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Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 1 Triggering CMS Wesley H. Smith U. Wisconsin – Madison CMS Trigger Coordinator.

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Presentation on theme: "Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 1 Triggering CMS Wesley H. Smith U. Wisconsin – Madison CMS Trigger Coordinator."— Presentation transcript:

1 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 1 Triggering CMS Wesley H. Smith U. Wisconsin – Madison CMS Trigger Coordinator Seminar, Texas A&M April 20, 2011 Outline: Introduction to CMS Trigger Challenges & Architecture Level -1 Trigger Implementation & Performance Higher Level Trigger Algorithms & Performance The Future: SLHC Trigger

2 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 2 LHC Collisions

3 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 3 LHC Physics & Event Rates At design L = cm -2 s pp events/25 ns xing ~ 1 GHz input rate “Good” events contain ~ 20 bkg. events 1 kHz W events 10 Hz top events < 10 4 detectable Higgs decays/year Can store ~ 300 Hz events Select in stages Level-1 Triggers 1 GHz to 100 kHz High Level Triggers 100 kHz to 300 Hz

4 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 4 Collisions (p-p) at LHC Event size: ~1 MByte Processing Power: ~X TFlop All charged tracks with pt > 2 GeV Reconstructed tracks with pt > 25 GeV Operating conditions: one “good” event (e.g Higgs in 4 muons ) + ~20 minimum bias events) Event rate

5 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 5 CMS Detector Design MUON BARREL CALORIMETERS Pixels Silicon Microstrips 210 m 2 of silicon sensors 9.6M channels ECAL 76k scintillating PbWO4 crystals Cathode Strip Chambers (CSC) Resistive Plate Chambers (RPC) Drift Tube Chambers (DT) Resistive Plate Chambers (RPC) Superconducting Coil, 4 Tesla IRON YOKE TRACKER MUON ENDCAPS HCAL Plastic scintillator/brass sandwich Today: RPC |η| < 1.6 instead of 2.1 & 4th endcap layer missing Level-1 Trigger Output Today: 50 kHz (instead of 100)

6 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 6 LHC Trigger & DAQ Challenges Computing Services 16 Million channels ChargeTimePattern 40 MHz COLLISION RATE kHz 1 MB EVENT DATA 1 Terabit/s READOUT 50,000 data channels 200 GB buffers ~ 400 Readout memories 3 Gigacell buffers 500 Gigabit/s 5 TeraIPS ~ 400 CPU farms Gigabit/s SERVICE LAN Petabyte ARCHIVE EnergyTracks 300 Hz FILTERED EVENT EVENT BUILDER. A large switching network ( ports) with total throughput ~ 400Gbit/s forms the interconnection between the sources (deep buffers) and the destinations (buffers before farm CPUs). EVENT FILTER. A set of high performance commercial processors organized into many farms convenient for on-line and off-line applications. SWITCH NETWORK LEVEL-1 TRIGGER DETECTOR CHANNELS Challenges: 1 GHz of Input Interactions Beam-crossing every 25 ns with ~ 23 interactions produces over 1 MB of data Archival Storage at about 300 Hz of 1 MB events

7 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 7 Level 1 Trigger Operation

8 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 8 CMS Trigger Levels

9 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 9 L1 Trigger Locations Underground Counting Room Central rows of racks for trigger Connections via high- speed copper links to adjacent rows of ECAL & HCAL readout racks with trigger primitive circuitry Connections via optical fiber to muon trigger primitive generators on the detector Optical fibers connected via “tunnels” to detector (~90m fiber lengths) Rows of Racks containing trigger & readout electronics 7m thick shielding wall USC55

10 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 10 CMS Level-1 Trigger & DAQ Overall Trigger & DAQ Architecture: 2 Levels: Level-1 Trigger: 25 ns input 3.2 μs latency Interaction rate: 1 GHz Bunch Crossing rate: 40 MHz Level 1 Output: 100 kHz (50 initial) Output to Storage: 100 Hz Average Event Size: 1 MB Data production 1 TB/day UXC   USC

