1. Commissioning of the ALICE HLT, TPC and PHOS systems
Kalliopi Kanaki
University of Bergen

2. Norwegian participation in:
High Level Trigger (HLT)
Time Projection Chamber (TPC)
PHOton Spectrometer (PHOS)
Online calibration framework
Front-End Electronics (FEE) for TPC/PHOS
ALICE GRID computing

3. Aims of HLT
Lossless data compression to match data acquisition and mass storage bandwidth
Online event reconstruction → fast pattern recognition (online tracking)
Physics triggers (e.g. open charm, J/ψ, jets, dielectrons) → event characterization
Rates of 1 kHz for p+p and 200 Hz for Pb+Pb (central) 3

4. HLT Processing Data Flow
DAQ: DAta Acquisition
ECS: Experiment Control System
DCS: Detector Control System

5. The TPC Detector Ongoing Norwegian contribution:
845 < r < 2466 mm
Drift length 2×2500 mm
readout pads
Ongoing Norwegian contribution:
Online cluster finding & tracking
Online krypton gas gain calibration

6. Online HLT Tracking – Dataflow
Cluster Finder
Track
Finder/Fitter
Global
Merging
36 Sectors
further
analysis…

7. Online Cluster Finder ADC sequences above threshold as input
Simple sequence matching between neighbouring pads
Centroids calculated as weighted mean of ADC values
Assigned 3D coordinates
Deconvolution scheme:
split clusters at local minima of charge distributions along time and pad direction

8. Online Tracking Algorithm
real space
3D space points as input
Conformal mapping
conformal space
“Follow-your-nose”: build tracks from outer to inner TPC-radius

9. HLT Cluster Status Full connectivity / all detectors included
Additional CPU power is expected

10. Benchmarks on HLT cluster - preparation for p+p runs
Setup for 1 sector
6 ClusterFinders running in parallel on 6 CPUs
1 Tracker running on 1 CPU
Results (with current configuration):
ClusterFinder: 240 Hz
Tracker: ~200 Hz (design value 1 kHz)
Significant improvement expected with additional CPU power

11. Event Display for Primaries
HMPID
TPC
PHOS
offline
HLT

12. HLT and Offline Efficiency for Primary Particles
Overall Efficiency:
HLT: 95%
Offline: 94%
HLT and offline analysis deliver comparable results
Running HLT code in AliRoot framework
→ comparison with full generator events (Pythia) 12

13. Krypton Gain Calibration
Kr decay products (e-,γ) deposit known energy
Dedicated cluster finder because of larger clusters
Energy calibration possible
9.4 keV
12.6 keV
29 keV
41.6 keV
19.6 keV

14. The PHOS Detector Information about the initial phase of the collision
High granularity electromagnetic calorimeter split in 5 modules
17920 detection channels of lead-tungstate crystals (PbWO4)
Optimized for measurements of γ ( GeV/c), π0 ( GeV/c) and η mesons ( GeV/c)

15. PHOS - HLT Operation Principle
2 channels
per crystal
PHOS
extract amplitude
&
timing information
HLT for PHOS
Online monitoring
&
calibration
Shower &
μ reconstruction
DAQ
Offline condition
database
MIPS deposit ~210 MeV in one crystal length → peak in the energy distribution

16. Online Calibration Framework
Motivation:
Several ALICE systems (DCS, DAQ, ECS, Offline) provide data, settings and tools required for producing and monitoring calibration data
System interfaces for data exchange
Provide similar environment to online Analysis Software / Detector Algorithms (DA) as in offline 17

17. HLT cluster ECS DCS DCS values Control DAQ Processed events DCS-portal
(Experiment Control System)
DCS
(Detector Control System)
DCS values
Control
DAQ
(Data Acquisition)
Processed events
DCS-portal
(Pendolino, FED)
ECS- proxy
Calculated
values
Trigger
decisions
DDL
Online event
monitoring
AliEve
(ALICE Event Monitor)
HLT cluster
HOMER
FEP
Event
data
OFFLINE
FEE
(Front-End-
Electronics)
Calibration data
OCDB
(Offline
Conditions DB)
OFFLINE-portal (Shuttle, Taxi)
DAQ
(Data Acquisition)
New calculated
calibration data
Shuttle
FEP = Front-End-Processor, DDL = Direct Data Link
HOMER = HLT Online Monitoring Environment including ROOT

18. Summary & Outlook... TPC/1st PHOS module operational, cosmics run
PHOS module calibrated with cosmics
HLT for TPC and PHOS operational for first physics runs
Similar efficiencies for primaries in offline and HLT
Kr gas gain calibration for TPC implemented
Most online calibration interfaces implemented and tested
& Outlook...
TPC/PHOS are being connected/commissioned
Integrated test with lasers/cosmics in December
Kr calibration test in February
On the way to p+p…

19. Backup slides

20. Calibration Input & Output
DCS
Input 
Output 
SCADA
AliEn
(Grid)
HLT - cluster
Front End
Devise
-portal
Taxi
Taxi-portal
FED
API
OCDB
(Offline)
Calibration
settings
OFFLINE DA
OCDB
Shuttle-
portal
Meta Data DB
Shuttle
Pendolino
Calibration&
Conditions
Pendolino-
portal
FXS
Amanda
Data
preparation
Monitoring
(AliEve)
Data
Subscriber
portal
DCS
Archive DB
current DCS
conditions
Homer 21

21. PHOS Commissioning PHOS cosmics run
Calibration of crystal gains using cosmic muons
MIPS deposit ~210 MeV in one crystal length → peak in the energy distribution
Equalization of electronic gains
Absolute energy calibration
HLT for PHOS
Data compression
Data integrity checks
Event display
Histogram plotting 22 22