additional particles that break down
into spectacular showers of debris. Two
detectors at distant points along the
Tevatron ring, CDF and another called
DZero, record the energies and trajecto-ries of these pieces of subatomic flotsam.
Working backward from this debris
can reveal ephemeral particles that don’t
live long enough to be seen directly. One
such particle is the Higgs. No one really
knows what the Higgs looks like, but the
most popular version would break down
into a pair of quarks, fundamental particles that make up larger entities such as
protons and neutrons. The pair of quarks
expected from the Higgs—a bottom
quark and its antimatter partner — would
in turn decay into jets of still other particles visible to the Tevatron.
As with Bigfoot, though, one snapshot
isn’t enough to claim discovery. Despite
upgrades over the years, the Tevatron
hasn’t produced enough collisions to
definitively rule out statistical flukes,
random fluctuations that could mimic
the Higgs.
“Discovering the Higgs boson has
always been a really long shot for the
Tevatron,” says Chris Quigg, a theoretical physicist at Fermilab.
T. DUBÉ
With the details of the Higgs still
unknown, the Tevatron could help rule
out some possible masses for the par-
ticle, though. Statistically speaking, it’s
easier to show what isn’t than to show
what is.
Elementary particles
u
up
c
charm
t
top
γ
photon
Leptons
I II III
νe
electron
neutrino
νµ
muon
neutrino
ντ
tau
neutrino
Z
Z boson
d
down
s
strange
b
bottom
e
electron
;
muon
τ
tau
Three generations of matter
Force carriers
For more than a quarter century, the
Tevatron has probed the standard mod-
el’s particles (shown); the top quark
was discovered at the Tevatron in 1995.
g
gluon
W
W boson
“We expect to complete our Higgs
analysis by March,” says Fermilab’s Rob
Roser.
Standard model defender
The Higgs is only one piece of a much
larger puzzle called the standard model
of particle physics. Stitched together
in the 1970s from earlier theories, this
modestly named cornerstone of modern
physics uses 16 elementary particles to
explain most of the clockwork that keeps
the universe ticking, with the notable
exception of gravity.
Throughout its long history, the Tevatron has risen to defend the standard
model again and again. The collider discovered a host of particles predicted by
the model — both a fundamental particle
and larger ones built of the fundamental
units — filling in the blanks of subatomic
family trees. Some of these particles
still haven’t been seen anywhere else:
certain baryons — composite particles
made of three quarks — for instance (SN:
9/27/08, p. 7; SN: 8/27/11, p. 14).
“The Tevatron really helped to estab-
lish how good the standard model is,”
says physicist Frank Wilczek of MIT,
who won a Nobel Prize for his contribu-
tions to the model. “It’s much better than
we anticipated in the early days.”
In 1995 the Tevatron discovered the
top quark, the last of the standard mod-
el’s six quarks to be spotted. Physicists
had expected to find the particle after