11 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 11 CMS Calorimeter Geometry EB, EE, HB, HE map to 18 RCT crates Provide e/  and jet,  E T triggers 1 trigger tower (.087  ✕.087  ) = 5 ✕ 5 ECAL xtals = 1 HCAL tower 2 HF calorimeters map on to 18 RCT crates Trigger towers: Δη = Δ ϕ = 0.087

12 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 12 ECAL Endcap Geometry Map non-projective x-y trigger crystal geometry onto projective trigger towers: Individual crystal 5 x 5 ECAL xtals ≠ 1 HCAL tower in detail +Z Endcap -Z Endcap

13 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 13 Calorimeter Trig. Processing Trigger Tower 25 Xtals (TT) TCC (LLR) CCS (CERN) SRP (CEA DAPNIA) DCC (LIP) TCSTTC Trigger Mbits/s OD DA kHz L1 Global TRIGGER Regional CaloTRIGGER Trigger Tower Flags (TTF) Selective Readout Flags (SRF) SLB (LIP) Data (Xtal Datas) Trigger Concentrator Card Synchronisation & Link Board Clock & Control System Selective Readout Processor Data Concentrator Card Timing, Trigger & Control Trigger Control System Level 1 Trigger (L1A) From : R. Alemany LIP

14 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 14 Calorimeter Trig.Overview (located in underground counting room) Calorimeter Electronics Interface Regional Calorimeter Trigger Receiver Electron Isolation Jet/Summary Global Cal. Trigger Sorting, E T Miss, ΣE T Global Trigger Processor Global Muon Trigger Iso Mu MinIon Tag Lumi- nosity Info. 4K 1.2 Gbaud serial links w/ 2 x (8 bits E/H/FCAL Energy + fine grain structure bit) + 5 bits error detection code per 25 ns crossing US CMS HCAL: BU/FNAL/ Maryland/ Princeton CMS ECAL: Lisbon/ Palaiseau US CMS: Wisconsin Bristol/CERN/Imperial/LANL CMS: Vienna 72  ✕ 60  H/ECAL Towers (.087  ✕.087  for  < 2.2 & ,  >2.2) HF: 2 ✕ (12  ✕ 12  ) Copper 80 MHz Parallel 4 Highest E T : Isolated & non-isol. e/  Central, forward,  jets, E x, E y from each crate MinIon & Quiet Tags for each 4  ✕ 4  region GCT Matrix μ + Q bits IC/LANL/UW

15 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 15 ECAL Trigger Primitives Test beam results (45 MeV per xtal):

16 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 16 CMS Electron/Photon Algorithm

17 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 17 CMS  / Jet Algorithm

18 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 18 L1 Cal. Trigger Synchronization BX ID Efficiency – e/ γ & Jets Sample of min bias events, triggered by BSC coincidence, with good vertex and no scraping Fraction of candidates that are in time with bunch-crossing (BPTX) trigger as function of L1 assigned E T Anomalous signals from ECAL, HF removed Noise pollutes BX ID efficiency at low E T values e/γ Jet/τ Forward Jet

19 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 19 L1 efficiency for electrons Sample of ECAL Activity HLT triggers (seeded by L1 ZeroBias) Anomalous ECAL signals removed using standard cuts EG trigger efficiency for electrons from conversions Standard loose electron isolation & ID Conversion ID (inverse of conversion rejection cuts) to select electron-like objects Efficiency shown w.r.t E T of the electron supercluster, for L1 threshold of 5 GeV (top), 8 GeV (bottom) Two η ranges shown: Barrel (black), endcaps (red) L1_EG5 L1_EG8 With RCT Correction

20 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 20 Jet Trigger Efficiency n minimum-bias trigger n jet energy correction: online / offline match n turn-on curves steeper

21 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 21 Reduced RE system |  | < ME4/1 MB1 MB2 MB3 MB4 ME1 ME2 ME3 *Double Layer *RPC Single Layer CMS Muon Chambers

22 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 22 Muon Trigger Overview |η| < 1.2|η| < < |η||η| < 2.1 |η| < 1.6 in 2009 Cavern: UXC55 Counting Room: USC55

