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
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
C.-E. Wulz
1
CMS Week, Sep. 2011
Recent L1 trigger developments
 new muon combination scheme proposed in GMT
−
−
−
−
−
instead of taking minimum PT of 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
C.-E. Wulz
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CMS Week, Sep. 2011
CSCTF PT assignment
Golden eta region: 1.2 < η < 2.1
2 or 3 station tracks with ME1
Improved ME1 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
PT thresholds ≥ 7 GeV and up
- Significant improvement in 2011 compared to the 2010 PT assignment,
especially for PT ≥ 7 GeV, lowering the trigger rate
C.-E. Wulz
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CMS Week, Sep. 2011
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 muon candidate. 4
layers were required in 2010. It was possible since
the chamber noise is lower than expected.
 efficiency in the barrel increased
Offline muon pT > 8GeV/c
• The optical links were arranged to obtain better
geometrical coverage in the region between wheels 0
and +/- 1  additional increase of the efficiency in
Offline muon pT > 7GeV/c
|| ~0.3
• 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
L1 RPC Trigger Efficiency including detector geometrical
acceptance and hit efficiency vs L1 CSC or DT trigger
determined by the BPTX trigger veto.
C.-E. Wulz
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CMS Week, Sep. 2011
Stability of L1RPC after automatic HV
versus pressure correction
no corrections from pressure changes
•
•
•
•
HV(p) corrections
at the beginning of each fill
Variation of
chamber efficiency
affects the absolute
trigger efficiency
(difficult to follow)
and pT spectrum
check fraction of
L1RPC candidates
with given pTCode
vs all.
after applied
modifications RPC
trigger pT spectrum
stable vs pressure
stability better in
barrel than in
endcaps
C.-E. Wulz
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CMS Week, Sep. 2011
RPC data synchronisation
• Only small modification of timing settings done in 2011
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CMS Week, Sep. 2011
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”)
C.-E. Wulz
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CMS Week, Sep. 2011
L1 jet energy calibration


