ALICE 3 full simulation

Simulation

Simulation software for Run 5

Current simulation approach for ALICE 3 is a specification of what it is used in the main O2 simulation package. It shares the same structure and possibly inherits all the features in place already. For all of the features that are not really Run-5 specific please refer to the official O2 Simulation Documentation.

Rationale for the "Upgrades" codebase

Run 5 code for the detectors is stored in the Detectors/Upgrades/ALICE3 directory and its suboflder strucure mimicks the same we have in Detectors. For specific data formats the plan is to keep the same approach in DataFormats/Upgrades.

Available modules

Run 5 executable is called o2-sim-run5 and accepts the same syntax as o2-sim. There is also the serial vertsion o2-sim-serial-run5 that is the serial implementation. The specific modules for Run 5 are enabled by passing their their IDs to the -m parameter of the o2-sim. A list of the available DetIDs is reproted in the table below:

Detector ID	Detector description
`A3IP`	Beam pipe
`TRK`	Barrel Tracker
`TF3`	Time Of Flight detectors
`FT3`	Forward endcaps
`RCH`	Ring Imaging Cherenkov detectors
`ECL`	Electromagnetic Calorimeter
`MI3`	Muon Identification
`FCT`	Forward Conversion Tracker
`A3ABSO`	Absorber
`A3MAG`	Magnet

Names are arbitrarily chosen and are such as to be orthogonal to any Run 3+ other DetID. The detector IDs of sensitive modules are mapped to the corresponding o2::detector::DetID class definition for convenience, so to be consistent with output names of the hit files.

Use the ALICE 3 magnetic field

By definition the o2-sim-run5 will use the Run 3 magnetic field configurations. Field description can be overridden with a custom macro with a path exported in the ALICE3_MAGFIELD_MACRO environment variable. The env var ALICE3_SIM_FIELD needs also to be set to ON. Example:

export ALICE3_SIM_FIELD=ON

export ALICE3_MAGFIELD_MACRO=../ALICE3Field.C

An exampling macro for a custom magnetic field is stored in Detectors/Upgrades/macros/ALICE3Field.C.

Run a simple simulation for run 5

The simplest command to be run to test the simulation is working is:

o2-sim-run5 -n 0

This will not produce any events but will spin the machinery and will produce the o2sim_geometry.root file with the whole geometry description. To enable a specific set of modules, e.g. the beampipe and the TOFs one can specify which modules to enable, e.g.:

o2-sim-run5 -n 10 -m A3IP TF3

Output of the simulation

The simulation will produce a o2sim_Hits<DetID>.root file with a tree with the hits related to that detector. Currently, hits are produced for: TRK, FT3, and TF3. More detectors will be included.

Reconstruction

WIP

Analysis

WIP