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Overview of the LHC Triggers and Plans for LHC Start-up

Overview of the LHC Triggers and Plans for LHC Start-up. Overview of the talk: Triggering Challenges at LHC Trigger Systems at LHC Pilot run Triggers (2007) Physics Triggers (2008). Minimum Bias Events. 22. 70 mb deep inelastic component.

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Overview of the LHC Triggers and Plans for LHC Start-up

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  1. Overview of the LHC Triggers andPlans for LHC Start-up Overview of the talk: • Triggering Challenges at LHC • Trigger Systems at LHC • Pilot run Triggers (2007) • Physics Triggers (2008) Costas Foudas, Imperial College London

  2. Minimum Bias Events 22 70 mb deep inelastic component • At full LHC Luminosity we have 22 events superimposed on any discovery signal. • First Level Event Selection requires considerable sophistication to limit the enormous data rate. • Typical event size: 1-2 Mbytes. Challenge 1 Costas Foudas, Imperial College London

  3. Trigger Challenge at LHC +30 MinBias Higgs ->4m • We want to select this type of event (for example Higgs to 4 muons) which are superimposed by this…… Costas Foudas, Imperial College London

  4. Challenge 2: Pileup Challege 2 • In-time pile up: Same crossing different interactions • New events come every 25 nsec  7.5 m radial reparation. • Out-of-time pile up: Due to events from different crossings. • Need to identify the bunch crossing that a given event comes from. P.Sphicas Costas Foudas, Imperial College London

  5. Trigger Goals at LHC • At LHC we want to select events that have: (1) Isolated leptons and photons, (2) -, central- and forward-jets (3) Events with high ET (4) Events with missing ET. • The QCD-are orders of magnitude larger than any exotic channel . • QCD events must be rejected early in the DAQ chain and selecting them using high ET cuts in the trigger will simply not work.  Need to select events at the 1:1011 level with almost no dead-time. • HLT must then be able to run full blown reconstruction software and selection filters • Indicative event rates: • Inelastic: 109 Hz; (2) Wl : 100 Hz • t-tbar:10Hz (4) H(100 Gev): 0.1 Hz • H(500 GeV): 0.01 Hz Challege 3 Costas Foudas, Imperial College London

  6. The CMS Trigger System • 40 MHz input • 100 KHz FLT rate • 3.2 sec Latency • 100 Hz written at the output • Event Size 1-2 Mbytes • The requirements on the Level-1 Trigger are demanding. • Level-1 Trigger: Custom made hardware processor. • High Level Trigger: PC Farm using reconstruction software and event filters similar to the offline analysis. Costas Foudas, Imperial College London

  7. The CMS L1 Calorimeter Trigger RCT GCT TPG FE GT P Y/N • Detector data stored in Front End Pipelines. • Trigger decision derived from Trigger Primitives generated on the detector. • Regional Triggers search for Isolated e/ and  and compute the transverse, missing energy of the event. • Event Selection Algorithms run on the Global Triggers • FE: Front End • P: Pipeline • RCT: Regional Calorimeter Trigger • GCT: Global Calorimeter Trigger • GT: Global Trigger 128x25ns=3.2 µsec later i.e. 128 bunch- crossings latency Synchronization Costas Foudas, Imperial College London

  8. Trigger and DAQ (CMS Example) Detector Frontend Level-1 Trigger Readout Systems Event Run Builder Networks Manager Control Filter Systems Computing Services • The First Level decision is distributed to the Front-end as well as the readout units. • Front-end and readout buffers take care of Poisson fluctuations in the trigger rate. • Hand-shaking using back-pressure guarantees synchronization Costas Foudas, Imperial College London

  9. The ATLAS Trigger System • 40 MHz input • 100 KHz Level 1 rate (similar with CMS) • 1 KHz Level 2 rate • 1-2 102 Hz HLT output • Event Size ~1 Mbyte • Traditional 3 level system. • Regions of interest. 2.5 ms ~10 ms ~2 kHz ~ sec ~200 Hz Costas Foudas, Imperial College London

