Probing Exotic Physics With HighEnergy Neutrinos Dan Hooper

Probing Exotic Physics With High-Energy Neutrinos Dan Hooper Particle Astrophysics Center Fermi National Laboratory dhooper@fnal. gov University of Kansas April 18, 2006

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 Te. V) Large Hadron Collider (14 Te. V)

How To Study Particle Physics? • Astrophysical accelerators are known to accelerate particles to at least ~1020 e. V (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

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)

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? !

Tools of the Trade: The First Generation AMANDA: • Below ~2 kilometers of Antarctic ice • Optical Cerenkov, E , th~20 -30 Ge. V • 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

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 6 x 10 -8 Ge. V cm-2 s-1

Tools of the Trade: The First Generation Successes of AMANDA • Atmospheric neutrino spectrum measured to ~100 Te. V; consistent with theoretical expectations • Sensitivity to diffuse neutrino flux in 100 Ge. V-100 Pe. V range approaching 10 -7 Ge. V cm-2 s-1 sr-1 • Nearing theoretical expectations for astrophysical sources

Tools of the Trade: The First Generation RICE • Array of radio antennas co-deployed with AMANDA • Effective Volume of ~1 km 3 at 100 Pe. V; several km 3 at 10 Ee. V • Limits on diffuse neutrino flux in 200 Pe. V-200 Ee. V range of 6 x 10 -7 Ge. V cm-2 s-1 sr-1 • Future radio deployments with Ice. Cube promising Anita-Lite • Balloon-based radio antennas • Limits on diffuse flux above ~Ee. V of ~10 -6 Ge. V cm-2 s-1 sr-1 • Full Anita flight in 2006 sensitivity of ~10 -8 Ge. V/cm 2 s sr observe the first UHE neutrino?

Tools of the Trade: The Next Generation Ice. Cube • Full Cubic Kilometer Instrumented Volume • 9 (of 80) strings currently deployed; 14 planned for next year

Tools of the Trade: The Next Generation Ice. Cube • 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

Tools of the Trade: The Next Generation Ice. Cube • 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) Ice. Cube

Tools of the Trade: The Next Generation Ice. Cube • 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! Ice. Cube

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 Ge. V, 3000 km 2 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

Cosmic vs. Manmade Accelerators Energy Reach • At modest energies (~Te. V and below), accelerator experiments constrain many exotic physics scenarios • Above ~Te. V, particle physics is very poorly constrained • Cosmic ray spectrum extends (at least) to ~1011 Ge. V • Neutrinos are expected to be produced up to similar energies 1011 Ge. V neutrino + target proton ECM~300 Te. V 1010 Ge. V neutrino + target proton ECM~100 Te. V 109 Ge. V neutrino + target proton ECM~30 Te. V 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

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 100 s or 1000 s of Mega-parsecs distant A new window into exotic physics!

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

Te. V Scale Gravity • ECM ~ MPL, KK Graviton Exchange • ECM > MPL, String Resonances • ECM >> MPL, Black Hole Production

Kaluza-Klein Graviton Exchange • Model dependent cross sections • Calculations not reliable very far above E ~Te. V 2/2 mp~Pe. V Alvarez, Halzen, Han, Hooper, PRL, hep-ph/0107057

Te. V String Resonances • Only mild model dependence (Chan Patton factors) • Valid at all energies Friess, Han, Hooper, PLB, hep-ph/0204112

Microscopic Black Hole Production • At center-of-mass energies above fundamental Planck scale, black holes can be formed • Naïve picture suggests geometric cross section, ~ R 2 sch • Te. V black holes rapidly Hawking radiate • Valid at all energies; dominant contribution at ECM>>Te. V See: Anchordoqui, Feng, Goldberg and Shapere, PLB, hep-ph/0311265; PRD, hep-ph/0307228; PRD, hep-ph/0112247

Microscopic Black Hole Production • Likely the most easily observed signature of Te. V 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

Te. V Scale Gravity At Pierre Auger • Sensitive to neutrinos above ~100 Pe. V • 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 Te. V string resonances

Te. V 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 Earth’s 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

Te. V 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

Te. V 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

Te. V Scale Gravity At Pierre Auger • Te. V string resonances enhance QH rate, suppress ES rate Model QH/ES Ratio SM 0. 05 2 Te. V 0. 11 1 Te. V 2. 1 Anchordoqui, Han, Hooper, Sarkar, Astropart. Phys. , hep-ph/0508312

