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Gunther Roland - MIT Quark Matter 2006 Gunther Roland Massachusetts Institute of Technology Triggering in CMS CMS Heavy Ion Groups: Athens, Auckland, Budapest,

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Presentation on theme: "Gunther Roland - MIT Quark Matter 2006 Gunther Roland Massachusetts Institute of Technology Triggering in CMS CMS Heavy Ion Groups: Athens, Auckland, Budapest,"— Presentation transcript:

1 Gunther Roland - MIT Quark Matter 2006 Gunther Roland Massachusetts Institute of Technology Triggering in CMS CMS Heavy Ion Groups: Athens, Auckland, Budapest, CERN, Chongbuk, Colorado, Cukurova, Iowa, Kansas, Korea, Los Alamos, Lyon, Maryland, Minnesota, MIT, Moscow, Mumbai, Rice, Seoul, Vanderbilt, UC Davis, UI Chicago, Yonsei, Zagreb

2 Gunther Roland - MIT Quark Matter 2006 2 Compact Muon Solenoid CASTOR (5.32 < η < 6.86) ZDC (z = ±140 m) Forward calorimeters One of two large p+p experiments at LHC “Large”: 2700 collaborators, $500M, 14500 tons

3 Gunther Roland - MIT Quark Matter 2006 3 p+p DAQ&Trigger Challenge: - 25 collisions per bunch crossing - 40MHz bunch crossing frequency - Rejection factor of O(10 6 ) needed CMS as a Heavy Ion Experiment 22  = 5 for Si tracker  = 10 for Calorimetry Capabilities High Precision Tracking over  <2.5 Muon Identification over  <2.5 High Resolution Calorimetry over  < 10 Forward coverage Large Bandwidth DAQ + Trigger

4 Gunther Roland - MIT Quark Matter 2006 4 switch Trigger in Pb+Pb vs pp Level-1 p+p Collision rate1GHz Event rate40MHz Output bandwidth100 GByte/sec Rejection99.7% Level 1 trigger - Uses custom hardware - Muon chamber + calorimeter information - Decision after ~ 3 μsec High Level Trigger p+p Input event rate100kHz Output bandwidth225 MByte/sec Output rate150Hz Rejection99.85% High level Trigger - ~1500 Linux servers (~12k CPU cores) - Full event information available - Runs “offline” algorithms

5 Gunther Roland - MIT Quark Matter 2006 5 switch Trigger in Pb+Pb vs pp Level-1 Pb+Pbp+p Collision rate3kHz (8kHz peak)1GHz Event rate3kHz (8kHz peak)40MHz Output bandwidth100 GByte/sec Rejectionnone99.7% Level 1 trigger - Uses custom hardware - Muon chamber + calorimeter information - Decision after ~ 3 μsec High Level Trigger Pb+Pbp+p Input event rate3kHz (8kHz peak)100kHz Output bandwidth225 MByte/sec Output rate10-100Hz150Hz Rejection97-99.7%99.85% High level Trigger - ~1500 Linux servers (~12k CPU cores) - Full event information available - Runs “offline” algorithms Main “hardware” task for CMS heavy ion running

6 Gunther Roland - MIT Quark Matter 2006 6 Heavy Ion Trigger Strategy

7 Gunther Roland - MIT Quark Matter 2006 7 Heavy Ion Trigger Strategy Select Hard Probes embedded in highly complex events –Best selection needs full event information, complex algorithms DAQ can deliver full Pb+Pb event stream to HLT –100 Gbyte/sec bandwidth –~12k 1.8GHz Opteron equivalent CPU cores 3KHz average rate, 8kHz max (1.5-4 CPU-seconds per event) Trigger strategy –Min-bias Pb+Pb trigger in Level-1 (+ muon/calo seed info) –Event selection/rejection in HLT selection Run “offline” algorithms on every Pb+Pb event

8 Gunther Roland - MIT Quark Matter 2006 8 Min bias trigger from HF Minimum bias trigger for p+p and Pb+Pb Forward Calorimeter (HF) 3.0<|η|<5.0 Similar to PHOBOS “Paddle” trigger HF

9 Gunther Roland - MIT Quark Matter 2006 9 Event Characterization in HLT Event plane resolution σ~0.12 rad Single Pb+Pb event, b=6fmEnergy in HF forward calorimeter Event characterization from Calorimeters - Centrality - Reaction plane calculated at High Level Trigger Unpacking Calo data takes ~100ms per min bias event event

10 Gunther Roland - MIT Quark Matter 2006 10 Good Resolution Pb+Pb dN/dy = 5000 p+p High Efficiency Run offline jet finder at HLT - modified iterative cone algorithm Performance as shown in offline studies Jet studies from CMS Note 2003/004 Heavy Ion Jet Finder Performance

11 Gunther Roland - MIT Quark Matter 2006 11 Jet Finder Timing Jet finder timing –Full modified iterative cone with background subtraction –Average execution time t ~ 0.25sec per min bias event –This corresponds to ~5% of HLT time budget No. of Events