  10. LHCb Trigger System I Visible collisions L = 2 1032 cm-2 s-1 10 MHz L0: [hardware] high Pt particles calorimeter + muons 4 μs latency 1 MHz HLT [software] 1 MHz readout ~1800 nodes farm ~2 kHz On tape: Exclusive selections Inclusive streams LHCb trigger: • Two trigger levels: • L0: hardware • HLT: software • Trigger Strategy: • Enhance the b content in sample • High Pt particles (e,,,hadrons) • Displaced tracks • Increase b content: 1%  ~50-60% • Follow seed particles of the decays • Trigger divided in alleys • Favor inclusive channels • Architecture is similar to CMS…. Costas Foudas, Imperial College London

  11. Level-1 Strategy • Selecting events using physics filters at the High Level Trigger level (HLT CPU farms) will not do. The rate must be cut earlier before the HLT is overwhelmed by MHz of background QCD jet events. • It follows that the first level of selection, the First Level Trigger, should include algorithms of considerable sophistication which can find Isolated Electrons, Jets and detect specific event topologies. • This is a challenging task because we only have 15x25 ns = 375 ns to accomplish it for all sub-triggers. Jets take longer: 24x25 nsec = 600 nsec; which is many orders of magnitude faster than offline. Costas Foudas, Imperial College London

  12. CMS L1 Latency Budget • Total Latency = 128 Bx or 3.2 sec Costas Foudas, Imperial College London

  13. The Calorimeter Trigger Task • Jet Triggers: Central, Tau and Forward jet finding and sorting. • Jet Counters: Count Jets in 12 different regions of the detector or 12 different thresholds within the detector. • Electron/ triggers: Select and Sort the e/ candidates from Regional Calorimeter Trigger. • Total Transverse, Total Missing Transverse and Total Jet Transverse Energy calculation. • Receive the Muon data and send them to the Global Muon Trigger. • Luminosity Monitoring and readout all the RCT and GCT data for every L1A. Costas Foudas, Imperial College London

  14. Jet Finders: A summary jet=(-1)ln(tan(jet/2))  • Particles strike the detectors and deposit their energy in the calorimeters. • Energy deposits in the calorimeters need to be recombined to reconstruct the transverse energy and direction of the original parton. • This is done using tools that are called Jet finders. Costas Foudas, Imperial College London

  15. Cone Jet Finders R0 • Searches for high transverse energy seeds and a cone in the - space is drawn around each seed. • Energy depositions within a cone are combined and the Et weighted  is calculated: • The new cone is drawn and the process is repeated until the cone transverse energy does not change Costas Foudas, Imperial College London

  16. Example Algorithms Electrons/photon finder Jet Finder • Electron (Hit Tower + Max) • 2-tower ET + Hit tower H/E • Hit tower 2x5-crystal strips >90% ET in 5x5 (Fine Grain) • Isolated Electron (3x3 Tower) • Quiet neighbors: all towerspass Fine Grain & H/E • One group of 5 EM ET < Thr. • Jet or t ET • 12x12 trig. tower ET sliding in 4x4 steps w/central 4x4 ET > others • t: isolated narrow energy deposits • Energy spread outside t veto pattern sets veto • Jet  t if all 9 4x4 region t vetoes off Costas Foudas, Imperial College London

  17. The GCT Design Concentrator Card (1/1) Leaf Card (1/8) Wheel Card (1/2) Costas Foudas, Imperial College London

  18. The GCT Design Wheel Concentrator Wheel 3 Jets Leafs e/ Leafs 3 Jets Leafs • 63 Source cards • 8 Leaf cards • 2 Wheel cards • 1 Concentrator 31 Source Cards 32 Source Cards Costas Foudas, Imperial College London

