The Tool-based Reconstruction Algorithm

for Characterising Showers*Dom Brailsford

FD sim/reco Meeting16/09/19

*Primary authors Dom Barker

Ed Tyley

Shower characterisation• Shower characterisation == the bit you do

after the pattern recognition

• Shower reconstruction is hard, particularly in a LArTPC

• The difficulty is frustrating because you primarily only need to know a few key pieces of information for physics analyses:

• Start position

• Initial direction

• Energy

• dE/dx

• *ID of the initial track stub

!2

Not another shower characterisation module?

• The Tool-based Reconstruction Algorithm for Characterising Showers (TRACS) is a shower characterisation module

• Developed by Dom Barker and Ed Tyley as part of the SBN shower reconstruction WG

• TRACS takes a recob::PFParticle as input and outputs a recob::Shower

• Just like PandoraShower and EMShower

• The key difference is TRACS outsources all of the characteristic calculations to a set of art tools where a tool has a specific purpose

• A tool to calculate the shower’s direction

• A tool to find the initial track stub’s hits

• A tool to calculate the initial track’s dE/dx

!3

Quick technical details

• You specify an arbitrarily sized list of the tools in FCL to configure the shower characterisation

• The only caveat is enough tools need to be run to characterise start position, direction, energy and dE/dx*

• *All current dE/dx need an initial track stub to function

• Every tool is exposed to the PFParticle under consideration, the art::Event and the ShowerElementHolder

• ShowerEleHolder holds the characteristics that each tool calculates, it can also hold an arbitrary number of transient objects as well as art data products destined for the ARTROOT output file

!4

Tools to be shown today• Shower start position

• ShowerStartPosition_tool: Takes the PFParticle’s vertex position as the start position (a la pandoraShower)

• Initial track stub finder

• Shower3DTrackHitFinder_tool: Tags space points contained in a cylinder whose axis is the calculated shower direction and starting at the calculated shower start position

• Initial track fitter

• ShowerPMATrackFinder_tool: Uses the Projection Matching Algorithm to form a track using the found initial track hits

• Shower direction

• ShowerPCADirection_tool: Applies a charge-weighted PCA to the shower space points; the primary axis is the shower direction (similar to pandoraShower)

• ShowerTrackTrajectoryPointDirection_tool: Takes the starting direction of the fitted track stub (recob::Track::DirectionAtPoint(1))

• dE/dx

• ShowerStandardCalodEdx_tool: Calculates a per-view dE/dx using the initial track hits. The tool calculates a per-view pitch by projecting the calculated shower direction into each view

!5

The sample used• Vertex-like particle gun

• Electron (0 < p < 4.5 GeV)

• Pi+ (0.5 GeV < p < 2.0 GeV)

• Fixed start pos (180,-300,580)

• Isotropic angle

• Downstream fcls:

• standard_g4_nooptical_dune10kt_1x2x6.fcl

• Disables the light sim

• standard_detsim_dune10kt_1x2x6.fcl

• standard_reco_dune10kt_nu_1x2x6.fcl

• For assessing the recob::Shower parameters, I only consider recob::Showers with the highest number of hits in an event AND which are also truth matched to the primary electron

!6

Quick aside: Pandora neutrino vertex position displacement

• | vertex_reco - vertex_true|

• Nice sharp peak at 0 cm

• Very broad second peak at ~120 cm

• Displacement is within 10 cm 34.6% of the time

0 50 100 150 200 250 300 350 400 450 500Dist. between true and reco. vertex (cm)

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Mis-vertexing examples

Reco vertex

True vertex

Reco vertex

True vertex

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Mis-vertexing examples

Reco vertex True

vertex

Reco vertex

True vertex

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Number of reco. showers

• The number of ALL recob::Showers in each particle gun event

• Total stats: 49700

• 16.4% of particle gun events do not contain a recob::Shower

0 1 2 3 4 5 6 7 8 9No. reco. showers

0

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Completeness/hit purity

33024 (66.4%) events contain at least one reco. shower truth matched to the primary electron

15110 (30.4%) events contain a primary electron-matched shower where the initial track stub contains at least one primary electron hit

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 shower with max No. hits)-Completeness (e

0

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hit-Initial track stub contains at least one primary e

matched showers-All primary e

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 shower with max No. hits)-Hit purity (e

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hit-Initial track stub contains at least one primary e

matched showers-All primary e

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*Shown for showers which contain the max no. of hits AND truth match to the primary electron