C.-E. Wulz
Uncorr

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

UNCORRECTED
2011 SO FAR
CORRECTED
2011 DATA
2011 DATA
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CMS Week, Sep. 2011
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
NEW CORRECTIONS
Monte Carlo
New corrections
Old corrections
±10%
2011 DATA
C.-E. Wulz
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CMS Week, Sep. 2011
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
C.-E. Wulz
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CMS Week, Sep. 2011
“post-quiet unpaired bunches”
beam 1
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CMS Week, Sep. 2011
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
C.-E. Wulz
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CMS Week, Sep. 2011
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
C.-E. Wulz
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CMS Week, Sep. 2011
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/ET cut which is unprescaled in
all prescale columns of the menu
C.-E. Wulz
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CMS Week, Sep. 2011
L1 trigger cross section monitoring
- Measured/Expected cross-section vs lumi section number for certification
- Currently used by shifters to fill Run Registry
- Goal is to generate GOOD/BAD LS ranges automatically
C.-E. Wulz
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CMS Week, Sep. 2011
Trigger cross section history
P. Musella, J. Pela
2e33
(EG15)
3e33
(EG20)
~August
~July
1.4e33
(EG12)
- Jumps due to the different selection of monitored trigger object
- Can check stability of the triggers
C.-E. Wulz
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CMS Week, Sep. 2011
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
i.e. expect ~ 85 kHz which should be
sustainable.
Note that the rate in cross-triggers starts
to be large.
C.-E. Wulz
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Prediction based on
3e33 data
(PU increase not
included)
CMS Week, Sep. 2011
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
QuadJet20_Central
+75%
C.-E. Wulz
C.-E. Wulz
Increase x 2
TripleEG_8_5_5
+20 %
18
ETM_30
+ 30%
CMS Week, Sep. 2011
CMS Week, Sep. 2011
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
+ 5%
SingleEG15
+4%
SingleMu14_Eta2p1
Roughly :
Seeds that are sensitive to PU
account for 25 - 30% of the rate.
C.-E. Wulz
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CMS Week, Sep. 2011
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:
• 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)
C.-E. Wulz
20
Measured rates (kHz)
at 3e33
CMS Week, Sep. 2011
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 deadtime of ~ 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.)
C.-E. Wulz
21
CMS Week, Sep. 2011
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
C.-E. Wulz
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CMS Week, Sep. 2011
Muon trigger PT cuts: rates
|eta|<2.4
|eta|<2.1
L=5E33
- Rate measured using NanoDST data,
projected to 5E33 luminosity
- >70% of total rate from |eta|>2.1
- Higher PT cuts less and less effective at high 
- Introduced  cut at 2.1
- Keep lower L1 thresholds
- Some gain in plateau efficiency
L1 Eta cut
C.-E. Wulz
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CMS Week, Sep. 2011
Muon trigger: efficiency losses and rates
L=5E33
Threshold
10
12
14
16
18
20
Eff loss for
pt>30GeV
0% (*)
0.3%
1.1%
1.4%
1.6%
2.0%
Rate
[kHz]
(|eta|<2.4)
44.5
35.1
28.4
23.2
20.9
18.9
Rate
[kHz]
(|eta|<2.1)
16.0
11.7
8.22
6.48
5.65
4.86
(*) efficiency loss computed wrt L1_SingleMu10
C.-E. Wulz
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CMS Week, Sep. 2011
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)
C.-E. Wulz
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CMS Week, Sep. 2011
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.
C.-E. Wulz
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CMS Week, Sep. 2011
BACKUP
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CMS Week, Sep. 2011
PU effect from 2.2 to 3e33: Jet seeds
L1_QuadJet28_Central
L1_QuadJet20_Central
L1_TripleJet28_Central
L1_TripleJet_36_36_12_Central
L1_DoubleTauJet44_Eta2p17
L1_DoubleTauJet36_Eta2p17
L1_DoubleTauJet40_Eta2p17
L1_DoubleTauJet32_Eta2p17
L1_DoubleJet64_Central
L1_DoubleJet52_Central
L1_DoubleJet52
L1_DoubleJet44_Central
L1_DoubleJet36_Central
L1_SingleJet128
L1_SingleJet92_Central
L1_SingleJet92
L1_SingleJet80_Central
L1_SingleJet68
L1_SingleJet52_Central
L1_SingleJet52
L1_SingleJet36
L1_SingleJet16
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
These plots show the ratios of L1 rates measured In two runs with different PU conditions (see slide 21),
normalized to the same luminosity.
C.-E. Wulz
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CMS Week, Sep. 2011
PU effect from 2.2 to 3e33: EGamma seeds
L1_TripleEG_8_8_5
L1_TripleEG_8_5_5
L1_TripleEG7
L1_TripleEG5
L1_DoubleEG_12_5_Eta1p39
L1_DoubleEG_12_5
L1_DoubleIsoEG10
L1_DoubleEG10
L1_DoubleEG5
L1_DoubleEG3
L1_SingleEG30
L1_SingleEG20
L1_SingleEG15
L1_SingleEG12
L1_SingleEG22
L1_SingleEG18
L1_SingleIsoEG12_Eta2p17
L1_SingleIsoEG12
L1_SingleEG5
0.9
C.-E. Wulz
0.95
1
1.05
29
1.1
1.15
CMS Week, Sep. 2011
1.2
PU effect from 2.2 to 3e33: Muon seeds (note: also GMT changes)
L1_TripleMu0
L1_DoubleMu_5_Open
L1_DoubleMu0_HighQ_EtaCuts
L1_DoubleMu0_HighQ
L1_DoubleMu5
L1_DoubleMu3p5
L1_DoubleMu3
L1_DoubleMu0
L1_SingleMu25
L1_SingleMu20
L1_SingleMu16_Eta2p1
L1_SingleMu16
L1_SingleMu14_Eta2p1
L1_SingleMu12_Debug
L1_SingleMu12
L1_SingleMu10
L1_SingleMu7
L1_SingleMu5_Eta1p5_Q80
L1_SingleMu3
L1_SingleMuOpen
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Recent GMT changes increased the muon rates in latest runs.
Hence the rate ratios do not correspond only to the PU effect.
C.-E. Wulz
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CMS Week, Sep. 2011
1.6
PU effect from 2.2 to 3e33: Global Sums
L1_ETT220
L1_HTM50
L1_HTT75
L1_HTT150
L1_HTT100
L1_HTT50
L1_ETM70
L1_ETM50
L1_ETM30
L1_ETM20
L1_ETM100
0
C.-E. Wulz
0.2
0.4
0.6
0.8
31
1
1.2
1.4
CMS Week, Sep. 2011
1.6
"PU effect from 2.2 to 3e33: Cross-triggers"
L1_HTT50_HTM50
L1_HTT50_HTM30
L1_Jet52_Central_ETM30
L1_Mu10_Jet36_Central
L1_Mu7_Jet20_Central
L1_Mu3_Jet28_Central
L1_Mu3_Jet20_Central
L1_Mu3_Jet16_Central
L1_Mu0_HTT75
L1_Mu0_HTT50
L1_Mu10_Eta2p1_DoubleJet_16_8_Central
L1_ETT300_EG5
L1_DoubleEG5_HTT75
L1_DoubleEG5_HTT50
L1_EG5_HTT125
L1_EG5_HTT100
L1_EG5_HTT75
L1_EG5_DoubleJet20_Central
L1_EG18_ForJet16
L1_MuOpen_DoubleEG5
L1_DoubleMuOpen_EG5
L1_Mu12_EG5
L1_Mu7_EG5
L1_Mu5_EG12
L1_MuOpen_EG12
L1_Mu3_EG5
0
C.-E. Wulz
0.2
0.4
0.6
32
0.8
1
1.2
1.4
1.6
CMS Week, Sep. 2011
1.8