011 DATA 2011 DATA L1 jet energy calibration • In 2010 running no jet energy corrections • Jet energy corrections were derived from Monte Carlo for 2011 and tested with data (Brown University) • Corrections tested up to 130 GeV (saturation value in 2010) • For higher luminosity need to extend corrections up to higher PT ΔR<0.5 match between L1 and RECO jets

  10. Monte Carlo NEW CORRECTIONS New corrections Old corrections ±10% 2011 DATA L1 jet energy calibration • New jet energy corrections derived from Monte Carlo using JetMET code • Tests on existing data and Monte Carlo • Extends high-PT region and improves low-PT region a little • Test run taken and validated ➔ ready for physics

  11. Recent L1 trigger developments (continued) • New beam gas triggers • triggers based on BSC not useable at current high luminosity • Present beam gas trigger based on HF, uses unpaired bunches • suffers from strong “albedo” after trains of colliding bunches • background from delayed nuclear reactions • New triggers use special BPTX signal after “quiet” period without collisions • 500 ns, “post-quiet unpaired BPTX signal” • thanks to BRM group for supplying this signal

  12. “post-quiet unpaired bunches” beam 1 beam 2

  13. Recent L1 trigger developments (continued) • new ideas for luminosity measurement • needed because of pileup effects distorting zero-counting method • proposed by Marco Zanetti and Nicola Bachetta • based on Pixel cluster counting • requires zero-bias trigger that is only active for a few bunch crossings in orbit • so that within rate budget (1 kHz at L1) each bunch crossing gets reasonable statistics within a lumi section (23 seconds) • luminosity depends strongly on bunch crossing • Global Trigger firmware update allows to select individual bunch crossings for a trigger algorithm

  14. L1 trigger rate capability • rate limits at Level 1 have been rechecked with real data • by applying progressively lower prescales to L1_SingleEG5 • CMS runs up to design value of 100 kHz without significant deadtime • deadtime problems sometimes observed were caused by beam conditions (PKAM events in Pixels) and not by high rate

  15. L1 trigger cross section monitoring - Cross-sections of selected (*) L1 triggers vs instantaneous luminosity - WBM fit is used to compute the “expected” cross-section - (*) single object triggers, with the lowest PT/ETcut which is unprescaled in all prescale columns of the menu

  16. L1 trigger cross section monitoring - Measured/Expected cross-section vslumi section number for certification - Currently used by shifters to fill Run Registry - Goal is to generate GOOD/BAD LS ranges automatically

  17. Trigger cross section history P. Musella, J. Pela 2e33 (EG15) 3e33 (EG20) 1.4e33 (EG12) ~July ~August - Jumps due to the different selection of monitored trigger object - Can check stability of the triggers

  18. Predictions for 5e33 based on the 3e33 data Data from run 175921 (3e33) used to emulate the “5e33 column” of the current menu : lead to 80 kHz + 10% (PU from 3e33 to 5e33) = about 90 kHz Current plan for the 5e33 menu : - quite similar to the “5e33 column” that we are running currently : unprescaled: EG20, SingleMu16_Eta2p1, SingleJet128 - A new L1 menu will be deployed though, with : - L1_DoubleEG_15_5 (7 kHz) taking over from DoubleEG_12_5 - brings the expected rate to 75 kHz + 10% PU = 82 kHz - L1_Muxx_MuOpen - to be defined - SingleMu10_ETM20 (tiny rate) - DoubleJet36_Central prescaled by only 5 - will add ~ 3 kHz Prediction based on 3e33 data (PU increase not included) i.e. expect ~ 85 kHz which should be sustainable. Note that the rate in cross-triggers starts to be large.

  19. Effect of Pile-Up on L1 rates : trigger x-sections in latest runs Example seeds (mostly unprescaled at 3e33) that are most sensitive to PU : TripleJet_36_36_12 EG18_ForJet16 (finally p’ed a bit) Xsection increased by 40% between 2e33 and 3e33 Increase x 2 QuadJet20_Central +75% ETM_30 + 30% TripleEG_8_5_5 +20 % 18 C.-E. Wulz CMS Week, Sep. 2011

  20. Effect of Pile-Up on L1 rates : trigger x-sections in latest runs Most seeds, especially the widely used higher thresholds seeds, behave better : SingleJet92 SingleEG15 + 5% + 4 % SingleMu14_Eta2p1 Roughly : Seeds that are sensitive to PU account for 25 - 30% of the rate. C.-E. Wulz

  21. The L1 menu (L1Menu_Collisions2011_v5) deployed for the 3e33 menu • Prediction of rates and first definition of prescales based on earlier data ( ~ 1e33) : • emulation of the total L1 rate for a given scenario at 3e33 was obtained from the • earlier data, using the L1Accept stream (“nanoDST”, ~ 5 kHz of L1A events, with • only the L1 information) • neglecting the PU effect: total predicted rate at 3e33 was ~ 73 kHz. • estimated PU effect from 1e33 to 3e33 : increase the total L1 rate by 10-15%. • i.e. we were expecting a total rate of 80 kHz. Rates actually measured at 3e33: Measured rates (kHz) at 3e33 • 80 kHz in run 176163 (Sept 12) at 2.9e33. • i.e. the predictions were in the right ballpark • see breakdown in the plot • biggest are • EG15 (16 kHz) • SingleMu16 (13 kHz) • DoubleJet44 (12 kHz)

  22. PU effect on total L1 rate in recent runs • Compare rates of two runs taken with prescale index = 2 : • run 176201, LS 135 – 145, lumi = 3e33 • - correct for the deadtimeof ~ 10% : L1A = 84 Hz • run 175921, LS 400 – 420, lumi = 2.2e33 • - correct for the fact that TripleJet seed was still unprescaled in that • run, while it is prescaled in 176201 : L1A = 57 Hz • PU effect on the total L1 rate, from 2.2e33 to 3e33 : + 8 %. • Assuming a similar slope between 3e33 and 5e33 : • - the PU would increase the L1 rate by about 10%. • (Things are likely to be a bit worse though, because cross-trigger seeds (low PT • objects, hence PU sensitivity) contribute more to the total rate at 5e33.)

  23. Muon trigger PT cuts: turn-on curves - Study per PT cut between 10-20 GeV/c with data from 1-2e32 running - Preparation of the 5e33 menu - Turn-on positions and slopes are OK

  24. |eta|<2.4 |eta|<2.1 Muon trigger PT cuts: rates - Rate measured using NanoDST data, projected to 5E33 luminosity - >70% of total rate from |eta|>2.1 - Higher PTcuts less and less effective at highh - Introducedhcut at 2.1 - Keep lower L1 thresholds - Some gain in plateau efficiency L=5E33 L1 Eta cut C.-E. Wulz CMS Week, Sep. 2011

  25. Muon trigger: efficiency losses and rates L=5E33 (*) efficiency loss computed wrt L1_SingleMu10

  26. Total RPC trigger rate • We do not expect significant non-linear effects in scaling from 3e33 cm-2s-1 to 5e33 cm-2s-1 • RPC rate on plots below is doubled RUN 176201 (peak lumi: 3.1e33cm-2s-1)

  27. Conclusions • Improvements to most L1 trigger systems have been made. • Rate capability has been rechecked with data. • Predictions for rates at 5e33 have been made, taking into account pileup. • Preparations to run at 5e33 are well under way.

  28. BACKUP

  29. These plots show the ratios of L1 rates measured In two runs with different PU conditions (see slide 21), normalized to the same luminosity.

  30. Recent GMT changes increased the muon rates in latest runs. Hence the rate ratios do not correspond only to the PU effect.

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