23 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 23 CMS Muon Trigger Primitives Memory to store patterns Fast logic for matching FPGAs are ideal

24 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 24 CMS Muon Trigger Track Finders Memory to store patterns Fast logic for matching FPGAs are ideal Sort based on P T, Quality - keep loc. Combine at next level - match Sort again - Isolate? Top 4 highest P T and quality muons with location coord. Match with RPC Improve efficiency and quality

25 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 25 DT L1 Muon Trigger Synchronization BX ID Efficiency – CSC, DT, RPC All muon trigger timing within ± 2 ns, most better & being improved RPC CSC  Log Plot

26 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 26 L1 Muon Efficiency vs. p T 01/04/2011 Barrel EndCap OverLap L1_Mu7 L1_Mu10 L1_Mu12 L1_Mu20

27 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 27 CMS Global Trigger

28 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 28 Global L1 Trigger Algorithms

29 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 29 “Δelta” or “correlation” conditions Unique Topological Capability of CMS L1 Trigger separate objects in η & Φ: Δ ≥ 2 hardware indices ϕ : Δ ≥ degrees Present Use: e γ / jet separation to avoid triggering twice on the same object in a correlation trigger objects to be separated by one empty sector (20 degrees)

30 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 30 High Level Trigger Strategy

31 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 31 All processing beyond Level-1 performed in the Filter Farm Partial event reconstruction “on demand” using full detector resolution High-Level Trig. Implementation 8 “slices”

32 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 32 Start with L1 Trigger Objects Electrons, Photons,  -jets, Jets, Missing E T, Muons HLT refines L1 objects (no volunteers) Goal Keep L1T thresholds for electro-weak symmetry breaking physics However, reduce the dominant QCD background From 100 kHz down to 100 Hz nominally QCD background reduction Fake reduction: e ±,  Improved resolution and isolation:  Exploit event topology: Jets Association with other objects: Missing E T Sophisticated algorithms necessary Full reconstruction of the objects Due to time constraints we avoid full reconstruction of the event - L1 seeded reconstruction of the objects only Full reconstruction only for the HLT passed events

33 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 33 Electron & Photon HLT “Level-2” electron: Search for match to Level-1 trigger 1-tower margin around 4x4-tower trig. region Bremsstrahlung recovery “super-clustering” Road along  — in narrow η-window around seed Collect all sub-clusters in road η “super-cluster” Select highest E T cluster Calorimetric (ECAL+HCAL) isolation “Level-3” Photons Tight track isolation “Level-3” Electrons Electron track reconstruction Spatial matching of ECAL cluster and pixel track Loose track isolation in a “hollow” cone basic cluster super-cluster

34 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 34 “Tag & probe” HLT Electron Efficiency Use Z mass resonance to select electron pairs & probe efficiency of selection Tag: lepton passing very tight selection with very low fake rate (<<1%) Probe: lepton passing softer selection & pairing with Tag object such that invariant mass of tag & probe combination is consistent with Z resonance Efficiency = Npass/Nall Npass → number of probes passing the selection criteria Nall → total number of probes counted using the resonance BarrelEndcap The efficiency of electron trigger paths in 2010 data reaches 100% within errors Electron (ET Thresh>17 GeV) with Tighter Calorimeter-based Electron ID+Isolation at HLT

35 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 35 Muon HLT & L1 Efficiency Both isolated & non-isolated muon trigger shown Efficiency loss is at Level-1, mostly at high-η Improvement over these curves already done Optimization of DT/CSC overlap & high-η regions

36 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 36 Jet HLT Efficiency Jet efficiencies calculated Relative to a lower threshold trigger Relative to an independent trigger Jet efficiencies plotted vs. corrected offline reco Anti-k T jet energy Plots are from 2011 run HLT_Jet370 Barrel Endcap All HLT_Jet240 Barrel Endcap All

