The `Event` class#

The Event class is nothing more than a collection of containers, which try to group variables together according to specific criteria.

Although in NAIA there is no event pre-selection of any kind, there are still plenty of choices that were made when deciding how to get or compute all the variables in the datamodel. For example, to get a rigidity value you first need to decide from which reconstructed track, and similar arguments apply to ToF, RICH, ECAL, and so on…

The main containers are derived from what gbatch thinks is the best association between all the subdetectors signals in the event. The result of these associations is called “particle” in gbatch terminology, and the first one (called “particle 0”, for obvious reasons) is the the most likely to represent the main particle that came through AMS.

Some additional containers are either alternative reconstruction of the subdetector signals used by the particle 0, or they represent different objects altogether. See the following table for details about each container.

Event class layout#
Container type	Name	Description
Header	header	Contains simple information like run number, run tag, event number, event mask and UTC time. Lightweight and meant to be used as a tool to quicly identify or select an event.
EventSummary	evSummary	Contains some aggregated variables to roughly describe the event.
DAQ	daq	Contains variables describing the status of the AMS DAQ system for the event.
TofBase	tofBase	Contains basic Tof variables that are accessed most frequently. Constructed from the particle 0 Tof objects.
TofPlus	tofPlus	Contains additional Tof variables that are accessed less frequently. Constructed from the particle 0 Tof objects.
TofBaseStandalone	tofBaseSt	Contains basic Tof variables that are accessed most frequently. Constructed from the particle 0 Tof objects, but this reconstruction avoids using any information from the Tracker track. Meant to be ued for the Track reconstruction efficiency evaluation.
TofPlusStandalone	tofPlusSt	Contains additional Tof variables that are accessed less frequently. Constructed from the particle 0 Tof objects, but this reconstruction avoids using any information from the Tracker track. Meant to be ued for the Track reconstruction efficiency evaluation.
EcalBase	ecalBase	Contains basic Ecal variables that are accessed most frequently. Constructed from the particle 0 ECAL shower.
EcalPlus	ecalPlus	Contains additional Ecal variables that are accessed less frequently. Constructed from the particle 0 ECAL shower.
TrTrackBase	trTrackBase	Contains basic Track variables that are accessed most frequently. Constructed from the particle 0 Tracker track.
TrTrackPlus	trTrackPlus	Contains additional Track variables that are accessed less frequently. Constructed from the particle 0 Tracker track.
SecondTrTrackBase	secondTrTrackBase	Contains basic Track variables (a subset of all the variables contained in TrTrackBase) for the “second track”. This track is selected by looking for the highest rigidity track (besides the primary one) with at least 5 hits.
TrTrackBaseStandalone	trTrackBaseSt	Contains basic Track variables reconstructed withouth using any Tof information. Constructed from the particle 0 track, but this reconstruction avoids using any information from the Tof. Meant to be ued for the Tof reconstruction efficiency evaluation.
TrdKBase	trdKBase	Contains basic TRD variables that are accessed most frequently. Constructed using the TrdK method in gbatch, using the Tracker track to select TRD hits.
TrdKBaseStandalone	trdKBaseSt	Contains basic TRD variables that are accessed most frequently. Constructed using the TrdK method in gbatch, using the Tof extrapolation to select TRD hits.
RichBase	richBase	Contains basic RICH variables that are accessed most frequently. Constructed using the particle 0 RICH ring.
RichPlus	richPlus	Contains additional RICH variables that are accessed less frequently. Constructed using the particle 0 RICH ring.
UnbExtHitBase	extHitBase	Contains basic variables for unbiased external hits. Constructed using Tof and TRD standalone information. If the event charge estimated by the Tof is greater than 1, then the highest charege hits are selected on both L1 and L9. Otherwise charge 1 hits closest to the standalone TRD (or Tof, if TRD is not availabel) extrapolation on L1/L9 are selected.
MCTruthBase	mcTruthBase	Contains basic MC truth variables that are accessed most frequently
MCTruthPlus	mcTruthPlus	Contains additional MC truth variables that are accessed less frequently

The Event class acts as an interface to group and access containers with information from the various subdetectors. This should be provided by the chain class as a transient view of the event information.

Note

Containers are actually made up from two classes. The first one is the one holding all the variables, while the second one adds the “read-on-demand” behavior to the container.

When navigating the doxygen documentation remember to go check the XXXData class, where “XXX” is the container Class, and you’ll find the description for all the container variables.

The event `Category`#

To avoid going through every event every single time you can perform a fast event filtering by looking at the event Category mask in the Header container.

Note

To check if an event belongs in a given set of categories you can use the Header::CheckMask method.

Categories can be combined into a single mask, to check many of them at once

// this mask will check for charge=1 according to both tracker and tof
NAIA::Category cat = NAIA::Category::Charge1_Trk | NAIA::Category::Charge1_Tof;

  for (NAIA::Event &event : chain) {
    // check charge with TOF and Tracker
    if (!event.header->CheckMask(cat))
      continue;

CheckMask will check that all categories are present in the event. If you want to perform the check in or rather than and you can use the MathAnyBit free function

// this mask will check for charge=1 according to both tracker or tof
NAIA::Category cat = NAIA::Category::Charge1_Trk | NAIA::Category::Charge1_Tof;

  for (NAIA::Event &event : chain) {
    // check charge with TOF or Tracker
    if (!NAIA::MatchAnyBit(event.header->Mask(), cat))
      continue;

(n.b: the CheckMask method uses the MatchAllBits free function)

The Event class#

The event Category#

The `Event` class#

The event `Category`#