1 / 16

Development of an Interaction Trigger in ATLAS

Development of an Interaction Trigger in ATLAS. Regina Kwee CERN / Humboldt-Universität zu Berlin. Gentner Day 18.November 2009, CERN. Outline. Motivation Introduction to Minimum Bias Events Designing an Interaction Trigger Trigger Performance Studies Summary and Outlook.

kiet
Télécharger la présentation

Development of an Interaction Trigger in ATLAS

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. Development of an Interaction Trigger in ATLAS Regina Kwee CERN / Humboldt-Universität zu Berlin Gentner Day 18.November 2009, CERN

  2. Outline • Motivation • Introductionto Minimum Bias Events • Designing an Interaction Trigger • Trigger Performance Studies • Summaryand Outlook Gentner Day at CERN

  3. Motivation • Strategyat ATLAS • studyinelasticinteractionsatlowluminosities • L ≈ 1031 cm-2 s-1 • larger bunchpitchof 75 ns • → single pp-collisions • pp-interaction rate is <<1 • 10 % ofthebunch-crossingscontain a pp-interaction • → Minimum-Bias Trigger • selectsany pp-interaction • forpp-interaction rate ≈1 • → pure randomtrigger • Operation of LHC with pp-collisionsat (nominal) • √s = 14 TeV • L ≈ 1034 cm-2 s-1 • bunch-crossing rate of25 ns → highevent rate r = L x σ ≈ 109inel. pp-collisions/s • Pile-up • expect per bunch-crossing around 20 piled-up collisions → one of the biggest challenges at LHC: understanding QCD-background as basis for each physics analysis Gentner Day at CERN

  4. Minimum Bias Measurments dNch/dη at η = 0 • Physicsprocessesaresoftinteractions: havelow Q2 (smallmomentumtransfer) • perturbative QCD is not applicableforsmall Q2 : differential cross-sectiondivergesforpT→ 0 → employphenomenologicalmodelstodescribe soft QCD → Monte-Carlo predictionsat LHC energiesarehighlyuncertain! CERN-OPEN-2008-020 pseudorapidity η = -ln(tan(θ/2)) 900 GeV 7 TeV 14 TeV firstmeasurements in ATLAS: kinematicspectraofcharged particlesdNch/dpTanddNch/dη Gentner Day at CERN

  5. Minimum Bias Events • inelasticcross-sectioncanbe sub-dividedintoitssinglecontributions • predictionstronglydepend on thetheoretical model, hereshownforpythia 6.214 (phojet 1.12) at 14 TeV: • dominant: non-diffractiveevents • precisedefinitionofminimumbiasevents:givenbythetriggersystem! σndiff≈ 55 (68) mb σsdiff≈ 14 (11) mb σddiff≈ 10 (4) mb σcdiff≈ -/- (1) mb single-diffractivedissociation (sdiff) double diffractivedissociation (ddiff) central-diffractive dissociation (cdiff) non-diffractive dissociation (ndiff) Gentner Day at CERN

  6. Event TopologiesPythia Generator Level at 14 TeV chargedstable primaryparticles pseudorapidity diffractiveeventsaremore forwarddirected transversemomentum ndiff sdiff ddiff ATLAS – work in progress ndiff sdiff ddiff ATLAS – work in progress trackmultiplicity mostlylow-pttracksfrom allinelasticprocesses ATLAS – work in progress ndiff sdiff ddiff lowermultiplicity in diffractiveevents (moreforward) Gentner Day at CERN

  7. Minimum Bias Trigger ATLAS has 2 independentminimumbiastriggers: • Minimum Bias • Trigger Scintillators (MBTS) • relative simple detectorsystem: 16 scintillatorcounters per sidebetweenInnerDetector (trackingsystem) andLAr-calorimeter • cover 2.1< |η| < 3.8 • will beusedforcommissioning sub-detectorsystems • has a shortlifetime due toradiationdamages: 3-4 months at a luminosity of 5*1032 cm-2s-1 Gentner Day at CERN

