The BaBar experiment is
expanding our understanding
of antimatter. Running at an
accelerator in Stanford, it
gathers data on the decay of
the rare B particles.
We have now recorded over
100 million B decays. Each
provides a lot of data (20
Mb+). This data is studied by
a team of over 500 physicists
from many countries,
including a strong contingent
from the UK
Data is distributed across
many sites, and may be
Manchester duplicated. Processing must
be spread across available
resources: we use dedicated
CPU farms at 9 UK institutes,
and also Lyon, Karlsruhe, and
Bologna as well as Stanford.
Rutherford Grid technology is used to
keep track of what data is
stored where, and what
Queen Mary computing power is best
placed to analyse it. It
provides the power and
flexibility we need.
For more information see
The BaBar sites are monitored. A live
map shows which are running and which
are down. It shows the number of
machines in use at each site, and the
progress of event simulation jobs.
A physicist selects events of a particular
type that they are interested in, and uses a
web browser to ask which sites have files
of this data.
Sites are given in order of preference: they
will probably want data from their local
site, and go to remote sites only for files
that don’t exist locally. The system handles
Jobs are launched to
analyse this data at local
and remote sites. All
authentication is done
through the Grid using a
web browser so all
resources are available
without further hassle.
Output from the jobs is collected
and merged back together to give
a complete and seamless set of
As Grid technology progresses over the next few years,this will become
smoother and easier to use, as the system will take over responsibility for
the decisions that at preset have to be made by the physicist.