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The HPS physics reconstruction is implemented in the HPS Java project as a chain of org.lcsim Drivers which process LCIO Data Format events that are accessed using the EventHeader API. The driver list is described in an lcsim xml steering file which is configured by the lcsim job manager.
What is a Driver?
In the context of LCSim and HPS Java, a Driver is an event processing component that operates on each event within a record processing loop and may add new object collections to the event. For example, a Driver could convert a collection of digits (raw data) to hits, or it could perform a track finding algorithm and add new track object collections.
The EVIO Data Format is converted into LCIO by an LCSimEventBuilder such as LCSimEngRunEventBuilder. The EvioToLcio command line tool reads EvioEvents with an EvioReader and then uses an event builder to create LCIO events representing the raw data. The driver chain is then run to perform the physics reconstruction which will add additional object collections to the event. The combined events with the data and recon collections are written out to an LCIO file. The LCIO output can be converted to ROOT DST Data Format for ROOT compatibility, or it may be loaded back into HPS Java for analysis.
This is the basic recipe for reconstructing HPS data:
Oftentimes, steps 1-3 are performed in the same job (process) for efficiency using the EvioToLcio command line utility.
The reconstruction Driver chain is defined in production steering files such as EngineeringRun2015FullRecon.lcsim, which are kept in this SVN folder and typically accessed as a class resource from a jar file.
The following information is current as of February 28, 2016 (Physics Run 2016) but it may become outdated as the reconstruction changes. Consult the latest versions of the steering files for the most up to date information.
Driver Name | Driver Class | Description |
---|---|---|
RfFitter | RfFitterDriver | converts accelerator's RF wave form to time and inserts into event |
EcalRunningPedestal | calculates per channel running averages for ECal signal pedestals | |
EcalRawConverter | EcalRawConverterDriver | converts ECal digits to CalorimeterHit collection with energy and time measurements |
ReconClusterer | ReconClusterDriver | performs calorimeter clustering algorithm on ECal hits |
CopyCollection | CopyClusterCollectionDriver | copies calorimeter clusters to new collection to preserve uncorrected energy measurements |
RawTrackerHitSensorSetup | RawTrackerHitSensorSetup | assigns RawTrackerHits to their sensors for use by track recon |
RawTrackerHitFitterDriver | RawTrackerHitFitterDriver | fits ADC vs time signal to produce fitted hits collection |
TrackerHitDriver | DataTrackerHitDriver | creates stereo pairs from from SVT strip hits |
HelicalTrackHitDriver | HelicalTrackHitDriver | creates 3D hits from clusters of stereo pairs |
TrackReconSeed345Conf2Extd16 | TrackerReconDriver | runs track finding using layers 3, 4 & 5 as a seed, layer 2 to confirm, and layers 1 and 6 to extend |
TrackReconSeed456Conf3Extd21 | TrackerReconDriver | runs track finding using layers 4, 5 & 6 as a seed, layer 3 to confirm, and layers 2 and 1 to extend |
TrackReconSeed123Conf4Extd56 | TrackerReconDriver | runs track finding using layers 1, 2 & 3 as a seed, layer 4 to confirm, and layers 5 and 6 to extend |
TrackReconSeed123Conf5Extd46 | TrackerReconDriver | runs track finding using layers 1, 2 & 3 as a seed, layer 5 to confirm, and layers 4 and 6 to extend |
MergeTrackCollections | MergeTrackCollections | merge collections from track finding into single output collection |
GBLRefitterDriver | GBLRefitterDriver | performs GBL track refit |
TrackDataDriver | TrackDataDriver | adds additional collections containing track information to output event |
ReconParticleDriver | HpsReconParticleDriver | creates output reconstructed particle collection, associating tracks with clusters also performs vertex reconstruction |
LCIOWriter | LCIODriver | writes output LCIO file |
CleanupDriver | ReadoutCleanupDriver | cleanup readout state for next event (clears assignments of SVT raw hits to sensors) |
AidaSaveDriver | AidaSaveDriver | saves AIDA plots to file at end of job |
Collection | Java Class | Created By | Description |
---|---|---|---|
BeamspotConstrainedMollerCandidates | ReconstructedParticle | HpsReconParticleDriver | Møller candidate particles required to point back to beamspot at the target |
BeamspotConstrainedMollerVertices | Vertex | HpsReconParticleDriver | Møller vertices required to point back to beamspot at the target |
BeamspotConstraintedV0Candidates | ReconstructedParticle | HpsReconParticleDriver | electron-positron candidate particles required to point back to beamspot at the target |
BeamspotConstraintedV0Vertices | Vertex | HpsReconParticleDriver | electron-positron vertices required to point back to beamspot at the target |
EcalCalHits | CalorimeterHit | EcalRawConverterDriver | calibrated ECal Hits |
EcalClusters | Cluster | ReconClusterDriver | reconstructed ECal clusters with uncorrected energies |
EcalClustersCorr | Cluster | CopyClusterCollectionDriver | reconstructed ECal clusters with corrected energies copied from EcalClusters and then updated |
EcalReadoutHits | RawTrackerHit | EcalEvioReader | ECal Hits in ADC counts |
EpicsData | GenericObject | LCSimEngRunEventBuilder | EPICS data banks |
FADCGenericHits | GenericObject | ||
FinalStateParticles | ReconstructedParticle | HpsReconParticleDriver | final state particles (electrons, positrons, photons) with 4-momenta |
GBLKinkData | GenericObject | ||
GBLKinkDataRelations | LCRelation | ||
GBLTracks | Track | ||
