fix: expand track seeding default cfg into non-sqrt values

[wdconinc]

Briefly, what does this PR introduce? Please link to any relevant presentations or discussions.

This PR updates the default error values used for track parameter estimation in the TrackSeedingConfig struct. The changes replace expressions involving square roots and unit conversions with their precomputed numerical values, making the code clearer. The numerical values are essentially identical (up to 4th digit rounding) to what was there before, just more easily interpretable. No major changes are expected by this PR.

Track parameter estimation error updates:

• Replaced computed expressions for locaError, locbError, phiError, thetaError, qOverPError, and timeError with their evaluated numerical values in the TrackSeedingConfig struct. This change clarifies the default error settings and removes the need for runtime computation.

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What kind of change does this PR introduce?

• Bug fix (issue: weird units removed)
• New feature (issue #__)
• Optimization (issue #__)
• Updated parameters, constants (issue #__)
• Updated documentation
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• This PR requires changes to geometry (epic PR: __)
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[Copilot]

Pull request overview

This PR updates the default track-parameter estimation covariance values in TrackSeedingConfig by replacing std::sqrt(...)-based expressions and unit conversions with precomputed numeric constants, aiming to make the defaults easier to interpret.

Changes:

• Replaced locaError, locbError, phiError, thetaError, qOverPError, and timeError default initializers with precomputed numeric values.
• Simplified the time error default from a derived expression to a direct ns-scaled constant.

Suppressed comments (1)

src/algorithms/tracking/TrackSeedingConfig.h:205

• timeError is now a magic number, and it's also rounded relative to the previous expression (sqrt(0.1 * mm / ns) * ns). To keep the change purely cosmetic/clarifying, consider using a more precise evaluated value and keep a brief derivation note inline.

  float timeError   = 5.475 * Acts::UnitConstants::ns;

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[wdconinc]

FYI @ShujieL @bschmookler This doesn't apply any real changes (by design) but should make it clearer what values are actually used now.

[Copilot]

🔵 Needs a closer look

The new constants are rounded/re-expressed enough to slightly change the configured default covariances, conflicting with the stated intent of being essentially identical to the prior expressions.

Review details

Suppressed comments (2)

src/algorithms/tracking/TrackSeedingConfig.h:204

• The new numeric defaults are rounded enough to slightly change the effective covariance (e.g., sqrt(1.5)=1.224744… vs 1.225). If the intent is to be numerically equivalent to the previous expressions, consider using the full evaluated constants (enough digits to round to the same float) rather than 3-decimal approximations.

  float locaError   = 1.225 * Acts::UnitConstants::mm;
  float locbError   = 1.225 * Acts::UnitConstants::mm;

src/algorithms/tracking/TrackSeedingConfig.h:208

• qOverPError/timeError were previously defined via sqrt-based expressions; rewriting them as low-precision decimals (and qOverPError as an inverted number) reduces traceability and can change the value slightly. Using a higher-precision evaluated coefficient (and a direct "/ GeV" form) keeps the intent clear while still removing runtime sqrt.

  float phiError    = 0.1414 * Acts::UnitConstants::rad;
  float thetaError  = 0.0447 * Acts::UnitConstants::rad;
  float qOverPError = 1. / (6.325 * Acts::UnitConstants::GeV);
  float timeError   = 0.0183 * Acts::UnitConstants::ns;

• Files reviewed: 1/1 changed files
• Comments generated: 0 new
• Review effort level: Lite

[github-actions]

Capybara summary for PR 2906

• rec_dis_10x100_minQ2=0_craterlake_10x100_MT (Δ: 402)
• rec_dis_10x100_minQ2=100_craterlake_tracking_only (Δ: 218)
• rec_dis_10x130_minQ2=1_craterlake_10x130 (Δ: 295)
• rec_dis_10x250_minQ2=1_craterlake_10x250 (Δ: 278)
• rec_dis_18x275_minQ2=0_craterlake_18x275 (Δ: 287)
• rec_dis_18x275_minQ2=0_craterlake_18x275_MT (Δ: 419)
• rec_dis_18x275_minQ2=0_craterlake_18x275_ST_MT (Δ: 335)
• rec_dis_18x275_minQ2=0_craterlake_18x275_Seeding_Seeding2 (Δ: 965)
• rec_dis_18x275_minQ2=100_craterlake_18x275 (Δ: 336)
• rec_dis_18x275_minQ2=100_craterlake_18x275_MT (Δ: 509)
• rec_dis_18x275_minQ2=100_craterlake_18x275_ST_MT (Δ: 468)
• rec_dis_18x275_minQ2=100_craterlake_18x275_Seeding_Seeding2 (Δ: 1705)
• rec_dis_5x41_minQ2=0_craterlake_5x41 (Δ: 288)
• rec_e_1GeV_20GeV_craterlake (Δ: 193)
• rec_pi_1GeV_20GeV_craterlake (Δ: 178)
• two_stage_raw_e_1GeV_20GeV_craterlake (Δ: 0)
• two_stage_rec_e_1GeV_20GeV_craterlake (Δ: 0)

Last updated 2026-09-04T21:31-04:00 007f312