Interactions News Wire #41-05
26 May 2005 http://www.interactions.org
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Source: PPARC
Content: Press Release
Date Issued: 26 May 2005
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Solving the Mysteries of Quarks
Particle Physicists are embarking on a new attempt to solve the mysteries
of quarks with the completion of the three most powerful supercomputers
ever applied to this problem, including one at the University of Edinburgh
for use by the UK Quantum Chromodynamics (UKQCD) collaboration of
scientists from seven British Universities.
Quarks are the fundamental particles that make up 99.9% of ordinary
matter; yet it is impossible to examine a single quark in the laboratory.
Consequently, some of the basic properties of quarks are not known, such
as their precise masses or why they exist in six different types. Quarks
are bound together by the Strong Force, which is weak when the quarks are
close, but increases steadily as you try to separate them, making it
impossible to isolate a single quark. Instead, the theory describing the
Strong Force, called Quantum Chromodynamics (QCD), has to be simulated on
huge computers.
The Edinburgh computer is the first of three similar machines and has been
operating since January 2005. The second computer is being inaugurated
today at the RIKEN Brookhaven Research Center in Brookhaven National
Laboratory in the USA. The third is part of the U.S. Department of Energy
Program in High Energy and Nuclear Physics, and is also installed at
Brookhaven where it is currently undergoing testing.
The computers are built with processing chips specifically designed for
the purpose, known as QCD-on-a-chip, or QCDOC for short. A little slower
than the microprocessor in your laptop, the QCDOC chip was designed to
consume a tenth of the electrical power, so that tens of thousands of them
could be put into a single machine. The computers were designed and built
jointly by the University of Edinburgh, Columbia University (USA), the
RIKEN Brookhaven Research Center (USA) and IBM.
Each QCDOC machine operates at a speed of 10 Teraflops, or 10 trillion
(i.e. million million) floating point operations per second. By
comparison, a regular desktop computer operates at a few Gigaflops (a
thousand million floating point operations per second), whilst IBM's
BlueGene, a close relative of QCDOC and the fastest computer in the world,
operates at over 100 Teraflops. Edinburgh's machine and part of the QCDOC
development costs were funded through a Joint Infrastructure Fund Award of
£6.6million administered by the Particle Physics and Astronomy Research
Council, who also fund the UK scientists in this field.
Professor Richard Kenway, who led UK participation in the QCDOC Project,
said "After five years building this machine, it's exhilarating to be able
to compute in days things which take everybody else months. Now we are
about to run QCDOC for months to do the most realistic QCD simulation yet.
It's like standing on the shore of a new continent after a long voyage,
we've chosen our path of exploration, but we don't know what we're going
to find."
Professor Richard Wade, Chief Executive of the Particle Physics and
astronomy Research Council welcomed the start of the QCDOC supercomputer
saying "The UKQCD collaboration has been a world-leading group for some
years, producing very elegant analysis methods to make the most of
available computing resources. With the power of the new supercomputer at
their fingertips, they will be able to make crucial advances to our
understanding of fundamental particles like quarks."
Notes for Editors
The Mysteries of Quarks
* Quarks never appear singly, but always as bound states of two or
more, called hadrons, such as the protons and neutrons that make up the
atomic nucleus. Thus, Nature hides its fundamental particles and we would
like to understand better how the Strong Force achieves this.
* Only the mass of the top quark is accurately known, because QCD
effects are small for such a heavy particle. To determine the masses of
the lighter quarks accurately (called up, down, strange, charm and
bottom), QCD effects have to be computed. These masses are needed for
detailed understanding of many phenomena and should eventually
be predicted by the much sought after Theory of Everything.
* There are six types of quark and this seems to be related to the
small difference between matter and antimatter, called CP violation, that
may help to explain why our Universe is dominated by matter (and hence why
we can exist at all). QCD simulations are needed to discover whether our
current theories can explain this, or there is some new physics at work.
