Supersymmetry’s appeal is that it
solves three major problems in physics: It
explains why the Higgs is so light; it provides a particle that serves as dark matter; and it implies that the three forces of
the standard model (electromagnetism
and the weak and strong nuclear forces)
unite into one at high energies.
If a simple version of supersymme-
try is correct, the LHC probably should
have detected superpartners already. As
the LHC rules out such particles at ever-
higher masses, retaining the appealing
properties of supersymmetry requires
increasingly convoluted theoretical
contortions, stripping the idea of some
of the elegance that first persuaded sci-
entists to embrace it.“If supersymmetry
exists, it is not my parents’ supersymme-
try,” Buckley says. “That kind of means it
can’t be the most compelling version.”
Still, many physicists are adopting
an attitude of “keep calm and carry
on.” They aren’t giving up hope that
evidence for the theory — or other new
particle physics phenomena — will
show up. “I am not yet particularly wor-
ried,” says theoretical physicist Carlos
Wagner of the University of Chicago.
“We just started this process.” The LHC
has delivered only 1 percent of the data
it will collect over its lifetime. Hopes of
quickly finding new phenomena were
too optimistic, Wagner says.
Experimental physicists, too, main-
tain that there is plenty of room for new
discoveries. But it could take years to
uncover them. “I would be very, very
happy if we were able to find some new
phenomena, some new state of matter,
within the first two or three years” of
running the LHC at its boosted energy,
Tiziano Camporesi of the LHC’s CMS
experiment said during a news confer-
ence at the International Conference on
High Energy Physics, held in Chicago in
August. “That would mean that nature
has been kind to us.”
But other LHC scientists admit they
had expected new discoveries by now.
“The fact that we haven’t seen some-
thing, I think, is in general quite surpris-
ing,” said Guy Wilkinson, spokesperson
for the LHCb experiment. “This isn’t a
failure — this is perhaps telling us some-
thing.” The lack of new particles forces
theoretical physicists to consider new
explanations for the mass of the Higgs.
To be consistent with data, those explanations can’t create new particles the
LHC should already have seen.
Some physicists — particularly those
of the younger generations — are ready
to move on to new ideas. “I’m personally not attached to supersymmetry,”
says David Kaplan of Johns Hopkins
University. Kaplan and colleagues
recently proposed the “relaxion” hypothesis, which allows the Higgs mass to
change, or relax, as the universe evolves.
Under this theory, the Higgs mass gets
stuck at a small value, never reaching the
high mass otherwise predicted.
Another idea, which Craig favors, is a
family of theories by the name of “neu-
tral naturalness.” Like supersymmetry,
this idea proposes symmetries of nature
that solve the problem of the Higgs mass,
but it doesn’t predict new particles that
should have been seen at the LHC.
One particularly controversial idea is
the multiverse hypothesis. There may
be innumerable other universes, with
different Higgs masses in each. Per-
haps humans observe such a light Higgs
because a small mass is necessary for
heavy elements like carbon to be pro-
duced in stars. People might live in a
universe with a small Higgs because it’s
the only type of universe life can exist in.
It’s possible that physicists’ fears will
be realized — the LHC could deliver the
Higgs boson and nothing else. Such a
result would leave theoretical physicists with few clues to work with. Still,
Hochberg says, “if that’s the case, we’ll
still be learning something very deep
about nature.” s
ATOM & COSMOS
Juno sends back first close-ups of Jupiter
Swirling clouds blanket Jupiter’s northern and southern poles in the first
closeup images of the planet taken by NASA’s Juno spacecraft. Such intimate
views of Jupiter have never been seen before.
Juno snapped a shot of the gas giant’s northern side (shown above) in
an August 27 flyby, from a distance of 195,000 kilometers. The prominent
bands that ring Jupiter’s middle fade at the poles, replaced with hurricane-like whorls. The poles are nearly invisible from Earth, making a specialized
space mission like Juno necessary to capture such rare images.
During the flyby, Juno’s eight science instruments were furiously collecting data. An infrared camera imaged Jupiter’s southern aurora, observing the phenomenon in detail for the first time. And another instrument
recorded 13 hours of radio emissions from the auroras.
Juno will study Jupiter’s interior, so scientists can better understand what
lies beneath the planet’s clouds (SN: 6/25/16, p. 16). The spacecraft arrived
at Jupiter on July 4. Its science instruments were switched off during its approach, making scientists wait for an image. — Emily Conover