1 / 45

Taller de Altas Energías Oviedo 2009

Taller de Altas Energías Oviedo 2009. Trigger/DAQ at LHC. Jorge F. de Trocóniz Universidad Autónoma de Madrid. Proton - Proton. 2804 bunch/beam. Protons/bunch. 10 11. Beam energy. 7 TeV (7x10 12 eV). 10 34 cm -2 s -1. Luminosity. Bunch. Crossing rate. 40 MHz. Proton.

hestia
Télécharger la présentation

Taller de Altas Energías Oviedo 2009

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Taller de Altas Energías Oviedo 2009 Trigger/DAQ at LHC Jorge F. de Trocóniz Universidad Autónoma de Madrid

  2. Proton -Proton 2804 bunch/beam Protons/bunch 1011 Beam energy 7 TeV (7x1012 eV) 1034cm-2s-1 Luminosity Bunch Crossing rate 40 MHz Proton Collision rate ≈ 107-109 Parton (quark, gluon) l e + l New physics rate ≈ .00001 Hz Higgs Event selection: 1in 10,000,000,000,000 e - Particle Z o e + Z o jet jet SUSY..... e - Collisions at the LHC

  3. Beam crossings: LEP, Tevatron & LHC • LHC will have ~3600 bunches • And same length as LEP (27 km) • Distance between bunches: 27km/3600 = 7.5m • Distance between bunches in time: 7.5m/c = 25ns Tevatron Run I Tevatron Run II

  4. pp Collisions at 14 TeV at 1034 cm-2s-1 • 20 min bias events overlap • H  ZZ, Z  mm H 4 muons: the cleanest (“golden”) signature And this (not the H though…) repeats every 25 ns

  5. Time of Flight c=30cm/ns; in 25ns, s=7.5m

  6. Physics selection at the LHC

  7. Trigger/DAQ Requirements • N (channels) ~ O(107); ≈20 interactions every 25 ns • need huge number of connections • need information super-highway • Muon, calorimeter and tracker information should correspond to each other • need to synchronize detector elements to better than 25 ns • In some cases: detector signal > 25 ns • integrate more than one bunch crossing of information • need to identify bunch crossing • Can store data at ≈ 102 Hz • need to reject most interactions • On-Line selection (cannot go back and recover events) • need extraordinary monitoring and understanding

  8. ( ) T REJECTED ACCEPTED Triggering • Task: inspect detector information and provide a first decision on whether to keep the event or throw it out The trigger is a function of : Event data & Apparatus Physics channels & Parameters • Detector data not (all) promptly available • Selection function highly complex  T(...) is evaluated by successive approximations, or TRIGGER LEVELS (possibly with zero dead time)

  9. Physics selection at the LHC L1 Trigger

  10. Particle Signatures in the Detector

  11. L1: Only Calo and Muon • Compare to tracker info • Pattern recognition much faster/easier • Complex algorithms • Huge amounts of data • Simple algorithms • Small amounts of data • Local decisions • Need to link sub-detectors

  12. Muon Trigger Calorimeter Trigger RPC CSC DT HF HCAL ECAL CSC local trigger DT local trigger RegionalCalorimeterTrigger Patterncomparator trigger CSC TrackFinder DT TrackFinder GlobalCalorimeterTrigger Pipelined 40 MHz, Latency < 3.2 s 4+4  4  4  MIP+Quiet bits Global Muon Trigger e/, j, ET, ETmiss, … 4 (with MIP/ISO bits) Global Trigger max. 100 kHz L1 Accept Level 1 Trigger Structure (CMS)

  13. L1 Muon Local Trigger (CMS)

  14. Strong magnetic field in iron return yoke (~2T) efficiently discriminates muons as a function of pT Muon Tracks with3.5, 4.0,4.5,6.0GeV/c Perform tracking analysis in real time for L1 Muon Trigger: Track-Finder L1 Muon Regional Trigger (CMS)

