Axions are hypothetical elementary particles which were first postulated by physicists in order to solve the so-called strong CP problem, a theoretical inadequacy of the strong interaction. However, in the past few years it has emerged that axions or axion-like particles (ALPs) could also help to solve other puzzles in modern physics. They are seen as promising candidates for constituents of dark matter and their existence might also explain the experiment/theory discrepancy when it comes to the value of the anomalous magnetic moment of muons, as has been recently shown by physicists from Mainz. The search for these ALPs is therefore a very topical issue. "In the last few years, physicists have developed numerous forms of related experiments, and have particularly concentrated on looking at ultra-light ALPs as possible candidates for what makes up dark matter," Prof. Matthias Schott explains. "Now, for the first time, we are proposing a detailed research program using the LHC's ATLAS Experiment where we can undertake a targeted search for relatively heavy ALPs, which, once found, could solve the problem associated with the anomalous magnetic moment of the muon."
The search can now begin. The European Research Council (ERC) is supporting the project, entitled 'Search for Axion-Like Particles at the LHC - Light@LHC', awarding an ERC Consolidator Grant of more than €1.5 million to Matthias Schott. The project will be carried out over the next 5 years within the PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU).
New analysis algorithms are based on artificial intelligence
When the LHC, the world's largest particle accelerator, comes back online in 2021 after its long break, Matthias Schott and his team of researchers will be focusing on two processes that occur following the collision of protons or lead atoms. Firstly, it is postulated that a Higgs-Boson decays into two ALPs which in turn decay into two photons; secondly, it is assumed that ALPs initially develop from two photons before decaying into two photons again.
Although this may sound simple, it is in fact highly complex. "We therefore need completely new approaches for identifying photons and analyzing the results," Schott illustrates. "In order to achieve the required sensitivity for photon detection, we have to develop special reconstruction algorithms, for example, which are based on modern concepts employed in connection with artificial intelligence. Of course, we hope that these developments will also prove successful in the other fields of physics covered by the ATLAS Experiment." But that's not the whole story. Even with the new, specially developed algorithms that will enable them to cover a very large search area, it will not be possible for the researchers to 'capture' all of the ALPs they may be hoping to net. In order to offset this, from 2021 CERN is expected to begin working on a new experiment in a side tunnel of the LHC. Around 480 meters behind the ATLAS Experiment, the FASER Detector will primarily be used to register particles that interact so weakly with other particles that they simply continue unimpeded on their original trajectory, making them invisible to previous detectors. "Hence FASER is predestined, so to speak, to look for ALPs. And with the help of the ERC grant, we plan to build a specially designed ALP-detecting component for the detector here in Mainz, and then transport it to CERN."
ERC Consolidator Grants for outstanding researchers
The ERC Consolidator Grant is one of the most richly endowed EU funding awards for individual researchers. The European Research Council uses these grants to support outstanding researchers in developing their own projects, usually seven to twelve years after they have completed their doctorates. In order to receive a grant, applicants must not only demonstrate excellence in research, but also provide evidence of the pioneering nature of their project and its feasibility.
Matthias Schott, born in Nuremberg in 1979, studied physics at the Friedrich-Alexander University Erlangen-Nuremberg and the University of Cambridge in the UK, and acquired his doctorate at the Ludwig-Maximilian University Munich. In 2008, he was awarded one of the eminent Fellowships of the CERN research center in Geneva and as a result of his outstanding research was appointed to a CERN Research Staff post in 2010. In August 2012, Matthias Schott came to JGU where he set up an Emmy Noether junior research group funded by the German Research Foundation (DFG); later he was awarded a Lichtenberg Professorship sponsored by the Volkswagen foundation, aiming at the high-precision measurement of the mass of the W boson at hadron colliders. After research stays at the Massachusetts Institute of Technology and the University College London, Matthias Schott continues his research as full professor for Experimental Particle Physics at JGU.