After almost six years of construction, scientists from the Institute of Physics at Johannes Gutenberg University Mainz (JGU) have sent a particle detector on its way to the CERN research center in Geneva in a heavy goods vehicle. The detector had been assembled in a warehouse in the Mainz district of Gonsenheim and was loaded on 11 May to begin its journey of over 1,000 kilometers via France to Geneva. At CERN, it will be part of the so-called NA62 experiment, which begins in July of this year. The experiment will measure an extremely rare decay of kaons. A kaon consists of a quark and an antiquark and is one of the “strange particles”. It is unstable and was first discovered in high-altitude radiation in the 1940s.

The particle detector manufactured in Mainz is a hadronic calorimeter, a measuring device that records heat production in physical processes. Its footprint is approximately three meters by three meters with a height of one meter. The weight of almost 40 tons is mainly due to the iron layers in the detector. Due to its extra width and weight, special transport is required to bring the calorimeter to its destination. For various reasons, however, the journey does not take the direct route via Switzerland, but takes a detour via France to Geneva.

Once there, the particle detector will be installed in the NA62 experiment over the next few weeks. This experiment will measure the extremely rare decay of a charged kaon into a pion and two neutrinos. To do this, the kaons must be produced in large quantities at CERN. In 10 billion kaon decays, the desired decay with a pion occurs only once. Because the scientists would like to record 100 such decays, over 1 trillion kaons must be produced and their decays studied. The experiment is expected to run for around three years. “We hope that the exact decay rate we will measure will deviate slightly from the theoretical predictions and that we will find the long-sought new physics beyond the known Standard Model,” explains Dr. Rainer Wanke from the Institute of Physics at JGU. “We therefore have the same goal as the large experiments at the LHC accelerator at CERN.” Wanke is responsible for the construction of the Mainz detector.

This detector is intended to distinguish the pions that are produced during the decay under investigation from muons, which occur very frequently in kaon decays. “To do this, we exploit the different interaction of the two particles with matter. In our detector, the particles interact with 24 layers of iron, each 2.5 centimetres thick, and are detected between the iron layers by generating light in scintillating plastic strips and connected photo sensors,” says Wanke.

The particle detector and the participation of the Mainz scientists in the NA62 experiment are funded by the German Federal Ministry of Education and Research (BMBF) and supported by JGU’s Cluster of Excellence “Precision Physics, Fundamental Interactions and Structure of Matter” (PRISMA).

Scientists at Johannes Gutenberg University Mainz are involved in various other research projects at CERN, including experiments at the LHC particle accelerator.