14 | New Scientist | 15 August 2020
PHYSICISTS have spotted the
Higgs boson performing a new
trick, but unfortunately it is
one that brings us no closer to
understanding the workings
of fundamental particles.
Researchers have long hoped to
see it doing something surprising,
which would help us make
progress in figuring out the
workings of the universe.
Discovered in 2012 at the CERN
lab near Geneva, Switzerland, the
Higgs gives all other fundamental
particles mass, according to the
standard model of particle physics.
However, despite the work of
thousands of researchers around
the world, nobody has been able
to figure out exactly how it does
that or why some particles are
more massive than others.
Some researchers have
suggested that particles have
different masses because there
is more than one type of Higgs
boson, with each type coupled to
a different range of other particles.
The only way to try to solve
that problem is by observing how
the Higgs interacts with other
particles using the Large HadronCollider at CERN. For the first time,
both of the major research groups
that use the collider – the CMS
and ATLAS collaborations – have
observed the Higgs decaying into
two muons, a sort of particle we
have never directly seen it interact
with before. Members of the two
groups presented this work at the
virtual International Conference
on High Energy Physics.The problem is, muons are
much less massive than the other
types of particles we have seen the
Higgs interact with, which means
the new discovery makes it more
likely that there is only one type
of Higgs. That behaviour is exactly
what we expect from the standard
model. Adam Gibson-Even at
Valparaiso University in Indiana
says it is an instance of “Higgs
boson, exactly as ordered”.
But this leaves the mystery
of why particles have different
masses completely unanswered.
While the result may not be
surprising, says Gibson-Even, it
is somewhat frustrating because
we know the standard model is
incomplete; in addition to not
explaining why particles have
different masses, it also doesn’t
account for dark matter or
dark energy. Nevertheless,
experimental results have been
entirely in line with the model.
“It’s a problem in the sense
that we know that the Higgsboson as-is doesn’t explain these
things,” says CMS researcher Freya
Blekman at the Free University
of Brussels, Belgium. If the same
Higgs interacts with both muons
and heavier particles, that closes
another avenue to solving the
question of mass.
The next step, says Blekman,
is to take even more accurate
measurements of the Higgsinteracting with a range of
different particles. Many of
these measurements need to
be more precise than those that
the LHC can provide, which is part
of the argument for building a
more powerful “Higgs factory”
collider, she says.
“We have removed scenarios,
but we don’t have an explanation
yet,” says Blekman. “But this is
what particle physics is about –
we have tens of thousands of
predictions and we have to
eliminate them.” ❚“This is what particle
physics is about – tens of
thousands of predictions
we have to eliminate”Particle physicsLeah CraneMAX^ BRICE/CER
NNews
The CMS detector at CERN
is studying the behaviour
of the Higgs bosonInsectsFruit flies have brain
cells that sense the
way the wind blowsSPECIFIC neurons in fruit flies fire
according to wind direction, helping
them form a neural map of their
surroundings. Algorithms inspired
by this may be able to help robots
navigate their environment.
Tatsuo Okubo at Harvard Medical
School and his colleagues wanted to
determine how wind direction was
characterised by a fruit fly’s brain.
While it is well known that wind
direction affects the behaviourof insects, no one had yet developed
a map of the neurons involved in
this phenomenon for any animal.
The researchers initially looked
for neurons that corresponded to
antennae because they thought
these would be the ones affected
by wind. “We then found these
beautiful ring-shaped neurons that
were next to neurons that affect
the head direction,” says Okubo.
They recorded the firing rate
of these ring neurons in a living
fruit fly while changing the wind
direction of its surroundings.
The team found that wind-
sensitive neurons had differentpreferences for wind direction,
firing more if the wind blew from
their favoured direction. This led
to a fluctuating firing pattern in
the overall population of neurons
corresponding to wind direction.
Moreover, when these cells were
silenced, the fly’s head direction
neurons reacted as if there were
no wind at all, suggesting that wind
information directly influences the
direction a fruit fly faces (Neuron,
doi.org/d53j).
It is unclear whether we have
such neurons too. “Humans can
definitely use wind for long-range
navigation like pathfinding, butexactly how they sense it or how
that feeds into a navigational
circuit – it’s still an open question,”
says Okubo.
These findings could one day be
used to give robots an additional
method of navigation, he adds.
“This research proves that
neurobiology still has a lot to learn
from small but sophisticated insect
brains,” says Ronny Rosner at
Newcastle University, UK. “This
will be particularly useful if we
want to develop the most efficient
algorithms for spatial orientation
of intelligent machines.” ❚
Jason Arunn MurugesuThe Higgs boson is still behaving,
which poses a massive problem