Neutrinos: From Cosmic Rays and Accelerators to Old Iron Mines and the Fate of the Universe

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Neutrinos From Cosmic Rays and Accelerators to
Old Iron Mines and the Fate of the Universe

• Alec Habig
• UMD Physics

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Neutrinos what are they?

• b decay appears to be a 2-body decay
• So, if energy is conserved, the outgoing electron
  will always have the same energy simple
  freshman mechanics

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The Silent Partner

• 1930 Pauli proposes a silent partner
• a 3rd body that doesnt interact
• Allows both a continuous spectrum and
  conservation of energy
• 1933 Fermi details b decay theory, names the
  neutrino

Solution
A 3-body decay!
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they really do exist!

• 1953 - Fred Reines and Clyde Cowan see inverse b
  decay at the Savannah River reactor

• The positron was observed in a tank of
  scintillating fluid. Reines gets 1995 Nobel
  Prize.

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More flavors of n

• 1949 Powell et al infer the presence of another
  n in p decay and of two more in m decay
• Add in the more recently observed t decay, and
• a n exists for each lepton
• and their anti-particles

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The bookkeeping particle

• Cataloging all the reactions, neutrinos are used
  to account for
• Conservation of Energy
• Conservation of lepton and flavor
• Conservation of angular momentum (spin)

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Neutrino properties

• These balancing acts work if the n has the
  following properties
• No electrical charge
• ns only interact via the weak force
• All ns are left-handed
• Spin -½
• Both by direct observation, and following from
  spin lefthandedness
• mn 0

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No Mass?

• Direct experimental results say
• Mass of ne lt 3eV!
• Compare to
• Mass of e 511 thousand eV
• Mass of p 938 million eV

n.b. 1eV 1.8x10-33 g!
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Oscillations!

• But, if neutrinos have any mass, quantum
  mechanics tells us they should oscillate
  between flavors
• The probability that a nm will change to a nt
  after traveling distance L is

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How to make a n?

• ne come from radioactive b decay and decay of m
• nm come from decays of m and p
• nt come from t decay
• Observed directly for the first time recently!
  (by the DONUT experiment)
• In practice, to get nm
• ms come from p decay
• ps come from high energy nucleon collisions
• So smack together some protons!

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Cosmic Rays

• Mother Nature sends the high energy protons to us
  from space
• Collisions with the atmosphere make particle
  showers

For more, see Scientific American, August 1999
issue
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Super-Kamiokande

• 50kT ultra-pure water
• 22.5kt fid. Volume
• 85m att. length
• 11134 50cm PMTs
• 40 coverage by photocathode
• 2ns timing
• 1800 20cm PMTs in veto shield
• Located in zinc mine near Kamioka, Japan

40 m
1 km (2700 mwe)
40 m
http//www-sk.icrr.u-tokyo.ac.jp/doc/sk/index.html
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SK images courtesy of Institute for Cosmic Ray
Research, The University of Tokyo
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Who is Super-K?
140 authors
35 insti- tutions
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UMD_at_Super-K, Summer 2001
Dan Gastler (UMD), floating in top of OD
Alec Habig (UMD) and Jim Stone (BU), fixing Tyvek
in barrel of OD
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UMD_at_Super-K, Summer 2001
Andrew Clough (UMD), making cable ends with Erik
Blaufuss (Maryland), Jeff Griskevich (UCI), and
Katy Mack (Caltech)
Dan and Erik replace a top OD PMT
(lots more pictures at http//neutrino.d.umn.edu/
superk)
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How does it work?
Graphics by Ed Kearns, Boston Univ.
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e, m, or t?

• Two similar events
• Seen in unrolled view
• e-like event at top
• Showers
• Fuzzy ring
• m-like event below
• One particle
• Crisp ring
• m decays makes e
• t cant see! Need very high energy to produce t

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How far did the n go?

• The ns come from cosmic rays hitting the
  atmosphere
• The n travels
• L 20km from above
• L 500km from the side
• L 10,000km from below

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The Results
ne
nm

• All ne data are consistent with expectations.
• Lowest E nm all low
• Higher E nm ok from above, low from below
• Data match nmlt-gtnt oscillations!

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Oscillation Parameters

• nm oscillating to nt (thus disappearing) fits the
  data well
• Values of parameters inside contours work
• Best fit values
• Dm2 2.1x10-3
• sin22q 1
• At 90 cl
• 1.5x10-3 lt Dm2 lt 3.4x10-3 eV2
• sin22q gt 0.92
• ne not involved

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Other Super-K ns

• Low-energy ns from fusion in core of the Sun
  (dozens per day)
• Very high-energy ns from Active Galactic Nuclei
  (black holes) or Gamma-Ray Bursts (if we were
  bigger or get lucky)
• Low-energy ns from Supernovae in our galaxy (the
  next time one happens!)
• Can also make statement about diffuse SN n
  background! (SN relics), probe star formation
  history of universe

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SNEWS
Super-Kamiokande (Japan) 50kton
7000 inv. b decay, 410 on 16O, 300 elast.
scattering, 4o pointing

• Supernova Early Warning System
• Watches for coincidence from worlds n detectors
• Issue SN alarm, hours before light breaks out!