Low completeness eventsWire/tick views Ortho3D

displayOnly

spacepoints are shown

Clusters are matched by

colour

Black spots are unused hits

!12

Low completeness events

100120140160180X300−250−200−150−100− 50−Y 450

500

550

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Z• Chain of trip ups

• Pat. rec. separates track stub and cascade bulk (pink line [track] attached to black splodge [shower])

• Start position of cascade bulk then placed at wrong end (green square)

• The track stub finder fails to find any initial hits

• Shower is thrown away as it is incomplete

• One of the much smaller showers (blue splodges) becomes the shower with the highest hits

!13

TRACS event display (shows space points)

A shower

A different shower

A track

Start pos.

Direction vector

Low completeness eventsWire/tick views Ortho3D

displaySpacepoints

and true trajectories

shown

Clusters are matched by

colour

Black spots are unused hits

Initial electron missing

space points

!14

Low completeness events• Another chain of trip ups

• Pat. rec. merges charged pion track with the whole electron shower

• Start position then picked to be the very end of the shower

• Charge-weighted PCA is biased towards centre of the pion track

• Track stub finder misses the shower space points as direction is mis-aimed

• Shower is thrown away due to being incomplete

• One of the much smaller showers (blue splodges) becomes the shower with the highest hits

110120130140150160170X350−300−250−200−150−Y

440

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620Z

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TRACS event display

Shower start position

0 10 20 30 40 50 60 70 80 90 100Distance between true and reco. shower start (cm)

210

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hit-Initial track stub contains at least one primary e

matched showers-All primary e

• Using ShowerStartPosition_tool

• Takes the PFP’s vertex as the shower start position

• Plot shows the distance between the true and reco shower start positions

• Nice sharp spike at 0 cm in all cases

• Wide tail is largely eliminated for showers in which the track stub contains a primary hit

!16

*Shown for showers which contain the max no. of hits AND truth match to the primary electron

The initial track stub finder

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Fraction of primary-matched hits

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nts• Shower3DTrackHitFinder_tool

• IDs track space points as those enclosed in a cylinder at the start of the shower

• Plot shows the fraction of shower-contained primary electron hits that are part of the initial track stub

• Not the same as completeness

• 45% of initial track stubs contain a non-zero fraction of primary electron hits

!17

*Shown for showers which contain the max no. of hits AND truth match to the primary electron

1− 0.8− 0.6− 0.4− 0.2− 0 0.2 0.4 0.6 0.8 1 (no units)trued • recod

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'DirectionAtPoint' initial track direction tool

PCA direction tool

1− 0.8− 0.6− 0.4− 0.2− 0 0.2 0.4 0.6 0.8 1 (no units)trued • recod

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'DirectionAtPoint' initial track direction tool

PCA direction tool

DirectionPrimary electron showers with

max. no. hitsInitial track contains one primary

electron hit

!18

• PCA outperforms the direction from the initial PMA track in all cases

• This study will be redone with a new tool which uses pandora’s sliding linear fit once it becomes available

*Shown for showers which contain the max no. of hits AND truth match to the primary electron

dE/dx

0 1 2 3 4 5 6 7 8 9 10dE/dx (MeV/cm)

0

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hit-Initial track stub contains at least one primary e

matched showers-All primary e• ShowerStandardCalodEdx_tool

• Shower direction (required to calculate pitch) calculated by PCA tool

• MIP peak sharpens for cases where the track stub contains a primary electron hit

!19

*Shown for showers which contain the max no. of hits AND truth match to the primary electron

Good recos

Summary and future• The Tool-based Reconstruction Algorithm for Characterising Showers (TRACS)

is a shower characterisation module

• Developed by Dom Barker and Ed Tyley as part of the SBN shower reconstruction WG

• Relies on pandora PFParticle input

• TRACS outsources all calculation to an arbitrary set of art tools, each of which calculates a specific shower parameter

• TRACS is now being configured for use in the DUNE FD

• Future tools are under development/will soon be available

• Fitting the initial track stub with pandora’s sliding linear fit

• An incremental fit-based track stub finder!21

Backups

1− 0.8− 0.6− 0.4− 0.2− 0 0.2 0.4 0.6 0.8 1 (no units)trued • recod

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'DirectionAtPoint' initial track direction tool

PCA direction tool

What causes the spike at 0