37 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 37 Summary of Current Physics Menu (5E32) by Primary Dataset Jet Single Jet, DiJetAve,MultiJet QuadJet, ForwardJets, Jets+Taus HT Misc. hadronic SUSY triggers METBtag MET triggers, Btag POG triggers SingleMu Single mu triggers (no had. requirement) DoubleMu Double mu trigger (no had. requirement) SingleElectron Single e triggers (no had. requirement) DoubleElectron Double e triggers (no had requirement) Photon Photons (no had. requirement) MuEG Mu+photon or ele (no had. requirement) ElectronHad electrons + had. activity PhotonHad Photons + had. activity MuHad Muons + had. activity Tau Single and Double taus TauPlusX X-triggers with taus MuOnia J/psi, upsilon + Commisioning, Cosmics, MinimumBias Expected rate of each PD is E32 Writing a total of O(360) Hz. (Baseline is 300 Hz)

38 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 38 Trigger Rates in 2011 Trigger rate predictions based mostly on data. Emulation of paths via OpenHLT working well for most of trigger table Data collected already w/ sizeable PU (L=2.5E32 → PU~7) Allows linear extrapolation to higher luminosity scenarios Emulated & Online Rates: Agreement to ≲ 30%, data-only check of measured rate vs. separate emulation

39 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 39 Approx. evolution for some triggers L=5E32 Single Iso Mu ET: 17 GeV Single Iso elec ET: 27 GeV Double Mu ET: 6, 6 GeV Double Elec ET: 17, 8 GeV e+mu ET: 17,8 & 8,17 GeV Di-photon: 26, 18 GeV e/mu + tau: 15, 20 GeV HT: 440 GeV HT+MHT: 520 GeV L=2E33 Single Iso Mu ET: 30 GeV Single Iso elec ET: 50 GeV Double Mu ET: 10,10 GeV Double Elec ET: 17, 8 GeV* e+mu ET: 17,8 & 8,17 GeV* Di-photon: 26, 18 GeV* e/mu + tau: 20, GeV HT: HT+MHT: Targeted rate of each line is ~10-15 Hz. Overall menu has many cross triggers for signal and prescaled triggers for efficiencies and fake rate measurements as well * Tighter ID and Iso conditions, still rate and/or efficiency concerns Possibly large uncertainty due to pile-up

40 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 40 HLT at 1E33 Total is 400 Hz

41 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 41 Prescale set used: 2E32 Hz/cm² Sample: MinBias L1-skim 5E32 Hz/cm² with 10 Pile-up Unpacking of L1 information, early-rejection triggers, non-intensivetriggers Mostly unpacking of calorimeter info. to form jets, & some muon triggers Triggers with intensive tracking algorithms Overflow: Triggers doing particle flow reconstruction (esp. taus) Total HLT Time Distribution

42 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 42 Extension-1 of HLT Farm – 2011

43 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 43 Future HLT Upgrade Options

44 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 44 Requirements for LHC phases of the upgrades: ~ Phase 1: Goal of extended running in second half of the decade to collect ~100s/fb 80% of this luminosity in the last three years of this decade About half the luminosity would be delivered at luminosities above the original LHC design luminosity Trigger & DAQ systems should be able to operate with a peak luminosity of up to 2 x Phase 2: Continued operation of the LHC beyond a few 100/fb will require substantial modification of detector elements The goal is to achieve 3000/fb in phase 2 Need to be able to integrate ~300/fb-yr Will require new tracking detectors for ATLAS & CMS Trigger & DAQ systems should be able to operate with a peak luminosity of up to 5 x 10 34

45 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 45 Detector Luminosity Effects H→ZZ → μμee, M H = 300 GeV for different luminosities in CMS cm -2 s cm -2 s cm -2 s cm -2 s -1

46 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 46 CMS Upgrade Trigger Strategy Constraints Output rate at 100 kHz Input rate increases x2/x10 (Phase 1/Phase 2) over LHC design (10 34 ) Same x2 if crossing freq/2, e.g. 25 ns spacing → 50 ns at Number of interactions in a crossing (Pileup) goes up by x4/x20 Thresholds remain ~ same as physics interest does Example: strategy for Phase 1 Calorimeter Trigger (operating 2016+): Present L1 algorithms inadequate above or w/ 50 ns spacing Pileup degrades object isolation More sophisticated clustering & isolation deal w/more busy events Process with full granularity of calorimeter trigger information Should suffice for x2 reduction in rate as shown with initial L1 Trigger studies & CMS HLT studies with L2 algorithms Potential new handles at L1 needed for x10 (Phase 2: 2020+) Tracking to eliminate fakes, use track isolation. Vertexing to ensure that multiple trigger objects come from same interaction Requires finer position resolution for calorimeter trigger objects for matching (provided by use of full granularity cal. trig. info.)