  19. CMS GCT Cards Source Leaf Concentrator GT Interface Costas Foudas, Imperial College London

  20. The Leaf Card (e±, Jets, ET, MET) Virtex-II Pro-P70 • Main processing devices: Xilinx Virtex II Pro P70 • 32 x 1.125 Gbit/sec Links with Serializers/Deserializers • Each serves 1/6 of the detector in Jet finding mode. 3x12 Channel 1.125 Gbit/s Optical Links Costas Foudas, Imperial College London

  21. Data Sharing Scheme η+ η- • Each Jet Leaf Card Serves 3 Regional calorimeter crates or 1/3 of half Barrel calorimeter (forward calorimeters have been included as edges of the barrel). • Each Leaf Searches for Jets using a 3x3 region sliding window. • Each Leaf has access to boundary data from neighbours via data duplication at the input of each Leaf Costas Foudas, Imperial College London

  22. CMS GCT Status Wheel Concentrator Wheel 3 Jets Leafs e/ Leafs 3 Jets Leafs By March 07 Leaf Card Leaf Card Source Card Source Card Source Card Source Card Source Card Source Card Source Card Source Card Source Card Source Card GTI • 63 Source cards • 8 Leaf cards • 2 Wheel cards • 1 Concentrator By March 06 31 Source Cards 32 Source Cards Concentrator Card By March 07 Costas Foudas, Imperial College London

  23. Trigger Commissioning and Testing without Beam : Patterns Tests • Install, integrate trigger chain and connect TTC system. • Propagate patters from the Trigger front end all the way to HLT and DAQ. • GCT is given here as an example but other systems will perform similar tests, • GCT: Electron Patterns Tests (March 07) (1) The Source Cards will beloaded with events containing 4 electrons in various parts of the detector. (2) Empty crossings will be loaded in between the electron events. Each Source Card can store half and orbit worth of data (~1500 thousand crossings) which can be either empty or test events. (3) The data will be propagated from the Source Cards via the optical links, to the two electron Leaf Cards and from there to the concentrator all the way to the Global Trigger and also to the DAQ. (4) The data will also be processed by the GCT emulator and the results of the emulator and the hardware will be compared. • Goals: (a) Exercise and validate a given trigger path. (b) Establish synchronization: 4 electrons should arrive at GT at the correct crossings with the correct energy, rapidity and phi. (c) Establish agreement between software and firmware Costas Foudas, Imperial College London

  24. Trigger Commissioning and Testing without Beam : Cosmic Ray Tests • Take Cosmic Ray (CR) runs. Trigger using the muon detectors (RPC,DT,CSC). However be aware that CR do not come synchronously with the clock and do not necessarily go through the interaction point where the muon systems are optimized to trigger. • Raw rate estimated ~ 1.8 KHz for muon momentum above 10 GeV. This should decrease a lot after cuts on timing and muon direction are folded in. • Goals: (a) Exercise and validate the data taking system. (b) Establish coarse synchronization. (c) Start aligning the detectors. • Almost no Level-1 cuts; HLT runs Level-1 simulation to validate the Level-1 trigger; Muon reconstruction at HLT but no momentum cuts. Costas Foudas, Imperial College London

  25. Pilot Run in 2007 (900 GeV) Does it make sense now ?? Costas Foudas, Imperial College London

  26. 900 GeV Beam Settings • Inelastic cross section @ 900 GeV: 40 mb • Cross section W → lν @ 900 GeV: 1 nb • Cross section Z → ll @ 900 GeV: 100 pb Costas Foudas, Imperial College London

  27. Particle Distributions: Will not be better at 900 GeV • Particles go forward and have energy below 1 GeV. • Need to be able to Trigger forward at low energy. • Obviously you do not want a transverse energy trigger. Costas Foudas, Imperial College London

