The LHCb DAQ and Trigger Systems: recent updates

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The LHCb DAQ and Trigger Systems recent updates

• Ricardo Graciani
• XXXIV International Meeting on Fundamental
  Physics.

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Overview

• LHCb
• The Original Design
• Trigger Rate
• From 200 Hz to 2000 Hz
• Level 1 suppression
• 1 MHz Readout
• Outlook

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LHCb

• LHC
• 40 MHz crossing rate
• 30 MHz with bunches from both directions
• Luminosity 21032 cm-2 s-1
• 10 to 50 times lower than _at_ ATLAS, CMS
• One Arm Forward Spectrometer
• LHCb rates
• (for visible events ? at least 2 tracks in
  acceptance)
• Total rate (minimum bias) 10 MHz
• bb 100kHz
• Whole decay of one B in acceptance 15kHz
• cc 600kHz

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The Spectrometer
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LHCb Physics Program

• Bs oscillation frequency, phase and ?Gs
• Bs?Ds?, J/?F, J/??, ?cF
• ? from Bd??0??
• ? with Bd?J/?KS as a proof of principle
• And ? from b?s penguin
• ? in various channels, differing sensitivity to
  new physics
• Time-dependent CP asymmetry of Bs?Ds-K and DsK-
• Time dependent CP asymmetries of Bd?pp- and Bs ?
  KK-
• Comparison of decay rates in the
  Bd?D0(Kp-,K-p,KK-)K0 system
• Comparison of decay rates in the
  B-?D0(Kp-,Kp-pp-)K- system
• Dalitz analysis of B- ? D0(KSp-p)K- and Bd ?
  D0(KSp-p)K0
• Rare decays
• Radiative penguin Bd ? K g, Bs ? F g, Bd ? ?g
• Electroweak penguin Bd ? K0 mm-
• Gluonic penguin Bs ? FF, Bd ? FKs
• Rare box diagram Bs? mm-
• Bc , b-baryon physics unexpected !

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The LHCb TP
HLT
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From 200 to 2000 Hz

• Initial Design
• 200 Hz of partial or fully reconstructed B final
  States.
• Exclusive B Trigger.
• Limitations
• Strong MC dependence
• Efficiency determination
• Detector Performance (vertex, proper time, PID)
• Backgrounds
• Huge MC samples are necessary.
• Conclusion
• Review strategy
• Use real Data for the above studies
• Re-evaluation of Computing needs
• Factor 10 reduction on MC needs
• Factor 10 increase on Trigger rate

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2 kHz Trigger Output
Output rate Trigger Type Physics Use
200 Hz Exclusive B candidates Specific final states
600 Hz High Mass di-muons J/?, b?J/?X
300 Hz D Candidates Charm, calibrations
900 Hz Inclusive b (e.g. b?m) B data mining

• Best guess at present (split between streams
  still to be determined)
• Exclusive reconstruction is kept
• Large inclusive streams to be used to control
  calibration and systematics (trigger, tracking,
  PID, tagging,)
• 10-15 acceptance for any channel on inclusive
  samples.

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Cost Estimate
200Hz 2000Hz
Hoffman 2007 Now 2008
CERN CPU(MSI2k) 2.0 0.9
CERN Disk(PB) 0.3 0.8
CERN Tape(PB) 1.2 1.4
Tier-1s CPU(MSI2k) 8.3 4.4
Tier-1s Disk(PB) 1.6 2.4
Tier-1s Tape(PB) 0.75 2.1
Tier-2s CPU(MSI2k) - 7.6
Tier-2s Disk(PB) - 0.02
Relative Cost Relative Cost 1.0 0.91
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DAQ Architecture
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The old System

• Detector L0 boards
• talk Gb Ethernet
• implement buffer to allow for Level 1 latency
• Two Data Streams
• Level-1 trigger with latency limit of 58 ms _at_1
  MHz
• 3.8 kB/event ? 4.3 GB/sec
• HLT traffic without latency limitations _at_ 40 kHz
• 30 kB/event ? 1.2 GB/s

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1 MHz DAQ
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Advantages

• Major simplification of the DAQ system
• Only one data flow through the system
• Elimination of the SFCs
• Event-Building in each CPU node
• Elimination of the Level-1 decision sorter
• No latency limitations for event processing
• Well suited for multi-core CPU architectures
• For the Trigger software
• ALL information available at all times in full
  precision and full granularity
• Better trigger efficiency
• Required Switching power 60 GB/s

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The Hardware Candidate

• Force10 equipment
• Port densities
• Biggest switch has 14 slots for line-cards
• Biggest port density is 90 Gb Ethernet ports per
  line-card (90/48 over-committed)
• 1490 1260 GbEthernet ports
• Switching Fabric
• Switching capacity is
• raw 1.6 Tb/sec,usable 1.2 Tb/sec (150 GB/s)

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Reviewed HLT Strategy
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Outlook

• LHCb had a very scalable and flexible DAQ schema.
• LHCb Trigger includes inclusive samples
• HLT rate from 200 to 2000 Hz.
• High-mass di-muon
• D
• Inclusive b
• Full L0 rate (1 MHz) sent to Online Filter Farm
  for a full software High Level Trigger.
• Review Vertical Trigger strategy for HLT.