Gail G' Hanson

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NEUTRINO FACTORIES AND MUON COLLIDERS

• Gail G. Hanson
• University of California, Riverside

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OK

• WHAT IS A MUON?
• WHAT IS A NEUTRINO?

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MUONS

• A MUON (m) IS LIKE AN ELECTRON, ONLY
• 200 TIMES HEAVIER.
• THE ELECTRON (e) IS THE LIGHTEST
• CHARGED PARTICLE.
• THE ELECTRON CANNOT DECAY SINCE A
• PARTICLE CAN DECAY ONLY TO PARTICLES LIGHTER
  THAN ITSELF, AND CHARGE MUST BE CONSERVED.

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• SINCE THE MUON IS HEAVIER THAN THE ELECTRON, IT
  CAN DECAY INTO IT
• THE EXTRA PARTICLES ARE NEUTRINOS.

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NEUTRINOS

• NEUTRINOS WERE FIRST SEEN (OR
• NOT SEEN) IN NUCLEAR DECAYS
• (BETA DECAY) IN WHICH AN EXTRA
• INVISIBLE MASSLESS PARTICLE WAS NEEDED TO
  DESCRIBE THE
• OBSERVATIONS

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NEUTRINOS

• NEUTRINOS (n), THEN ARE INVISIBLE
• MASSLESS PARTICLES.
• LATER IT WAS FOUND THAT NEUTRINOS
• CAME IN THREE FLAVORS

( )
( )
( )
ne e-
nm m-
nt t-
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NEUTRINOS

• (THE TAU (t) IS A THIRD MEMBER OF THIS FAMILY,
  LIKE A MUON, BUT EVEN HEAVIER.)
• THE FLAVOR, WHICH IS CALLED LEPTON
• NUMBER, IS CONSERVED.

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NEUTRINOS

• NOW JUST WHEN PHYSICISTS THOUGHT
• THEY HAD ALL OF THIS UNDERSTOOD,
• TWO PUZZLING OBSERVATIONS WERE MADE.

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DEFICIT OF SOLAR NEUTRINOS

• ELECTRON NEUTRINOS (ne) ARE
• PRODUCED BY THE NUCLEAR FUSION REACTIONS
  RESPONSIBLE FOR THE ENERGY OF THE SUN.
• THEORETICAL PREDICTIONS WERE MADE FOR THE
  NUMBER THAT SHOULD BE OBSERVED ON EARTH - THE
  SOLAR MODEL.

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DEFICIT OF SOLAR NEUTRINOS

• OBSERVATIONS OF THESE ELECTRON NEUTRINOS DID NOT
  AGREE WITH THE PREDICTIONS - ONLY ABOUT ONE-HALF
  THE PREDICTED NUMBER WERE OBSERVED (FIRST BY RAY
  DAVIS - 2002 NOBEL PRIZE - AT THE HOMESTAKE MINE
  IN SOUTH DAKOTA).

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DEFICIT OF ATMOSPHERIC NEUTRINOS

• AN EXPERIMENT IN JAPAN, KAMIOKANDE, CONFIRMED
  DAVISS RESULT (MASATOSHI KOSHIBA - 2002 NOBEL
  PRIZE).
• KAMIOKANDE, FOLLOWED BY SUPERKAMIOKANDE, ALSO
  OBSERVED A DEFICIT OF MUON NEUTRINOS (nm),
  PRODUCED BY COSMIC RAYS IN THE EARTHS ATMOSPHERE.

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NEUTRINO OSCILLATIONS

• BOTH OF THESE OBSERVATIONS CAN BE EXPLAINED IF
  THE ELECTRON NEUTRINOS FROM THE SUN AND THE MUON
  NEUTRINOS PRODUCED BY COSMIC RAYS CHANGE TO
  ANOTHER FLAVOR OF NEUTRINO BEFORE REACHING THE
  EARTH.

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NEUTRINO OSCILLATIONS

• SOLAR NEUTRINOS
• ne nm or nt
• ATMOSPHERIC NEUTRINOS
• nm nt
• NEUTRINOS OSCILLATE FROM ONE FLAVOR TO ANOTHER

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NEUTRINO OSCILLATIONS

• HOWEVER, FOR OSCILLATION TO OCCUR
• Dm2 m (n2) 2 - m (n1) 2 CANNOT BE 0
• FOR THE PAIRS OF NEUTRINOS INVOLVED.
• THIS MEANS THAT SOME NEUTRINOS MUST HAVE MASS!

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MUON COLLIDERS

• MEANWHILE, OTHER PHYSICISTS WERE DEVELOPING
  STORAGE RING ACCELERATORS IN WHICH POSITIVE AND
  NEGATIVE MUONS WOULD COLLIDE.
• COLLIDING m AND m- BEAMS OFFERED THE POSSIBILITY
  OF SMALLER, CHEAPER HIGH ENERGY COLLIDERS,
  BECAUSE MUONS RADIATE LESS THAN ELECTRONS.

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COMPARISON OF HIGH ENERGY COLLIDERS
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HIGGS FACTORY
m
m-
HIGGS
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NEUTRINO FACTORY

• FIRST STEP TOWARDS A MUON COLLIDER
• ONE MUON BEAM IN A STORAGE RING.
• AN INTENSE NEUTRINO BEAM FROM
• THE MUON DECAYS .
• A NEUTRINO FACTORY!

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NEUTRINO FACTORY
m-
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NEUTRINO FACTORY

• NO OTHER COMPARABLE SOURCE OF ELECTRON NEUTRINO
  OR ELECTRON ANTINEUTRINO BEAMS (ne OR ne).
• CONVENTIONAL NEUTRINO BEAMS ARE MUON NEUTRINOS
  (FROM p m nm).

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HOW TO MAKE A MUON BEAM

• A MUON BEAM IS MADE FROM DECAYS OF PIONS ( p-
  m- nm ), WHICH HAVE BEEN PRODUCED FROM PROTONS
  STRIKING A TARGET.
• ONE MAJOR PROBLEM IS HOW TO MAKE THE MUON BEAM
  NARROW - QUICKLY, BEFORE THE MUONS DECAY. THIS
  IS CALLED COOLING THE BEAM.

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INTERNATIONAL MUON IONIZATION COOLING EXPERIMENT
(MICE)
Experimental demonstration of ionization cooling
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n
p
m
MICE