  15. Technologies in Level-1 systems • ASICs (Application-Specific Integrated Circuits) used in some cases • Highest-performance option, better radiation tolerance and lower power consumption (a plus for on-detector electronics) • FPGAs (Field-Programmable Gate Arrays) used throughout all systems • Impressive evolution with time. Large gate counts and operating at 40 MHz (and beyond) • Biggest advantage: flexibility • Can modify algorithms (and their parameters) in situ • Communication technologies • High-speed serial links (copper or fiber) • LVDS up to 10 m and 400 Mb/s; G-link, Vitesse for longer distances and Gb/s transmission • Backplanes • Very large number of connections, operating at ~160 Mb/s

  16. BTI Finds alignment between hits at the right BX TRACO Finds correlations between inner and outer BTI segments Kills ghosts and selects “best” 2 muon segments for any BX Trigger Server Trigger Bus Trigger Boards L1 Muon Trigger: Local Segment-Finder

  17. LUTS LUTS PHYSICS L1 Muon Trigger: Track-Finder Algorithm

  18. Stratix FPGA on mezzanine VME Interface, Control & Readout -neighbor, ETTF, WS connections -neighbor connections Input Receiver CMS Muon Track-Finder Board

  19. CMS Muon Track-Finder Trigger

  20. L1 Calo Trigger: e/g Algorithm ET( ) + max ET( ) > ETmin Isolated “e/g” ET( ) / ET( ) < HoEmax At least 1 ET( , , , ) < Eisomax Fine-grain: ≥1( ) > R ETmin

  21. L1 Calo Triggers: jet and  Algorithms • Issues are jet energy resolution and tau identification • Single, double, triple and quad thresholds possible • Possible also to cut on jet multiplicities • Also ETmiss, ΣET and ΣET(jets) triggers “-like” shapes identified for  trigger Sliding window: • granularity is 4x4 towers = trigger region • jet ET summed in 3x3 regions ,  = 1.04

  22. Global Trigger • Global Trigger: a very large OR-AND network that allows for the specification of complex conditions. • Trigger Menu for LHC luminosity L=2x1033 cm-2s-1 • Thresholds chosen to yield of 16 kHz • DAQ bandwidth at startup 50 kHz • Safety factor of 3 • Available bandwidth split in four groups • Inclusive muon, di-muon • Inclusive electron, di-electron • Inclusive tau, di-tau • jets, ET, ETmiss, combinations } 4.7 kHz } 4.3 kHz } 3.0 kHz } 3.6 kHz

  23. L1 Trigger Decision Loop • Synchronous 40 MHz digital system • Typical: 160 MHz internal pipeline • Latencies: • Readout + processing: < 1ms • Signal collection & distribution: ≈ 2ms Local level-1 trigger Global Trigger 1 Primitive e, g, jets, µ ≈ 2-3 µs latency loop Trigger Primitive Generator Front-End Digitizer Pipeline delay ( ≈ 3 µs) Accept/Reject LV-1

  24. Signaling and Pipelining

  25. Physics selection at the LHC DAQ

  26. Trigger/DAQ systems

  27. Detectors Detectors Lvl-1 Front end pipelines Lvl-1 Front end pipelines Readout buffers Readout buffers Lvl-2 Switching network Switching network Lvl-3 HLT Processor farms Processor farms “Traditional”: 3 physical levels CMS: 2 physical levels Online Selection Flow ATLAS, LHCb, ALICE CMS

  28. Trigger/DAQ parameters ATLAS No.Levels Level-1 Event Readout Filter Out Trigger Rate (Hz) Size (Byte) Bandw.(GB/s) MB/s (Event/s) 3 105 1.5x106 5 150 (102) LV-2 3.5x103 2 105 106 100 100(102) 3 LV-0 5x106 2x105 4 40 (2x102) LV-1 2x104 4 Pb-Pb103 5x106 51250 (2x102) p-p 500 106 100 (102) CMS LHCb ALICE

  29. Technology Evolution

  30. Lvl-1 trigger Detector Front-ends Readout Switch fabric Controls Event Manager Farms Computing services DAQ: basic blocks • Current Trigger/DAQ elements Detector Front-ends, feed L1 trigger processor Readout Units: buffer events accepted by L1 trigger Switching network: interconnectivity with HLT processors Processor Farm + control and monitoring

