francesca sarri, infn e università di pisa mcws, 25/10/2006 lnf 1 tau/jet/e t miss triggers in...
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1Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
TAU/JET/ETAU/JET/ETTMISSMISS
TRIGGERS IN ATLASTRIGGERS IN ATLAS
2Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
OUTLINEOUTLINE
Tau/Jet/ETMISS trigger description :
what is in the TDR and what is new.
An example of an analysis : optimization of tau and ET
MISS triggers for W at L=1031-32
3Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
TAU/JET/ETAU/JET/ETTMISSMISS SOURCES AND SOURCES AND
INTEREST FOR PHYSICSINTEREST FOR PHYSICS
• Standard Model: – inclusive Wτν (Zττ) production – QCD.
• SM and MSSM Higgs: – 100-150 GeV SM Higgs: qqH(ττ)– A/H ττ– H+ τν (mH+ < mtop and mH+ > mtop)
• SUSY • Compositness
4Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
The ATLAS triggerThe ATLAS trigger
Level 1 (hardware):Defines Regions of Interest (RoI).Uses Calo cells and Muon chambers with reduced granularity.e/, jet candidates.
Level 2 (software):Seeded by LVL1 RoI.Full granularity of the detectorPerforms calo-track matching
Event Filter (software):Offline-like algorithms.Refines LVL2 decisionFull event building
~200 Hz
~2 kHz
2s
10ms
1s
<75(100) kHz
Exe
cutio
n tim
e
TIER 0 mass storage
High Level Trigger
5Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
LVL1 Trigger Rates LVL1 Trigger Rates
Selection at 2x1033 cm-2 s-1 Rates (KHz)MU20 0.8
2MU6 0.2
EM25I 12.0
2EM15I 4.0
J200 0.2
3J90 0.2
4J65 0.2
J60+xE60 0.4
TAU25+xE30 2.0
MU10+EM15I 0.1
OTHERS (pre-Scales,calibration,…)
5.0
TOTAL 25
6Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
HIGH LEVEL TRIGGER RATESHIGH LEVEL TRIGGER RATESSelection Physics coverage 2x1033 cm-2s-1 Rates
(Hz)
ElectronHiggs, new gauge bosons, extra dim., SUSY, W/Z, top
e25i, 2e15i ~40
PhotonHiggs, SUSY, extra dim.
60i, 220i ~40
Muon
Higgs, new gauge bosons, extra dim., SUSY, W/Z, top, B-Physics
m20i, 2m102m6 with mB /mJ/
~50
JetsSUSY, compositness, resonances
j400, 3j165, 4j110 ~25
Jet & ETmiss SUSY, leptoquarks j70 + xE70 ~20
tau & ETmiss
Extended Higgs models (e.g. MSSM), SUSY
35 + xE45 ~5
Otherspre-scales, calibration, …
~20
Total ~200
The rates for the HLT taken considering the EF performances equal to those one of the OFFLINE.
7Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
LVL1 CALORIMETRIC SIGNAL PROCESSINGLVL1 CALORIMETRIC SIGNAL PROCESSING
TAU/JET/ETAU/JET/ETTMISSMISS triggers are calorimetric but they use triggers are calorimetric but they use
two different processorstwo different processors
8Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
TAU TRIGGERTAU TRIGGER
9Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Hadronic Tau Trigger (I)Hadronic Tau Trigger (I) (ATL-COM-DAQ-2003-030)
LVL1 trigger: look at 4X4 matrix of calorimetric towers ( = 0.1 x 0.1 each trigger tower).ET threshold for the central core (EM+Had) and isolation thresholds between core and 12 external towers for e.m. and had. calorimeters.
