New tracking volume Λ decays
Test of new tracking volume setting.
See the campaign index for bug context and variant definitions.
All plots are produced by analysis/acceptance/plot_lambda_endpoints.py, filtered to lam_is_first == 1 (primary = Sullivan lambdas), and grouped by daughter count nd ∈ {0, 1, 2, ≥3, any}.
I.The most explanatory plots
Decay types
Decay types are determined by MCParticle daughters of the primary lambdas coming from the interaction point. (Primary = from Sullivan process)
During analysis we calculate daughters and what are the daughters:
0no daughters1&22 daughters pπ- or nπ0 - anticipated lambda decays3>2 daughters4/5/6/71 daughter p / π+ / n / π08other - non-standard 1- or 2-daughter combination
Primary Λ decay codes — counts per category
Endpoint Z & Angle
Λ endpoint Z — by number of daughters
Step histograms per daughter-count category plus a dashed outline for the combined sample.
Λ endpoint Z for lambdas with 2 daughters
Λ angle θ with Z+ (mrad)
Endpoint in ZX and ZY
Scatter. Primary Λ endpoint ZX — coloured by n daughters
Per-event scatter of Λ endpoints in the ZX plane. Colour encodes number of recorded daughters (0, 1, 2, ≥3).
Scatter. Primary Λ endpoint ZY — coloured by n daughters
II. 1-D Λ endpoint Z distributions
Λ endpoint Z corresponds to MCParticle.endpoint.z of lambdas. I.e. the point where Geant4 decayed lambdas.
These plots just use number of daughters, not categories like above.
Λ endpoint Z 1D (all)
Λ endpoint Z — categories overlaid
Step histograms per daughter-count category plus a dashed outline for the combined sample.
Λ endpoint Z 1D by N-daughters
Λ endpoint Z — any nd
Λ endpoint Z — nd = 0
Λ endpoint Z — nd = 1
Λ endpoint Z — nd = 2
Λ endpoint Z — nd ≥ 3
III. Λ polar angle with respect to +Z
The EIC hadron-beam crossing angle (25 mrad) is marked on both plots.
Primary Λ polar angle θ (mrad), categories overlaid
IV. ZX plane (EIC detector overlay)
ZX Scatter — by daughter count
Scatter. Primary Λ endpoint ZX — coloured by n daughters
Per-event scatter of Λ endpoints in the ZX plane. Colour encodes number of recorded daughters (0, 1, 2, ≥3).
ZX 2D histograms
ZX endpoint density — any nd
ZX endpoint density — nd = 0 (undecayed)
Primary Λ with no recorded daughters.
ZX endpoint density — nd = 1
ZX endpoint density — nd = 2
Canonical two-body Λ decay topology (p π- or n π0).
ZX endpoint density — nd ≥ 3
V. ZY plane
ZY 2D Scatter
Scatter. Primary Λ endpoint ZY — coloured by n daughters
ZY 2D Histograms
ZY endpoint density — any nd
ZY endpoint density — nd = 0
ZY endpoint density — nd = 1
ZY endpoint density — nd = 2
ZY endpoint density — nd ≥ 3
VI. Z vs. -R plane (EIC detector overlay, lower half)
R = sqrt(X² + Y²) is plotted with a minus sign so that points fall into the lower half of the detector cross-section, which is where the hadron-beam pipe bends.