47 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 47 Phase 1 Upgrade Cal. Trigger Algorithm Development Particle Cluster Finder Applies tower thresholds to Calorimeter Creates overlapped 2x2 clusters Cluster Overlap Filter Removes overlap between clusters Identifies local maxima Prunes low energy clusters Cluster Isolation and Particle ID Applied to local maxima Calculates isolation deposits around 2x2,2x3 clusters Identifies particles Jet reconstruction Applied on filtered clusters Groups clusters to jets Particle Sorter Sorts particles & outputs the most energetic ones MET,HT,MHT Calculation Calculates Et Sums, Missing Et from clusters

48 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 48 Upgrade Algorithm Performance: Factor of 2 for Phase I Factor of 2 rate reduction Higher Efficiency Isolated electrons Taus Efficiency QCD Rate (kHz) Isolated electrons Taus Efficiency QCD Rate (kHz) Phase 1 Algorithm Present Algorithm Present Algorithm Present Algorithm Present Algorithm Phase 1 Algorithm

49 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 49 uTCA Calorimeter Trigger Demonstrators  processing cards with 160 Gb/s input & 100 Gb/s output using 5 Gb/s optical links. four trigger prototype cards integrated in a backplane fabric to demonstrate running & data exchange of calorimeter trigger algorithms 

50 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 50 CMS CSC Trigger Upgrades Improve redundancy Add station ME-4/2 covering  = Critical for momentum resolution Upgrade electronics to sustain higher rates New Front End boards for station ME-1/1 Forces upgrade of downstream EMU electronics Particularly Trigger & DAQ Mother Boards Upgrade Muon Port Card and CSC Track Finder to handle higher stub rate Extend CSC Efficiency into  = region Robust operation requires TMB upgrade, unganging strips in ME-1a, new FEBs, upgrade CSCTF+MPC ME4/2

51 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 51 CMS Level-1 Trigger  5x10 34 Occupancy Degraded performance of algorithms Electrons: reduced rejection at fixed efficiency from isolation Muons: increased background rates from accidental coincidences Larger event size to be read out New Tracker: higher channel count & occupancy  large factor Reduces the max level-1 rate for fixed bandwidth readout. Trigger Rates Try to hold max L1 rate at 100 kHz by increasing readout bandwidth Avoid rebuilding front end electronics/readouts where possible Limits:  readout time  (< 10 µs) and data size (total now 1 MB) Use buffers for increased latency for processing, not post-L1A May need to increase L1 rate even with all improvements Greater burden on DAQ Implies raising E T thresholds on electrons, photons, muons, jets and use of multi-object triggers, unless we have new information  Tracker at L1 Need to compensate for larger interaction rate & degradation in algorithm performance due to occupancy

52 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 52 CMS Level-1 Trigger  5x10 34 Occupancy Degraded performance of algorithms Electrons: reduced rejection at fixed efficiency from isolation Muons: increased background rates from accidental coincidences Larger event size to be read out New Tracker: higher channel count & occupancy  large factor Reduces the max level-1 rate for fixed bandwidth readout. Trigger Rates Try to hold max L1 rate at 100 kHz by increasing readout bandwidth Avoid rebuilding front end electronics/readouts where possible Limits:  readout time  (< 10 µs) and data size (total now 1 MB) Use buffers for increased latency for processing, not post-L1A May need to increase L1 rate even with all improvements Greater burden on DAQ Implies raising E T thresholds on electrons, photons, muons, jets and use of multi-object triggers, unless we have new information  Tracker at L1 Need to compensate for larger interaction rate & degradation in algorithm performance due to occupancy