  28. CMS Trigger for Pilot Run 2007 CMS Trigger Mode of Operation: • L1T identifies collisions and accepts all events • HLT verifies L1T bits, and stream events to calibration, e, , jets.. • In other words we need a Minimum Bias Trigger just to ‘see’ beams. • Ideas on how to do this: • (1) Random Level-1 triggers at 1% level. • (2) CMS will be using the OPAL scintillators mounted at the • front face of the Hadron Forward Calorimeter (HF). • (3) Energy/Et over threshold from the first 2 rings around • the beams pipe (both sides) in coincidence. • (4) Feature Bits from the forward regions will be used to • count trigger towers over threshold. Costas Foudas, Imperial College London

  29. Beam Hallo Trigger (2007) Costas Foudas, Imperial College London

  30. Scintillator Trigger 2007 • To be installed at the front faces of HF • Useful for : (a) Commissioning (b) Calibration (may be) (c) Alignment OPAL Scintillators Costas Foudas, Imperial College London

  31. Beam Pipe Rings Trigger 2007 GCT Ring-Energy Over Threshold OR OR AND GT Logic and Trigger Decision • GCT can compute the energy or • transverse energy in rings around • the beam pipe form both sides • of the calorimeter; energy is better. • Global Trigger can set threshold • on energy or transverse energy. • Forward and Rear in Coincidence • Simple Activity Triggers • Useful for: (a) Commissioning (b) Calibration (may be) (c) Alignment Costas Foudas, Imperial College London

  32. Feature Bits Trigger 2007 • Feature bits are derived from the energy of a trigger tower after applying programmable thresholds. • These bits end up also on GCT along with the jet data. • GCT can count number of towers over threshold around the beam and place cuts such as N>10 on both calorimeters. • It is obvious from the second plot that Et will not do but we need energy. Costas Foudas, Imperial College London

  33. Pilot Run 2007 HLT CMS • Minimum selection at Level-1. • Validate Level-1 Triggers using the Level-1 emulators running in HLT. Migrate algorithms to Level-1 as soon as they are understood. • Main rate reduction at HLT. • CMS (CSC): Halo Muons for alignment. • We should be able to time the detectors. • Validate detector and data taking concepts • A course alignment will be possible. Costas Foudas, Imperial College London

  34. Physics Event rates in2007 Costas Foudas, Imperial College London

  35. Expectations for 2007 Pilot Run • To gain the first experience with LHC beams validate as much as possible the detectors and prepare for the 2008 Physics run. • Some calibration studies may be possible from phi-symmetry • However, we should also see : Costas Foudas, Imperial College London

  36. Pilot Run HLT ATLAS/CMS • CMS: Minimum selection at Level-1. • CMS:Validate Level-1 Triggers using the Level-1 emulators running in HLT. Migrate algorithms to Level-1 as soon as they are understood. • CMS:Main rate reduction at HLT. • CMS (CSC) +ATLAS: Halo Muons for alignment. • ATLAS: Activity HLT trigger based on tracking, calorimeter and scintillators. • ATLAS: Muon (5 GeV) OR Calorimeter (10 Gev e/gamma) OR Jet (25 GeV) Costas Foudas, Imperial College London

  37. LHCb Level-0 Decision Calorimeters Muon Detectors Pile up Veto • Selects high Pt particles. • Level-0 decision derived from calorimeter, muon and pileup veto information: 10 MHz 1 MHz (@ 1032) • Pile-up Veto removes crossings with multiple vertices. Costas Foudas, Imperial College London

  38. LHCb plans: Pilot run 2007 • Goal: Select single High-Pt particles. • Start selection using the hadronic calorimeter to select clusters with High-Pt. • Trigger rate = 50 – 100 Hz • The data will be used for: (a) Timing alignment (b) Detector main alignment with B-field= off (c) Turn on Magnetic Field and test E/p (RICH) (d) Test Velo with Magnetic Field off and validate impact parameter algorithms Costas Foudas, Imperial College London

