Tracing the first nanosecond of the Big Bang with particle jets

Professor of Experimental Particle Physics Mikko Voutilainen sees the universe as a fascinating puzzle, most of whose pieces remain undiscovered.

What are your research topics?

I investigate how elementary particles behave when studied using the highest energies and examined at the smallest scales ever achieved by humanity. The goal is to better understand the origins of matter and space, and precisely what took place in the Big Bang.

In more concrete terms, I analyse at the European Organisation for Nuclear Research (CERN) data generated when protons are collided with other protons in the Large Hadron Collider (LHC) particle accelerator. In these collisions, quarks and gluons inside protons are released, producing particle jets. My group specialises in the precise measurement and calibration of these jets.

Where and how does the topic of your research have an impact?

In 2012 the world celebrated the discovery of the Higgs boson, which explains the mass of elementary particles, but how did the Higgs field itself form in the Big Bang? The Big Bang produced as much antimatter as ordinary matter, but what has become of the former? The current structure of the universe was formed through dark matter, but what is this dark matter?

The universe is a fascinating puzzle, most of whose pieces remain undiscovered. Particle physics takes us to the moment before the first nanosecond of the Big Bang, where we may find answers to these questions.

Every discovery can alter our perception of reality, as well as impacting technological progress. Research conducted at CERN has resulted in, among other things, the world wide web, which we come across in all web browsers. Quantum theory used by modern quantum computers, such as the important Bell’s theorem, has been developed at CERN. Research at CERN has also benefited the development of future energy systems, such as fusion energy, superconductors and high-energy chargers.

What is inspiring in your field right now?

In recent years, I have been particularly interested in the possible instability of the standard model of particle physics observed after the discovery of the Higgs boson. In addition to the mass of the Higgs boson, this instability is strongly associated with the mass of the top quark and the coupling constant of strong interaction.

The interpretation of measurements of top quark mass and strong interaction is extremely sensitive to jet calibration, which is why there is a lot of demand for our group’s expertise. In fact, we’ve received funding for our measurements from the European Research Council (ERC), among other sources.

At the same time, deficiencies in the standard model can also imply new, yet-to-be-discovered particles, of which we may have seen indications in the highest-energy collisions of the previous run. Investigating this hint with the data from the ongoing third run is very exciting, but also challenging. In this case too, jets play a key role.

A third inspiring thing has been the rapid development of artificial intelligence, or, rather, machine learning, including in particle physics. It has opened up a lot of unprecedented ways to analyse data and find new information in enormous amounts of data. Here too, the expertise of our group has been strong.


Mikko Voutilainen is the Professor of Experimental Particle Physics at the Faculty of Science.