ATLAS LArOnline Software: Identifiers

[ATLAS Collector] - [CaloPerf] - [Offline Identifiers] - [HighVoltage Identifiers]- [TriggerTower Identifiers]

Introduction & short Glossary for LArOnlineID use

  • DETECTOR DESCRIPTION : To every calorimeter cell corresponds several possible descriptions. In Atlas
    a cell can be described by its "geometric" components (detector,z-side,region,sampling,eta,phi)
    or by its "hardware" components (detector,z-side,feedthrough, FEC slot,FEB channel)

  • IDENTIFIERS : An identifier is a 32-bit integer in which all the information
    regarding the object is encoded by every calorimeter cell is identified by identifiers
    to every cell is associated a geometric identifier called "offline identifier"
    to every cell is associated an hardware identifier also called "online identifier"
    - Only the "online identifier" associated to the cell is a persistent data
    - An identifier needs to be interpreted via an "Helper" specific to the decsription used

  • HELPERS : a "helper" provides the framework of the identifier description :
    - in our case there are "online helpers" and "offline Helpers"
    - Helpers contains the complete description of the identifiers in terms of "FIELDS"
    defined in a "DICTIONARY" (which, in Atlas, is an xml file):
    For an offline identifier, the fields are: "detector","z-side","region","sampling","eta","phi"
    For an online identifier, the fields are: "detector","z-side","feedthrough","FEC slot","FEB channel"
    - Helpers also provides all functionalities needed to access the identifier or a set of identifiers (identifiers of a specific sub-system, per eta, etc...)

  • DETECTOR STORE : Helpers are accessed via LArIdManager/CaloIdManager or from DetectorStore directly

  • LARCABLING SERVICE : there are connections between distinct descriptions :
    - as only the online identifiers are persistent data, there has to be a connection between
    those latter and the other descriptions
    - such a connection is done in LArTools/LArCablingService
    - the mapping between offline and online identifiers is defined and put into a Database
    - the methods to translate offline into online (and reversed) are defined in LArCablingSvc

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