12 Gunther Roland - MIT Quark Matter 2006 12 Online Muon finding Muon finding in HLT - L1: muon chambers stubs (Hardware) - L2: muon chambers stubs (HLT - fast) - L3: Match with tracker info (HLT - slow) Performance as shown in offline studies - Si tracker info allows resolution of upsilon family Dimuon invariant mass (GeV) Quarkonium studies from CMS Note 2006 Upsilon family

13 Gunther Roland - MIT Quark Matter 2006 13 Muon L2 timing Timing of L2 muon finder –Muon chamber stand-alone reconstruction – Average t ~ 0.1sec per min bias event –~2% of HLT time budget No. of Events

14 Gunther Roland - MIT Quark Matter 2006 14 Muon L3 timing Timing of muon L3 algorithm –Reduces background by factor 4 –Called for 1.6% of min bias events –Average execution time 10 +/- 3 sec –Need speed-up by factor ~5 for design luminosity run

15 Gunther Roland - MIT Quark Matter 2006 15 Event Size Bias Event size bias from trigger –Centrality bias from dimuon and jet trigger –Increase in event-size by factor 2-3 vs min bias –Determines rate of events to tape Jets ~ 6MB L3 di-muons ~ 5MB

16 Gunther Roland - MIT Quark Matter 2006 16 High Level Trigger Simulations Production x-sections (Pythia pp) Production rates in “Pb+Pb”

17 Gunther Roland - MIT Quark Matter 2006 17 High Level Trigger Simulations Production X-sections LuminosityN coll Acc(y,p T )Eff(y,p T ) Acceptance, BREfficiency 1 + Bkg/Sig(y,p T ) Trigger Table x DAQ rate Signal rate d 2  /dydp T Trigger rate (signal + bkg) Rate to tape Production rate Acceptance, efficiency, backgrounds measured and parametrized from full offline simulation + algorithms Output Rates to tape Timing of offline algorithms and event size bias measured on full simulations

18 Gunther Roland - MIT Quark Matter 2006 18 Trigger table Strawman trigger table for design lumi (V0.09) 220 Many more channels to be added, in particular multi-object triggers (e.g. dimuons + jets) Prescales and thresholds can be adjusted as function of e.g. centrality and instantaneous luminosity

19 Gunther Roland - MIT Quark Matter 2006 19 Physics example - Jet trigger and R AA Rates to tape with HLT Min bias with HLT Min bias HLT improves hard probe statistics by more than factor 10 Expect that jet trigger will increase range for charged hadron R AA by more than factor 2 (to ~200 GeV/c) Centrality info at HLT important for improving R CP via centrality dependent prescales and thresholds Note: HLT rates only counted within respective trigger channel

20 Gunther Roland - MIT Quark Matter 2006 20 Physics example - Y’/Y vs p T (10 6 sec @ design lumi) Calculations: Gunion and Vogt Detailed studies of Upsilon family feasible with HLT with HLT L3 selection

21 Gunther Roland - MIT Quark Matter 2006 21 a kind of summary… Centrality HF, ZDC Reaction Plane HF, EE, HE  EP <0.1 Rad Mult. d 2 N/d    Inner tracker, Totem          E T flow d 2 E T /d    EB,EE,HB,HE,HF Castor, ZDC   7 d 3 N/dp T d  d  Inner Tracker |  | 1GeV/c Primary vertex Inner Tracker  vtx <10  m Sec. vertex tag Inner Tracker  vtx ~ 100 - 10  m Central Jets EB,EE,HB,HE N > 10 7 |  | 50 GeV Forward Jets HF 3 < |  |<5  0 d 3 N/dp T d  d  EB,EE |  |<2.5,3<p T <20GeV Photons EB,EE |  |<3.0 Electrons EB,EE |  |<3.0 Single muons MB, ME |  | 3 GeV/c J/  MB, ME N > 10 5 |  | 1..3GeV/c Y,Y’,Y’’ MB, ME N > 20k |  | 0 GeV/c Z 0 MB, ME N > 10k |  | 0 GeV/c  * MB, ME |  |<2.4 Global TrackingCalorimetryMuons = to be investigated

22 Gunther Roland - MIT Quark Matter 2006 22 a kind of summary… Centrality HF, ZDC Reaction Plane HF, EE, HE  EP <0.1 Rad Mult. d 2 N/d    Inner tracker, Totem          E T flow d 2 E T /d    EB,EE,HB,HE,HF Castor, ZDC   7 d 3 N/dp T d  d  Inner Tracker |  | 1GeV/c Primary vertex Inner Tracker  vtx <10  m Sec. vertex tag Inner Tracker  vtx ~ 100 - 10  m Central Jets EB,EE,HB,HE N > 10 7 |  | 50 GeV Forward Jets HF 3 < |  |<5  0 d 3 N/dp T d  d  EB,EE |  |<2.5,3<p T <20GeV Photons EB,EE |  |<3.0 Electrons EB,EE |  |<3.0 Single muons MB, ME |  | 3 GeV/c J/  MB, ME N > 10 5 |  | 1..3GeV/c Y,Y’,Y’’ MB, ME N > 20k |  | 0 GeV/c Z 0 MB, ME N > 10k |  | 0 GeV/c  * MB, ME |  |<2.4 Global TrackingCalorimetryMuons = to be investigated = available at HLT Most physics info available at HLT Allows optimal use of bandwidth w/ best efficiency and minimal bias