  39. Staged commissioning plan for protons@7TeV Mike Lamont 2008 Stage I II III No beam Beam Widely varying conditions in 2008 2009 III Beam No beam Steady state operation in 2009 Costas Foudas, Imperial College London

  40. Pilot physics Month in 2008 From Mike Lamont talk at CMS week Rapidly changing conditions, with collision rate below 50kHz till 156x156 Costas Foudas, Imperial College London

  41. 2008 Physics Run ATLAS/CMS • At 1031 commissioning of the LHC Trigger algorithms can be tried. • Algorithm cuts will be relaxed. • Level-1 Rate will be up to 50 KHz. • Redundancy between triggers will be used to compute the trigger efficiency using data. • 200 Hz ‘on tape’ • Emphasis: To understand the Trigger and the detector at LHC running conditions. Costas Foudas, Imperial College London

  42. Rates at 1031-33 cm–2s–1 1033 1032 1031 108 107 106 105104103 Assume in 2008: L1T Out < 5x104 Hz HLT Out < 1.5x102 Hz 102 101 100 101 100 10-1 We cannot trigger on all minbias Jet and soft lepton triggers need to be operational at 1031 cm–2s–1 Isolated electron triggers also need to be operational at 1032 cm–2s–1 All triggers need to be operational at 1033 cm–2s–1 Costas Foudas, Imperial College London

  43. Level-1 Trigger Arsenal Minimum Bias • Hadron Calorimeter Feature bits • Program HB, HE & HF feature bits to ID towers with energy greater than noise • HF ET rings • Implemented on GCT - but to get minbias efficiently one needs to use HF E rather than ET • Beam Scintillation counters • Any TOTEM elements available (doubt it..) Normal L1 triggers Can operate e-gamma, jet, … triggers with low thresholds (above noise) and muons with no threshold (any muon segment found) -- & no isolation Costas Foudas, Imperial College London

  44. Lowest Nominal L1 Trigger Thresholds • Electron/ trigger • A trigger tower pair (50 crystals) over threshold - so 5 above noise (40 MeV) implies about 2 GeV minimum • We will use non-isolated e/ path • Jet trigger • A jet is composed of 288 trigger towers with nominal noise floor of ~250 MeV per tower which implies a minimum threshold of 10 GeV if we stay above 3 • Muon trigger • Muon will not make it until it gets to 3 GeV • Accept poor quality and possibly when any segment is seen in the DTTF or CSCTF or RPC Costas Foudas, Imperial College London

  45. DAQ Configurations From Sergio Cittolin, Monday Plenary Costas Foudas, Imperial College London

  46. 2008: Startup Trigger • Take all minimum bias identified at L1T to HLT There will be sufficient bandwidth 20-50 kHz • Validate L1T and run simple HLT algorithms (1) HLT algorithms could be calorimeter and muon based Minimal use of tracking Apply thresholds (none applied at L1) Stream data by trigger type (2) Calibration triggers • ECAL: 0 • Jets:  + Jet • Tracks: J/y→ mmisolated (3) Prescale minbias as needed Output bandwidth limit 1 GB/s Rate limit 500-1000 Hz full events, 1-2 MB/events Costas Foudas, Imperial College London

  47. 2008 Operations @ 75ns, 25ns • For luminosities above 1031 cm–2s–1 we need to set thresholds at L1 and refine object ID at HLT • 75ns operation possible till we see a luminosity of 1033 cm–2s–1 • Average of 5 interactions per crossing at the peak. Only in-time pileup relevant • Going to 25ns - 1 operation, i.e. at 33% bunch intensity, keeps the luminosity about the same but pileup goes down: • Now about 1-2 interactions per crossing • Pileup plays a less significant role Costas Foudas, Imperial College London

  48. Electron Trigger Data vsTrigger Emulator I Costas Foudas, Imperial College London

  49. Electron Triggers vsTrigger Emulator II Costas Foudas, Imperial College London

  50. Electron Trigger Datavs Trigger Emulator III Costas Foudas, Imperial College London

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