DarkSide-Experiment: Geant4 Simulation & ROOT Analysis Framework

This repository contains the official Monte Carlo simulation and data analysis source code for the DarkSide-Experiment experiment, proposed by Team Ribera del Deuterium (Valladolid, Spain) for the CERN Beamline for Schools (BL4S) 2026 competition.

Overview

Our experiment aims to search for the Dark Photon ($A'$) via the decay of neutral pions ($\pi^0 \rightarrow \gamma A'$) produced by a 5 GeV/c proton beam hitting a Tungsten target. The long-lived Dark Photon decays into an electron-positron pair ($A' \rightarrow e^+ e^-$), which we track using Delay Wire Chambers (DWCs) and separate using the MNP33 dipole magnet.

Geant4 Simulation

The simulation is built using the Geant4 toolkit (based on the B4 example architecture).

• Custom Physics (PhysicsList.cc): Implements the non-Standard Model Dark Photon with a mass of 100 MeV/c² and forces the $\pi^0$ branching ratio to include the $A'$.
• Detector Geometry (DetectorConstruction.cc): Includes the Tungsten Target ($Z=0$), upstream/downstream DWCs, the MNP33 Dipole Magnet ($B = 0.05$ T), and a 4x4 Lead-Glass ECAL.
• Truth Tracking (SteppingAction.cc): Captures the exact energy and ID of the generated $A'$ and its daughter leptons.

ROOT Analysis (skimmer.c & graphs.c)

The analysis scripts process the raw simulation data (geant4.root) to simulate the logic of a real trigger and reconstruction algorithm.

• skimmer.c: Applies topological cuts (asymmetry, spatial separation) and kinematic reconstruction using a "Thin Lens" approximation for the magnetic field.
• graphs.c: Generates the Invariant Mass Spectrum, Vertex Z-Position, and 3D Opening Angle plots using TLorentzVector.

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Authors

Team Ribera del Deuterium

• Nicolás Rodríguez-Álvarez (Student Team Leader)
• Alan Martín Blanch
• Marcos García-Martínez
• Rodrigo Jiménez-Pequeño
• Hugo Gil-García
• Adrián Prieto-Arribas
• Samuel Vara-Gutiérrez
• Mentor: Fernando Rodríguez Merino
• Supporting Teacher: Lorena Gracia-García

IES Parquesol, IES Jiménez Lozano, IES Fuentesaúco (Castile and León, Spain).

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License

This project is licensed under the MIT License - see the LICENSE file for details.