Muon Identifiers

1
Muon Identifiers

• David Adams
• BNL
• December 2001

2
Contents

• Definitions
• Use cases
• Requirements
• Design issues
• Implementation
• Status
• Future

3
Definitions

• Identifier
• Label used to identify a piece of the detector
• Technology
• Muon has four MDT, CSC, RPC and TGC
• Channel
• Independently read out piece of the detector
• Station
• Geographical region of the muon detector
• BIL, BOS,

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Definitions (cont)

• Module
• Collection of channels of the same technology
  organized into a mechanical structure
• At each station there is at most one module for
  each technology

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Use cases

• 1. Label
• We want an association between digits (signals
  read from the detector) and the channel
• Create an identifier for each channel
• Include the appropriate channel identifier as
  part of the digit

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Use cases (cont)

• 2. Navigating the hierarchy
• The detector description is hierarchical
• Use the identifiers to navigate the hierarchy
• Each identifier provides a mean to access its
  parent, children and siblings

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Use cases (cont)

• 3. Muon digit container
• Muon digit container can be used as follows
• Create an identifier for a technology, e.g. MDT
• The technology ID is used to fetch the associated
  list of module identifiers
• The module ID is used as a key to fetch the
  digits associated with that module
• Each digit is queried for its channel ID
• The channel ID is then used as a key to access
  calibration or alignment information

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Requirements

• 1. Identifiers follow detector description
• Provide identities for
• Muon system
• Technologies
• Modules
• Channels
• Match the detector hierarchy
• 2. Consistent with ATLAS ID scheme
• ATL-SOFT-2001-004
• Ed S. Goldfarb and A. Schaffer

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Requirements (cont)

• 3. Identifiers carry the actual structure
• Impossible to construct non-physical identifiers
• 4. Identifiers have an ordering mechanism
• So identifiers can be used as keys in associative
  containers (e.g. maps)
• 5. Mechanism for navigating the hierarchy
• Up (from channel to its module)
• Down (from module to its list of channels)
• Neighbor (to adjacent element) not needed

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Requirements (cont)

• 6. Connection to ATLAS Identifier class
• Identifiers must convert to and from standard
  ATLAS Identifier objects
• Allows access to calibration and geometry
  databases
• Provides index required for persistent references
  to detector elements

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Design Issues

• 1. Avoiding cyclic dependencies.
• Identifiers know about their parents but not
  their children
• Channels know their module
• Modules do not know their channels
• Child class (or some other higher level class or
  function) constructs the corresponding list of
  child IDs from the parent ID

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Design issues (cont)

• 2. Atlas-specific constraints
• Connection with Identifier class
• Require conversion to and from ATLAS Identifier
• Where to obtain muon structure
• Use the external identifier dictionary when it is
  available
• For now an approximate description is fixed
• Do we need Ma/Meesen hash conversion?
• If so we can use the conversion to the ATLAS
  Identifier class

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Design issues (cont)

• 3. Fetching detector attributes
• Alignment and calibration information pertinent
  to a particular detector element is not obtained
  directly from the corresponding identifier
• The identifier is used as a key to access the
  appropriate database
• 4. Identifiers carry the detector structure
• Separate class for each level
• Numbers of and associations between identifiers
  specified by identifier dictionary

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Design Issues (cont)

• 5. Identifier validity
• Do not throw exception or crash if user attempts
  to construct an invalid identity
• Instead identifiers can be in an invalid state
• This allows default identifiers required for C
  containers

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Status

• Current implementation
• All classes in package MuonSpectrometer/MuonIdenti
  fiers
• MuonStationName (enum)
• MuonTechnology (enum)
• MuonStructure (will use the identifier
  dictionary)
• MuonStationId
• MuonModuleId
• MuonChannelId
• Each class has a component test
• Built and tested successfully in 2.3.0

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Future

• 1. Read structure from identifier dictionary
• Dictionary not yet available
• 2. Add classes for the other technologies
• As needed for muon digit container or elsewhere
• 3. Add conversions to and from ATLAS Identifier
  objects
• The ATLAS identifiers need to be modified for the
  new identification scheme