HelicalTrackHitRelations | LCRelation | HelicalTrackHitDriver | relation from HelicalTrackHits to StripClusterer_SiTrackerHitStrip1D |
HelicalTrackHits | TrackerHit | HelicalTrackHitDriver | 3D hits combining StripClusterer_SiTrackerHitStrip1D hits in axial/stereo layers |
MatchedToGBLTrackRelations | LCRelation | ||
MatchedTracks | Track | TrackerReconDriver | primary collection of reconstructed tracks merged from collections with tracks generated from different strategies |
PartialTracks | Track | ||
RotatedHelicalTrackHitRelations | LCRelation | HelicalTrackHitDriver | relation from RotatedHelicalTrackHit to HelicalTrackHit |
RotatedHelicalTrackHits | TrackerHit | HelicalTrackHitDriver | HelicalTrackHits rotated into SeedTracker tracking frame: x→y, y→z, z→x |
SVTFittedRawTrackerHits | LCRelation | RawTrackerHitFitterDriver | relation from SVTRawTrackerHits to SVTShapeFitParameters |
SVTRawTrackerHits | RawTrackerHit | SvtEvioReader | Si sensor single strip hits |
SVTShapeFitParameters | GenericObject | RawTrackerHitFitterDriver | results of the ADC vs sample number fits for SVT data |
StripClusterer_SiTrackerHitStrip1D | TrackerHit | DataTrackerHitDriver | 1D Si strip clusters |
TargetConstrainedMollerCandidates | ReconstructedParticle | ||
TargetConstrainedMollerVertices | Vertex | ||
TargetConstrainedV0Candidates | ReconstructedParticle | HpsReconParticleDriver | electron-positron pairs with the vertex z fixed to the target position and (x,y) constrained to beamspot |
TargetConstrainedV0Vertices | Vertex | HpsReconParticleDriver | |
TrackData | GenericObject | ||
TrackDataRelations | LCRelation | ||
TrackResiduals | GenericObject | ||
TrackResidualsRelations | LCRelation | ||
TriggerBank | GenericObject | LCSimEngRunEventBuilder | trigger information for the event |
UnconstrainedMollerCandidates | ReconstructedParticle | HpsReconParticleDriver | |
UnconstrainedMollerVertices | Vertex | HpsReconParticleDriver | |
UnconstrainedV0Candidates | ReconstructedParticle | HpsReconParticleDriver | electron-positron pairs with unconstrained vertex |
UnconstrainedV0Vertices | Vertex | HpsReconParticleDriver |
SVT data banks are handled by an SvtEvioReader and converted into RawTrackerHit and GenericObject collections.
Various modes of EVIO ECal data are converted using the EcalEvioReader.
The following collections are added to the event by the ECal reader.
The default builder will also convert and write DAQ config information, EPICS data, and scaler bank data into the output LCSim events, if these banks are present in the EVIO data.
These are the steps in the HPS Java track reconstruction:
The tracking packages in lcsim form the basis for HPS's tracking algorithms through usage and extension. Seed Tracker is used for track finding using a set of input tracking strategies. The track fit from lcsim is further refined using a Java implementation (port) of the GBL C++ algorithm.
This paper describes the LCIO track parameters.
These slides provide some details about how tracking strategies are used (see pages 4 & 8).
These are the basic steps of the ECal reconstruction:
The copied collection will be updated with corrected energies in the step which creates recon particles.
This CLAS Note describes the basic clustering algorithm.
This HPS Note covers position corrections and other analysis.
The ReconParticleDriver creates ReconstructedParticle objects representing the final state particles from the event reconstruction. These are tracks with matching clusters (when applicable). It also performs vertex reconstruction and creates a number of candidate particle collections.
The ReconParticleDriver is sub-classed by the actual HpsReconParticleDriver from the steering which adds Moller candidate collections.
HPS Java Reconstruction Packages
The HPS Java Documentation can be used to browse the packages and classes used for physics reconstruction.
Java Package | Description | Notes | Module |
---|---|---|---|
org.hps.evio | converts EVIO raw data to LCIO | evio readers for converting EVIO raw data to LCIO events | evio |
org.hps.recon.ecal | ECal reconstruction utilities | primarily for converting from raw data to CalorimeterHits | ecal-recon |
org.hps.recon.ecal.cluster | ECal hit clustering framework | includes recon clustering and GTP/CTP hardware emulation clusterers | ecal-recon |
org.hps.recon.tracking | track reconstruction from SVT hits | based on Seed Tracker from lcsim | tracking |
org.hps.recon.tracking.gbl | GBLtrack refit | ported from C++ to Java; actual Java package now outside HPS Java | tracking |
org.hps.recon.particle | builds ReconstructedParticles from tracks and clusters | builds reconstructed particles from input event collections | recon |
org.hps.recon.vertexing | vertex reconstruction | based on Billoir vertexing algorithm | recon |
org.hps.recon.filtering | event skimming utilities | recon |
These lcsim packages are used extensively within the HPS Java reconstruction code.
Java Package | Description | Notes | Module |
---|---|---|---|
org.lcsim.event | physics event interfaces (implemented by LCIO) | interfaces used extensively in HPS Java Drivers | |
org.lcsim.util.loop | event processing loop | extends Freehep loop classes for lcsim usage | |
org.lcsim.job | lcsim job manager which reads lcsim xml steering files | ||
org.lcsim.lcio | Java implementation of LCIO file format | implements event interfaces | |
org.lcsim.recon.tracking.seedtracker | Seed Tracker track reconstruction algorithm | basis for HPS Java tracking | |
org.lcsim.util | Driver class for event data processing | ||
org.lcsim.conditions | detector conditions system backend | ||
org.lcsim.geometry, org.lcsim.detector | detector description and geometry classes |