The Standard Model of Particle Physics has been measured impressively and with high precision over the last three decades and has been confirmed time and again. However, the model leaves many questions unanswered, especially about the origin of dark matter in the universe. Particle Physics therefore expects a more advanced theory that includes the standard model but also provides answers to the questions that remain unanswered. Such a theory should, it is assumed, occur on an energy scale of around 1 teraelectronvolt (TeV). The LHC accelerator at CERN is expected to find new particles and phenomena in this energy range.

Another, complementary and equally promising way to search for new physics is at lower energy scales: New physics can have an impact on particle decays, the rate of which then differs from the standard model expectation. However, the prerequisite for sensitivity to new physics is the rarity of the decay within the standard model, so that a very high total number of reactions investigated is required.

The NA62 experiment at CERN is pursuing precisely this goal. It is searching for the decay of the charged kaon into a charged pion and two unobservable neutrinos. According to the standard model, this decay should only occur once in 12 billion kaon decays. The experiment was set up at CERN over several years until mid-2016 and has been successfully collecting data ever since. The very first data from 2016 have now been analyzed and were presented a few days ago by Radoslav Marchevski from Johannes Gutenberg University Mainz (JGU) at an international conference in La Thuile, Italy. Exactly one candidate of the extremely rare sought-after decay was found in the analyzed data set. “This is extremely surprising because, according to the standard model, we would have expected only 0.4 events on average after this time,” explained Dr. Rainer Wanke, who heads the group at JGU.

Despite this promising result, however, it is still far too early to draw any conclusions. The result shown is based on just one percent of the entire data set expected by the end of this year. The data for 2017 is therefore currently being analyzed at full speed, which could then already provide a clear answer to the discovery of new physics.

The NA62 collaboration consists of around 140 scientists from 13 European and North American countries. From Germany, a group from Johannes Gutenberg University Mainz is involved and is responsible for the muon veto system. The group also supervises the PC farm for online data processing of the experiment and plays a leading role in data analysis.

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).