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README.variables.md

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Output tree variables in remoll

The output trees are organized into several independent arrays:

  • ev.* - primary event information
  • part.* - primary particles
  • bm.* - beam information
  • hit.* - detector hits
  • sum.* - detector sums
  • units.* - unit conversions
  • rate - weight variable for conversion to event rates

All fields are filled in Geant4's internal system of units. This ensures consistency when combining variables with different units together.

To plot variables in other units when using ROOT, a helper branch units is stored as well. If you wish to plot variables not in their stored units, you can use the units branch to renormalize them:

T->Draw("hit.pz/GeV:hit.z/m")

This will plot momentum in GeV versus position in meters (and even label the axes accordingly with "hit.pz/GeV").

Primary event information

The branch ev is filled once for each event with information related to the entire event.

  • ev.A Physics asymmetry [ppb]
  • ev.Am Measured asymmetry (scaled by beam polarization) [ppb]
  • ev.xs Physics process cross section [ub]
  • ev.Q2 Momentum transfer Q2 [MeV^2] (not available for all processes)
  • ev.W2 Invariant mass squared [MeV^2] (not available for all processes)
  • ev.thcom Polar angle theta in center-of-mass [rad] (not available for all processes)
  • ev.beamp Beam momentum magnitude at primary vertex [MeV]

Examples:

T->Draw("ev.A/ppb","ev.thcom > 90*deg")
  • rate Weight variable for conversion to event rates [???]

Examples:

T->Draw("ev.A/ppb","rate * (ev.thcom > 90*deg)")

Primary particles

The branch part is filled with as many entries as the number of primary particles. In the case of the Moller generator this means there will be two part entries per event.

  • part.pid Geant4 particle type per http://pdg.lbl.gov/2018/reviews/rpp2018-rev-monte-carlo-numbering.pdf
  • part.v[xyz] Particle initial position, global coordinates [mm]
  • part.p Particle initial momentum magnitude, lab frame [MeV]
  • part.p[xyz] Particle initial momentum components, lab frame [MeV]
  • part.s[xyz] Particle initial polarization components, lab frame [1]
  • part.th Particle initial polar angle, lab frame [rad]
  • part.ph Particle initial azimuthal angle, lab frame [rad]
  • part.tp[xyz] Particle "true" momentum (if no multiple scattering effects)
  • part.trid Geant4 track ID number (1 = first particle created, stored per tj[xyz] entry)

Examples:

T->Draw("part.th/deg","part.pid == 11")
  • part.tj[xyz] std::vector of particle trajectory positions [mm]

Beam information

The branch beam is filled once for each event with the position and direction of the primary vertex after going through multiple scattering in the target.

  • bm.[xyz] Beam interaction vertex, global coordinates [mm]
  • bm.d[xyz] Beam interaction direction, lab frame [rad]
  • bm.th Beam direction polar angle, lab frame [rad]
  • bm.ph Beam direction azimuthal angle, lab frame [rad]

Examples:

T->Draw("bm.th/deg")

Hit information

The branch hit is filled for every hit.

  • hit.id Hit identifier
  • hit.det Detector identifier
  • hit.vid Volume ID number (not yet implemented)
  • hit.pid Geant4 particle type per http://pdg.lbl.gov/2018/reviews/rpp2018-rev-monte-carlo-numbering.pdf
  • hit.trid Geant4 track identifier (1 = first particle created)
  • hit.mtrid Geant4 mother track identifier (0 = particle from gun)
  • hit.t Hit time [ns]
  • hit.[xyz] Hit position, global coordinates [mm]
  • hit.[xyz]l Hit position, local coordinates [mm]
  • hit.r Hit position radial, global coordinates [mm]
  • hit.ph Hit position azimuthal, global coordinates [mm]
  • hit.p Particle momentum magnitude [MeV]
  • hit.p[xyz] Particle momentum components, lab frame [MeV]
  • hit.s[xyz] Particle polarization components, lab frame [1]
  • hit.v[xyz] Particle creation vertex position [mm]
  • hit.e Particle energy [MeV]
  • hit.m Particle rest mass [MeV]
  • hit.edep Energy deposited in this detector by this hit [MeV]

Examples:

T->Draw("hit.x/m:hit.y/m","hit.pid < 20")

Detector sum

The branch sum is filled for every detector that had hits during the current event.

  • sum.det Detector identifier
  • sum.vid Volume identifier (not yet implemented)
  • sum.edep Energy deposited in this detector by all hits [MeV]

Examples:

T->Scan("sum.det:sum.edep","sum.det < 20")

The branch sum.by_pid is filled for every detector that had hits and for every particle type among those hits.

Examples:

T->Scan("sum.det:sum.by_pid.x:sum.by_pid.pid:sum.by_pid.edep","sum.det < 20")