Research

The thesis investigates the reconstruction of extensive air shower (EAS) core positions from sparse hit patterns on dual-layer water Cherenkov detector (WCD) arrays, as proposed for the Southern Wide-field Gamma-ray Observatory (SWGO). The central contribution is BiLayerEdgeConv, a graph neural network architecture that treats the electromagnetic and muonic detector layers as separate graph structures and fuses their learned representations through a bidirectional cross-attention mechanism. The work is supervised by Dr. J.A. Martínez Castro (CIC-IPN) and Dr. I.D. Torres Aguilar (INAOE).

Each detector layer is modelled as a k-nearest-neighbor graph over station coordinates. The upper branch applies EdgeConv operators to electromagnetic signals — integrated charge, arrival timing, and PMT amplitude — while the lower branch processes muonic responses from the shielded detector volume. After independent feature extraction, a bidirectional multi-head cross-attention module allows each layer's node embeddings to attend to the other layer's spatial context. Learned gating coefficients control the information flow, enabling the network to weight inter-layer correlations adaptively. The fused representation is passed to a regression head that predicts the shower core position (x, y).

Training and evaluation use CORSIKA-generated showers propagated through a Geant4 detector simulation. The architecture achieves a mean absolute error of 45 m on the core position task — within one station spacing of the 161-tank reference array — and a median error of 29.5 m, representing sub-station-pitch resolution. The full model comprises 119,845 trainable parameters, making it compact enough for deployment in online reconstruction pipelines.

SWGO— The Southern Wide-field Gamma-ray Observatory is a next-generation ground-based detector under development in South America, targeting the 100 GeV–PeV energy range with a double-layer water Cherenkov detector array. The collaboration spans 80+ institutions across 14 countries. Misonia contributes to the core position reconstruction pipeline as a student member.
swgo.org

HAWC— The High-Altitude Water Cherenkov Observatory operates at 4,100 m elevation on Sierra Negra, Puebla, Mexico, observing TeV gamma-rays and cosmic rays. Simulation frameworks developed for HAWC (HAWCSim, CORSIKA) inform the architectural decisions in the SWGO thesis work. Misonia participates through the CIC-IPN laboratory.
hawc-observatory.org