MINOS detector ready to take first data

Today, (August 14th), sees the start of data collection on the Main
Injector Neutrino Oscillation Search (MINOS) detector, situated in the
Soudan iron mine, Minnesota, USA. UK particle physicists, working within
an international collaboration, will use the MINOS detector to investigate
the phenomenon of neutrino mass – a puzzle that goes to the heart of our
understanding of the Universe.

Neutrinos are pointlike, abundant particles with very little mass. They
exist in three types or ‘flavours’ and recent experiments (including those
at SNO – the Sudbury Neutrino Observatory) have demonstrated that
neutrinos are capable of oscillating between these flavours (electron, tau
and muon). This can only happen if one or more of the neutrino flavours
does have mass, in contradiction to the Standard Model of particle
physics.

The MINOS detector will start measurements of cosmic ray showers penetrating
the Earth. It is situated in the Soudan Mine, Minnesota. The 30-metre-long
detector consists of 486 massive octagonal planes, lined up like the
slices of a loaf of bread. Each plane consists of a sheet of steel about 8
metres high and 2 BD cm thick, covered on one side with a layer of
scintillating plastic that emits light when struck by a charged
particle.

“MINOS can separate neutrino interactions from their antimatter counterpart
s – the antineutrinos.” explains UK MINOS spokesperson, Jenny Thomas from
University College London. “The data taken now from neutrinos produced in
cosmic ray cascades may provide new insight into why the Universe is made
of more matter than antimatter. At least, for the first time we will be
able to compare the characteristics of neutrinos and anti-neutrinos coming
from the atmosphere.”

However, MINOS has more ambitious plans in place for August 2004. Whilst
most experiments like SNO measure neutrinos coming from the Sun, when
complete, MINOS will instead study a beam of man-made neutrinos, all of
the same type or ‘flavour’ – the muon neutrino flavour. This beam will be
created at Fermi National Accelerator Laboratory (Fermilab) and sent
straight through the Earth to Soudan – a distance of 735 kilometres. No
tunnel is needed because neutrinos interact so rarely with matter. A
detector is currently being built just outside Fermilab, known as the
‘near’ detector, similar but smaller than the now operational MINOS
detector, known as the ‘far’ detector. The ‘near’ detector will act as a
control, studying the beam as it leaves Fermilab, then the results will be
compared with those from the ‘far’ detector to see if the neutrinos have
oscillated into electron or tau neutrinos during their journey.

A million million neutrinos will be created at Fermilab each year, but
only 1,500 will interact with the nucleus of an atom in the far detector
and generate a signal; the others will pass straight through.20

“The realisation that neutrinos oscillate, first demonstrated by the Super
Kamiokande experiment in Japan, has been one of the biggest surprises to
emerge in particle physics since the inception of the Standard Model more
than 30 years ago.” says Jenny Thomas. “The MINOS experiment will measure
the oscillation parameters of these neutrinos to an unprecedented accuracy
of a few percent; an amazing feat considering neutrinos can usually pass
directly through the Earth without interacting at all and that their
inferred masses are estimated to be less than 1eV. (The weight ratio of a
neutrino to a 1kg bag of sugar is the same as the ratio of a grain of sand
to the weight of the earth!). The parameter measurement will open up an
entire new field of particle physics, to understand what effect on the
universe this tiny neutrino mass has.”

Within two years of turning on the neutrino beam, MINOS should produce an
unequivocal measurement of the oscillation of muon neutrinos with none of
the uncertainties associated with the atmospheric or solar neutrino
source. If indeed the findings are positive, then a new era in particle
physics will begin. Theorists will have to incorporate massive neutrinos
into the Standard Model, which will have exciting implications. Furthermore
cosmologists will have a strong candidate for the ‘missing mass’ of the
Universe (which dynamical gravitational measurements show must exist). The
experimental side will be just as exciting as we plan new experiments to
measure precisely how the different neutrinos change their flavour.

