Dan Hooper

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Probing Exotic Physics With High-Energy Neutrinos

• Dan Hooper
• Particle Astrophysics Center
• Fermi National Laboratory
• dhooper_at_fnal.gov

University of Kansas April 18, 2006
2
How To Study Particle Physics?

• Traditionally, particle physics has been studied
  using collider experiments
• Incredibly high luminosity beams very large
  numbers of collisions can be observed
• Energy is technology/cost limited
• Tevatron (1.96 TeV)
• Large Hadron Collider (14 TeV)

3
How To Study Particle Physics?

• Astrophysical accelerators are known to
  accelerate particles to at least 1020 eV (about
  8 orders of magnitude beyond present collider
  experiments)
• Astroparticle physics is generally luminosity
  limited few events, enormous detectors
• Cosmic neutrinos are perhaps the most
  useful, due to their weakly
  interacting nature
• Provides a natural complementarity with
  collider experiments

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Where Do High-Energy Cosmic Neutrinos Come From?

• Fermi acceleration yields cosmic sources of
  high-energy protons
• Protons colliding with surround matter and
  radiation produce ?s
• ? decays generate neutrinos

• Promising sources include
• Gamma-ray bursts
• Blazars (active galactic nuclei)
• Microquasars
• UHE protons/nuclei
• (scattering with the CMB/CIRB)

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Where Do High-Energy Cosmic Neutrinos Come From?

• Fermi acceleration yields cosmic sources of
  high-energy protons
• Protons colliding with surround matter and
  radiation produce ?s
• ? decays generate neutrinos

• Promising sources include
• Gamma-ray bursts
• Blazars (active galactic nuclei)
• Microquasars
• UHE protons/nuclei
• (scattering with the CMB/CIRB)

But, how do we detect them?!
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Tools of the Trade The First Generation

• AMANDA
• Below 2 kilometers of Antarctic ice
• Optical Cerenkov, E?,th20-30 GeV
• Effective Area of 50,000 sq meters
• Sensitive to muons, EM/hadronic showers
• 7 years of data in current form

• ANTARES
• Under construction in Mediterranean Sea
• Slightly larger effective area, and lower energy
  threshold than AMANDA
• Northern hemisphere location

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Tools of the Trade The First Generation

• The Successes of AMANDA
• 800 live days of AMANDA data analyzed (over 4
  years)
• Sky map with thousands of neutrinos largely
  atmospheric
• Limits on point sources at the level of 6x10-8
  GeV cm-2 s-1

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Tools of the Trade The First Generation

• Successes of AMANDA
• Atmospheric neutrino spectrum measured to 100
  TeV consistent with theoretical expectations
• Sensitivity to diffuse neutrino flux in 100
  GeV-100 PeV range approaching 10-7 GeV cm-2 s-1
  sr-1
• Nearing theoretical expectations
• for astrophysical sources

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Tools of the Trade The First Generation

• RICE
• Array of radio antennas co-deployed with AMANDA
• Effective Volume of 1 km3 at 100 PeV several
  km3 at 10 EeV
• Limits on diffuse neutrino flux in 200 PeV-200
  EeV range
• of 6 x10-7 GeV cm-2
  s-1 sr-1
• Future radio deployments with IceCube promising
• Anita-Lite
• Balloon-based radio antennas
• Limits on diffuse flux above EeV
• of 10-6 GeV cm-2 s-1 sr-1
• Full Anita flight in 2006
• ?sensitivity of 10-8 GeV/cm2 s sr
• observe the first UHE neutrino?

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Tools of the Trade The Next Generation

• IceCube
• Full Cubic Kilometer Instrumented Volume
• 9 (of 80) strings currently deployed 14 planned
  for next year

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Tools of the Trade The Next Generation

• IceCube
• Full Cubic Kilometer Instrumented Volume
• 9 (of 80) strings currently deployed 14 planned
  for next year
• Sensitive to muon tracks, EM/hadronic showers,
  and tau-unique events

Double Bang
Muon Track
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Tools of the Trade The Next Generation

• IceCube
• Full Cubic Kilometer Instrumented Volume
• 9 (of 80) strings currently deployed 14 planned
  for next year
• Sensitive to muon tracks, EM/hadronic showers,
  and tau events
• Will have sensitivity needed to observe
  high-energy cosmic neutrinos (following
  arguments tied to cosmic ray spectrum)

IceCube
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Tools of the Trade The Next Generation