* The Theory of Everything is very likely to permit protons to
decay. If so, the proton lifetime must be enormous, since no decay has yet
been observed. Experimental lower bounds on the lifetime, together with
QCD simulations, place restrictions on what the Theory of Everything can
be and have already ruled out some candidates.
* At enormously high temperatures and densities, such as may be
found in neutron stars, everyday matter made of bound quarks may melt into
a new type of matter. This change of phase, which is being searched for at
Brookhaven National Laboratory by colliding gold and lead nuclei at high
energies, is accessible to QCD simulations.
What happens may tell us about what is going on inside some of the most
exotic objects in the Universe.
The UKQCD Collaboration
UKQCD is a collaboration of particle physicists from the Universities of
Edinburgh, Southampton, Swansea, Liverpool, Glasgow, Oxford and Cambridge.
It was formed in 1989 and has exploited a series of novel architecture
computers for QCD simulations, becoming one of the leading projects in
this field world wide. QCDOC gives UKQCD for the first time the fastest
computer in the world available for QCD simulations.
Images
Images can be downloaded from
http://www.pparc.ac.uk/Nw/qcd_images.asp
Lattice3.jpg, Credit Ian McVicar
In lattice QCD space-time is approximated by a four-dimensional box of
points, similar to a crystal lattice
Proton.jpg, Credit Ian McVicar
The proton consists of three quarks, two up and one down, living in a
complicated soup of dynamical quarks, antiquarks and gluons, which have
'colour' charges. The total colour charge of the proton is zero. Lattice
QCD enables us to calculate the mass of the proton and its internal
structure
Ed_qcdoc_front.jpg
Professors Christine Davies and Richard Kenway, and Technician Andrew Main
with the 12,288 processor QCDOC machine at Edinburgh in November 2004
Asic_closeup.jpg
The QCDOC chip integrates 50 million transistors on a 1.3cm 1.3cm die and
consumes approximately 5 Watts at a clock speed of 400 MHz.
Populated_mb.jpg
A fully populated mother board containing 32 daughter boards each with 2
QCDOC chips.
Full_wc_cabinet.jpg
A water-cooled QCDOC rack containing 16 mother boards with 1024 QCDOC
chips. The upper compartment holds Ethernet switches.
Contacts
PPARC Press Office:
Julia Maddock, 01793 442094, Email:
Julia.maddock@pparc.ac.uk
University of Edinburgh:
Professor Richard Kenway, 0131 650 5245, Email
rdk@epcc.ed.ac.uk
University of Glasgow:
Professor Christine Davies, 0141 330 4710, Email
c.davies@physics.gla.ac.uk
University of Liverpool:
Professor Alan Irving, 0151 794 3782, Email
aci@amtp.liv.ac.uk
University of Oxford:
Dr Mike Teper, 01865 273 972, Email
m.teper1@physics.ox.ac.uk
University of Cambridge:
Professor Ron Horgan, 01223 337 839 Email
r.r.horgan@damtp.cam.ac.uk
University of Southampton:
Professor Chris Sachrajda, 023 8059 2105, Email
cts@hep.phys.soton.ac.uk
University of Wales Swansea:
Dr Chris Allton, 01792 295 738, Email
c.r.allton@swansea.ac.uk
PPARC
The Particle Physics and Astronomy Research Council (PPARC) is the UK's
strategic science investment agency. It funds research, education and
public understanding in four broad areas of science - particle physics,
astronomy, cosmology and space science.
PPARC is government funded and provides research grants and studentships to
scientists in British universities, gives researchers access to world-class
facilities and funds the UK membership of international bodies such as the
European Organisation for Nuclear Research, CERN, the European Space
Agency and the European Southern Observatory. It also contributes money
for the UK telescopes overseas on La Palma, Hawaii, Australia and in
Chile, the UK Astronomy Technology Centre at the Royal Observatory,
Edinburgh and the MERLIN/VLBI National Facility.