1. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 1 ATLAS Tau Trigger Belanger-Champagne, C; Benslama, K; Bosman, M; Brenner, R; Casado, MP; Czyczula, Z; Dam, M; Demers, S; Farrington, S; Igonkina, O; Kalinowski, A; Kanaya, N; Osuna, C; Pérez, E; Ptacek, E; Reinsch; A; Saavedra, A; Sopczak, A; Strom, D; Torrence, E; Tsuno, S; Vorwerk, V; Watson, A; Xella, S X-th International workshop on Tau Lepton Physics Novosibirsk, 22 – 25 Sep, 2008

2. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 2 Contents LHC start-up ATLAS experiment Motivation of tau trigger ATLAS Trigger and Tau Trigger Tau Trigger Efficiency from data Timing measurements Conclusions

3. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 3 ATLAS first event ATLAS first event (10 Sep) Triggered by L1TAU, L1 Min. Bias and L1JET

4. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 4 LHC project LHC cooldown status (24 Sep):

5. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 5 Expected LHC Performance Year/Parameter20082009 Beam energy5 TeV7 TeV Peak luminosity10 31 cm -2 s -1 10 33 cm -2 s -1 Integrated luminosity ~10 pb-1~few fb-1 Latest news: Start-up in spring 2009.

6. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 6 ATLAS experiment

7. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 7 Length= 55 m Width = 32 m Height = 35 m Depth =100 m Underground cavern in Point 1 for the ATLAS detector The Underground Cavern at Point-1 for the ATLAS Detector

8. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 8 15-April-2008 ATLAS RRB 8 37 Countries 169 Institutions 2500 Scientific Authors total (1800 with a PhD, for M&O share) Albany, Alberta, NIKHEF Amsterdam, Ankara, LAPP Annecy, Argonne NL, Arizona, UT Arlington, Athens, NTU Athens, Baku, IFAE Barcelona, Belgrade, Bergen, Berkeley LBL and UC, HU Berlin, Bern, Birmingham, UAN Bogota, Bologna, Bonn, Boston, Brandeis, Bratislava/SAS Kosice, Brookhaven NL, Buenos Aires, Bucharest, Cambridge, Carleton, Casablanca/Rabat, CERN, Chinese Cluster, Chicago, Chile, Clermont-Ferrand, Columbia, NBI Copenhagen, Cosenza, AGH UST Cracow, IFJ PAN Cracow, UT Dallas, DESY, Dortmund, TU Dresden, JINR Dubna, Duke, Frascati, Freiburg, Geneva, Genoa, Giessen, Glasgow, Göttingen, LPSC Grenoble, Technion Haifa, Hampton, Harvard, Heidelberg, Hiroshima, Hiroshima IT, Indiana, Innsbruck, Iowa SU, Irvine UC, Istanbul Bogazici, KEK, Kobe, Kyoto, Kyoto UE, Lancaster, UN La Plata, Lecce, Lisbon LIP, Liverpool, Ljubljana, QMW London, RHBNC London, UC London, Lund, UA Madrid, Mainz, Manchester, CPPM Marseille, Massachusetts, MIT, Melbourne, Michigan, Michigan SU, Milano, Minsk NAS, Minsk NCPHEP, Montreal, McGill Montreal, FIAN Moscow, ITEP Moscow, MEPhI Moscow, MSU Moscow, Munich LMU, MPI Munich, Nagasaki IAS, Nagoya, Naples, New Mexico, New York, Nijmegen, BINP Novosibirsk, Ohio SU, Okayama, Oklahoma, Oklahoma SU, Olomouc, Oregon, LAL Orsay, Osaka, Oslo, Oxford, Paris VI and VII, Pavia, Pennsylvania, Pisa, Pittsburgh, CAS Prague, CU Prague, TU Prague, IHEP Protvino, Regina, Ritsumeikan, UFRJ Rio de Janeiro, Rome I, Rome II, Rome III, Rutherford Appleton Laboratory, DAPNIA Saclay, Santa Cruz UC, Sheffield, Shinshu, Siegen, Simon Fraser Burnaby, SLAC, Southern Methodist Dallas, NPI Petersburg, Stockholm, KTH Stockholm, Stony Brook, Sydney, AS Taipei, Tbilisi, Tel Aviv, Thessaloniki, Tokyo ICEPP, Tokyo MU, Toronto, TRIUMF, Tsukuba, Tufts, Udine/ICTP, Uppsala, Urbana UI, Valencia, UBC Vancouver, Victoria, Washington, Weizmann Rehovot, FH Wiener Neustadt, Wisconsin, Wuppertal, Würzburg, Yale, Yerevan ATLAS Collaboration

9. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 9 Barrel toroids

10. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 10 Barrel: 3 independent readouts: I (inner) - M (middle) - O(outer) Muon spectrometer (barrel) O M I Chambers alternate with barrel toroids

11. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 11 Tile barrel Tile extended barrel LAr forward calorimeter (FCAL) LAr hadronic endcap (HEC) LAr EM endcap (EMEC) LAr EM barrel Calorimetry

12. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 12 Tracking detectors ~ 6m long, 1.1 m radius Si Strips Tracker : SCT Transition Radiation Tracker : TRT Pixels Beam pipe

13. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 13 ATLAS Trigger HLTHLT DATAFLOWDATAFLOW 40 MHz 75 kHz ~2 kHz ~ 200 Hz 120 GB/s ~ 300 MB/s ~2+4 GB/s Event Building N/work Dataflow Manager Sub-Farm Input Event Builder EB SFI EBN DFM Lvl2 acc = ~2 kHz Event Filter N/work Sub-Farm Output Event Filter Processors EFN SFO Event Filter EFP ~ sec ~4 GB/s EFacc = ~0.2 kHz Trigger DAQ RoI Builder L2 Supervisor L2 N/work L2 Proc Unit Read-Out Drivers FE Pipelines Read-Out Sub-systems Read-Out Buffers Read-Out Links ROS 120 GB/s ROB LV L1 D E T R/O 2.5  s Calo MuTrCh Other detectors Lvl1 acc = 75 kHz 40 MHz ROD LVL2 ~ 10 ms ROIB L2P L2SV L2 N RoI RoI data = 1-2% RoI requests underground (USA15) surface (SDX1)

14. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 14 ATLAS contributions Poster by Z.Czyczula (Copenhagen), “Tau Physics with First Data at ATLAS” Talks: –M.P.Casado (Barcelona), “ATLAS tau trigger” –F.Sarri (Pisa), “Search of the Higgs boson decaying into tau-leptons at ATLAS” –A.Kalinowski (Univ. of Regina), “Tau Lepton Reconstruction and ID with the ATLAS Detector at LHC”

15. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 15 Tau Trigger Motivation ATLAS tau trigger aims at selecting hadronic decays of tau leptons, mainly one or three charged pions plus neutrals and one neutrino. It is difficult due to the high rate and occupancy but increases tremendously the physics potential. More information about tau triger in CERN-OPEN-2008-020

16. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 16 Motivation at 10 31 cm -2 s -1 Fundamental for W→  (first source of taus, 200000 with tau15i in 100 pb -1 at 10 31 cm -2 s -1 ). Measure: –Cross section  (pp→W)xBR(W→  ). –Leptonic branching fractions of W. –Lepton universality. Relevant only for very first data at low instantaneous luminosity due to trigger rates. See CERN-OPEN-2008-020 ATLAS preliminary

17. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 17 Motivation at 10 33 cm -2 s -1 Essential in the following studies: –Charged Higgs of Minimal Supersymmetric Standard Model (MSSM) H ± → . –In states with more than one lepton, like SM Higgs boson, MSSM neutral Higgs boson, Z’ boson decays, or decay chains in SUSY particles.

18. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 18 Z’→  → hh at 800 GeV Trigger: tau35i (*) + met40 Collinear mass distribution for a hadron- hadron final states for a Z’ signal of 800 GeV. (Collinear aproximation: visible products and neutrino travel together.) Reconstructed visible mass distribution for hadron-hadron final states for a Z’ signal of 800 GeV. (*) tauXXi: First part is type of particle, “XX” is the E T threshold, and “i” indicates an isolation requirement in addition. ATLAS preliminary

19. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 19 The first level trigger (L1) finds regions of activity in the detector, and passes this information to the second level trigger (L2). The second level accesses the data in the region of activity determined by L1 (a few percent of the total). The third level trigger (or Event Filter) can also operate in the region determined by L2. ATLAS Trigger: Regions of Interest (RoI)

20. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 20 Level 1 Tau Trigger –Tau Cluster: Energy in the two most energetic neighboring EM towers + the central 2x2 hadronic towers. -EM Isolation: Energy in the isolating ring between 2x2 and 4x4 in the EM calorimeter. -Hadronic Isolation: Energy in the isolating ring between 2x2 and 4x4 in the hadronic calorimeter.  x  = 0.1 x 0.1 |  | < 2.5

21. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 21 Performance of L1 Tau Trigger Efficiencies normalized with respect to offline (optimized to select those tau events which are likely to be reconstructed with the offline tau algorithms). Dijet sample 8<pT<140 GeV ATLAS preliminary ATLAS preliminary

22. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 22 HLT (L2 + EF) Selection Basic concepts: Guided and simultaneous reconstruction (for the different regions of activity) Each level uses the information of the preceeding level The reconstruction is done simultaneously for the different regions of activity. The rejection is applied as soon as possible. The second level trigger access only a few % of the total amount of data. In the third level the whole even is also accessible. Iso lation pt> 15GeV Cluster shape track finding Iso lation pt> 15GeV Cluster shape track finding TAU15i + tau15i + tau15 + tau +  cand + Signature  L1 seed  STEP1 STEP4 STEP3 STEP2 time Example: Z   +  - tau15i

23. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 23 Tau HLT Selection Refine ( ,  ) with the calorimeter and calculate shape variables Determine tracking variables including recalculation of ( ,  ) Matching of calorimeter cluster and track collection L2 selection EF selection Similar to L2, but using sophisticated offline algorithms. The whole event and detailed calibrations are available.

24. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 24 L2 variables (high energy taus) Calorimeter Tracking ATLAS preliminary

25. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 25 Event Filter variables (high energy taus) ATLAS Calorimeter ATLAS preliminary

26. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 26 Efficiencies per level Efficiencies calculated with respect to the preceeding level.

27. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 27 Efficiency curves Efficiencies normalized with respect to offline. tau20i ATLAS preliminary

28. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 28 Rates per level Rates calculated on QCD background for L= 10 31 cm -2 s -1.

29. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 29 Tau Trigger Menus MenuMotivation Single tauTo be used in combination with other triggers (as MissET, leptons or jets), except for very high E T. Single trackSelect RoIs with a single track to align the tracker & for E/p measurements. tau + missing ET Wide spectrum of physics. At 10 31 priority is W→  tau + l (+jets)Double tau decays (Z,H/A,…) tau + tau (+jets)As tau + l (+jets) with both taus decaying hadronically tau + jets, tau + bjets ttbar studies Commiss. itemsHLT decision is neglected, record only a fraction.

30. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 30 Tau Trigger Menu at 10 31 cm -2 s -1

31. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 31 Z→  : important at 10 31 cm -2 s -1 14000 events with tau15i in 100pb -1 at 10 31 cm -2 s -1. Measure: –  trigger efficiency in Z→  (h) lepton –  ID efficiency. –Detector calibration: E T miss &  -jet energy scale determination. –Cross section (SM measurement) See CERN-OPEN-2008-020 ATLAS preliminary

32. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 32 Efficiency measurement on data Z→  →lep hadron –Tag the lepton (electron or muon) and probe the other side. –Background: top and QCD. –Expect 1200 signal events in 100pb -1 with 30% background. –Do first single tau trigger turn-on curves. 30pb -1

33. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 33 Efficiency measurement on data tau + MissET trigger with ttbar –Tag 4jet25, study tau decay offline. –Background: hadronic ttbar, single top and QCD. –Expect ~130 signal events in 100pb -1 with ~85 background events. –Strategy to determine combined tau trigger efficiency with first data.

34. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 34 Timing results Time in ms, per RoI Time in ms, per event Mean algorithm execution time for each signature of the tau slice. The average execution time of each algorithm remains roughly equal between signatures, while the average total time per event decreases as a result of the lower number of RoIs per event for high energy signatures. Timing is important in HLT because it gives latency. If it takes too long, we can not process data!

35. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 35 Conclusions The tau trigger has recorded the first single beam events from the LHC. The detector and trigger will be commissioned as soon as we have the first collisions. The tau trigger will be used standalone for high thresholds and in combined mode for low energies. Hope to have early measurements with tau data and maybe some discoveries next year…

36. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 36 Backup slides

37. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 37 Level 1 Trigger Schematic view of the level 1 trigger Hardware based

38. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 38 Resolution at each level ATLAS Preliminary

39. TAU08, NovosibirskM. Pilar Casado (IFAE & UAB) 39 Single Tau Trigger Rates Min. bias with  =70mb, lumi 10 31 cm -2 s -1 Only statistical errors