Coincidence server securely hosted by Brookhaven
National Lab
SSL sockets
Server 10s coincidence window
PGP signed email
Email alarms to astronomers
(Mini-BooNE, KamLAND, Borexino, AMANDA, LIGO
also sensitive to nearby SN but not yet sending
alarms to SNEWS)
Sudbury Neutrino Observatory (Canada) 1.7kton
H2O, 1kton D2O
Sign up yourself to receive an alert at
http//snews.bnl.gov/
710 inv. b decay, 160 2H breakup, 45 elast.
scattering, 17o pointing
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Experimental Disaster

• After repairs, SK was slowly refilled with water
• One PMT failed, imploded
• Shock wave crushed neighbors
• Chain Reaction
• 2/3 of all PMTs crushed

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Recovery Work

• In the summer of 2002, 47 of ID tubes and all OD
  tubes were replaced
• ID tubes with acrylic shields
• UMD people worked all summer
• SK is operational again
• Data taking resumed in Dec. 2002!

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Our Work in the OD (2002)
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UMD_at_Super-K, Summer 2005
Rose Smith (UMD), with Tom Kreicbergs (Hawaii),
Aaron Herfurth (BU), and Kirsti Hakala (UMD)
John Eastman (UMD) , Photographer
Prepared 6,000 replacement PMTs (being installed
now!)
(lots more pictures at http//neutrino.d.umn.edu/
east0108)
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Accelerators

• Make our own high energy protons

• Shoot them into a fixed target

• Focus the resulting ps into a beam
• Let the ps decay to ns

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MINOS

• Main Injector Neutrino Oscillation Search
• A direct end-to-end n oscillation experiment
• Make our own ns
• Measure them at the source
• Near Detector
• Measure them again 735km away
• Far Detector
• Watch them change flavor!

http//www-numi.fnal.gov
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Who is MINOS?
Argonne Athens Benedictine Brookhaven
Caltech Cambridge Campinas Fermilab
College de France Harvard IIT Indiana
ITEP-Moscow Lebedev Livermore
Minnesota-Twin Cities Minnesota-Duluth
Oxford Pittsburgh Protvino Rutherford Sao
Paulo South Carolina Stanford Sussex Texas
AM Texas-Austin Tufts UCL Western Washington
William Mary Wisconsin
32 institutions 175 physicists
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A cross-country n beam

• The ns start at Fermilab, aimed down a bit
  (3.3o)
• ns pass under Wisconsin, Lake Superior, and
  Duluth, oscillating as they travel
• Beam is observed again at the Soudan Mine

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The Old Iron Mine

• Soudan Iron mine has been a state historical park
  since the 1960s
• A new cavern has been excavated at the bottom of
  the mine
• Adjacent to Soudan2 expt. and Historical Tour
• Crygenic Dark Matter Search (CDMS) in Soudan2 hall

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Expanding the Lab
Spring 2000

• Excavation complete 12/00
• Experimental construction started August 2001
• Tours started summer 2002
• Come see us!
• http//www.soudan.umn.edu

March 2001
December 2000
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The MINOS Far Detector

• Made of 1 x 8m steel octagons
• Sandwiched with plastic scintillator
• Steel is magnetized to 1-2 Tesla
• 5.4kt total steel (3.3kt fiducial)
• 486 layers 31m long
• Near detector similar but smaller

½ Far Det. in cavern
The whole thing!
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MINOS Starts to Grow
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Current View of MINOS

• Far Detector is finished!

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Schedule

• Far detector completed July 2003
• Started taking Cosmic Ray data
• Many atmospheric neutrino events have been seen!
• Near detector finished mid 2004
• n beam started beginning of 2005
• Running beautifully now
• 2-3 years data taking needed to meet
  expectations, 5-10 years hoped for
• Achieved exposure equal to K2K in December 2005

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Scintillator

• Scintillator emits light when a charged particle
  passes through
• MINOS uses plastic scintillator strips
• 4cm wide, 8m long
• Light carried out of the ends to Photomultiplier
  tubes via optical fiber
• 192 strips per plane
• Alternate planes at right angles to get 3D view

Scintillator graphics courtesy of Doug Michael,
Caltech
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More Scintillator
A module
A blue LED lights up the Scintillator
An M16 PMT
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Scintillator layout

• 8 modules cover one far detector steel plane
• Four 20-wide modules in middle (perp. ends)
• Four 28-wide modules on edges (45 deg ends)
• Two center modules have coil-hole cutout

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Plane Assembly

• MINOS planes are assembled from parts which can
  fit down the shaft
• Two ½ layers of steel welded together to form 1
  thick, 12 ton plane
• 1 ton scintillator attached to that
• Plane hung like a file folder

