The ATLAS Trigger and Data Acquisition System John

The ATLAS Trigger and Data Acquisition System John Strong Royal Holloway, University of London John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004

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

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. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 3

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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 4

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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 5

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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 6

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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 7

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

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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 9

The LHC & experiment layout • 7 Te. V on 7 Te. V pp collider – ~ 27 km of 8. 3 T superconducting dipoles at 1. 8°K – Luminosity of 2. 1033 cm-2 s-1 initially, design 1. 1034 cm-2 s-1 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 10

LHC Physics (1) • 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 • AND - Something has to happen by ~1 Te. V – 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 Te. V scale John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 11

LHC Physics (2) Rate at design luminosity Inelastic Channel X-section Rate/s Ineleastic 0. 1 b 109 B-physics B physics 200 2. 106 & CPμb violation Jet (>250 Ge. V) 100 nb 103 W ℓν 20 nb 2. 102 Jet (q&g) physics t-t production 1 nb 10 W -> lν Higgs (100 Ge. V) 20 pb 2. 10 -1 t-t production Z’ (1 Te. V) 10 pb 10 -1 Ge. V/c 2) Higgs (500 Higgs Ge. V) (m=100 1 pb 10 -2 Higgs (m=500 Gev/c 2) Lepton decay branching ratio ~10 -2 selection power for Higgs ~1013 A special piece of hay in a haystack ~109 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 12

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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 13

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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 14

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

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 IT, Indiana, Innsbruck, Iowa SU, Irvine UC, Istanbul Bogazici, KEK, Kobe, 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 SU, Milano, Minsk NAS, Minsk NCPHEP, Montreal, FIAN Moscow, ITEP Moscow, MEPh. I 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 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 Countries Total Scientific Authors 1600 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 16

The LHC and ATLAS • LHC has – a high luminosity 1034 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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 17

The ATLAS Sub-Detectors • Inner tracker – pixels (silicon) • (3 layers) precision 3 -D points; • 1. 4 108 channels; occupancy 10 -4 – silicon strips • (4 layers) precision 2 -D points; • 5. 2 106 channels; occupancy 10 -2 – transition radiation tracker (straw tubes) • (40 layers) continuous tracker + electron identification; • 4. 2 105 channels; 12 -33% occupancy John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 18

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

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

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

Sub-Detectors (cont. ) • solenoid – between tracker and calorimeters 4 m x 7 m x 1. 8 T • calorimetry –electromagnetic • liquid argon (accordion) detector + lead –hadronic • scintillator tiles & liquid argon + iron – 2. 3 105 channels; occupancy 5 -15% • muon system –air-core toroid magnet system –trigger - resistive plate and thin gap chambers –precision – monitored drift tubes – 1. 3 106 channels; occupancy 2 -7. 5% John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 22

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

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

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

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

ATLAS Trigger Physics programme is luminosity dependent § low luminosity (2. 1033 cm-2 s-1) - first ~2 years • high PT programme (Higgs etc. ), b-physics programme (CP etc. ) § high luminosity (1034 cm-2 s-1) • high PT 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) John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 27

ARCHITECTURE Trigger 40 MHz DAQ Three logical levels Hierarchical data-flow ~3 ms LVL 1 - Fastest: Only Calo and Mu Hardwired On-detector electronics: Pipelines ~ ms LVL 2 - Local: LVL 1 refinement + track association Event fragments buffered in parallel ~ sec. LVL 3 - Full event: “Offline” analysis Full event in processor farm ~ 100 Hz Physics John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 10’s PB/s (equivalent) ~ 100 MB/s 28

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

Trigger design (cont. ) • Level 1 – inclusive triggers • Level 2 – confirm Level 1, some inclusive, some semiinclusive, 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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 30

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

LVL 1 T/DAQ system overview n n n LVL 2 n n n EF n n Latency: 2. 5 ms (max) Hardware based (FPGA, ASIC) Calo/Muon (coarse granularity) Latency: ~10 ms (average) Software (specialised algs) Uses LVL 1 Regions of Interest All sub-dets, full granularity Emphasis on early rejection Latency: few sec (average) Offline-type algorithms Full calibration/alignment info Access to full event possible John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 32

LVL 1 Overview • Identify basic signatures of interesting physics –muons –em/tau/jet calo clusters –missing/sum ET • Hardware trigger –programmable and custom electronics (FPGA + ASIC) –programmable thresholds • Decision based on multiplicities and thresholds John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 33

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

Em cluster trigger algorithm Trigger efficiency vs cluster threshold 1 x 1, 2 x 1 and 2 x 2 cell groupings (50 Ge. V 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. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 35

Level 1 Jet and em trigger (cont. ) Jet Ro. I Multiplicity (ET > 5 Ge. V) EM Ro. I multiplicity vs. threshold multiplicity John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 ET [Ge. V] 36

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

Level 1 Muon trigger (cont. ) all h b c all b h J/ c Single-µ cross section Level-1 muon trigger from Muon Trigger Chambers Main single-muon background comes from hadrons (pi/K decays in flight) 2 -µ cross section 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. John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 38

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

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

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

Region of interest mechanism • LVL 1 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 inner detector data in the same localities • The Region of Interest is the geometrical location of a LVL 1 signature. • It is passed to LVL 2 where it is translated into a list of corresponding readout buffers • LVL 2 requests Ro. I data sequentially, one detector at a time, only transfers as much data as needed to reject the event. • The Ro. I 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 John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 42

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) Emphasis on early event rejection • Reconstruction in Regions of Interest (Ro. Is) – Ro. I size/position derived from previous step(s) Emphasis on minimising a. Processing time b. Network traffic John Strong – The ATLAS Trigger and DAQ System – PSI - 30 th April 2004 43

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

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

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

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

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