Our Research
What is Experimental Particle Physics?
Experimental Particle Physics (EPP) is the experimental arm of high energy particle physics. Our research is in probing matter to discover the underlying structure of matter; attempting to answer the age old question What are we made of?'.
Around 460 B.C., the Greek philosopher, Democritus, develop the idea of atoms. He questioned what happened when matter was divided continually; could we go on forever or would we reach a final point? He believed the latter, that you could only cut something up a finite number of times, until you reached the `atom'. His ideas were squashed by a more famous Greek philosopher, Aristotle. It wasn't until the 1800s when the English chemist, John Dalton performed experiments with various chemicals and that showed that matter did consist of elementary lumpy particles, the atoms of Democritus.
Accepted as existing today, the atom was thought to be the smallest that matter could be reduced to but the atomic revolution at the end of the 19th and beginning of the 20th centuries proved this wrong. The power of the atomic bomb and the potential danger in radiation indicated that there was still much to be discovered inside the atom. The atom was found to have a very small but heavy centre, the nucleus, made up of protons which were positively charged and neutrons, having no charge. This centre was surrounded by negative charge, electrons.
Probing the inside of an atom is not as easy as just getting the sharpest knife in your kitchen drawer. In the same way that we break the shell of an egg to see what is inside we `break' atoms to see their contents. The methods for doing this require very strong forces. Throwing a pingpong ball at a wall will do no damage but a bullet will leave a hole. We use very fast and light particle, like protons and electrons, to break open atoms, and even smaller particles. We measure what comes out and use that to work backwards and determine what was in there to start with. Another method used is to collide two particles together. The resultant pieces tell us what the colliding particles were made of. For the particles to break into the atom, or the other particle they are colliding with, they must be travelling at speeds near the speed of light, 300 million metres a second. Particles are accelerated to these speeds by electric fields in machines called, unsurprisingly, accelerators. These accelerators are either linear or circular, but always large; the largest linear accelerator is 3.2km long and the circumference of the largest circular accelerator is 27km.
Detecting the particles that are liberated from atoms, and smaller particles, is a mamoth task too. Detectors weigh thousands of tonnes and have many different functions;
there are sections to measure the energy of particles along with equipment to determine their trajectories. The knowledge of the 90 odd stable atoms was once easily summarised by the now familiar periodic
table. The much smaller particles now referred to as fundamental particles is summerised in the following diagram. This shows the paritcles that make up all matter, along with the particles that `carry' the four forces, gravity, elecromagnetism, the strong, and weak forces.
Group Compositition
(for more info see the
Group members page)
- 12 PhD and Masters students
What experiments do we work on?
ATLAS: the acronym
ATLAS stands for A Toroidal Large hadron collider AparatuS. ATLAS is
a detector designed, primiarily, to detect the Higgs particle. It is
in the process of being built at the European
Organisation for Nuclear Research, and is expected to be completed
and running by 2007.
The ATLAS Experiment for the Large Hadron Collider is under construction at
CERN, the European Organisation for
Nuclear Research in Switzerland.
Its goal is to explore the
fundamental nature of matter and the basic forces that shape our
universe. ATLAS is the largest
collaborative effort ever attempted in the physical sciences. There
are 2000 physicists participating from more than 150 universities
and laboratories in 34 countries. You can see a bit more
about the work that Melbourne is doing for ATLAS at our
ATLAS Activities page.
Belle:
The main aim of the experiment is to investigate differences
between matter and antimatter. This is done by comparing the decay
properties of particles and antiparticles. It is hoped that the
results from Belle will help answer some of the big questions such as
why an imbalance between matter and anti-matter exists in the
universe.
Specifically Belle studies B-meson and anti-B-meson decays resulting
from the collision of electrons and positrons at the KEKB B-factory.
These particles are very short-lived, decaying in about 2 trillionths
of a second. It is hoped that by studying the decay properties of the
B-mesons, a deeper understanding of
CP-violation
will be possible.
