Difference: LHCbTrackingStrategies (5 vs. 6)

Revision 62008-09-15 - ManuelSchiller

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META TOPICPARENT name="LHCbTracking"

Tracking strategies used in LHCb

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* THIS PAGE IS WORK IN PROGESS, AND PROBABLY STILL CONTAINS MISTAKES AND OMISSIONS, MORE DETAILS/CORRECTIONS ARE TO FOLLOW *

* TODO: *

  • * check if there is a good description of track types somewhere (with sketch) *

Tracks are found by different tracking strategies. A tracking strategy is mainly concerned with how tracks are found in the different subdetectors in general, while tracking algorithms specify how tracks are found in detail. This page attempts to give an overview of the different tracking strategies, the algorithms that implement them and the types of tracks resulting from their application. It also lists the input required by algorithms implementing a strategy.

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Introduction

Tracks are found by different tracking strategies. A tracking strategy is mainly concerned with how tracks are found in the different subdetectors in general, while tracking algorithms specify how tracks are found in detail. This page attempts to give an overview of the different tracking strategies, the algorithms that implement them and the types of tracks resulting from their application. It also lists the input required by algorithms implementing a strategy.
  The order in which strategies are discussed respects dependencies among the strategies, so we will not discuss a strategy before we explain where its input comes from. This means that one has to start with the strategies and algorithms that reconstruct tracks from hits rather than those which already need tracks as input. Furthermore, all strategies have been placed in different categories, depending on the type of tracks they produce.
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  As a track may be found by different algorithms, or segments of the same track might be available in different track containers on the TES, so there is a clone killing stage which collects tracks from the various locations, selects the best candidate if there are several (whatever that may mean in practice), and writes the resulting combined collection to an output container, per default Rec/Track/Best. This is usually what one uses in the end for physics analyses. The clone killer is described in more detail in section Clone Killer near the end of this page.
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This page is organized as follows:

Track types

Track types available in LHCb are:

  • VeloR track (2D Velo track in RZ projection)
  • Velo track (full 3D Velo track)
  • T track
  • Upstream track
  • Downsteam track
  • Long track

The following sketch gives you a more graphical impression:


LHCb track types

Strategies and Algorithms

 

Velo Tracking

This category contains strategies to find tracks in the Velo (See also this page.).
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 Algorithms:
  • TrackEventCloneKiller: This is the standard clone killer run in our reconstruction jobs. It removes clones by looking at the hit content of tracks; among two clones, the track with more hits is saved to the output location.
  • TrackBuildCloneTable/TrackCloneCleaner: The combination of these algorithms flags clones by comparing track parameters and flagging the lower quality ones as clones for subsequent analysis by adding an info field to the track. This allows to e.g. apply successively harder cuts on clones during an analysis.
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META FILEATTACHMENT attachment="tracktypes.svg" attr="" comment="Track types in LHCb" date="1221489275" name="tracktypes.svg" path="tracktypes.svg" size="11610" stream="tracktypes.svg" user="Main.ManuelSchiller" version="1"
 
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