Te. V Scale Gravity At Pierre Auger • Auger is very sensitive to microscopic black hole production Model (MPL) QH/ES Ratio SM 0. 05 8 Te. V 0. 10 3 Te. V 0. 54 2 Te. V 2. 0 1 Te. V 36. 0 Anchordoqui, Han, Hooper, Sarkar, Astropart. Phys. , hep-ph/0508312

Te. V Scale Gravity At Ice. Cube • Most sensitive in the Te. V-Pe. V 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

Te. V Scale Gravity At Ice. Cube • Cross section measurements possible by comparing upgoing to downgoing events (absorption in the Earth) Alvarez, Han, Halzen, Hooper, PRL, hep-ph/0107057

Te. V Scale Gravity At Ice. Cube • Cross section measurements possible by comparing upgoing to downgoing events (absorption in the Earth) Energy range suitable for RICE! See, Hussain and Mc. Kay, PLB, hep-ph/0500183 Alvarez, Han, Halzen, Hooper, PRL, hep-ph/0107057

Te. V Scale Gravity At Ice. Cube • 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 Pe. V (5 Te. V C of M) Hooper, PRD, hep-ph/0203239

Te. V Scale Gravity At Ice. Cube • Even more information can be extracted using entire angular distribution of events Alvarez, Han, Halzen, Hooper, PRD, hep-ph/0202081, Jain, Kar, Mc. Kay, Panda, Ralston, PRD, hep-ph/0205052

Te. V Scale Gravity At Ice. Cube 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

Other Strongly Interacting Physics Scenarios For Neutrino Astronomy SM Electroweak Instanton Induced Interactions • Transitions between degenerate vaccua (with different B+L) are possible within the context of the SM • Below “Sphaleron” mass, MW/ W ~ 8 Te. V, 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

Electroweak Instantons at Auger • Substantial deviations expected above 1010 Ge. V • 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

Long Baseline Measurements • Colliders probe phenomena at (very) sub-second scales • Solar neutrino experiments probe scales of /m ~ 10 -4 s/e. V (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 Te. V / E ) • Powerful test of neutrino decay, quantum decoherence, Lorentz violation, …

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 • Caveat: Energy losses in source might modify (Kashti and Waxman, astro-ph/0507599)

Neutrino Decay • Scenario 1: All mass eigenstates decay to lightest mass eigenstate (or invisible) with normal hierarchy; flavor ratios of: e: : = cos 2 S : (1/2) sin 2 S ≈ 6 : 1 • Scenario 2: Same, but with inverted hierarchy: e: : = U 2 e 3 : U 2 3 ≈ 0 : 1 • Scenario 3: (only) 3 decays invisibly; with normal hierarchy, flavor ratios of: e: : ≈ 2 : 1 • Many other scenarios possible

Measuring Neutrino Flavor Ratios • With Ice. Cube: -Muons/showers roughly translates to / tot -Tau unique events provide confirmation Beacom, Bell, Pakvasa, Hooper and Weiler, hep-ph/0307025 • With Auger: -ES/QH roughly translates to / tot -Low event rate yields less sensitivity Anchordoqui, Han, Hooper and Sarkar, hep-ph/0508312

Flavor Ratios At Ice. Cube • Ratio of muons to showers translates to flavor ratio (Example: E 2 d. N/d. E = 10 -7 Ge. V cm-2 s-1, 2 x 10 -8 Ge. V cm-2 s-1) Beacom, Bell, Pakvasa, Hooper and Weiler, hep-ph/0307025

Flavor Ratios At Pierre Auger • Deviations in QH/ES translate to deviations in flavor ratios Anchordoqui, Han, Hooper and Sarkar, hep-ph/0508312

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 • This is the similar to the prediction from pion decay (after oscillations), and thus is very difficult to distinguish

Quantum Decoherence • To probe effects of quantum decoherence, another (nonpion) 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 • Potentially distinguishable from quantum decoherence effects Hooper, Morgan and Winstanley, PLB, hep-ph/0410094

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 Ee. V range at 4 -4. 5 significance (4% of flux) • Supporting data from Sugar, as well as galactic plane excess seen by Fly’s Eye Anchordoqui, Goldberg, Gonzalez-Garcia, Halzen, Hooper, Sarkar and Weiler, PRD hep-ph/0506168

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

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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