Generation of neutrino events (GENIE)

Generation of neutrino events (GENIE)

  • Table of contents
  • [Generation of neutrino events (GENIE)]
    • [Selecting generated interactions: FilterNeutrinosActiveVolume module]
      • [Selecting events with interactions in selected volumes]
        • [Interactions in the active volumes of the detector]
        • [Interaction location via volume name]
        • [Interaction location via volume coordinates]
      • [Selecting events with a specific interaction type]
      • [Selecting events via a specific current type]

Selecting generated interactions: FilterNeutrinosActiveVolume module

There are a few facilities in LArSoft and ICARUS code which allow filtering of events based on the features of the interaction(s).

They are implemented as art filters, which allow to write an event into the output art ROOT file only if it satisfies some requirements.

ICARUS has its own flavor of selector implemented in [FilterNeutrinosActiveVolume]{style=”font-family: monospace;”} filter module.
Note that this module has nothing that is specific to ICARUS and can be actually used in any LArSoft experiment (but at present it is distributed in ICARUS LArSoft{.project}).

Three types of requirements are supported: interaction location, interaction type and weak current type.
An event (intended as art event, possibly containing multiple interactions in std::vector<simb::MCTruth> data products) is selected if all the requirement types in the configuration are satisfied. For example, if all three types are specified, the selected events must contain an interaction with the requested current type and interaction type and location.

Also note that when using art filter modules an event will be accepted in its entirety. For example, an event with two interactions will be selected even if only one of them satisfies all the requirements of the filter, and both interactions will be included in the selected event.

Selecting events with interactions in selected volumes

Events can be selected if they have a neutrino-like interaction in a specified volume.

The location of the interaction is determined by the position (EndPosition()) of its incoming neutrino-like particle.
There are a few ways to specify the volumes: the interaction will be accepted if it happens in any of the specified volumes.

Interactions in the active volumes of the detector

The active volume is defined as the volume in between the anode and cathode planes, limited by the field cage. That volume is fully instrumented and permeated by a uniform electric field.
One can assume that only ionization produced in the active volume will be measured by the wires, while the same is not true for scintillation light, that can originate from outside it and still be detected.

In ICARUS detector geometry description the active volume is described by several (eight, in v08_50_02{.version} default geometry) volumes called volTPCActive.

To select only events that have at least a neutrino interaction (of any type) in the active volume, the job configuration filter_genie_active.fcl or the module FHiCL settings icarus_FilterNeutrinoActive (from FilterNeutrinoActive.fcl) can be used.
The explicit configuration of the module, instead, will look like:\

physics.filters.selectInActiveVolume: {

  module_type: "FilterNeutrinosActiveVolume" 
  inActive:     true

}

(do not forget to ask RootOutput to filter the events with the SelectEvents configuration parameter).

Note that if the active volume requirement is requested, no other location requirement can be specified.

Interaction location via volume name

Events can be required to have at least one interaction in any of the specified volumes, described by the name they have in the GDML detector geometry.
For example:

physics.filters.selectInActiveVolume: {

  module_type: "FilterNeutrinosActiveVolume" 

  volumeNames: [ "volTPC", ".*CRT.*" ]

}

will select interactions happening in any of the volumes called volTPC (in the default ICARUS detector in v08_50_02{.version}, there are eight of them), or in any volume whose name contains CRT.
As this example shows, multiple volumes can be specified, and the specification is actually a C++ "default" regular expression (see e.g. [std::regex]{style=”font-family: monospace;”}).

These volumes are selected in additions to the ones specified by coordinates (below), but can't be specified together with the request of active volume (inActive: true). Hint: LArSoft convention prescribes the active volumes to be called volTPCActive, so for compliant detectors like ICARUS inActive: true is actually a shortcut for volumeNames: [ "volTPCActive" ]. This also allows to specify additional volumes.

Interaction location via volume coordinates

Events can be required to have at least one interaction in any of the specified box-shaped volumes, described by the coordinate ranges on each dimension.
For example:

physics.filters.selectInActiveVolume: {

  module_type: "FilterNeutrinosActiveVolume" 

  volumeBoxes: [
    {
      Xmin: -150.0
      Ymin: -150.0
      Zmin:  -50.0
      Xmax:  -50.0
      Ymax:  -50.0
      Zmax:  +50.0
    },
    {
      Xmin:   50.0
      Ymin:   50.0
      Zmin:  150.0
      Xmax:  150.0
      Ymax:  -50.0
      Zmax:  +50.0
    }
  ] # volumeBoxes

}

will select interactions happening in one of two 1 meter cubes centered in ( &plusm;1 ; &plusm;1 ; 0 ) meters, specified in world coordinates and in centimeters.
These volumes are selected in additions to the ones specified by name, but can't be specified together with the request of active volume (inActive: true).

Selecting events with a specific interaction type

The filter module [FilterNeutrinosActiveVolume]{style=”font-family: monospace;”} described above allows to narrow the selection by requiring also a specific neutrino interaction type.
For example, this configuration requires an neutral current interaction via resonant production of a pion (neutral or positive charged) and neutron:\

physics.filters.selectInActiveVolume: {

  module_type:      "FilterNeutrinosActiveVolume" 

  interactionTypes: [
    1007, # simb::kResNCNuNeutronPiPlus
    1008  # simb::kResNCNuNeutronPi0
  ]

}

The interaction types are coded in nusimdata:source:nusimdata/SimulationBase/MCNeutrino.h{.source} (type simb::int_type_).

This requirement can be specified together with the current type (below) and the interaction location requirements.

Selecting events via a specific current type

The filter module [FilterNeutrinosActiveVolume]{style=”font-family: monospace;”} described above allows to narrow the selection by requiring also a specific neutrino current type:\

physics.filters.selectInActiveVolume: {

  module_type: "FilterNeutrinosActiveVolume" 
  weakCurrent:  NC

}

The allowed values for weakCurrent are charged (or CC), neutral (or NC), and any (which still requires a weak interaction to be present).

Again note that an event will be accepted in its entirety, and an event with two interactions will be selected even if only one of them satisfies the requirement of the filter.

This requirement can be specified together with the interaction type and the interaction location requirements.