‘The run-up was stunning’
‘We were initially going to present the ATLAS results at the big ICHEP conference in Melbourne, but in the end it was decided to announce the Higgs discovery in Geneva, together with CMS. So I saw the announcement from Australia, with hundreds of colleagues from around the world. That was an emotional moment, for sure. Everybody was happy.
But frankly for me not as strong a moment as when we saw the Higgs peak sticking out by 5 sigma a week before at the unblinding of the new data. Again sharper than the times before, with even less data then. It was really stunning to see the evidence grow so much in a few months. At the time I was working on the decay of the Higgs particle into two W particles, with a team of young researchers at Nikhef. We were also using self-learning algorithms for the first time, with which we hoped to see the signal even better.
After the discovery, we also used that to be the first to properly measure the spin of the Higgs particle: zero, as you would expect from a scalar boson. Hard proof that we really had found a Higgs particle. For me, the discovery of the Higgs particle was above all the beginning of many exciting new questions. Big questions, for example, about why the universe consists of matter and not antimatter. Is that asymmetry already in the Higgs particle? We are really just at the beginning of getting answers. We will need the LHC accelerator until the end to measure and analyze precisely enough.
My question to the Higgs particle? How do you feel about another Higgs particle? The Higgs self-coupling tells us how the Higgs field fills the vacuum of the universe. This cannot be measured yet, but it is super exciting. If only because it could turn out that the universe is metastable and the empty space could spontaneously condense into a sea of Higgs particles at any moment.’
This interview was originally published in Nikhef magazine DIMENSIES #7