• IceCube
• Full Cubic Kilometer Instrumented Volume
• 9 (of 80) strings currently deployed 14 planned
  for next year
• Sensitive to muon tracks, EM/hadronic showers,
  and tau events
• Will have sensitivity needed to observe
  high-energy cosmic neutrinos (following
  arguments tied to cosmic ray spectrum)

Likely to observe first cosmic high-energy
neutrinos in coming years!
IceCube
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Tools of the Trade Cosmic Ray Experiments

• The Pierre Auger Observatory
• Southern cite currently under construction in
  Argentina
• First data released in 2005 (no neutrino data
  yet)
• Sensitive above 108 GeV, 3000 km2 surface area
• Neutrino ID possible for quasi-horizontal showers
  and Earth-skimming, tau-induced showers
• AGASA experiment places limits on
• UHE neutrino fluxes
• EUSO/OWL
• Satellite/space station based
• Enormous aperture
• Future uncertain

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Cosmic vs. Manmade Accelerators

• Energy Reach
• At modest energies (TeV and below), accelerator
  experiments constrain many exotic physics
  scenarios
• Above TeV, particle physics is very poorly
  constrained
• Cosmic ray spectrum extends (at least) to 1011
  GeV
• Neutrinos are expected to be produced up to
  similar energies
• 1011 GeV neutrino target proton ? ECM300 TeV
• 1010 GeV neutrino target proton ? ECM100 TeV
• 109 GeV neutrino target proton ? ECM30 TeV
• Well beyond the reach of any planned collider
  experiment!
• Luminosity
• High-energy neutrino experiments will never
  observe as many collisions as accelerator
  experiments
• Much less precision than manmade accelerators
  provide

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Cosmic vs. Manmade Accelerators

• Extremely Long Baselines
• Collider experiments study phenomena that take
  place over small fractions of a second
• Solar, atmospheric, and long baseline neutrino
  experiments study somewhat longer
  timescales/greater distances
• High energy neutrinos are likely to be observed
  from sources 100s or 1000s of Mega-parsecs
  distant
• A new window into exotic physics!

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The Role of Neutrino Astronomy in Exploring
Exotic Physics

• Focus on scenarios which benefit from the
  strengths of neutrino astronomy in contrast to
  collider programs
• 1) Models with substantial deviations from the SM
  
• at energies beyond the reach of colliders
• 2) Models with substantial deviations from the SM
  over
• timescales and/or propagation lengths beyond the
• range observable at colliders

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TeV Scale Gravity

• ECM MPL, KK Graviton Exchange
• ECM gt MPL, String Resonances
• ECM gtgt MPL, Black Hole Production

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Kaluza-Klein Graviton Exchange

• Model dependent cross sections
• Calculations not reliable very far above
  E?TeV2/2mpPeV

Alvarez, Halzen, Han, Hooper, PRL, hep-ph/0107057
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TeV String Resonances

• Only mild model dependence (Chan Patton factors)
• Valid at all energies

Friess, Han, Hooper, PLB, hep-ph/0204112
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Microscopic Black Hole Production

• At center-of-mass energies above fundamental
  Planck scale, black holes can be formed
• Naïve picture suggests geometric cross section, ?
  ? R2sch
• TeV black holes rapidly Hawking radiate
• Valid at all energies dominant contribution at
  ECMgtgtTeV

See Anchordoqui, Feng, Goldberg and Shapere,
PLB, hep-ph/0311265 PRD, hep-ph/0307228
PRD, hep-ph/0112247
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Microscopic Black Hole Production

• Likely the most easily observed signature of TeV
  gravity
• Open questions remain
• -Energy loss to gravitational waves
• -Many model dependent features
• -P brane production likely to dominate, but
  behavior of
• Hawking radiation unknown

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TeV Scale Gravity At Pierre Auger

• Sensitive to neutrinos above 100 PeV
• Above the range of KK graviton exchange
• A neutrino-nucleon cross section measurement at
  Auger energies would provide a powerful test of
  microscopic black hole production and/or TeV
  string resonances

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TeV Scale Gravity At Pierre Auger

• Quasi-Horizontal, Deeply Penetrating Air Showers
  
• Most neutrino induced airshowers cannot be
  distinguished from hadronic/photonic primaries
• Hadronic/Photonic UHECRs interact at top of
  Earths atmosphere Neutrinos interact at all
  column depths (nearly) equally
• Quasi-horizontal air showers, generated deep
  inside of the atmosphere, can be identified as
  neutrino initiated events

