Mining For Ghosts

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Mining For Ghosts

• Neutrinos in the Minnesotan Wilderness at the
  Soudan Underground Laboratory

Jeff Hartnell, Graduate Lecture Supper St. Johns
College, Tuesday 20th May 2003
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Overview

• Neutrino A what?
• The amazing properties of the neutrino
• Cosmic Gall
• The MINOS experiment
• A video clip or two!
• Mining the neutrinos
• What did I do in Minnesota?

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Neutrino A What?

• Ghostly particle, first postulated in 1930 by
  Pauli to restore the Law of Conservation of
  Energy
• Radioactive beta decay
• n ? p e-
• End up with less energy than you started with
  missing energy is carried away by an invisible
  particle (?)
• n ? p e- ?

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Neutrinos Fundamental Particles of Matter

• Two families Leptons and quarks
• Three generations We are primarily made of the
  first generation
• Leptons come in pairs The e, ? ? all have an
  associated neutrino ?e, ?? ??

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Whats Special About Neutrinos?

• Incredibly light weight thought to be a million
  times lighter than the lightest of the other
  matter particles (the electron)
• Amazingly penetrating, mainly due to having zero
  electric charge. A neutrino can pass through
  light-years of material without interacting
• They can change into each other, called
  oscillations (this is what Im researching)

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Where Can I Find a Neutrino?

• We are all radioactive (only slightly!) and are
  constantly emitting neutrinos
• 100s of billions of neutrinos are pouring through
  us every second from the sun
• Neutrinos are created when high energy cosmic
  rays strike the Earths atmosphere
• We can make neutrinos with a high energy particle
  accelerator (What I do!)

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Neutrino Anomalies Why They Are Interesting!

• Only a third of the electron neutrinos we expect
  to see from the sun actually arrive at Earth
• As you move away from a nuclear reactor the
  electron neutrinos start to disappear
• Muon neutrinos produced in the atmosphere by
  cosmic rays disappear depending on how far away
  they were created

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Neutrino Oscillations

• Neutrinos can change from one type to another
  due to quantum mechanics
• This is very strange behaviour. You start with,
  say, an electron neutrino, you dont do anything
  to it but when you next look it has become a muon
  neutrino!
• This happens as a function of time or
  equivalently distance when they are all
  travelling at near the speed of light
• P(na ? nb) sin22q sin2(1.27 Dm2 L/E)

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Cosmic Gall by John Updike

• Neutrinos they are very small
• They have no charge they have no mass
• they do not interact at all.
• The Earth is just a silly ball
• to them, through which they simply pass
• like dustmaids down a drafty hall
• or photons through a sheet of glass.
• They snub the most exquisite gas,
• ignore the most substantial wall,

cold shoulder steel and sounding brass, insult
the stallion in his stall, and, scorning
barriers of class, infiltrate you and me. Like
tall and painless guillotines they fall down
through our heads into the grass. At night, they
enter at Nepal and pierce the lover and his
lass from underneath the bed. You call it
wonderful I call it crass.
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The MINOS Experiment

• Aim to make a precision measurement of Dm2 and
  prove oscillatory behaviour of neutrinos
• Fire a beam of neutrinos through the earth
• Measure the neutrino energy spectrum at beginning
  and end compare and discover which ones have
  disappeared

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How to Detect a Neutrino

• Cant actually see a neutrino, you only see
  what is produced when it reacts
• ?? n ? p ?-
• Only see the proton and muon
• The neutrino sneaks into the detector unseen,
  then a highly energetic proton and muon appear
  from nowhere a contained event

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The Life Cycle of a Neutrino in the MINOS
Experiment
(Video clip thanks to PPEP)
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Detecting Charged Particles

• You can only see particles that emit and absorb
  light.
• For particles to do this they have to have a
  charge like the proton and muon.
• You can track the particle by designing the
  detector to be a segmented, grid-like structure

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Sandwiches of Steel
500 planes at 10 tons each!
5400 tons in total
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Building the MINOS Far Detector
Video by Jerry Meier and the Soudan Underground
Laboratory Crew
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What did I do at the Soudan Underground
Laboratory in the Wilds of Northern Minnesota?
Soudan Mine
Chicago
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Hiked Across Frozen Lakes in 200C!!!
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Visited Frozen Waterfalls
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Sampled a few too many of the local beverages?
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Ok, So What Did I Do Work Wise? ?

• Started at 730am (prompt!) with a 3 minute
  pitch-black, shaky ride down the mine shaft
• Was responsible for ensuring the experiment was
  taking data
• Wrote software to analyse the data and debug the
  detector
• Fixed various hardware problems, miswirings,
  broken components, etc
• Came back to the surface at 530pm didnt see
  the sun ALL week!!!
• My local Minnesotan friends referred to us as
  Neutrino Trolls

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Summary

• The neutrino A fundamental matter particle
• The exciting anomalies of neutrinos
• The MINOS Experiment
• Mining for neutrinos how to see them
• Working at the Soudan Underground Laboratory (as
  a Neutrino Troll)

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The End
Thank you!
http//www-pnp.physics.ox.ac.uk/hartnell/
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An Aside Neutrinos and Nobels

• 1988 Nobel prize to Lederman, Steinburger and
  Schwartz for the discovery of a second type of
  neutrino (??) in 1963
• 1995 Nobel prize (1/2) to Reines for actually
  discovering the neutrino
• 2002 Nobel prize (1/2) to Davis and Koshiba for
  detection of cosmic neutrinos from the sun and
  a star exploding in a supernova