Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 1 TAU/JET/E T MISS TRIGGERS IN ATLAS

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 2 OUTLINE  Tau/Jet/E T MISS trigger description : what is in the TDR and what is new.  An example of an analysis : optimization of tau and E T MISS triggers for W  at L=

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 3 TAU/JET/E T MISS SOURCES AND INTEREST FOR PHYSICS Standard Model: –inclusive W  τν (Z  ττ) production –QCD. SM and MSSM Higgs: – GeV SM Higgs: qqH(ττ) –A/H  ττ –H +  τν (m H + m top ) SUSY Compositness

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 4 The 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 detector Performs calo-track matching Event Filter (software): Offline-like algorithms. Refines LVL2 decision Full event building ~200 Hz ~2 kHz 2s2s 10ms 1s <75(100) kHz Execution time TIER 0 mass storage High Level Trigger

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 5 LVL1 Trigger Rates Selection at 2x10 33 cm -2 s -1 Rates (KHz) MU MU60.2 EM25I12.0 2EM15I4.0 J J J650.2 J60+xE600.4 TAU25+xE302.0 MU10+EM15I0.1 OTHERS (pre-Scales,calibration,…)5.0 TOTAL  25

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 6 HIGH LEVEL TRIGGER RATES SelectionPhysics coverage2x10 33 cm -2 s -1 Rates (Hz) Electron Higgs, new gauge bosons, extra dim., SUSY, W/Z, top e25i, 2e15i ~40 PhotonHiggs, SUSY, extra dim.  60i, 2  20i ~40 Muon Higgs, new gauge bosons, extra dim., SUSY, W/Z, top, B-Physics m20i, 2m10 2m6 with m B /m J/  ~50 Jets SUSY, compositness, resonances j400, 3j165, 4j110 ~25 Jet & E T miss SUSY, leptoquarksj70 + xE70 ~20 tau & E T miss 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.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 7 LVL1 CALORIMETRIC SIGNAL PROCESSING TAU/JET/E T MISS triggers are calorimetric but they use two different processors

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 8 TAU TRIGGER

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 9 Hadronic Tau Trigger (I) Hadronic Tau Trigger (I) (ATL-COM-DAQ )   LVL1 trigger: look at 4X4 matrix of calorimetric towers (  = 0.1 x 0.1 each trigger tower). E T 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 E T contained in a 3x7 cell cluster and E T in a 7x7 cell cluster and on track multiplicity For |  |<2.5 as in the TDR

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 10 Hadronic Tau Trigger (II) Hadronic Tau Trigger (II) (ATL-COM-DAQ ) 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 E T contained in a cone size of  R=0.2 and 0.1 normalized to the total jet E T ;  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 p T of the highest p T track. as in the TDR

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 11 EFFECT OF TRIGGER SELECTIONS E T coreEM iso HAD iso

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 12 TAU 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 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.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 13 JET AND E T MISS TRIGGER

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 14 identify hadronic jets using calorimetric data; classify them according to E T ; 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 E T and low E T 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 E T maximum. - 4x4 jet element (or 3x3 or 2x2) trigger cluster to measure the jet E T. Trigger cluster size : -big enough to have a good energy resolution for high E T jets (containment) -not too big for low E T jets (noise and pileup) RoI size and step size : -spatial resolution and jet separation. For |  |<3.2 LVL1 JET TRIGGER as in the TDR

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 15 ROI L2 Jet Jet Cone Size several iterations needed: timing is an important key. 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.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 16 JETS 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 p T 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 < P T < 1120 GeV

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 17 E T MISS TRIGGER E T MISS is a global variable. LVL1 : Calorimeter energies summed into a map with a granularity  = 0.2 x 0.2. Ex, Ey, E T, E T MISS are computed. E T MISS trigger is not a standalone trigger, but it will be used in association with jet or tau trigger. Rapidity coverage : critical for E T MISS trigger performances. For |  |<5 Rapidity coverage Mean value of E T MISS All0.9 GeV |  | < 55.6 GeV |  | < 48.8 GeV |  | < GeV as in the TDR For QCD events : trigger rate (KHz) E T MISS (GeV)

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 18 LVL2 possible strategy: Based on LVL1 Missing E T “ROI” (with scalar E T, ΣE x, ΣE y ) 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 E T MISS Trigger at LVL2 and EF EF possible strategy: Using FEB header ΣE X, ΣE Y from RODs Using full cell data. For both of these, add muons.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 19 Algorithms for Tau/Jet/E T MISS 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.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 20 “Trigger aware analysis” from user perspective Trigger optimization and prospects for W  with 100 pb -1 (few weeks of data taking at very low luminosity cm -2 s -1 ) Data samples: events W   dijet events (J1-J2-J3) For topological studies ~10^8 events from fast simulation Daniel Froidevaux and Elzbieta Richter-Was

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 21 Why W  ?  Extract signal for most abundant source of  -leptons as early as possible. This requires a performant  and E T miss trigger from the very start! For L = , 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 E T miss performance). Expected rates for 100 pb -1 W    hadron W  e Z    hadron .B (pb)  30i + xE35 ~ 15000~ ~ 1300  20i + xE25 ~ 60000~ ~ 3500 Efficiencies of ~ 80% for the  trigger and of ~ 50% for the id/reco of  hadronic decays were assumed.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 22 Algorithm to “emulate” LVL1 trigger  seed “RoI” with topo-clusters, accept if E T > 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”.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 23 More on LVL1-like RoI’s L1 tower multiplicity < <> = 1.5 multiplicity <> = 0.78 Total QCD E T spectrum signal E T spectrum  R between RoI’s  R between RoI’s