  31. Event Building • Form full-event-data buffers from fragments in the readout. Must interconnect data sources/destinations. Event fragments : Event data fragments are stored in separated physical memory systems Full events : Full event data are stored into one physical memory system associated to a processing unit Hardware: Fabric of switches for builder networks PC motherboards for data Source/Destination nodes

  32. CMS Detector Readout: 3D-EVB Fed Builder : Random traffic Readout Builder : Barrel shifter

  33. ATLAS: Level-2 and EVB • Regions of Interest (RoI): • If the Level-2 delivers a factor 100 rejection, then input to Level-3 is 1 kHz. • At an event size of 1 MB, this needs 1 GB/s • Dividing this into ~100 receivers implies 10 MB/s sustained – easily doable. • Elements needed: ROIBuilder, L2PU (processing unit), a lot of control and synchronization.

  34. Physics selection at the LHC HLT

  35. Event Filter: A Processor Farm • Basic elements: PC, Linux, Network • Despite recent growth, it’s a mature process: basic elements are all mature technologies. • Very cost-effective: • Linux is free but also very stable, production-quality. • Interconnect: Ethernet, Myrinet (if more demanding I/O); both technologies inexpensive and performing. • O(1000) processors.

  36. CMS HLT Filter Farm

  37. HLT Requirements and Operation • Strategy/design guidelines: • Use offline software as much as possible • Ease maintenance, but also best understanding of the detector • Boundary conditions: • Code runs in a single processor, which analyzes one event at a time • HLT (or Level-3) has access to full event data (full granularity and resolution) • Limitations: • CPU time • Output selection rate (~102 Hz) • Precision of calibration constants • Main requirements: • Satisfy physics program: high efficiency • Selection must be inclusive (to discover the unpredicted as well) • Efficiency must be measurable from data alone

  38. HLT Regional Reconstruction (I) Global • process (e.g. DIGI to RHITs) each detector fully • then link detectors • then make physics objects Regional • process (e.g. DIGI to RHITs) each detector on a "need" basis • link detectors as one goes along • physics objects: same

  39. HLT Regional Reconstruction (II) • For this to work: • Need to know where to start reconstruction • Seeding • For this to be useful: • Slices must be narrow • Slices must be few • Seeds from Level-1: • e/g triggers: ECAL • m triggers: Muon systems • Jet triggers: E/HCAL

  40. HLT Example: Electron Selection (I) • Bremsstrahlung recovery: • Seed cluster with ET>ETmin • Road in f around seed • Collect all clusters in road  “supercluster” and add all energy in road • “Level-2” electron: • 1-tower margin around 4x4 area found by Level-1 trigger • Apply “clustering” • Accept clusters if H/EM < 0.05 • Select highest ET cluster

  41. HLT Example: Electron Selection (II) • “Level-2.5” selection: add pixel information • Very fast, high rejection (e.g. factor 14), high efficiency (e=95%) • Pre-bremsstrahlung • If # of potential hits is 3, then demanding  2 hits quite efficient

  42. HLT Example: Electron Selection (III) • “Level-3” selection • Full tracking, loose track-finding (to maintain high efficiency): • Cut on E/p everywhere, plus • Matching in h (barrel) • H/E (endcap) • Optional handle (used for photons): isolation

  43. Online Physics Selection Event rate Level-1 HLT output Online Selection

  44. Conclusions • The Level-1 trigger takes the LHC experiments from the 25 ns timescale to the 10 ms timescale. • Custom hardware, huge fan-in/out problem, fast algorithms on coarse-grained, low-resolution data. • Depending on the experiment, the next filter is carried out in one or two (or three) steps. • Commercial hardware, large networks, Gb/s links. • If Level-2 present: low throughput needed (but need Level-2). • If no Level-2: three-dimensional composite system. • High-Level trigger: to run software algorithms that are as close to the offline analysis as possible • Large processor farm of PCs running Linux. • Control and Monitoring is highly non trivial.

  45. Graphical Summary

More Related