1. Implementation of DHLT Monitoring Tool for ALICE
Seforo Mohlalisi – UCT
Supervisor : Z. Buthelezi (iThemba Labs)‏
Co-Supervisors : Z.Z. Vilakazi (iThemba Labs)‏
R. Fearick (UCT)‏

2. Outline Introduction to ALICE Muon Spectrometer
Dimuon High Level Trigger (dHLT)‏
Purpose of dHLT monitoring
How to implement monitoring
Other work

3. Introduction to ALICE Its assemble of detectors
Study strongly matter at extreme energy densities
Production of hadrons, electrons, muons, photons
SA works on muon arm

4. ALICE

5. Muon Spectrometer Detects muon from decays of J/Ψ and γ
Lots data of produced and bottle neck DAQ
High Level Trigger (HLT) – high selectivity
Triggering
Select region of interest
Data Compression
HLT is made up of cluster of computers placed between FEE and DAQ
Dimuon HLT specifically for dimuon arm

6. HLT Architecture
The detectors receive the trigger signals and the associated information from the
Central Trigger Processor (CTP), through a dedicated Local Trigger Unit (LTU)‏
interfaced to a Timing, Trigger and Control (TTC) system. The readout electronics
of all the detectors is interfaced to the ALICE standard Detector Data Links (DDL).
The data produced by the detectors (event fragments) are injected on the DDLs.
At the receiving side of the DDLs there are PCI boards, called DAQ Read-Out
Receiver Cards (D-RORC). The D-RORCs are hosted by PCs, the Local Data
Concentrators (LDCs). Each LDC can handle one or more D-RORCs. The D-RORCs
perform concurrent and autonomous DMA transfers into the PCs memory, with
minimal software supervision. In the LDCs, the event fragments originated by the
various D-RORCs are logically assembled into sub-events. The role of the LDCs is
to ship the sub-events to a farm of PCs called Global Data Collectors (GDCs), where
the whole events are built (from all the sub-events pertaining to the same trigger).
Besides having a DDL common to all the sub-detectors, the other major
architectural feature of the ALICE data acquisition is the event builder, which is
based upon an event building network.
The sub-event distribution is performed by the LDCs, which decide the destination
of each sub-event. This decision is taken by each LDC independently from the
others (no communication between the LDCs is necessary); the synchronization is
obtained using a data-driven algorithm. The algorithm is designed to fairly share
the load on the GDCs.

7. DHLT Analyses data online to select events relevant to muons
reconstructing clusters, hits, trigger records, tracks
Pub/Sub framework
Monitoring e.g. visualization and error handling

8. Detector Control System
DHLT COMPONENTS
Detector Control System
And
Conditions Database
HLT Control
Task Manager
Tracking
Chamber
readout
Trigger
Chamber
Readout
Detector
Calibration
Data
Detector
Configuration
data
DDL stream
data
DDL stream
data
Online hit
reconstruction
Tracking
Algorithm
dHLT
decision
maker
DDL stream
data
Monitoring
data
To DAQ
To dHLT Monitoring

9. Monitoring Visualization of event
Raw data, Hits, tracks, trigger records
Plots
Transverse momentum (pt) - distributions and cuts
Efficiency curves
(iii) Invariant mass spectra, etc
Scalers : number of tracks found, number of events processed etc.
Status information : connection status, error messages

10. Objectives Improving existing framework message queue
Data channels and channel manager
Extend ALIEVE (ALICE Event Visualization Environment)
Displaying and handling of errors

11. Monitoring Structure

12. Other work: Auxiliary Tools
Implemented dHLTdumpraw for dumping
DDL data from muon spectrometer
DHLT internal data block clusters, tracks etc
Implemented findLibDeps.py
Locates library dependencies
For standalone compilation
Testing muon raw data decoder

13. Other work: Analysis CERN summer school project – Offline Based
Convert existing macro to analysis task
CheckESD.C to AliAnalysisTaskCheckESD
Calculate physics efficiency, PID, Resolution
Core components of Analysis Task:
UserCreateOutputObjects, UserExec, Terminate
All tasks inherit from AliAnalysisTaskSE

14. Analysis Cont... Multiple data sources Multiple platforms
ESD, AOD, MC Truth
Multiple platforms
Locally,Proof,Grid
Discovered several problems
Missing track in muon reconstruction
Low efficiency in PHOS detector

15. …..END
“I do not know what I may appear to the world, but to myself I seem to have been only a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.”
Isaac Newton