um

1
um neutrinos?

• an introduction

Paul Nienaber Fermilab
2
begin with the end in mind

• whats our current picture of the particle zoo?
• how do neutrinos fit into that picture?
• how do you generate/detect neutrinos?
• what do you mean, neutrinos oscillate?
• whats the MiniBooNE neutrino experiment?

3
whats in the world?

• What do particle physicists do?
• investigate the fundamental structure of matter,
  space, and time
• How do we do that?
• one approach analyze that is, examine
  differences, make distinctions at root, take
  things apart
• What have we found out?
• fundamental simplicity small number of basic
  constitutive components

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particles, particles, particles

• identify/classify particles by mass (energy)
• identify/classify particles by charge
• ( / / 0 )
• ordinary matter is made of atoms
• most everyday experience of electric charge comes
  from negatively charged electrons
• dense, positively charged core nucleus
• nucleus composite, too!
• contains protons () and neutrons (0)
• -- which raises another question

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particles, particles, particles

• if protons are , and squeezed into the tiny
  nucleus, why dont they electrically repel?
• ADDITIONAL FORCE only operates at very short
  distances called the STRONG force
• are the three constituents of atoms protons,
  neutrons, and electrons all equivalently
  fundamental?
• NO protons and neutrons are composite electrons
  are not
• protons and neutrons are built from constituents
  called QUARKS

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particles, particles, particles

• before quarks
• after quarks
• quarks feel the STRONG force
• electrons and their two heavier cousins do not
• is this the whole zoo?
• no

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particles, particles, particles

• certain radioactive decays revealed the existence
  of additional, elusive denizens of the particle
  zoo

• they have NO electric charge
• these new particles hardly interact with other
  particles at all (no strong, no charge)
• if they have a mass, its very, very tiny
• these are the neutrinos (little neutrals)
• each pairs with an electrically partner

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headline nus

• neutrinos abound in the universe in every
  gallon of space, there are a million neutrinos
• they come from stars, from the sun, and are
  leftover relics from the Big Bang
• they pass through matter essentially without a
  trace they are very difficult to detect
• still, neutrinos matter! they are a crucial part
  of our understanding the workings of matter
• Two of the 2002 Physics Nobel Prize winners were
  neutrino physicists
• Ray Davis neutrinos from the Sun
• Masatoshi Koshiba supernova neutrinos

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intermission
10
vellcome to ze laborratory

• so how do you do a neutrino experiment?
• three ingredients
• BEAM
• TARGET
• DETECTOR
• since neutrinos interact so rarely, need LOTS of
  beam and LOTS AND LOTS of target/detector

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eye of neut, toe of frog?

• need a source or beam of neutrinos recipe?
• neutrinos come from
• reactions inside the atomic nucleus
• fusion (inside stars and the Sun)
• fission (nuclear power plants)
• decay of certain subatomic particles
• these neutrino parent particles are produced
  when fast-moving protons smack into matter
• in the upper atmosphere (atmospheric neutrinos)
• in a particle physics laboratory near you
  (accelerator neutrinos)

requires making particles which decay into
neutrinos
which you accomplish by slamming protons into a
chunk of matter,
Making neutrinos
letting the parents decay
( and perhaps filtering out the leftovers).
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catch me if you can

• now you have a pitcher need a catcher
• catching a particle only works if the particle
  is electrically charged
• see a neutrino ONLY if it hits something and
  knocks out or produces a charged particle
• one way a neutrino can interact run into
  something and change into its own charged partner
  
• tagger reaction

?e
X
X
?
e-
??
X
X
?
?-
??
X
X
?
?-
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catch me if you can

• need LOTS of detector material
• cant sacrifice sensitivity
• must consider COST
• one popular method Cerenkov detector

• if a charged particle moves through a liquid at a
  speed faster than the speed of light in the
  liquid, the liquid will give off a shock wave
  burst of light
• called Cerenkov light
• light pulses are very dim need exquisitely
  sensitive light detectors and VERY clear liquid

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catch me if you can
short track

• Cerenkov light comes out at a specific angle, and
  maps out a cone as it moves away from the track
• different kinds of particles make different
  tracks and therefore make different kinds of rings

short, scattering track (electron)
sharp-edged, open ring
fuzzy ring
track direction
light sensor array
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neutrinos oscillate ?!

• if I make a beam entirely of (e.g.) muon
  neutrinos, and place my detector immediately
  downstream, I detect 100 muon neutrinos

neutrin -o- taker
(100-x) ?? ?!!
x ?e

• BUT if I move the detector a distance away, a
  small fraction of the muon neutrinos can change
  into electron neutrinos

and then back again!
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neutrinos oscillate ?!

• this astonishing behavior is actually not unusual
  in the weird and counter-intuitive world of
  quantum physics
• particles behave like ________
• wave frequency depends on energy (mass)
• neutrino oscillation demonstrates that, contrary
  to what we once thought, neutrinos have mass

E mc2 !
WAVES
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MiniBooNE experiment
? decay pipe ?
Booster start with protons
Decay region
protons strike beryllium
Magnetic focuser horn
450 m earth ????e?
MiniBooNE detector
Absorber filter out all but neutrinos
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MiniBooNE detector

• 12 m diameter tank
• 800 tons ultra-pure mineral oil
• 1500 8 light sensors (photo-multiplier tubes)

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eye spy. . .

• MiniBooNEs goal is to test a previous experiment
  performed at Los Alamos
• if that result is confirmed, our picture of the
  particle zoo will have to change
• MiniBooNE started running in August 2002, and
  will run for at least three years
• weve collected more than 200,000 neutrino events
  so far

some new kind of nu?
a typical MiniBooNE event
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solving future puzzles

• weve made a lot of progress in understanding the
  fundamental structure of matter, and work at
  Fermilab has been a big part of that progress
• neutrino physics, and particularly oscillations
  are one of the current exciting avenues of
  investigation
• stay tuned! the voyage of exploration continues

. . . . . . thanks!