Current best source of documentation source code in the LCTuple git repository.
Branches storing related data are prefixed with the same string. This table describes what each prefix means and with the code used to populate it.
| Prefix | Meaning | Reference |
|---|---|---|
mc |
Monte Carlo Particles | MCParticleBranches |
th |
Tracker Hits Clusters | TrackerHitBranches |
ts |
Track State | TrackBranches |
tr |
Reconstructed Track | TrackBranches |
tr2mc |
Track to MC Map | LCRelationBranches |
tc |
Tracker Hits | TrackerHitBranches |
st |
Sim Tracker Hits | SimTrackerHitBranches |
Truth particles are the event generator output. Each element in the array corresponds to a truth particle.
| branch | Meaning |
|---|---|
mcmo(xyz) |
Truth particle momentum, xyz components. |
Each element in the array corresponds to a recontructed track. The track parameters are stored under the track state collection of branches. The index to the right track state element is stored in the trsip branch.
| branch | Meaning |
|---|---|
trchi2 |
Chi2 of the track fit |
trndf |
Number of degrees of freedom of the track fit |
trsip |
Index of track state (ts branches) at interaction point |
trsfh |
Index of track state (ts branches) at the first hit |
trslh |
Index of track state (ts branches) at the last hit |
trsca |
Index of track state (ts branches) at the calorimeter |
Each element in the array corresponds to a state (parameters at a given radius) of a reconstructed track. Each track has multiple entries corresponding to its different state. There are tr branches that give the index into ts for that track. For example, trsip is the track state at the interaction point.
| branch | Meaning |
|---|---|
tsdze |
d0 parameter |
tszze |
z0 parameter |
tsphi |
phi parameter |
tsome |
Curvature [1/mm] of the track. Propotional to magnetic field. |
tstnl |
tanλ, with λ = pitch angle. |
tscov |
Covariance matrix. Stored as array of size 15 per hit. See table. |
tsrp(xyz) |
Global reference position of the track state. |
Track momentum is not explicitely stored, but can be calculated using the formula p cosλ = 0.3 B / Ω. B=3.57T is the magnetic field and Ω is the radius of curvature.
For track state at a layer, the tsdze and tszze branches correspond to the local coordinates and not d0/z0.
The covariance matrix is stored as an array of size 15 per hit. The indices per hit are defined as follows.
| index | Meaning |
|---|---|
| 0 | cov(d0,d0) |
| 1 | cov(ϕ,d0) |
| 2 | cov(ϕ,ϕ) |
| 3 | cov(Ω,d0) |
| 4 | cov(Ω,ϕ) |
| 5 | cov(Ω,Ω) |
| 6 | cov(z0,d0) |
| 7 | cov(z0,ϕ) |
| 8 | cov(z0,Ω) |
| 9 | cov(z0,z0) |
| 10 | cov(tanλ,d0) |
| 11 | cov(tanλ,ϕ) |
| 12 | cov(tanλ,Ω) |
| 13 | cov(tanλ,z0) |
| 14 | cov(tanλ,tanλ) |
Tracker hits come in two flavours: simulated and digitized. The simulated hits are the exact hits output by the detector simulation and are represented by the Marlin framework as SimTrackerHit. The digitized hits include smearing from readout electronics and are represtented by TrackerHit. The naming convention here will be similar; simulated hits are the Geant4 output and tracker hits are the digitized hits.
There are two types of digitization available. The current default is a simplistic digitization based on smearing simulated hits using a gaussian function. The second is a work-in-progress digitization that uses a realistic pixel detector model, including clustering. Some branches, mainly reating to clustering of hits, are only available for the latter.
When detailed digitization is turned ON (and only for the tracking detectors for which is ON), these branches give information about single hits (pixels or strips), cluster of hits and the true energy deposit from Geant4.
Indices for the navigation from clusters to hits and from clusters to the true energy deposits are given in the table below as well.
Only the most important branches are displayed below, see source code linked above for a list of all branches.
Simulated hits start with the st (simulated tracker) prefix.
| branch | Meaning |
|---|---|
stci(0,1) |
CellID of ladder/module in which the energy is deposited |
stpo(x,y,z) |
Position of simulated hit (global coordinates) |
stedp |
True Energy deposit (GeV) |
sttim |
True time of arrival (ns) |
stmo(x,y,z) |
True momentum of incoming particle |
tsmcp |
Index in the mc* branches of the true particle |
stptl |
Path length in active silicon of the true particle |
Tracker hits start with the th (tracker hit) prefix.
| branch | Meaning |
|---|---|
thci(0,1) |
CellID of ladder/module in which the cluster is formed |
thpo(x,y,z) |
Reconstructed position of the cluster |
thcov(...) |
Covariance matrix of reconstructed position |
thedp |
Reconstructed energy deposit (GeV) |
thsrc |
Dominant composition of cluster (0=prompt, 1=secondary, 2=BIB) |
The following are available only in the ACTS branch.
| branch | Meaning |
|---|---|
thlo(x,y) |
Location coordinates of the simulated hit. |
thld(x,y) |
Uncertainty on the local coordinates. |
The following are available only for the realistic digitization.
| branch | Meaning |
|---|---|
thcidx |
Index in the hits branches of the first hit of the cluster |
thclen |
Number of hits in the cluster (used to loop over tc* branches) |
Available for realistic digitization only.
| branch | Meaning |
|---|---|
tcedp |
Energy collected (in electrons!) on the given hit |
tctim |
Time measured (ns) on the given hit |
tcrp(0,1) |
Local index (x,y) of hit within the module/ladder |
Some relations between branches are stored in the LCRelation set of branches. For example, the tr2mc branches store the relation between a reconstructed track and the corresponding truth particle that created it.
| branch | Meaning |
|---|---|
tr2mcf |
Track index from tr branches. |
tr2mct |
To matched MC particle in mc branches. |
h2m(f,t) |
Tracking cluster collection from/to Truth energy desposits |
In the case of the track to MC map, tr2mct is the same as tr2mcf due to the one-to-one nature of this mapping.
The tr2th* branches contain the association from a track (see Track Information, prefixed with tr) to hits used to fit the track (see Tracker Hit Information, prefixed with th).
| branch | Meaning |
|---|---|
tr2thf |
Track index inside tr* branches. |
tr2tht |
Tracker hit index inside th* branches. |
tr2thw |
Tracker hit index inside the track (ie: 0 means first hit) |