Notes for Editors

Images

A picture of UK spokesperson Jenny Thomas, and a selection of pictures of
MINOS are available at http://www.pparc.ac.uk/Nw/Press/MINOS.asp

Additional MINOS images are at http://www.fnal.gov/pub/presspass/press_releases/MINOS_photos

Standard Model

The Standard Model of Particle Physics, the theory that we have been using
for 30 years to describe the fundamental particles (quarks and leptons)
and forces (bosons) works very well. It has successfully predicted and
accounted for what’s seen in experiments at LEP (the Large Electron
Positron collider at CERN), the Tevatron at Fermilab in the US and other
particle physics experiments.20

The Standard Model is a quantum theory that describes the building blocks
of matter in the Universe – the fundamental particles – and how they
interact through the fundamental forces of electromagnetic, strong and
weak. The fourth force of gravity, is not currently part of the model.

Matter particles are divided into three generations comprising six quarks
of increasing mass (up, down, strange, charm, bottom and top) and six
leptons (the electron, muon, and tau and their respective neutrino
partners, predicted to have zero mass). Each particle also has an
antiparticle of opposite charge.

The SNO results

The Sun emits electron neutrinos, created in vast numbers by the thermonucl
ear reactions that fuel our parent star. Since the early 1970s, several
experiments have detected neutrinos arriving on Earth, but they have found
only a fraction of the number expected from detailed theories of energy
production in the Sun.20

Data taken entirely from the Sudbury Neutrino Observatory [SNO] in Canada
shows without doubt that the number of observed solar neutrinos is only a
fraction of the total emitted from the Sun – clear evidence that they have
chameleon type properties and change type en-route to Earth.

Funding

Funding for the MINOS experiment has come from the Office of Science of
the U.S. Department of Energy, the UK’s Particle Physics and Astronomy
Research Council, the U.S. National Science Foundation, the State of
Minnesota and the University of Minnesota. More than 200 scientists from
Brazil, France, Greece, Russia, United Kingdom and the United States are
involved in the project.

Fermilab is a national laboratory funded by the Office of Science of the
U.S. Department of Energy, operated by Universities Research Association,
Inc.

PPARC has funded the UK’s involvement at 6 million [pounds], including 2
million [pounds] worth of hardware. The total project cost is about $150
million, of which $60 million is on detectors and the balance on the beam
line from Fermilab.

Collaboration

Institutions from the USA, UK, Brazil, France and Russia are part of the
MINOS collaboration.
For a full list (with contact details), please see:
http://www-numi.fnal.gov/collab/institut.html

UK institutions involved are: University College London, Rutherford
Appleton Laboratory, Universities of Cambridge, Oxford and Sussex.

The UK groups have provided:

• Engineering deign
• Software for data analysis
• Data acquisition for both detectors – Near (not yet completed) and Far (completed)
• Far detector electronics
• Calibration detector at CERN (MINOS third detector) – used to calibrate the ‘near’ and ‘far’ detectors by using a beam of better-understood particles (electrons, pions, muons and protons) from CERN.
• Near detector readout (fibre optic cables, photo multiplier tubes and assemblies)
• Light-injection system to calibrate all 200,000 detector readout channels

Contact Details

UK Institutions:

Dr Jenny Thomas

UK Spokesperson

UCL, London

Email: jthomas@hep.ucl.ac.uk

Tel: +44 (0) 20 7679 7159

Dr Mark Thomson

University of Cambridge

Tel: +44 1223 76512220

Fax: +44 1223 35392020

e-mail: thomson@hep.phy.cam.ac.uk

Dr Alfons Weber

University of Oxford

Tel: +44 (1865) 2-7331520

FAX: +44 (1865) 2-7341820

Email: A.Weber@physics.ox.ac.uk

G.F. Pearce

Rutherford Appleton Lab

Email: G.F.Pearce@rl.ac.uk

Tel + 44 (0) 1235 445676

Fax +44 (0) 1235 445808

P.G. Harris

University of Sussex

E-mail: P.G.Harris@sussex.ac.uk

Tel: +44 (0)1273 877214

Press Offices

Fermilab

Kurt Riesselmann, Fermilab Public Affairs, Tel 001-630-840-3351,

Email kurtr@fnal.gov

PPARC

Julia Maddock, PPARC Press Office, Tel +44 (0)1793 442094,
Email julia.maddock@pparc.ac.uk

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 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 Laboratory for Particle Physics (CERN), and the
European Space Agency. 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, which includes the Lovell Telescope at Jodrell Bank
observatory.

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both small local projects and national initiatives aimed at improving
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