  8. Minimum Bias Trigger ATLAS has 2 independentminimumbiastriggers: • Minimum Bias • Trigger Scintillators (MBTS) • relative simple detectorsystem: 16 scintillatorcounters per sidebetweenInnerDetector (trackingsystem) andLAr-calorimeter • cover 2.1< |η| < 3.8 • will beusedforcommissioning sub-detectorsystems • has a shortlifetime due toradiationdamages: 3-4 months at a luminosity of 5*1032 cm-2s-1 • InnerDetectorbased • Minimum Bias Trigger • provide a complementaryapproach • cover centraldetectorregion |η| < 2.5 • triggerrequirements: • introduceaslittlebiasaspossible • suppressefficientlyemptybunch-crossingand beam-backgroundevents • → mywork! Gentner Day at CERN

  9. Minimum Bias Trigger ATLAS has 2 independentminimumbiastriggers: • InnerDetectorbased • Minimum Bias Trigger • provide a complementaryapproach • cover centraldetectorregion |η| < 2.5 • triggerrequirements: • introduceaslittlebiasaspossible • suppressefficientlyemptybunch-crossingand beam-backgroundevents • → mywork! transitionradiation tracker (TRT) silicon strip detector (SCT) pixel detector Gentner Day at CERN

  10. The ATLAS Trigger System • The systemhasbeendesignedtocopewith ~ 1.5 PB data per second • Itfollowstheconceptof an „earlyrejection“ → 3 triggerlevels • L1: hardware + internaltrigger • L1 latency 2.5 μs • L2: softwaretrigger • reconstructsphysicsobjects foundby L1, tracks. • L2 latency 10 ms • EF: softwaretrigger • usesmoredetailedcalibrationsconstantsas L2, else same as L2 • EF latency ~ 1 second Generally „region-of-interests“, RoI‘s, areprocessed –unlike in minimumbiastriggers! Gentner Day at CERN

  11. ID based Minimum Bias Trigger • L1:randomtriggeron filledbunches → avoidsbias • L2:SpacePointCounter • forms 3d-detector hits in wholepixeland SCT (spacepoints) detector • operate just abovenoiselevel→ suppressemptybunch-crossingevents • needstobe robust against HV trips→ dynamicmaskingofnoisymodules • EF: TrackCounter • reconstructsiliconlow-pt-tracks • requireonetrackclosetothe IP → suppress beam-gas/-haloevents • Features/Status • algorithmsarehighlyconfigurable→ providesflexibilitytoreact on different beam backgroundconditions • a back-uptriggerusingonly TRT hitsat L2 hasbeendeveloped (TRT provedtobeverystableduringfirst beam operations) • all minbiastriggershavealreadytakenand still take (cosmic) data! Gentner Day at CERN

  12. Performance Studies • triggerefficiencyat L2 • An SCT spacepointsisformedby a coincidenceof 2 strips • → intrinsicnoisesuppression SCT spacepoints ATLAS – work in progress ndiff sdiff ddiff empty ATLAS – work in progress cutat 3 SCT spacepointsat L2 suppresses all emptyevents Gentner Day at CERN

  13. Performance Studies • triggerefficiencyat L2 • triggerefficiencyat EF ATLAS – work in progress ATLAS – work in progress cutat 3 SCT spacepointsat L2 + additional cutat 1 trackwith |z0| < 200 mm at EF cutat 3 SCT spacepointsat L2 suppresses all emptyevents Gentner Day at CERN

  14. Performance Studies • triggerbias → change in distribution (e.g. η, pT, Nch) whichisintroducedbythetriggercondition (hereshownfor 3 SCT spacepoints) ID ndiff sdiff ddiff ndiff sdiff ddiff ATLAS – work in progress ATLAS – work in progress nobiasexpected in η (measurewithin ID range) morestudiesneededfor multiplicitydependence Gentner Day at CERN

  15. Summary and Outlook • minimumbiasstudiesareneededto understand propertiesofinelasticinteractions→ they form dominant QCD background in LHC enviroment • minimumbiasevents will form pile-upathighluminosityruns → studyatlowluminosities, designed an interactiontrigger • Thesis plan (adaptedtonew LHC schedule) → preparefordetectorandtriggercommissioningwithminimumbiastriggers • moreperformancestudiesongoing→ will determinetheemploymentof (all) minbiastriggers • functionalityprovided, lookingforwardforcollsions! Gentner Day at CERN

  16. Danksagung Manythankstomysupervisors Nick Ellis (CERN) and Hermann Kolanoski (Humboldt-University) andmyformersupervisor Klaus Mönig (DESY) as well astomy ATLAS colleguesand CMS friends andthe BMBF forcreatingthe Wolfgang-Genter-Program! Gentner Day at CERN

More Related