23 Gunther Roland - MIT Quark Matter 2006 23 Additional info

24 Gunther Roland - MIT Quark Matter 2006 24 Data Samples Centrally produced fully simulated Heavy Ion Events (OSCAR 3.9.8 / ORCA 8.7.3) Signal: Pythia multijet (unquenched) Background: Hydjet events –hi05_hydjet_x0_bB_pt07 with B = 0, 9, 12 Used for size and jet, di-muon timing studies

25 Gunther Roland - MIT Quark Matter 2006 25 Event Size Study For each b, digitized the mixed events using ORCA 8.13.3 using example production config Write DIGI files for 10 and 40 events Use file sizes and the particle and hit counts from log files to estimate differential event size Estimate base (empty) event size from this data and known pp event size

26 Gunther Roland - MIT Quark Matter 2006 26 Timing Study – Jet Finder ORCA 8.13.3, Pileup subtraction jet finder –CMS AN 2003-004 : V. Gavrilov, O. Kodolova, A. Oulianov, I. Vardanian –Used the implementation by C. Roland Used COBRA TimeMe framework and ROOT TstopWatch –Records time spent in a part of the code and the number of invocations, creates average timings –Add extra timers to study timing of different parts of the algorithm

27 Gunther Roland - MIT Quark Matter 2006 27 Event size in Pb+Pb vs p+p Total “fudge factor” of 5 for initial p+p run But: “Factor” is really combination of offset+factor – Don’t expect zero-suppression, HLT info, occupancy factor to be proportional to soft particle multiplicity – Rather than guess shift/factor for every contribution, we added 2 x p+p “extra size” to Pb+Pb for initial and steady- state runs (2MB, 1MB) Worst case: What if it really is a factor of 5? – dNch/dy for min bias Pb+Pb < 1000 compared to 20x7 for design lumi p+p at 14TeV – I.e. 12x less rate than p+p (8kHz vs 100kHz) – Still ok relative to p+p

28 Gunther Roland - MIT Quark Matter 2006 28 Timing Study – Di-muon trigger ORCA 8.13.3 with Heavy Ion di-muon trigger –CMS AN 2006-011 M. Bedjidian, O. Kodolova –Implementation provided by O. Kodolova Used COBRA TimeMe framework Added many extra timers and trace output Measured Level 1 selectivity and Level 2 timing and selectivity Measured L3 timing

29 Gunther Roland - MIT Quark Matter 2006 29 Event size in Pb+Pb vs p+p 0-suppressionHLT-objects MC vs real occupancy From Computing RTAG: CMS-Note 2004/031

30 Gunther Roland - MIT Quark Matter 2006 30 B

31 Gunther Roland - MIT Quark Matter 2006 31 Trigger Quality: beam gas rejection Beam-Gas Rejection –Gas pressure $ is expected to be low –For p+p collisions at 14TeV, only 20 * beam gas events per hour are expected Expectations and truth do not always match, we have a contingency –Pb(5.5TeV)+gas collisions are √s NN ~100GeV All particles go forward For beam-gas inside the detector Volume triggering on HF will remove these from the data $ 10 -11 Torr: cf 10 -10 at RHIC (warm sections) Proc. 2003 Particle accelerator conference * From the LHC machine working group

32 Gunther Roland - MIT Quark Matter 2006 32 Trigger Quality: beam gas rejection Hits from beam gas outside the detector volume are partially shadowed from near HF. Alternatively, HF has two layers –For real collisions (center of detector) inside layer has more hits –For beam gas outside the detector volume outside layer has more hits This scheme would need implemented in the HLT. Truth with geometrical acceptance

33 Gunther Roland - MIT Quark Matter 2006 33 Event size - 2 Fold event-size vs b with Glauber b distribution –Add 1MB to match pp – => event size distribution – => average event size for min-bias

34 Gunther Roland - MIT Quark Matter 2006 34 Assumptions - 4 Production cross-sections, charged multiplicity – Cross sections from Pythia 6.236 5.5 TeV p+p Implemented in HIROOT – Soft background/full simulations: Hydjet Three samples: dN/dy ~ 3300, 575 and 65 for b = 0,9 and 12fm – dN/dy for pp @ 14TeV ~ 7 i.e. pp total at full lumi is dN/dy ~ 140 Corresponds to ~ 2x PbPb@12fm Glauber: Project nuclear densities of colliding nuclei to determine number of participant nucleons, number of binary collisions HIROOT: ROOT with generator (Pythia etc) interface and collection of analysis classes

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