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 24 Energy resolution for signal RoI and threshold efficiency Threshold: 0.75 * 20 GeV 90% efficient at E T visible = 20 GeV 2x2 RoI 4x4 RoI

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 25 Energy resolution for background RoI and threshold efficiency Threshold: 0.75 * 20 GeV Factor 10 rejection at E T visible = 20 GeV 2x2 RoI 4x4 RoI 2x2 RoI

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 26 Isolation for EMTau RoI QCD signal 1.E T L1otherEM /E T L1core < E T L1otherHAD /E T L1core < E T L1core /E T L1tower > E T L1otherEM /E T L1coreEM < E T L1otherHad /E T L1coreHad < 1.0 L1core = 2x2 L1tower = 4x4 Full cirles: with threshold E T L1tower > 0.75 * 20 GeV Isolation very loose.... Factor 5 rejection at 80% efficiency but almost no improvement if E T threshold added.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 27 More on E T miss : we have only off-line available truth off-line Atlfast E T miss is calculated at EM scale, from calo only. E T miss, E T MissFinal, E T TruthNonInt, E T MissAtlfast

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 28 LVL1 trigger: “ E T L1tower 20 GeV Isol + E T miss 20 GeV ” ( this means E T L1tower 0.75 * 20 GeV and isol_1+ isol_2 ) Rates: 0.02 Hz signal  2* 10 5 events for 100pb Hz QCD bgd S/B ~ Concluding on LVL1-like selection Isolation criteria rather weak. We use E T miss from uncalibrated calo at EM scale... L=10^31

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 29 The LVL2 like selection: explore track-seeded reconstruction Algorithm for tauL2 :  start from track with p T > 9 GeV accept if no more than 2 associated tracks in  R 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 E T MISS as at LVL1 Signal response = 1.16  = 0.17 Bgd response = 0.86  = 0.18

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 30 Concluding on LVL2-like selection LVL2 trigger: “E T L2tower 20 GeV + track quality + id EM2 + id all Cal + E T missFinal 20 GeV” Rates: 0.01 Hz signal  10 5 signal events “on tape”for 100pb -1 5 Hz QCD bgd S/B ~ Loose triger selection, now we have to supress bgd in off-line analysis L=10^31

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 31 Off-line analysis ~ 10^8 QCD events in fine p T bins E T miss > 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, E T miss has no instrumental tails ! ~ LVL2 thresh. We start offline analysis with S/B ~ and predicted ~10^5 signal events “on tape” Need rejection ~ 10^3 for effic ~ 50% or increase E T miss threshold How fast bgd is supressed with the off-line E T miss threshold.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 32 Now we can go back to plot from page 25: Atlfast Off-line 60 GeV

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 33 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 tau3P discriPDERS > % 6.5% 46% 3.0% % 3.5% 23% 1.0% % 1.0% 4% 0.2% signal bgd signal bgd pT = 20 – 40 GeV Now we can go back to full-sim samples After L2 track-based trigger, discrimination fairly flat as function of p T tau1p (tau3p) ; track-based offline algorithm to identify 1-prong (3-prong) tau decay.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 34 Summary:  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 ~ ~ 10^5 signal events accepted for 100pb-1 Increasing E T 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 E T MISS reco before attacking “New Physcics”.

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 35 BACKUP SLIDES

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 36 Sistema calorimetrico di ATLAS Tile Calorimeters Electromagnetic Liquid Argon Calorimeters Forward Liquid Argon Calorimeters η=1.475 η=1.8 η=3.2 Hadronic Liquid Argon EndCap Calorimeters EM LAr |  | < 3 : Pb/LAr X 0 3 sezioni longitudinali 1.2  =  – 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 longitudinali

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 37 Tau Trigger Rate

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 38

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 39 More on E T miss : we have only off-line available

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 40 S.Levy, HCP session, July 2005

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 41 Signal and background at 14 TeV cross-section (PYTHIA) signal ~ 10 x higher QCD bgd ~ x higher than in CDF. ( ERW, ATL-PHYS ) <> = 16.6 GeV <> = 22.6 GeV <> = 18.4 GeV spectrum rather soft for E T miss, p T vis signal (ATL-PHYS )

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 42 Results from past studies (ATLAS) E/p measurements for calibration of hadronic calorimeters C. Biscarat COM-CAL Rejection Hz rates predicted after HTL at 10^33.trigger-like: ETmiss > 35 GeV + pTjet > 20 GeV preselection: veto iso lepton, veto iso photon tau-jet selection: track with p T > 30 GeV single-track: veto if extra tracks p T >1 GeV in tau cone narrow-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%

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 43 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 only and to estimate how much bgd suppression is possible: ~ 10^8 QCD events in fine p T bins

Francesca Sarri, INFN e Università di Pisa MCWS, 25/10/2006 LNF 44 Off-line analysis ~ 10^8 QCD events in fine p T bins 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 ~ and predicted ~10^5 signal events “on tape” Need rejection ~ 10^3 for effic ~ 50% or increase E T miss threshold