Finding the Beam Spot

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Introduction

The beam position needs to be measured precisely because of the following reasons:

  • Important input for physics e.g. b-tagging, lifetime, etc.
  • For patter recognition (input for HLT and offline).
  • Extraction of the tracking impact parameter resolution.
  • Quick check of global alignment.
  • Provide feedback to accelerator groups.
  • Beam monitor.

The algorithm used to calculated the transverse beam position is the so called d0-phi algorithm. This is a robust and fast $\raisebox{-1.3ex}\chi^2$ fit which just needs 1000 good tracks to reach micron precision. Using a Log-Likelihood fit, the beam width can be extracted using 20000 good tracks. A more detail description can be found in the CMS note # [].

Determination of beam postion using an EDAnalyzer

Review status

Reviewer/Editor and Date (copy from screen) Comments
FranciscoYumiceva - 10 Feb 2007 first version of page

Responsible: FranciscoYumiceva
Last reviewed by: FranciscoYumiceva - 10 Feb 2007
Latex rendering error!! dvi file was not created.

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Topic revision: r3 - 2007-02-10 - FranciscoYumiceva



 
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