Skip to content

psa.md

Latest commit

 

History

History
50 lines (38 loc) · 3.2 KB

psa.md

File metadata and controls

50 lines (38 loc) · 3.2 KB

Pulse Shape Analysis (PSA)

PSA extracts hit positions and charge information from raw pad traces (AtRawEvent) to produce an AtEvent containing AtHit objects.

Class Hierarchy

AtPSA is the abstract base class in AtReconstruction/AtPulseAnalyzer/. All concrete PSA implementations inherit from it.

Class Hits per pad Description
AtPSAMax 1 Places one hit at the time bucket of peak ADC. Charge stored is the peak ADC value; total trace integral also stored on the hit. Optional sub-TB time correction via charge-weighted average of peak region.
AtPSAFull 1 or many Designed for long traces (e.g. beam tracks). Traces with a signal window <50 TBs get one hit at the peak; traces ≥50 TBs are split into 50-TB windows with one hit per window and charge = average ADC in that window.
AtPSASpectrum 1 or many Uses ROOT TSpectrum for peak finding; can find multiple peaks per pad. Supports optional background subtraction and interpolation.
AtPSAHitPerTB many One hit per time bucket above threshold. Produces a dense 3D charge distribution with no peak-finding assumptions. Configurable TB range.
AtPSATBAvg many Divides the trace into windows of N TBs (default 5) and creates one hit per window whose average charge exceeds threshold. Hit Z is at window center. Skips saturated pads when a max threshold is set. Can operate on a pad augment instead of the raw ADC.
AtPSADeconv 1 FFT-deconvolves the electronics response function from the raw trace and applies a Butterworth low-pass filter to recover the ionization current. Reconstructed charge saved as "Qreco" augment on the pad. Hit placed at charge-distribution weighted average. Requires a response function (SetResponse).
AtPSADeconvFit 1 Extends AtPSADeconv; instead of the weighted average, fits the deconvolved charge distribution with a Gaussian using the longitudinal diffusion coefficient for improved Z resolution.
AtPSAIterDeconv 1 Extends AtPSADeconv with iterative corrections to the reconstructed current.
AtPSASimple2 — Deprecated. Use AtPSASpectrum or AtPSAMax instead.

Running PSA

PSA is applied by AtPSAtask, which wraps any AtPSA subclass:

auto psa = std::make_unique<AtPSAMax>();
psa->SetThreshold(45);                          // ADC threshold; optional
auto psaTask = new AtPSAtask(std::move(psa));
psaTask->SetInputBranch("AtRawEventFiltered");  // default: "AtRawEvent"
psaTask->SetPersistence(true);
fRun->AddTask(psaTask);

Chaining PSA Methods

AtPSAComposite allows running multiple PSA methods in sequence on the same event, for example to handle different pad types with different algorithms:

auto composite = std::make_unique<AtPSAComposite>();
composite->AddPSA(std::make_unique<AtPSAMax>());
composite->AddPSA(std::make_unique<AtPSADeconv>());

Output

PSA produces an AtEvent stored as a branch in the output TTree. Each AtHit in the event carries:

  • 3D position (x, y, time-bucket → z via drift velocity)
  • Charge (meaning depends on algorithm — peak ADC, window average, etc.)
  • Trace integral (sum of all ADC values over the trace)
  • Pad number and timestamp metadata