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Multiplexing

• Light detected by 16 pixel PMTs
• 8 fibers per pixel, ganged together to reduce
  electronics costs by 8x

One of 3 Ham. M16 PMTs in this Mux Box
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Front End Electronics

• Fibers from each strip end are multiplexed onto
  PMT pixels
• Signals amplified, shaped, and trackedheld by
  VA chips
• Hit and Timing information sent upstream from
  this Front End rack

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Data Gathering

• VME Master crate
• VA Readout Controllers VARCs
• Charge from PMTs digitized by 14-bit ADCs
• Time stamped to 1.6ns by internal clock
• 2/6 or 2/36 pre-trigger applied
• Hits given absolute GPS time
• Data read out over PVIC bus to computer room
• 4/5 plane software trigger applied, hits time
  ordered
• Data formatted in ROOT

1 of 16 VME crates Digitizes 72 mux boxes Each
w/3 16-pixel PMTs
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De-multiplexing

• If we read out eight fibers with one PMT pixel
• How to figure out which strip a particle really
  went through?
• Matching hits on both ends of a strip helps in
  the simplest track case
• For multiple hits on a plane and showers
• All the different possible hypotheses of which
  strip was really hit tested against the possible
  real physics
• Best fitting hypotheses saved
• Reconstructing close multiple muons is very
  difficult!

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A Cosmic Ray De-multiplexed

• Success rate for Cosmic Rays
• 94 of hits correctly associated with their
  strips
• 97 of CR events successfully sorted out

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A Double Cosmic Ray m

• A real event
• Two Cosmic Ray ms, from same initial interaction

See live events at http//farweb.minos-soudan.org/
events/LiveEvent.html
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n interactions in MINOS

• First beam neutrino event!
• In time with beam, coming from Fermilab
• n interacts in rock or steel, resulting particles
  splash through detector
• Charged particle curves in magnetic field (more
  at the end as it slows down)
• Scintillation light read out of strips
• Each pixel is a lit up strip!

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3D reconstruction

• 8.5 GeV electron
• es make showers which quickly peter out

• 16.5 GeV muon
• s are single, penetrating particles

MINOS simulations courtesy of Brett Viren,
Brookhaven Natl. Lab
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Expected MINOS results

• Compare nm spectrum near and far
• Here are expected results given 3 different sets
  of oscillation parameters
• With same L (735km), lower E ns will oscillate
  to nt and disappear
• With no ne originally in the beam, any ne
  appearing will be very interesting!

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Comparative Resolution

• MINOS can make very precise measurements of the
  oscillation parameters
• MINOSs expected precision (green) is compared to
  SKs (yellow) for three different values of Dm2

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So What?

• ns change flavor as they go along, and thus have
  some small mass.
• Big Deal.
• Its something not predicted by the Standard
  Model!
• Perhaps a hint towards a Grand Unified Theory
  theorists have new fundamental parameters their
  theories must explain.

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Fate of Universe?

• ns play a role
• One n has a Very Small mass
• (assuming m is comparable to Dm)
• But there are incredible numbers of them sloshing
  about
• They could be an appreciable fraction of the
  total mass of the universe!

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Dark Matter

• Galactic rotation curves luminous matter not
  enough
• Disk stability also needs a Dark Matter halo

Galaxy M31 image by Jason Ware.
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Rocks, dust, gas?

• Big Bang Nucleosynthesis calculations limit total
  number of baryons (p, n i.e., normal stuff )
• Not enough dark rocks etc. can exist without
  changing the cosmic ratio of H, He, Li
• Need non-baryonic dark matter. ns qualify, and
  they have mass

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Hot Dark Matter

• ns are hot, i.e., have kinetic energy much
  larger than rest mass
• If all DM is hot, universe is too runny
  matter too smoothly distributed for galaxies to
  form
• Simulations say there can still be as much total
  mass in HDM as all the baryons but not enough
  to be all the DM needed!

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Cold Dark Matter

• Particles with large rest mass (compared to
  kinetic energy)
• e.g. WIMPS or Axions
• Alone, too lumpy at large scales, galaxy
  super-clusters dont form
• But, ColdHot Dark Matter models reproduce
  large scale structure rather well - add in those
  ns!

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Simulated Universe, ColdHot Dark Matter
Real Galaxy Survey
Courtesy of Margaret Geller and Emilio Falco,
Harvard-Smithsonian Center for Astrophysics
Courtesy of Greg Bryan and Mike Norman, UIUC
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Neutrinos

• Elusive but numerous
• Massive ns have both theoretical and cosmic
  consequences
• We observe nmlt-gtnt flavor oscillations (and thus
  n mass) in cosmic rays with Super-K
• MINOS is studying these oscillations using a
  precision man-made beam with before after
  measurements

This powerpoint is online at http//neutrino.d.um
n.edu/habig/Neutrinos.ppt
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• 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.

-John Updike