Highest Energy Neutrinos and Detection Methods

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Highest Energy Neutrinos and Detection Methods

• Ben Chevis
• HEP Seminar
• April 26, 2006

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Neutrino Sources

• M. Spiro D. Vignaud, Nucl Phys A654 1999 350c

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Greisen-Zatsepin-Kuzmin(GZK) Limit

• Cosmic rays with energies above 51019 eV will
  interact with the cosmic microwave background
  photons to produce pions. This process would
  continue until the energy of the cosmic ray fell
  below the pion production threshold.
• However the AGASA (Akeno Giant Air Shower Array)
  experiment found cosmic rays above this limit.
  Possible explanations
• 1. Instrument error or incorrect interpretation
  of the data
• 2. Local source of the cosmic rays
• 3. Ultra High energy neutrinos created at great
  distances and later reacting locally

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GZK Neutrinos

• Two possibilities
• Cosmic rays above the GZK limit will interact
  with the CMB and can produce ultra high energy
  neutrinos
• The ultra high energy cosmic neutrino emitted
  from the far-away sources barely interact with
  the 3k photons avoiding the energy loss by the
  GZK mechanism, but might later collide with the
  relic neutrinos to initiate the neutrino
  cascades.

• Images by Shigeru Yoshida, Chiba University

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Example of detector currently being built
IceCube

• 1 km3 detector area
• Designed to detect 107 1020 eV neutrinos
• Expect 0.2 40 GZK neutrinos per year (1/1000 of
  primary neutrino intensity)

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Problems with IceCube and GZK neutrinos
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Detection Methods
optical Cerenkov

• Super Optical Cerenkov Detectors
• Radio Cerenkov Detectors
• Air Shower Radio Signals
• Acoustic Detectors

radio Cerenkov
acoustic
incoming neutrino
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Super Optical Cerenkov Detectors

• At energies gt1018 eV neutrino induced showers and
  muons produce so much cerenkov radiation that
  photo-multiplier tubes of current detectors are
  triggered over several hundred meters. Examples
• To fix this the distance between PMTs would need
  to be increased.
• There is a proposal to add an outer ring to the
  IceCube detector. IceCube-Plus would be 300 500
  m from the outer most strings with 13 18
  strings.

100 GeV ? 20m 1 PeV ? 400m 1 EeV ? 600 - 700m
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Radio Cerenkov Detectors

• It was suggested by Askaryan in 1962 that any
  electromagnetic cascade in a dielectric material
  (gas, liquid or solid) should rapidly develop net
  negative charge asymmetry due to electron
  scattering processes and positron annihilation
  which will create Cerenkov radiation

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Radio Cerenkov Detectors

• RICE (Radio Ice Cerenkov Experiment)
• radio receivers placed in the holes drilled for
  the AMANDA optical modules
• GLUE (Goldstone Lunar Ultra high energy neutrino
  Experiment)
• two radio antennas looking for radio signals
  produced by neutrinos passing through the moon
• FORTE (Fast Orbit Radio Transient Experiment)
• satellite searching for radio signals from
  Greenland ice
• ANITA (Antarctic Impulsive Transient Antenna)
• balloon mounted detector searching for radio
  signals from Antarctic ice
• SalSA (Saltdome Shower Array)
• large salt dome used as detector medium

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Air Shower Radio Signals
Flys Eye

• The deflection of electron positron pairs in the
  earths magnetic field produce radio signals from
  air showers.
• The frequencies are expected to be as low as a
  few hundred MHz

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Air Shower Radio Signals

• LOPES (LOfar PrototypE Station) attached to
  KASCADE/GRANDE AUGER (Karlsruhe Shower Core and
  DEtector)
• pyramid shaped radio antennae
• CODALEMA (Cosmic ray Detection Array with
  Logarithmic ElectroMagnetic Antennas)
• conical radio antennae array

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Acoustic Detectors

• The energy produced by particle cascades in a
  small volume of matter during a short time will
  overheat that volume, leading to a pressure
  pulse. The amplitude of this pulse measures the
  cascade energy.
• The frequency of the pulse is estimated to be
  10-100 kHz
• The detection media is most often water but ice
  and salt are being studied.

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Acoustic Detectors

• SAUND (Study of Acoustic Ultrahigh-energy
  Neutrino Detection)
• hydrophones located near the Bahamas
• Salt Dome
• Acoustic waves in the Hockley salt mine in Texas

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Comparison of Radio, Acoustic and Optical Cascades

• Dr. P. Buford Price

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Conclusion

• Though the techniques for all of the shown
  experiments are more than thirty years old,
  recent technological advances have revived them
  as possible neutrino detectors. Expect to hear
  more about them.

GLUE
Hydrophone at ITEP
ANITA
FORTE
SAUND
Acoustic detector at DESY
SalSA
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Fin
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References

• This presentation is largely based on a paper by
  Rolf Nahnhauer, astro-ph/0411715, Alternative
  Detection Methods for Highest Energy Neutrinos
• Also work by Shigeru Yoshida, Chiba University
  and David Waters of University College London
  were very helpful

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Extra slides
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