+ track multiplicity in the RoI
second layer of EM calorimeter
LVL2 trigger: look at the shower shape in the 2nd layer of e.m. calorimeter and at the track multiplicity inside the RoI defined at LVL1.Cut on the ratio between ET contained in a 3x7 cell cluster and ET in a 7x7 cell cluster and on track multiplicity
For | |<2.5as in the TDR
10Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Hadronic Tau Trigger (II)Hadronic Tau Trigger (II) (ATL-COM-DAQ-2003-030)
LVL3 (Event Filter) :look at the complete event.The variables of the offline algorithms are used as an approximation of the LVL3 trigger five variables:number of reconstructed tracks, within R = 0.3 of the candidate calorimeter cluster, between 1 and 3; cut on isolation fraction, defined as the difference between the ET contained in a cone size of R=0.2 and 0.1 normalized to the total jet ET;cut on EM jet radius, an energy weighted radius calculated only in the e.m. calorimeter ;cut on EM energy fraction, defined as the fraction of the total jet energy in the e.m. calorimeter;threshold on the pT of the highest pT track.
as in the TDR
11Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
EFFECT OF TRIGGER SELECTIONSEFFECT OF TRIGGER SELECTIONSET core EM iso HAD iso
12Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
TAU TRIGGER EVOLUTIONTAU TRIGGER EVOLUTION
) from EMSamp2 Calo variables (more variables used
than in the TDR)
Tracking
(# of tracks, charge,…)
Final decision : matching of cluster and tracks, energy estimate
LVL2 : Calorimeter based approach
Perform tracking
and obtain
Calorimeter variables
Final decision : matching of cluster and tracks, energy estimate with energy flow
LVL2 :Tracking based approach
New:studied for Very Low
Lumi 1031 cm-2 s-1
Current approach
For the LVL1 different RoI sizes are under study (timing, resolution and efficiency,…)
Under developing an EF tracking based
algorithm.
13Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
JET AND EJET AND ETTMISSMISS
TRIGGERTRIGGER
14Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
• identify hadronic jets using calorimetric data;• classify them according to ET;• provide multiplicity of jets passing required threshold;• provide the coordinates of the candidates to the LVL2;• have an energy resolution as good as possible for high ET and low ET jets.
JET ELEMENT : = 0.2 x 0.2 (now only one sample in depth)
Algorithm :- 2x2 jet element cluster (0.4x0.4) to identify a jet RoI, it is a local ET maximum.- 4x4 jet element (or 3x3 or 2x2) trigger cluster to measure the jet ET.
Trigger cluster size : -big enough to have a good energy
resolution for high ET jets (containment)-not too big for low ET jets (noise and
pileup)RoI size and step size :
-spatial resolution and jet separation.
For | |<3.2
LVL1 JET TRIGGER LVL1 JET TRIGGER as in the TDR
15Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
ROIROI
L2L2JetJet JetJet
Cone SizeCone Size
several iterations needed: several iterations needed: timing is an important timing is an important key.key.
LVL2 JET RECONSTRUCTION LVL2 JET RECONSTRUCTION LVL2 starts from LVL1 RoI information (, φ location) Iterative cone algorithm (R=0.4) to calculate weighted , φ energy center. Possible granularities : cell-based, LVL1 trigger towers,….
Jet calibration (energy scale and resolution) has an important effect on trigger efficiency.
16Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
JETS AT THE EVENT FILTERJETS AT THE EVENT FILTER
Results of the study:
Jet reconstruction is better with a higher size of RoI,
Higher size of RoI requires more time,
Topological clusters are faster than calorimeter towers but Towers reconstruct better pT of jets
Study of jet reconstruction at the EF : Size of Region of Interest (RoI):
16 (0.4x0.4), 32 (0.8x0.8), 64 (1.6x1.6) Different types of clusters:
topological clusters or calorimeter towers Algorithms:
Fast KT, Cone
Dijets samples with 35 GeV < PT < 1120 GeV
17Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
EETTMISSMISS TRIGGER TRIGGER
ETMISS is a global variable.
LVL1 : Calorimeter energies summed into a map with a granularity = 0.2 x 0.2. Ex, Ey, ET, ET
MISS are computed.
ETMISS trigger is not a standalone trigger, but it will be
used in association with jet or tau trigger.
Rapidity coverage : critical for ETMISS trigger
performances.
