1. The ATLAS Trigger and Data Acquisition System John Strong Royal Holloway, University of London

2. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 2 Talk outline Trigger and DAQ basics The LHC and ATLAS 14 TeV Physics The ATLAS Detector ATLAS Trigger and DAQ design – Level 1 trigger – High level trigger and data acquisition Current status

3. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 3 TDAQ basics The DAQ challenge is to – get information from the detectors and put it on permanent storage media quickly and accurately – supply the trigger with information in a timely fashion – buffer (temporarily store) data while the trigger does its job – Zero or very low “dead-time” The trigger (filter or event selection) challenge is to reduce the event rate to one the DAQ can transfer to permanent storage by – selecting interesting interactions – throwing away “background” Take care, once rejected they are non-recoverable TDAQ also has to deal with – Calibration runs, run control, data monitoring, bookkeeping etc.

4. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 4 TDAQ starting point from Physics –what is the experimental programme TDAQ should be flexible enough to accommodate changes to programme from the Detector –what data are available and when size, granularity and occupancy of detectors from the Accelerator –what rates and structures start-up and design luminosity

5. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 5 TDAQ design process develop algorithms to match the physics programme and off-line selections –off-line algorithms not fast enough –need high, unbiased and known efficiency –need large rate reduction from non-relevant processes develop systems to collect data required and run algorithms at rates needed to match accelerator and detector performance use trigger to remove backgrounds as soon as possible Get as much ‘interesting physics’ data as possible to tape for off-line analysis

6. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 6 Trigger Design Inclusive and exclusive triggers –inclusive - select events with certain characteristics single (or few) particle triggers e.g. high p T leptons –unbiased sample (or relatively so) –does not exclude ‘new’ physics –exclusive - select physics channel under study use to recognise well known processes –accept, scale (sample) or reject »need to monitor efficiency As selection criteria are tightened –Background rejection improves –BUT event selection efficiency tends to decrease

7. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 7 The matching problem Ideally –off-line algorithms select phase space which just encloses the physics channel –trigger algorithms just enclose the off-line selection In practice, this doesn’t happen –Would need to match the off-line algorithm selection –BUT off-line the algorithm can be changed, data re-processed and recalibrated –On-line algorithms have tight time constraints SO, make sure on-line algorithm selection is well known, controlled and monitored

8. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 8 Background Physics channel Off-line Matching problem (cont.) On-line

9. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 9 TDAQ basics Trigger and DAQ not an exact science –NO truth - NO 'right choice' Main question asked is Does it do the job & can we afford it? One major problem is interconnection and data flow. ALEPH barrel end-view Partially cabled TPC

10. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 10 The LHC & experiment layout 7 TeV on 7 TeV pp collider – ~ 27 km of 8.3T superconducting dipoles at 1.8°K – Luminosity of 2.10 33 cm -2 s -1 initially, design 1.10 34 cm -2 s -1

11. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 11 LHC Physics (1) AND - Something has to happen by ~1 TeV – Higgs mechanism regulates divergences in the Standard Model – If no Higgs, then should see “effects” e.g. in the W-W x-section – Other theories – supersymmetry, technicolor predict particle production at, or before, the TeV scale Still many unknowns in the Standard Model – Origin of mass – symmetry breaking – generation hierarchy – A possible solution: the Higgs boson – Next step: hunt the Higgs Unknown mass – cover wide range Small x-section – need high luminosity ALSO - Explore new energy domain – Supersymmetry; compositeness; the unexpected

12. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 12 Inelastic B physics & CP violation Jet (q&g) physics W -> lν t-t production Higgs (m=100 GeV/c2) Higgs (m=500 Gev/c2) LHC Physics (2) Lepton decay branching ratio~10 -2 selection power for Higgs~10 13 A special piece of hay in a haystack~10 9 Rate at design luminosity ChannelX-sectionRate/s Ineleastic 0.1 b 10 9 B-physics 200 μb 2.10 6 Jet (>250GeV) 100 nb 10 3 WℓνWℓν 20 nb 2.10 2 t-t production 1 nb 10 Higgs (100 GeV) 20 pb 2.10 -1 Z’ (1 TeV) 10 pb 10 -1 Higgs (500 GeV) 1 pb 10 -2

13. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 13 LHC Physics (3) Higgs signal extraction very difficult –Searches for H  ZZ  leptons (e or μ), H  γγ ; also H  ττ, H  bb but a lot of other interesting physics –SUSY and other ‘new’ physics High-p T particles – particularly leptons - are likely to be signature of such physics (and Higgs) –Of interest in their own right and must be understood as backgrounds to new physics B physics and CP violation; quarks, gluons and QCD; top quarks W and Z bosons

14. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 14 Effect of p T cut on minimum-bias events Simulated H  4μ event + 17 minimum-bias events Can try to use this in trigger to select interesting events

15. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 15 ATLAS Detector Diameter 25 m Barrel toroid length 26 m Total length 44 m, height 22 m Overall weight 7000 Tons

16. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 16 ATLAS Collaboration Albany, Alberta, NIKHEF Amsterdam, Ankara, LAPP Annecy, Argonne NL, Arizona, UT Arlington, Athens, NTU Athens, Baku, IFAE Barcelona, Belgrade, Bergen, Berkeley LBL and UC, Bern, Birmingham, Bonn, Boston, Brandeis, Bratislava/SAS Kosice, Brookhaven NL, Bucharest, Cambridge, Carleton/CRPP, Casablanca/Rabat, CERN, Chinese Cluster, Chicago, Clermont-Ferrand, Columbia, NBI Copenhagen, Cosenza, INP Cracow, FPNT Cracow, Dortmund, JINR Dubna, Duke, Frascati, Freiburg, Geneva, Genoa, Glasgow, LPSC Grenoble, Technion Haifa, Hampton, Harvard, Heidelberg, Hiroshima, Hiroshima IT, Indiana, Innsbruck, Iowa SU, Irvine UC, Istanbul Bogazici, KEK, Kobe, Kyoto, Kyoto UE, Lancaster, Lecce, Lisbon LIP, Liverpool, Ljubljana, QMW London, RHBNC London, UC London, Lund, UA Madrid, Mainz, Manchester, Mannheim, CPPM Marseille, MIT, Melbourne, Michigan, Michigan SU, Milano, Minsk NAS, Minsk NCPHEP, Montreal, FIAN Moscow, ITEP Moscow, MEPhI Moscow, MSU Moscow, Munich LMU, MPI Munich, Nagasaki IAS, Naples, Naruto UE, New Mexico, Nijmegen, Northern Illinois, BINP Novosibirsk, Ohio SU, Okayama, Oklahoma, LAL Orsay, Oslo, Oxford, Paris VI and VII, Pavia, Pennsylvania, Pisa, Pittsburgh, CAS Prague, CU Prague, TU Prague, IHEP Protvino, Ritsumeikan, UFRJ Rio de Janeiro, Rochester, Rome I, Rome II, Rome III, Rutherford Appleton Laboratory, DAPNIA Saclay, Santa Cruz UC, Sheffield, Shinshu, Siegen, Simon Fraser Burnaby, Southern Methodist Dallas, NPI Petersburg, Stockholm, KTH Stockholm, Stony Brook, Sydney, AS Taipei, Tbilisi, Tel Aviv, Thessaloniki, Tokyo ICEPP, Tokyo MU, Tokyo UAT, Toronto, TRIUMF, Tsukuba, Tufts, Udine, Uppsala, Urbana UI, Valencia, UBC Vancouver, Victoria, Washington, Weizmann Rehovot, Wisconsin, Wuppertal, Yerevan 151 Institutions from 34 CountriesTotal Scientific Authors 1600

17. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 17 The LHC and ATLAS LHC has –a high luminosity 10 34 cm -2 s -1 –short bunch separation 25 ns (bunch length ~1 ns) This results in – ~ 23 interactions / bunch crossing at design luminosity beam lifetime of ~ day (beam-beam interactions major effect) – ~ 70 charged particles (mainly soft pions) / interaction ~1000 charged particles / bunch crossing – 7.5 m bunch separation ‘debris’ from 3 bunch crossings in ATLAS –one entering inner tracker; –one exiting calorimeter; –one in muon system »bunch crossing identification needed

18. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 18 The ATLAS Sub-Detectors Inner tracker –pixels (silicon) (3 layers) precision 3-D points; 1.4 10 8 channels; occupancy 10 -4 –silicon strips (4 layers) precision 2-D points; 5.2 10 6 channels; occupancy 10 -2 –transition radiation tracker (straw tubes) (40 layers) continuous tracker + electron identification; 4.2 10 5 channels; 12-33% occupancy

19. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 19 Inner Detector Layout

20. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 20 ATLAS event in the tracker

21. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 21 Tracker end-view of event

22. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 22 Sub-Detectors (cont.) solenoid –between tracker and calorimeters 4 m x 7 m x 1.8T calorimetry –electromagnetic liquid argon (accordion) detector + lead –hadronic scintillator tiles & liquid argon + iron – 2.3 10 5 channels; occupancy 5-15% muon system –air-core toroid magnet system –trigger - resistive plate and thin gap chambers –precision – monitored drift tubes –1.3 10 6 channels; occupancy 2-7.5%

23. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 23 ATLAS Calorimeters and Inner Tracking Detectors EM Accordion Calorimeters Hadronic LAr End Cap Calorimeters

24. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 24 Accordion calorimeter

25. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 25 Accordion calo em shower

26. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 26 A Barrel Toroid

27. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 27 ATLAS Trigger Physics programme is luminosity dependent  low luminosity (2.10 33 cm -2 s -1 ) - first ~2 years high P T programme (Higgs etc.), b-physics programme (CP etc.)  high luminosity (10 34 cm -2 s -1 ) high P T programme (Higgs etc.), searches for new physics –trigger must select physics and reject background with good (high) efficiency well known and monitored efficiency (well matched to off-line selection) with high reliability in shortest possible time (and lowest cost)

28. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 28 ARCHITECTURE 40 MHz TriggerDAQ 10’s PB/s (equivalent) ~ 100 Hz~ 100 MB/sPhysics Three logical levels LVL1 - Fastest: Only Calo and Mu Hardwired LVL2 - Local: LVL1 refinement + track association LVL3 - Full event: “Offline” analysis ~3  s ~ ms ~ sec. Hierarchical data-flow On-detector electronics: Pipelines Event fragments buffered in parallel Full event in processor farm

29. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 29 Experiment TDAQ comparisons

30. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 30 Trigger design (cont.) Level 1 –inclusive triggers Level 2 –confirm Level 1, some inclusive, some semi- inclusive, some simple topology triggers, vertex reconstruction (e.g. two particle mass cuts to select Zs) Level 3 –confirm Level 2, more refined topology selection, near off-line code

31. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 31 Trigger rates and decision times

32. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 32 T/DAQ system overview Latency: 2.5s (max) Latency: 2.5s (max) Hardware based (FPGA, ASIC) Hardware based (FPGA, ASIC) Calo/Muon (coarse granularity) Calo/Muon (coarse granularity) Latency: ~10 ms (average) Latency: ~10 ms (average) Software (specialised algs) Software (specialised algs) Uses LVL1 Regions of Interest Uses LVL1 Regions of Interest All sub-dets, full granularity All sub-dets, full granularity Emphasis on early rejection Emphasis on early rejection Latency: few sec (average) Latency: few sec (average) Offline-type algorithms Offline-type algorithms Full calibration/alignment info Full calibration/alignment info Access to full event possible Access to full event possible LVL1 LVL2 EF

33. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 33 LVL1 Overview Identify basic signatures of interesting physics –muons –em/tau/jet calo clusters –missing/sum E T Hardware trigger –programmable and custom electronics (FPGA + ASIC) –programmable thresholds Decision based on multiplicities and thresholds

34. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 34 em cluster trigger algorithm

35. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 35 Em cluster trigger algorithm Trigger efficiency vs cluster threshold 1 x 1, 2 x 1 and 2 x 2 cell groupings (50 GeV electrons) 2 x 1 cell sharper threshold than 1 x 1 2 x 1 cell and 2 x 2 cell threshold nearly identical. 2 x 1 half the background rate of 2 x 2.

36. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 36 Level 1 Jet and em trigger (cont.) EM RoI multiplicity vs. threshold Jet RoI Multiplicity (E T > 5 GeV) E T [GeV] multiplicity

37. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 37 Level 1 Muon trigger RPC: Restive Plate ChambersTGC: Thin Gap ChambersMDT: Monitored Drift Tubes RPC - Trigger Chambers - TGC

38. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 38 Level 1 Muon trigger (cont.) Single-µ cross section 2-µ cross section h all b c h b c J/  Level-1 muon trigger from Muon Trigger Chambers Main single-muon background comes from hadrons (pi/K decays in flight) Steeply falling cross section with increasing pt of muon (and even steeper drop off of b/g) means rate can be controlled by fine-tuning threshold.

39. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 39 Estimated Level-1 accept rates

40. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 40 Level 2 system philosophy fundamental granularity of detectors –no special readout from front-ends –no inherent loss of data quality guidance from LVL1 - Region of Interest (RoI) –Only process data from areas indicated by Level 1 –reduces data to be moved to T2 processors Processing scheme –Requires updating!

41. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 41 Regions of Interest (RoIs)

42. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 42 Region of interest mechanism LVL1 selection is mainly based on local signatures identified at coarse granularity in muon detectors and calorimeter. Further rejection can be achieved by examining full granularity muon, calo and and inner detector data in the same localities The Region of Interest is the geometrical location of a LVL1 signature. It is passed to LVL2 where it is translated into a list of corresponding readout buffers LVL2 requests RoI data sequentially, one detector at a time, only transfers as much data as needed to reject the event. The RoI mechanism is a powerful and important way to gain additional rejection before event building Order of magnitude reduction in dataflow bandwidth, at small cost of more control traffic

43. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 43 HLT event selection strategy Processing in Steps –Alternate steps of feature extraction / hypothesis testing –Events can be rejected at any step if features do not fulfil certain criteria (signatures) Reconstruction in Regions of Interest (RoIs) –RoI size/position derived from previous step(s) Emphasis on early event rejection Emphasis on minimising a. Processing time b. Network traffic

44. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 44 Milestone schedule

45. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 45 ATLAS cavern – April 2002

46. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 46 ATLAS cavern – April 2003

47. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 47 Atlas cavern – April 2004

48. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 48 A Toroid End Cap cryostat’s journey