Christoph Genster M.Sc.

Dr. Christoph Genster
  • Joined January 2016 as a PhD student
  • Postdoc July 2019 - March 2020
  • Focus of research: The Low Level Data Reconstruction Algorithms for the JUNO Experiment

  • Phone: +49 2461 61 4735
  • E-mail:


  • PhD in Physics
    RWTH Aachen University
    Thesis topic: Software and hardware development for the next-generation liquid scintillator detectors JUNO and OSIRIS
  • M.Sc. in Physics
    RWTH Aachen University
    Master Thesis: Development and test of reconstruction methods for muon tracks in the JUNO liquid scintillator neutrino detector
  • B.Sc. in Physics
    RWTH Aachen University
    Bachelor Thesis: Supersymmetric Quantum Mechanics

The Low Level Data Reconstruction Algorithms for the JUNO Experiment


The experimental site of the JUNO detector is confined by its distance to the nuclear power plants. In order to achieve the maximum sensitivity on the neutrino mass hierarchy the detector has to be placed in 53 km distance to both reactors. Due to this the underground lab has only 700 m rock overburden. With a sophisticated simulation that includes the actual 3D model of the surrounding mountains the flux of atmospheric muons was determined to be about 3 Hz in the whole detector with a mean energy of <E> = 215 GeV. Therefore they are among the most energetic particles to cross the detector and the will produce several million photoelectrons. More importantly muons can collide with the carbon in the liquid scintillator and break them apart. This is called spallation and produces a variety of cosmogenic isotopes. Some of those are an indistinguishable background for the reactor neutrino measurement. 9Li and 8He are the most prominent cosmogenic isotopes because they have a long livetime and their decay mimics the correlated decay of IBD events. Since those isotopes are produced by the muon along its track they cannot travel too far from it. Utilizing this the background can be removed by vetoing a confined volume around the muon track. Therefore a reliable track reconstruction of muons is essential in order to achieve the full physics potential.

Tracking in liquid scintillator

Tracking in liquid scintillator (LS) is a challenge because the light emission is isotropic and not directional. For point-like events this an advantage, but for an extensive track one has to make use of the fact that all iostropic light emissions along the track add up. Since the travel speed of photons is reduced by the refractive index of the LS vg = c0 / nLS a forward moving light front in shape of a cone is formed. The construction is similar to a Cherenkov-light cone and carries information about the track's position and direction. Commonly this approach is called the fastest light model because it utilizes only the first light that is detected.

Application of the cone model

In JUNO the cone model is implemented to study its tracking performance and to provide a powerful tool for muon reconstruction. The provided software framework includes a detailed simulation of the detector and its full response as well as different reconstruction tools for several stages from signal processing to event reconstruction. Within this framework several different muon samples are produced, visualized and reconstructed. In an experimental setup the general method has to be taylored to the detector features. This includes properties of the LS like absorption and re-emission, optical effect like refraction or scattering on different materials and PMT acceptance and efficiency. Furthermore the performance of previous reconstruction stages like waveform reconstruction influence the results. Further development of the model is done to better describe the real physics situation present.

Reconstruction in sub-detectors

The central detector of JUNO is placed in a large cylindrical water tank. It shields the liquid scintillator from external radioactivity and is also instrumented with PMTs to act as a water Cherenkov veto. The information provided by this subdetector is less detailed due to a more coarse PMT placement, but it can give a fast overview of the topology of a muon event. A cluster finder algorithm is under development to identify if muons traverse the whole detector or stop inside it anf if there a bundles of muons instead of single tracks. The result can be used to trigger and seed an according reconstruction method with the detailed information of the central detector.