Calibration Streaming at Tier 0

ID Alignment Stream


Composition: Custom trackfit and hit data of generic tracks with pT > 2GeV.

Purpose: derive and update a set of calibration and alignment constants, after every fill, processing the stream to accumulate residuals and other histogram quantities before prompt reconstruction.

Processing requirements:
• Pixel and SCT: 50 CPU/KSI2k for derivation of silicon alignment constants;
• TRT: 20? CPU/KSI2k for derivation of TRT alignment constants;
– The constants are then verified by re-reconstruction on an independent part of the calibration stream within 12 hours.

Working target (remains to be shown achievable):
- Express and calibration streams reconstructed within 8hours;
- Primary data stream reconstruction (“prompt” reconstruction) beginning in 24hours.


• Design a local stream of information that will be accumulated over time and that will be used to produce the new alignment constants every 24 hours.

How To



1. ByteStream:
– The streams will be originated at each SFO and the files transferred to Tier-0:
• So we need to investigate a model where we write custom byte stream files with raw data of the tracks suitable for alignment as found in the EF.
• This would make use of the Byte Stream converter infrastructure and possibly give us a better bandwidth usage.
2. ROB list:
- This list will than be used to reconstruct the tracks suitable for alignment and calibration.


  • SizeOfTrack using ATLAS simulation

Definition of a not suitable track: If, for all the Trk::Surfaces of a track, a MeasurementBase exist without a matching Trk::TrackParameters the track is ignored. The size is than obtained summing up the size of:
  • measured LocalParameters () and their covariance() matrix;
  • trackParameters();
  • the Perigee: parameters() and their covariance() and error() matrix;
  • Identifier();
  • OverAllFitQuality of the track.
The choice made is time dependent, and will evolve with the study itself.
  • Plots

Use of 300 generated events of single Muons with pT=50GeV and Eta<3.0:

  • Study with alignment algorithm

This study is based on the RobustAlignAlg wich makes use of overlap residuals to calculate alignment constants. For simplicity, we have used an early version (11.0.0) that was used for analyse CTB results. The run is the 2102470 and the number of events is 25000. Each event has one single pion.
The study divide the algorithm in two parts: one that retrives information and other that performs calculation. To simplify the problem we have used only the Pixel RPhi overlap residuals. From the original 25000 tracks we have 3582 hits (almost 2000 tracks) that are of the overlap type. The residual for each hit is calculated online, but the overlap residual is calculated offline. To process this information we need the following information for each hit on a module: moduleID, bec, dettype, layer, ring, side, sector and residual. This information is colected to an ASCII file. The information regarding the 3582 hits file has a size of 110kB, but we can divide the file in two:

  • one with the moduleID and residual information.
  • another with moduleID, bec, dettype, layer, ring, side, sector.
The second has information that can be stored in a database (or retrivede in athena knowing the moduleID), and acessed offline using the moduleID. So, at the end for our 3582 hits we need a file of size 76 kB wich means 11 Bytes/hit.


• ATLAS High-Level Trigger, Data Acquisition and Controls Technical Design Report, ATLAS Collaboration, CERNLHCC- 2003-022, June 2003.
• THE ATLAS COMPUTING MODEL,D. Adams et al., ATLSOFT- 2004-007, January 2005.
• ATLAS detector calibration model – preliminary subdetector requirements, R. Hawkings, F. Gianotti, March 2005.

-- BelmiroPinto - 27 Jul 2006

Topic attachments
I Attachment History Action Size Date Who Comment
JPEGjpg Options_Of_b.3.jpg r2 r1 manage 27.6 K 2006-07-31 - 17:00 BelmiroPinto  
JPEGjpg Problems_of_Simplest_Offline_Way.jpg r2 r1 manage 31.6 K 2006-07-31 - 17:00 BelmiroPinto  
GIFgif SizeOFSimpleTrack_twiki.gif r2 r1 manage 4.6 K 2006-07-28 - 03:50 BelmiroPinto  
JPEGjpg The_Problem.jpg r2 r1 manage 35.2 K 2006-07-31 - 17:00 BelmiroPinto  
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