Steve Boyd, University of Warwick

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Steve Boyd, University of Warwick
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If we are to understand why we are here and
the basic properties of the universe we live in,
we must understand the neutrino.
American Physical Society Report - 2004
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• A little bit of history
• What are they?
• Where do they come from?
• Why study them?
• A recent surprise
• The T2K Project

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CRISIS
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Neils Bohr
At the present stage of atomic theory we have no
arguments for upholding the concept of energy
balance in the case of b-ray disintegrations.
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Wolfgang Pauli
Desperate remedy..... I do not dare publish
this idea.... I admit my way out may look
improbable.... Weigh it and pass
sentence.... You tell them. I'm off to a
party
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• What are neutrinos?

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Electron Neutrino, ne
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Very tiny mass (lt0.0000001)
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x 500
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Electron Neutrino, ne
0
Very tiny mass (lt0.0000001)
Very tiny mass (lt0.0000001)
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In experiments neutrinos are NEVER seen. We can
only detect them through the byproducts of their
interactions with matter. Type of the charged
particle detected used to infer the type of
incoming neutrino.
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3 Lepton Types
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3 Antiparticles
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• Where do they come from?

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Everywhere
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From the Big Bang
Artist's conception
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From the Big Bang
Artist's conception
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From Astrophysical Objects
Supernovae created the heavy elements (us) and
neutrinos appear to be important to the
explosion dynamics.
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From the Sun
70 million per cm2 per second at the Earth
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From Cosmic Rays.
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Geoneutrinos
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From Us.
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So why don't we notice?
n are almost ghosts. They interact extremely
weakly with matter. To a neutrino a planet is
mostly empty space.
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"The chances of a neutrino actually hitting
something as it travels through all this howling
emptiness are roughly comparable to that of
dropping a ball bearing at random from a cruising
747 and hitting, say, an egg sandwich."
Douglas Adams
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500,000,000,000,000 solar n just went through you
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• Why do we study them?

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• Probes of environments that we otherwise
• cannot see
• Probes of objects too far away for anything
• else
• Cosmological and astrophysical
• implications
• Matter/Antimatter imbalance

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• Probes of environments that we otherwise
• cannot see
• Probes of objects too far away for anything
• else
• Cosmological and astrophysical
• implications
• Matter/Antimatter imbalance

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• Probes of environments that we otherwise
• cannot see
• Probes of objects too far away for anything
• else
• Cosmological and astrophysical
• implications
• Matter/Antimatter imbalance

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Universal Structure
m????? eV
m????? eV
m????? eV
m????? eV
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• Probes of environments that we otherwise
• cannot see
• Probes of objects too far away for anything
• else
• Cosmological and astrophysical
• implications
• Matter/Antimatter imbalance

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Why is there more matter than antimatter?

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Why is there more matter than antimatter?
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Sub-Atomic Talk Show Disasters
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CP Violation
Q. Is there a difference between the physics of
matter and antimatter? A.Yes there is.
We study this here with an experiment called BaBar
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Matter-Antimatter Asymmetry
Q. Is there a difference between the physics of
matter and antimatter? A.Yes there is.
We've never seen it in neutrinos, though.
Leptogenesis
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How to study this?
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Neutrino Oscillations
THE discovery in neutrinos of the last 20 years
A typical neutrino experiment
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The Sun is Broken!!!
Ray Davis Early 1970s
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An atom a day
Only
1 Ar atom every two days
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Less than expected
Expected
Measured
Number n observed
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Neutrino Oscillations
THE discovery in neutrinos of the last 20 years
Neutrinos were changing flavour between sun and
detector!
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Prob. It is ne
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Distance Travelled
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Eh?
Q. How can a ne spontaneously turn into a nm?
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Eh?
Q. How can a ne spontaneously turn into a nm? A.
The ne isn't a particle. It's three!
ne that thing which was always
produced/detected with an electron
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Quantum Stuff
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Long journey

• This can only happen if n1,n2,n3 have
• different masses
• Only gives us differences in masses

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Why so important?

• The Standard Model of Particle Physics
• has no explanation for a non-zero, but tiny,
• neutrino mass so we are in unknown
• physics territory.
• Neutrino masses link to GUT theories.
• Has cosmological implications (mass balance,
• structure)

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The T2K Experiment
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• University of Warwick
• University of Sheffield
• Imperial College, University of London
• Oxford University
• University of Liverpool
• University of Lancaster
• Queen Mary College, University of London
• Rutherford-Appleton Laboratories

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295 km
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295 km
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JPARC Facility
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JPARC Facility
TARGET
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295 km
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Super-Kamiokande
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Super-Kamiokande
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Water Cerenkov
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Electron-like has a fuzzy ring
Muon-like has a sharp edged ring and particle
stopped in detector.
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Open Questions

• How much do n1,n2 and n3 weigh?
• Why are they so much lighter than all the other
  massive particles?
• Are neutrinos the same as antineutrinos?
• Are neutrinos the reason we are here at all?

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...these kind of findings have implications
that are not limited to the laboratory. They
affect the whole of society not only our
economy, but our very view of life, our
understanding of our relations with others, and
our place in time. Bill Clinton
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sin2(2q)
L
Dm2 m12-m22
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Why do blue sky research?

• 5 of jobs in UK are in physics-based sectors
• Gross added value from physics sectors was
  estimated to be 70 billion pounds in 2005
• Synergy between PP projects and industry
  industry acquires added skills base for other
  applications
• Training - 50 of PP PhDs go into other sectors

Radioisotope production Sensors for medical
applications High level computing for biological
modelling Spin off tools for other science (e.g.
DIAMOND) Nuclear fusion research Muon tomography
in border security Airport scanners Rock
Imaging Cancer treatment using next gen cyclotrons