The Melbourne group has seven PhD students participating in physics
anlysis at the Belle experiment. In collaborating with the University
of
Sydney
and
Wollongong we are making substantial contribution to data anaysis
and the design, construction, upgrading and monitoring of the Silicon
Vertex Detector
(SVD), one of the
most important components of the Belle detector.
PET: Positron Emission Tomography is an medical imaging technique,
which allows 3-Dimensional imaging of internal organs within the body via
the use of positron emitting radioisotopes. The resultant positron self-annhilates
producing two anti-parallel gamma-ray photons. PET scanners detect these
coincident pairs of gamma-photons using a ring that surrounds the patient.
The Melbourne Experimental Particle Physics (EPP) group in collaboration
with the Medical Radiation Physics Group at the University of Wollongong
is involved in the design of a new PET detector module. The new design utilise
silicon pixel detectors coupled to both pixellated scintillators and readout
electronics. The new detector module will provide an improvement in spatial
resolution in comparison with standard PET cameras.
Grid: "The Grid", as it is commonly named, is heralded as the
future of computing for industry, education, and research alike. It is
in the nature of research for the questions posed to become more
complex, requiring larger computing resources for each generation of
experiment. This is especially true within high energy physics where
experimental data is increasing exponentially (Belle data is tens of
terabytes; ATLAS data will reach tens of petabytes). Modern
experiments will have to provide access to petabytes of data, hundreds
of teraflops of computing power, for thousands of researchers located
in many institutions around the world. More sophisticated
collaborative high performance computing techniques will be required.
We are investigating one such technique, Grid computing, with the aim
of facilitating large scale collaborative research in current and
future experiments. More info available at
Grid Activities.
Experiments that we have been involved in, in the past have included,
NOMAD &
Triumf.
Facilities
The facilities at Melbourne inlcude a computer lab for our analysis work
and hardware production and testing areas for detectors for Belle
and ATLAS. Computing facilities include a high person to workstation
ratio, PCs for instumentation, 9 high performance linux
wrokstations, 2 high performance alphas, a pbs job management
facility, and access to a cluster. Hardware facilities include a
custom designed precision detector assembly system, and glueing,
bonding and testing equipment.
Travel
As the two main experiments that Melbourne works on are based overseas
the group spends a lot of time in Europe and Japan. We have an
appartment in the town of St.Genis in France, just across the
Switzerland-France border from CERN. The group car is used to travel
between the CERN sites and the appartment. In Japan the group house is
located a short drive from KEK. Group members also spend time at
international conferences, presenting work and collaborating with
colleagues.
Melbourne
Despite being a long way from particle physics experiments Melbourne is
a fantastic place to live. It is a large and vibrant city. For more about
how great Melbourne is talk to anyone in the group or visit some of the tourism
pages for Melbourne, and Victoria.
Grants
Financing fundamental research is of critical importance. The work that
we do would not be possible without the grants we receive:
This grant is a 5 year grant and started in 2002. More info:
http://www.arc.gov.au/funded_grants/selection_discovery_projects.htm
- ARC LIEF (Linkage, Infrastructure, Equipment and Facilities):
This grant is a 1 year grant. This grant goes towards equipment that allows
us to contribute to the experiments that we work on. More info:
http://www.arc.gov.au/funded_grants/selection_linkage_infrastruct.htm
The Department of Education, Science and
Technology provides us with a grant that is used for travel. This
is crucial to enable students and staff to collaborate with
colleagues internationally. This grant is for 4 years and was
renewed in 2002.
EPP,
in partnership with Computer Science and the MARCC group in ITS
(all at Melbourne Uni), has a VPAC Expertise Program Grant. This
grant funds a post-doc position and is for one year. More info:
http://www.vpac.org/content/research_and_development/grants/expertise_projects.php
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Revision: r7 - 11 Apr 2006 - LyleWinton
