TrackMaker
Tracks
Tracks are Atlfast physics output entities which correspond to
the following physics user analysis objects, namely
A track is described by the following five helix parameters.
- phi0
- z0 - projection of the impact parameter onto the z axis
- cot(theta) - theta is the angle of the particle track with at the origin
- charge / pt
- r0 - radius of curvature of the helix
Atlfast Tracks comprise a TrackTrajectory and an association with the Monte Carlo particle responsible for its creation.
They also implement the ITrackTrajectory interface which provides the standard kinematic methods found in IKinematic as well as methods specific to track kinematics.
TrackMaker Overview
The TrackMaker is an Athena-Algorithm which is created at the start of a job and executed once per event.
The following three public methods are executed by Athena, and are needed to honour the IAlgorithm interface
- initialise - create helper classes and declare any jobOptions properties
- execute - perform the algorithm's function once per event
- finalise - perform any end of job tasks
In order to do its job, the algorithm performs the following sequential operations to create Tracks.
- Retrieve the relevant Monte Carlo HepMC::Particles from the TES
using TesIO member variable.
- Determine TrackTrajectory from the HepMC::Particle.
- Smear the helix parameters according to desired parameterisations.
- Create a Track from the smeared TrackTrajectory.
- Store Tracks to the TES, using the TesIO member variable.
TrackMaker uses the helper Smear class to smear Monte Carlo four momenta
according to the proper parameterisation.
TrackMaker uses the helper class TesIO to perform input/output operations
from the TES.
User Requirements Satisfied
The design fulfills requirements of Sec 3.1.2 in the
ARD.
TrackMaker Detail
jobOptions Properties
jobOptions properties are steering parameters which can be set by the user in
the jobOptions file.
They are declared in the constructor and initialised to
Default Values
The options for this algorithm are:
- McPtMinimum - Acceptance cut
- McEtaMaximum - Acceptance cut
- DoSmearing - Flag to determine whether to smear or not
- Luminosity - LHC luminosity (high/low)
- Bfield - Magnetic field, needed for track trajectory calculations
- RandSeed - Used by the smearer
- MC_eventLocation - location in TES of input MCParticles
- OutputLocation - location in TES of output Tracks
Initialisation
The initialise method is called once at the beginning of the job.
It is here that the TesIO and Smearer objects are instantiated.
The job of the TrackSmearer is to take a Track object and smear its five trajectory parameters.It does this using parameterised smearing matrices, specific to each particle type.
The initialisation process is shown in the
TrackMaker
initialisation sequence diagram.
Execution
The execute method is performed once per event and carries out the main operation of the algorithm.
The execution process is shown in the
TrackMaker
execution sequence diagram
Class Diagram
The various classes discussed above are shown in the class diagram.
DefaultReconstructedParticleMaker class diagram
