U of R physicists helping lay the
groundwork for understanding the nature of nuclear matter
Everyone knows how to take a traditional photograph – load the film
into a camera, snap the shot, and then develop the film. But how do you
take a picture of a subatomic particle whose lifespan is only 26 billionths
of a second? Your camera would have to have a powerful lens and a really
fast shutter speed.
University of Regina physics professor Dr. Garth Huber is part of a team
that has taken such a picture using the only “camera” in the world capable
of doing this type of work – the Thomas Jefferson National Accelerator
Facility in Newport News, Virginia. Their work, recently published in the
prestigious international physics journal Physical Review Letters,
is helping others understand the nature of the visible universe.
So why would you study a subatomic particle which is so small and
“In general terms, the aim of my research is to better understand the
fundamental structure of nuclear matter,” Huber explains. “Everything in
the universe is made up of atoms, and each atom in turn contains subatomic
particles called hadrons which are basically the building-blocks of matter.
The type of hadrons I study – particles called pions – are incredibly
important in the Yukawa model of nuclear physics because they are
responsible for holding the nucleus of the atom together and thus giving
form to everything around us.”
The pion’s function is relatively straightforward: the constant exchange of
pions between protons and neutrons is a major component of the nuclear
strong force which binds the nucleus together and helps give the atom its
form. But pion structure itself has not yet been completely defined –
something that isn’t surprising given the particle’s small size and
incredibly short lifespan.
To help define this structure, in 2001 Huber and a group of 52 other
scientists from more than a dozen institutions designed an experiment to
basically take a “snapshot” of a pion. The experiment was conducted in 2003
at the Jefferson Lab, where electrons were sent into a liquid hydrogen
target and interacted with a cloud of virtual pions surrounding the
hydrogen nucleus. The escaping charged pions and scattered electrons were
then detected at precisely the same instant.
Since that time, Huber and his colleagues have been analyzing the data –
developing the film, if you will – to construct what amounts to a
“numerical snapshot” of the pion at the instant of scattering. To say the
project is finished would be inaccurate, however – others will now use this
picture to help refine theories on the structure of matter.
“We are a long way from an all-encompassing understanding of the universe,
but by better-defining the structure of the pion, we can get a better
understanding of the strong nuclear force responsible for nearly all of the
visible matter around us. This might not have a practical application for
most people, but for theorists trying to determine how matter is formed and
continues to exist, it will be important.” Huber notes. “The pion is
usually pictured as a relatively simple system consisting of one quark and
one anti-quark, and has special importance because it is the lightest known
quark/anti-quark state. With the published data from our experiment,
however, theorists will have the opportunity to develop a clearer idea of
the pion’s structure. ”
Interestingly, one of these theorists who will be studying Huber and his
team’s pion snapshot is also from the U of R – fellow physics professor Dr.
Randy Lewis. Together with his own team of researchers, Lewis predicts the
numerical value of the pion form factor – precisely the same quantity that
Huber and his team have now measured experimentally. Armed with Huber and
his team’s snapshot, Lewis and his team will now have the opportunity to
conduct further theoretical work and provide a clearer idea of the pion’s
structure using a powerful technique called Lattice Quantum
Together, the two teams are doing important work, says Zisis Papandreou,
Head of the U of R Physics Department. “In their article, Dr. Huber and his
international team of colleagues have published significant and unique
data,” he says. “Based on these data, theorists can now develop more
advanced models of the interactions between subatomic particles, helping
change the way we look at the world – and the universe – around us. Indeed,
the close collaboration between the teams of Dr. Huber and Dr. Lewis on the
pion charge form factor and other research topics promises to shed new
light on the forces that govern and determine the nature of matter.”
Huber is currently involved in plans to conduct additional experiments at
the Jefferson Lab. These experiments would further measure and define the
pion’s structure during its brief but significant 26-nanosecond existence.
Huber and his team’s article – “Determination of the Pion Charge Form
Factor at Q2 = 1.60 and 2.45 (GeV/c)2” – can be found in the November 10,
2006 edition of Physical Review Letters.
For further information, contact Dr. Garth Huber at
(306) 585-4240 or firstname.lastname@example.org.