For ||<5
Rapidity coverage
Mean value of ET
MISS
All 0.9 GeV
|| < 5 5.6 GeV
|| < 4 8.8 GeV
|| < 3 12.5 GeV
as in the TDR
For QCD events :
trig
ger
rate
(K
Hz)
ETMISS (GeV)
18Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
LVL2 possible strategy:
• Based on LVL1 Missing ET “ROI” (with scalar ET, ΣEx, ΣEy)
• Based on LVL1 Jet ROIs - Use cell data for each RoI• Based on Trigger Towers: - Refine with better calibration and replace saturated
towers• For all the above, add muons
Possible Strategies for EPossible Strategies for ETTMISSMISS Trigger at Trigger at
LVL2 and EFLVL2 and EF
EF possible strategy:
• Using FEB header ΣEX, ΣEY from RODs
• Using full cell data.• For both of these, add muons.
19Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Algorithms for Tau/Jet/ETMISS triggers are still under
development : not a final decision taken.
ATLAS physics groups have started now to include trigger information in the simulations to perform analysis : a trigger part to perform a Trigger Aware Analysis has been added in the last releases of the ATLAS software.
The Tau Trigger slice is going to be added now : no analysis available with the “true” simulation of the tau trigger.
Trigger effects can be emulated : next slides will show an analysis.
20Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
““Trigger aware analysis”Trigger aware analysis” from user perspectivefrom user perspective
Trigger Trigger optimizationoptimization and and prospectsprospects for W for W with 100 with 100 pbpb-1-1 (few weeks of data taking (few weeks of data taking at very low luminosity 10at very low luminosity 103131-10-103232 cm cm--
22ss-1-1 ) )Data samples:18 000 events W 124000 dijet events (J1-J2-J3)For topological studies ~10^8 events from fast simulation
Daniel Froidevaux and Elzbieta Richter-Was
21Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Why W Why W ? ? Extract signal for most abundant source of -leptons as early
as possible. This requires a performant and ETmiss trigger
from the very start! For L = 2 1033, baseline plan is to trigger on 25I + XE30 at
LVL1 (for a rate of about 2 kHz) and to raise the thresholds to 35i + xE45 at the HLT (for an output rate of about 5 Hz) .
Measurment of W / W e to confirm good understanding of trigger/reco/identification efficiencies
E/p measurement in single-prong decay for calorimeter calibration.
Assumed that trigger chain is fully operational and that the detector operates more or less as expected (especially in terms of ET
miss performance).
Expected rates for 100 pb-1
W hadron
W e Z hadron
.B (pb) 11200 17300 1500
30i + xE35
~ 15000 ~ 250000 ~ 1300
20i + xE25
~ 60000 ~ 560000 ~ 3500
Efficiencies of ~ 80% for the trigger and of ~ 50% for the id/reco of hadronic decays were assumed.
22Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Algorithm to “emulate” LVL1 Algorithm to “emulate” LVL1 triggertrigger
seed “RoI” with topo-clusters, accept if ET > 5 GeV
calculate energy in 2x2 and 4x4 towers of 0.1x0.1 (x)
noise subtraction not applied, cells with negative energy suppressed from enegy counting
energy in HAD (originaly at EM scale) multiplied by 1.25
remove overlapping “RoI” with iterative procedure, imposing separation by R > 0.3
missing energy taken from ”uncalibrated calo off-line”.
23Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
More on LVL1-like RoI’sMore on LVL1-like RoI’sL1 towermultiplicity
multiplicity
<<> = 1.5
multiplicity
<> = 0.78
Total QCD
ET spectrum
signal
ET spectrum R between RoI’s
R between RoI’s
24Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Energy resolution for signal RoI and Energy resolution for signal RoI and threshold efficiency threshold efficiency
Threshold: 0.75 * 20 GeV90% efficient at ET
visible = 20 GeV
2x2 RoI
4x4 RoI
25Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Energy resolution for background RoI Energy resolution for background RoI anand d threshold efficiencythreshold efficiency
Threshold: 0.75 * 20 GeVFactor 10 rejection at ET
visible = 20 GeV
2x2 RoI
4x4 RoI
2x2 RoI
26Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Isolation for EMTau RoIIsolation for EMTau RoI
QCDsignal
1. ETL1otherEM/ET
L1core < 1.02. ET
L1otherHAD/ETL1core < 0.25
3. ETL1core/ET
L1tower > 0.54. ET
L1otherEM/ETL1coreEM < 1.0
5. ETL1otherHad/ET
L1coreHad < 1.0
L1core = 2x2L1tower = 4x4
Full cirles: with threshold ET
L1tower > 0.75 * 20 GeV
Isolation very loose .... Factor 5 rejection at 80% efficiency but almost no improvement if ET threshold added.
27Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
More on EMore on ETTmissmiss : we have only off-line : we have only off-line
availableavailable
truth
off-line
Atlfast
ETmiss is calculated at EM scale, from calo only.
ETmiss, ET
MissFinal, ETTruthNonInt, ET
MissAtlfast
28Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
LVL1 trigger: “ ET
L1tower 20 GeV Isol + ETmiss 20 GeV ”
( this means ETL1tower 0.75 * 20 GeV and isol_1+ isol_2 )
Rates: 0.02 Hz signal 2* 105 events for 100pb-1
60 Hz QCD bgd S/B ~ 0.0003
Concluding on LVL1-like selectionConcluding on LVL1-like selection
Isolation criteria rather weak. We use ET
miss from uncalibrated calo at EM scale...
L=10^31
29Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
The LVL2 like selection:The LVL2 like selection:explore track-seeded reconstructionexplore track-seeded reconstruction
Algorithm for tauL2 : start from track with pT > 9 GeV accept if no more than 2 associated tracks in R < 0.2 and pT > 2 GeV store info on “track quality” of leading track for futher discrimination build energy from simplified Eflow (energy overestimated by 10%-20%
mostly because noise not suppressed) calo identification variables from EM2 or all EM calo Same definition for ET
MISS as at LVL1
Signal response < >
= 1.16 = 0.17
Bgd response < > = 0.86 = 0.18
30Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Concluding on LVL2-like selectionConcluding on LVL2-like selection
LVL2 trigger:“ET
L2tower 20 GeV + track quality + id EM2 + id all Cal + ETmissFinal 20
GeV”
Rates: 0.01 Hz signal 105 signal events “on tape”for 100pb-1 5 Hz QCD bgd S/B ~ 0.002
Loose triger selection, now we have to supress bgd in off-line analysis
L=10^31
31Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Off-line analysisOff-line analysis
~ 10^8 QCD events in fine pTbins
ETmiss > 60 GeV gives bgd: rejection 10^3, signal: accept
10% -> still 10^4 evt for 100pb-1, S/B ~ 0.2 without refined tau indentification
Results with only fast-sim offline, ETmiss has no instrumental tails !
~ LVL2 thresh.~ LVL2 thresh.
We start offline analysis with S/B ~ 0.002 and predicted ~10^5 signal events “on tape”Need rejection ~ 10^3 for effic ~ 50% or increase ET
miss
thresholdHow fast bgd is supressed with the off-line ET
miss threshold.
32Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Now we can go back to plot from page Now we can go back to plot from page 2525::
Atlfast
Off-line60 GeV
33Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Verify what off-line tauid rejection is possible.... since some discriminantion power already explored when accepting LVL2 (calo+tracks) candidates.
We take tauL2 candidate “on tape” (after LVL2 tauiD) and check efficiency for matching tau1P, tau3P identified with PDE-RS optimisation (one MVA technique among many)
tau1P tau3PdiscriPDERS > 0.85 68% 6.5% 46% 3.0% 0.90 50% 3.5% 23% 1.0% 0.95 40% 1.0% 4% 0.2%
signal bgd signal bgdpT = 20 – 40 GeV
Now we can go back to full-sim samplesNow we can go back to full-sim samples
After L2 track-based trigger, discrimination fairly flat as function of pT
tau1p (tau3p) ; track-based offline algorithm to identify 1-prong (3-prong) tau decay.
34Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
SummarySummary:: LVL1 and LVL2 selection (calo+tracks) emulated for W analysis With rather soft selection ETmiss > 20 GeV + EMTauRoI > 20 GeV
estimated for 10^31: 60 Hz after LVL1 5 Hz after LVL2 For off-line analysis start with S/B ~ 0.002 ~ 10^5 signal events accepted for 100pb-1 Increasing ET
MISS threshold helps in the background rejection: at 60 GeV threshold, supression 10^2-10^3 at 10% efficiency. Offline tau selection has to do the final work to extract the
signal.
Low luminosity provides unique opportunity to study low energy hadronic signatures in ATLAS (in view of SUSY) : important possibility to verify the understanding of tauID and ET
MISS reco before attacking “New Physcics”.
35Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
BACKUP SLIDESBACKUP SLIDES
36Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Sistema calorimetrico di ATLAS
Tile CalorimetersTile Calorimeters
Electromagnetic Liquid Argon Calorimeters
Electromagnetic Liquid Argon Calorimeters
Forward Liquid Argon CalorimetersForward Liquid Argon Calorimeters
η=1.475
η=1.8
η=3.2
Hadronic Liquid Argon EndCap CalorimetersHadronic Liquid Argon EndCap Calorimeters
EM LAr || < 3 :
Pb/LAr 24-26 X0
3 sezioni longitudinali 1.2
= 0.025 0.025 – 1% equal.
Central Hadronic || < 1.7 :
Fe(82%)/scintillatore(18%)
3 sezioni longitudinali 7.2
= 0.1 0.1
End Cap Hadronic 1.7 < < 3.2 :
Cu/LAr – 4 sezioni longitudinali
< 0.2 0.2
Forward calorimeter 3 < < 4.9 :
EM Cu/LAr – HAD W/LAr
3 sezioni longitudinaliEE
8.1%8.1
%9.41
E
37Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Tau Trigger RateTau Trigger Rate
38Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
39Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
More on EMore on ETTmiss :miss : we have only off-line we have only off-line
availableavailable
40Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
S.Levy, HCP session, July 2005
41Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Signal and background at 14 TeVSignal and background at 14 TeV
cross-section (PYTHIA)
signal ~ 10 x higher QCD bgd ~ 102-103 x higherthan in CDF. ( ERW, ATL-PHYS-2000-023)
<> = 16.6 GeV
<> = 22.6 GeV
<> = 18.4 GeV
spectrum rather softfor ET
miss, pTvis
signal
signal
signal
(ATL-PHYS-2000-023)
42Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Results from past studiesResults from past studies (ATLAS) (ATLAS) E/p measurements for calibration of hadronic calorimeters
C. BiscaratCOM-CAL-99-0003
Rejection 70 340 2
280Hz rates predicted after HTL at 10^33
.trigger-like: ETmiss > 35 GeV + pTjet > 20 GeVpreselection: veto iso lepton, veto iso photontau-jet selection: track with pT> 30 GeVsingle-track: veto if extra tracks pT>1 GeV in tau conenarrow-jet: calo isolation
total id rejection: 10^5
Events for 100 pb-1: | 5270 W | 3630 W | 320 QCD jets (bb)
total id effic: ~ 25%
43Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Off-line analysis
We don’t have enough events to continue with full-sim samples.We have move to fast-sim samples to study topological selection onlyand to estimate how much bgd suppression is possible:
~ 10^8 QCD events in fine pTbins
44Francesca Sarri, INFN e Università di
Pisa
MCWS, 25/10/2006 LNF
Off-line analysis ~ 10^8 QCD events in fine pTbins
Vetoying any other jet‘a la CDF’ gives 30% accept for signal 25% acept for bgd
We have looked at few more distribributions.... nothing obvious to optimise on...
We started offline analysis with S/B ~ 0.002 and predicted ~10^5 signal events “on tape”
Need rejection ~ 10^3 for effic ~ 50%or increase ET
miss threshold