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TeV Scale Gravity At Pierre Auger

• Earth-Skimming Tau Neutrinos
• UHE ?e, ??s are efficiently absorbed through
  charged current interactions in the Earth
• ??s produce ?s which can decay before losing
  their energy
• (tau regeneration)
• Earth-skimming ??s can decay in the atmosphere,
  and be detected by Auger

Figure from Bertou et al., astro-ph/0104452
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TeV Scale Gravity At Pierre Auger

• Quasi-Horizontal, Deeply Penetrating Showers
  
• Rate increases with increasing cross section
• Earth-Skimming Tau Neutrinos
• Rate decreases with increasing cross section due
  to absorption in the Earth
• ?The ratio of these two rates provides an
  effective measurement of the neutrino-nucleon
  cross section at ultra-high energies

Anchordoqui, Han, Hooper, Sarkar, Astropart.
Phys., hep-ph/0508312
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TeV Scale Gravity At Pierre Auger

• TeV string resonances enhance QH rate, suppress
  ES rate

Model QH/ES Ratio
SM 0.05
2 TeV 0.11
1 TeV 2.1
Anchordoqui, Han, Hooper, Sarkar, Astropart.
Phys., hep-ph/0508312
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TeV Scale Gravity At Pierre Auger

• Auger is very sensitive to
• microscopic black hole production

Model (MPL) QH/ES Ratio
SM 0.05
8 TeV 0.10
3 TeV 0.54
2 TeV 2.0
1 TeV 36.0
Anchordoqui, Han, Hooper, Sarkar, Astropart.
Phys., hep-ph/0508312
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TeV Scale Gravity At IceCube

• Most sensitive in the TeV-PeV energy range
• Well suited to probe KK graviton exchange
• Sensitive to muons, taus and
• showers, enabling a direct probe of
• black hole production via
• Hawking radiation

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TeV Scale Gravity At IceCube

• Cross section measurements possible by comparing
  upgoing to downgoing events (absorption in the
  Earth)

Alvarez, Han, Halzen, Hooper, PRL, hep-ph/0107057
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TeV Scale Gravity At IceCube

• Cross section measurements possible by comparing
  upgoing to downgoing events (absorption in the
  Earth)

Energy range suitable for RICE!
See, Hussain and McKay, PLB, hep-ph/0500183
Alvarez, Han, Halzen, Hooper, PRL, hep-ph/0107057
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TeV Scale Gravity At IceCube

• Cross section measurements possible by comparing
  upgoing to downgoing events (absorption in the
  Earth)
• With reasonable cosmic fluxes (Waxman-Bahcall in
  figure below), KM scale experiments can
  accurately measure the neutrino-nucleon cross
  section up to 10 PeV (5 TeV C of M)

Hooper, PRD, hep-ph/0203239
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TeV Scale Gravity At IceCube

• Even more information can be extracted using
  entire angular distribution of events

Alvarez, Han, Halzen, Hooper, PRD,
hep-ph/0202081, Jain, Kar, McKay, Panda,
Ralston, PRD, hep-ph/0205052
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TeV Scale Gravity At IceCube

• Multi-Channel Measurements
• KK gravitons, string resonances contribute to
  shower rate only
• Use shower/muon ratio to test for deviations from
  SM prediction
• Hawking radiation from microscopic black holes
  generates taus, muons and showers

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Other Strongly Interacting Physics Scenarios For
Neutrino Astronomy

• SM Electroweak Instanton Induced Interactions
• Transitions between degenerate vaccua (with
  different BL) are possible within the context of
  the SM
• Below Sphaleron mass, ? MW/?W 8 TeV, such
  transitions are exponentially suppressed Above
  this energy, enormous cross sections expected
• Neutrino-nucleon cross section,
• based on QCD-like picture/data
• Ideally suited for Auger

See Ringwald Nuc Phys B (1990), Aoyama and
Goldberg PLB (1987), Ahlers, Ringwald and Tu,
astro-ph/0506698
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Electroweak Instantons at Auger

• Substantial deviations expected above 1010 GeV
• Roughly 4 QH showers/yr predicted, roughly 30
  times more
• than CC/NC alone
• Very strong probe of Electroweak Instanton
  Induced Interactions

Anchordoqui, Han, Hooper, Sarkar, Astropart.
Phys, hep-ph/0508312
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Long Baseline Measurements