53 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 53 Tracking needed for L1 trigger Muon L1 trigger rate Single electron trigger rate Isolation criteria are insufficient to reduce rate at L = cm -2.s L = L = 2x10 33 MHz Standalone Muon trigger resolution insufficient We need to get another x200 (x20) reduction for single (double) tau rate! Amount of energy carried by tracks around tau/jet direction (PU=100) Cone 10 o -30 o ~dE T /dcos  

54 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 54 The Track Trigger Problem Need to gather information from 10 8 pixels in 200m 2 of silicon at 40 MHz Power & bandwidth to send all data off-detector is prohibitive Local filtering necessary Smart pixels needed to locally correlate hit P t information Studying the use of 3D electronics to provide ability to locally correlate hits between two closely spaced layers

55 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS D Interconnection Key to design is ability of a single IC to connect to both top & bottom sensor Enabled by “vertical interconnected” (3D) technology A single chip on bottom tier can connect to both top and bottom sensors – locally correlate information Analog information from top sensor is passed to ROIC (readout IC) through interposer One layer of chips No “horizontal” data transfer necessary – lower noise and power Fine Z information is not necessary on top sensor – long (~1 cm vs ~1-2 mm) strips can be used to minimize via density in interposer

56 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 56 Track Trigger Architecture Readout designed to send all hits with P t >~2 GeV to trigger processor High throughput – micropipeline architecture Readout mixes trigger and event data Tracker organized into phi segments Limited FPGA interconnections Robust against loss of single layer hits Boundaries depend on p t cuts & tracker geometry

57 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 57 Tracking for electron trigger Present CMS electron HLT Factor of 10 rate reduction  : only tracker handle: isolation Need knowledge of vertex location to avoid loss of efficiency - C. Foudas & C. Seez

58 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 58 Tracking for  -jet isolation  -lepton trigger: isolation from pixel tracks outside signal cone & inside isolation cone Factor of 10 reduction

59 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 59 CMS L1 Track Trigger for Muons Combine with L1  trigger as is now done at HLT: Attach tracker hits to improve P T assignment precision from 15% standalone muon measurement to 1.5% with the tracker Improves sign determination & provides vertex constraints Find pixel tracks within cone around muon track and compute sum P T as an isolation criterion Less sensitive to pile-up than calorimetric information if primary vertex of hard-scattering can be determined (~100 vertices total at SLHC!) To do this requires  information on muons finer than the current 0.05  2.5° No problem, since both are already available at and 0.015°

60 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 60 CMS L1 Trigger Stages Current for LHC: TPG  RCT  GCT  GT Proposed for SLHC (with tracking added): TPG  Clustering  Correlator  Selector Trigger Primitives Regional Correlation, Selection, Sorting Jet ClusteringSeeded Track ReadoutMissing E T Global Trigger, Event Selection Manager e /  jet clustering 2x2,  -strip ‘TPG’ µ track finder DT, CSC / RPC Tracker L1 Front End Regional Track Generator

61 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 61 CMS Level-1 Latency Present CMS Latency of 3.2 μsec = MHz Limitation from post-L1 buffer size of tracker & preshower Assume rebuild of tracking & preshower electronics will store more than this number of samples Do we need more? Not all crossings used for trigger processing (70/128) It’s the cables! Parts of trigger already using higher frequency How much more? Justification? Combination with tracking logic Increased algorithm complexity Asynchronous links or FPGA-integrated deserialization require more latency Finer result granularity may require more processing time ECAL digital pipeline memory is MHz samples = 6.4 μsec Propose this as CMS SLHC Level-1 Latency baseline

62 Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 62 CMS Trigger Summary Level 1 Trigger Select 100 kHz interactions from 1 GHz (10 GHz at SLHC) Processing is synchronous & pipelined Decision latency is 3  s Algorithms run on local, coarse data from Cal., Muons Processed by custom electronics using ASICs & FPGAs Higher Level Triggers: hierarchy of algorithms Level 2: refine using calorimeter & muon system info. Full resolution data Level 3: Use Tracking information Leading to full reconstruction The Future: SLHC Refined higher precision algorithms for Phase 1 Use Tracking in Level-1 in Phase 2


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