ALICE 3 FORWARD DETECTOR

This is top page for the FD3 detector documentation.

ALICE 3 Tracker Barrel

This is top page for the TRK detector documentation.

Specific detector setup

Configurables for various sub-detectors are presented in the following Table:

Subsystem	Available options	Comments
`TRKBase.layoutVD`	`kIRIS4` (default), `kIRISFullCyl`, `kIRIS5`, `kIRIS4a`	link to definitions
`TRKBase.layoutMLOT`	`kCylindrical`, `kSegmented` (default)	`kSegmented` produces a Turbo layout for ML and a Staggered layout for OT
`TRKBase.layoutSRV`	`kPeacockv1` (default), `kLOISymm`	`kLOISymm` produces radially symmetric service volumes, as used in the LoI

For example, a geometry with fully cylindrical tracker barrel (for all layers in VD, ML and OT) can be obtained by

o2-sim-serial-run5 -n 1 -g pythia8hi -m A3IP TRK FT3 TF3 \

--configKeyValues "TRKBase.layoutVD=kIRISFullCyl;TRKBase.layoutMLOT=kCylindrical"

Custom Geometry Configuration

The geometry of the ML and OT layers can be overridden by providing a custom plain-text configuration file via TRKBase.configFile=filename.txt. The parser interprets the file differently depending on the active TRKBase.layoutMLOT setting (kCylindrical or kSegmented).

General Syntax Rules

Separators: All columns must be separated by a single TAB (\t). Using spaces will result in a parsing error.
Comments: Any line starting with a forward slash (/) is treated as a comment and ignored.
Layer Count: The parser reads valid lines sequentially. The first valid line corresponds to Layer 0, the second to Layer 1, and so on.
Material Budget Mode: All layer definitions accept an optional matBudgetMode parameter at the end of the line (e.g., 0 = Thickness, 1 = X2X0). If omitted, it defaults to Thickness.

1. Cylindrical Layout (`kCylindrical`)

When TRKBase.layoutMLOT=kCylindrical is used, each layer requires a minimum of 3 parameters to define the TRKCylindricalLayer.

Format: rInn \t length \t thick \t [optional_mode]
*(Note: rInn, length, and thick map directly to the constructor arguments for the cylindrical layer, typically corresponding to Radius, Length, and Thickness).*

Example for kCylindrical:

/ Configuration for kCylindrical layout - ALICE3 TRK
/ rInn  length  thick [optional_mode]
0 127.985 0.1
0 127.985 0.1
0  127.985 0.1
0  127.985 0.1
0  127.985 0.1
0  255.9 0.1
0  255.9 0.1
0  255.9 0.1

2. Segmented Layout (`kSegmented`)

When TRKBase.layoutMLOT=kSegmented is used, each layer requires a minimum of 5 base parameters to define the geometry. The parser distinguishes between Middle Layers (ML) and Outer Layers (OT) based on the sequential layer index.

*(Note: The 5 base parameters map directly to: Inner Radius (rInn), Thickness (thick), Tilt Angle (tiltAngle), Number of Staves (nStaves), and Number of Modules per stave (nMods)).*

Middle Layers (ML) - Indices 0 to 4 The first 5 valid lines are parsed as TRKMLLayer objects. These layers require a 6th parameter for the staggering offset (stagOffset).

Format: rInn \t thick \t tiltAngle \t nStaves \t nMods \t stagOffset \t [optional_mode]

Outer Layers (OT) - Indices 5 and above From the 6th valid line onwards, lines are parsed as TRKOTLayer objects. These layers do not have a staggering offset. The optional mode parameter shifts to the 6th column.

Format: rInn \t thick \t tiltAngle \t nStaves \t nMods \t [optional_mode]

Example for kSegmented:

/ Configuration for kSegmented layout - ALICE3 TRK
/ --- ML LAYERS (Indices 0 to 4) ---
/ rInn  thick tilt  nStaves nMods stagOffset  [optional_mode]
7.0 0.01  11.2  10  11  0.0 1
9.0 0.01  11.9  14  11  0.0 1
12.0  0.01  11.4  18  11  0.0 1
20.0  0.01  0.0 26  11  1.17  1
30.0  0.01  0.0 38  11  0.89  1
/
/ --- OT LAYERS (Indices 5 to 7) ---
/ Outer layers do NOT have stagOffset.
/ rInn  thick tilt  nStaves nMods [optional_mode]
45.0  0.01  0.0 32  22  1
60.0  0.01  0.0 42  22  1
80.0  0.01  0.0 56  22  1