23 November 2019 | New Scientist | 43>understanding of fundamental physics.
We didn’t discover new physics, true.
This may appear disappointing, because
of course discovering new particles is
always very glamorous and exciting. But
being able to disprove some scenarios and
hypotheses is important to help us guide
our explorations towards the most
promising directions.Hasn’t the no-show of new particles broken the
successful model of particle physics over the past
few decades: theorists propose new particles
and experimentalists find them?
It hasn’t always been like that in the history of
particle physics. There have been times when
theory has guided experiments, and there
have been times when the experiments were
discovering plenty of new particles and theory
was trying to make sense of them. Now,
perhaps more than ever, we need to make
progress on the experimental side to give some
hints to theorists about the most promising
direction for developing new ideas.The likes of supersymmetry, a theory that
would fill in gaps in our understanding of the
universe that the standard model of physics
can’t, predict a bevy of new particles, but the LHC
has detected no sign of them. Does that mean
these theories have ceased to be viable?
We have to be very careful about that.
I consider supersymmetry a very nice
theory. The fact that we haven’t found any
sign of it as yet may indicate two things.
One, supersymmetry is wrong. Fine. Or,
supersymmetry sits at an energy scale
above where we are exploring now, or
alternatively manifests itself through
particles that are extremely light and
extremely weakly interacting.
Our goal is not to run behind a given
theory. Theories are good benchmarks,
but nature may have chosen a completely
different way. We have to address the open
questions – and there are many, many of
them – related to the Higgs boson and its mass,
the problem of dark matter, the problem of
matter-antimatter asymmetry, and so on.You mention dark matter, this vast quantity of
unseen matter that cosmological observations
tell us must be there. The LHC hasn’t been able
to make anything that looks like a dark matter
particle. So where are they hiding?
Dark matter could be either extremely light
or extremely heavy. The window that we have
explored so far might not be large enough,
or dark matter might not have the type ofRichard Webb: How difficult is it to manage the
thousands of physicists at CERN?
Fabiola Gianotti: Well, I’m a physicist myself,
so I feel really at home. What is very nice in this
place is that it is always about teamwork. We
always try to get different points of view
around the table.The LHC is shut for an upgrade until 2021,
and you have a decade or so’s worth of data since
it started up in 2008. Are you happy with what
it has achieved so far?
Of course, we are extremely happy.
The discovery of the Higgs boson was a
monumental one because this particle is
very special, very different from the other
16 elementary particles that we had
discovered and measured before.
The Higgs is related to the most obscure
and problematic sector of the standard model,
the theory that describes the elementary
particles and their interactions. And it is a
unique tool to look for physics beyond the
standard model that could help us elucidate
other mysteries.But the LHC hasn’t discovered anything
new and unexpected.
The precise measurement of the Higgs boson
and many other well-known particles has
allowed us to make a step forward in ourPROFILE
Fabiola Gianotti has been a researcher at
CERN since 1994. As head of its ATLAS
experiment, a collaboration involving
3000 people, she was one of two
scientists charged with revealing the
details of the Higgs boson discovery in
- She has been CERN’s director-
general since 2016 and was recently
appointed for a second term
“ It is the duty
and the right
of humanity to
understand how
nature works”