The Higgs boson is something of the publicity-shy star of the physics world. Researchers had searched for it for nearly 60 years, until it was finally discovered in 2012 at the Large Hadron Collider (LHC), a 27-kilometre particle accelerator at CERN in Geneva. Thousands of physicists around the world – many of them from DESY – helped in the search, because the Higgs boson was the last missing particle in a theory that describes the known elementary particles and three of their fundamental interactions. This theory, known as the Standard Model of particle physics, is highly precise in many of its predictions, but it still leaves several questions unanswered. The Higgs boson could help answer them.

 The Higgs boson is named after the British theorist Peter Higgs, who suggested in 1964 that the Universe must contain an invisible field with which certain elementary particles interact and through which they get their mass. The stronger the interaction, the heavier the particle. Without the Higgs field, all elementary particles would be massless; atoms and the matter we know could not exist. The discovery in 2012 was a sensation, but it was only the beginning of a comprehensive investigation.

“Fully understanding the Higgs boson is one of the most pressing tasks in particle physics, because it plays a central role in particle physics theory,” says physicist Martina Ojeda who started an Emmy Noether Group at DESY on 1 September with support from the German Research Foundation (DFG). “Its properties determine how the universe came into being and how it will end, and it may be a gateway to dark matter – a form of matter as yet unknown that accounts for around 80 per cent of the matter in our universe.”

That is why researchers would like to know every detail about this mysterious particle. Martina Ojeda’s focus is measuring its ‘width’. Short-lived particles such as the Higgs cannot be measured with a tape measure, however. When particle physicists talk about ‘width’, they do not mean the spatial extent of the Higgs particle, but rather a quantity related to its extremely short lifetime. It can only be determined through a skilful combination of theory and measurement data. 

The data in question are collected by the ATLAS detector, to which DESY scientists also make key contributions. However, they are not precise enough for a direct measurement of the width. That is why indirect methods are used, for example studying Higgs boson decays into other particles known as W or Z bosons. These methods would normally require additional assumptions to be made. However, Martina Ojeda and her group are focusing on using the theoretical toolkit of ‘effective field theories’ and data from the ATLAS detector at the LHC to avoid the need for these assumptions. In the long run, their work should help to develop more robust models for measurements in the upcoming phase of the LHC, in which DESY also plays an important role. It could also provide further information on new physical processes beyond the Standard Model.

After completing her PhD in Toronto, Martina Ojeda conducted research on the Higgs boson at DESY and CERN. She has returned to DESY and its ATLAS team on 1 September 2026 with her Emmy Noether Research Group. The Emmy Noether Programme of the German Research Foundation (DFG) enables exceptionally qualified researchers at an early stage of their careers to lead an independent research group for a period of six years.