• Colliders probe phenomena at (very) sub-second
  scales
• Solar neutrino experiments probe scales of ?/m
  10-4 s/eV
• (supernovae may, in future, improve
  on this)
• High energy cosmic neutrinos capable of improving
  on this by a factor of 107 (L / 100 Mpc) (10
  TeV / E?)
• Powerful test of neutrino decay, quantum
  decoherence, Lorentz violation,

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Cosmic Neutrino Flavors

• Astrophysical accelerators generate neutrinos
  through charged pion decay
• ?/- ? ? ?? ? e ?e ?? ??
• Neutrinos produced in the ratio
• ?e???? 1 2 0
• After oscillations, this leads to ?e???? 1
  1 1
• Caveat Energy losses in source might modify

(Kashti and Waxman, astro-ph/0507599)

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Neutrino Decay

• Scenario 1 All mass eigenstates decay to
  lightest mass eigenstate (or invisible) with
  normal hierarchy flavor ratios of
• ?e???? cos2?S (1/2) sin2?S (1/2)
  sin2?S 6 1 1
• Scenario 2 Same, but with inverted hierarchy
• ?e???? U2e3 U2?3 U2?3 0
  1 1
• Scenario 3 (only) ?3 decays invisibly with
  normal hierarchy, flavor ratios of
• ?e???? 2 1
  1
• Many other scenarios possible

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Measuring Neutrino Flavor Ratios

• With IceCube
• -Muons/showers roughly translates to ??/?tot
• -Tau unique events provide confirmation
• With Auger
• -ES/QH roughly translates to ?? /?tot
• -Low event rate yields less sensitivity

Beacom, Bell, Pakvasa, Hooper and Weiler,
hep-ph/0307025
Anchordoqui, Han, Hooper and Sarkar,
hep-ph/0508312

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Flavor Ratios At IceCube

• Ratio of muons to showers translates to flavor
  ratio
• (Example E2 dN/dE 10-7 GeV cm-2 s-1, 2 x
  10-8 GeV cm-2 s-1)

Beacom, Bell, Pakvasa, Hooper and Weiler,
hep-ph/0307025
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Flavor Ratios At Pierre Auger

• Deviations in QH/ES translate to deviations in
  flavor ratios

Anchordoqui, Han, Hooper and Sarkar,
hep-ph/0508312
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Quantum Decoherence

• In many pictures of quantum gravity, information
  loss may be expected during propagation (black
  hole formation/radiation, quantum foam, etc.)
• Regardless of initial flavors, cosmic neutrinos
  gradually evolve toward
• ?e ?? ?? 1 1 1
• This is the similar to the prediction from pion
  decay (after oscillations), and thus is very
  difficult to distinguish

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Quantum Decoherence

• To probe effects of quantum decoherence, another
  (non-pion) source of neutrinos is needed
• Photodisintegration of UHE nuclei generates
  neutrons which decay producing uniquely electron
  anti-neutrinos
• After oscillations, such a source yields
• ?e ?? ?? 3 1 1
• Potentially distinguishable from quantum
  decoherence effects

Hooper, Morgan and Winstanley, PLB,
hep-ph/0410094
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UHE Neutron Sources and Quantum Decoherence

• UHE neutrons can travel multi-kpc scales without
  decaying
• Neutral UHECRs can reveal point sources
• Can be used to infer the presence of lower energy
  neutrons which decay generating (anti-)neutrinos
• Cygnus region point source detected by AGASA in
  EeV range at 4-4.5? significance (4 of flux)
• Supporting data from Sugar, as well as galactic
  plane excess seen by Flys Eye

Anchordoqui, Goldberg, Gonzalez-Garcia, Halzen,
Hooper, Sarkar and Weiler,

PRD hep-ph/0506168
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Summary and Conclusions

• High energy neutrino astronomy provides a new
  window into plausible exotic physics scenarios
  that are beyond the reach of planned and proposed
  collider experiments
• Very high energies, very long baselines are in
  many cases uniquely assessable with neutrino
  astronomy

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The Future of Particle Physics

• Greater energies scales continue to be explored
  with colliders (Tevatron, LHC, ILC, VLHC,)
• Greater energies prove to be increasingly
  expensive and technically challenging
• Future of collider-based particle physics is
  uncertain
• To overcome these challenges, a broad vision of
  experimental particle physics is needed
• Cosmic ray physics, neutrino astronomy, gamma-ray
  astronomy and early Universe cosmology each
  contribute to our understanding of particle
  properties and interactions under conditions
  inaccessible to colliders
• Complementary should be taken advantage of

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THE END