rice = “radio ice cherenkov experiment” the problem: –mean free path of uhecr’s (e>10 20...
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RICE = “Radio Ice Cherenkov Experiment”
• The Problem:– Mean free path of UHECR’s (E>1020 eV) limited by photoproduction on CMB:
pCMBp(“GZK”)
– m.f.p. ~ 10 Mpc only sensitive to processes in last 30Myr!
– At lower energies (1017-18 eV), reactions such as pCMBpe+e-
– Similar limitations for gamma-ray astronomy (pair production on CMB)
• A solution (kinda): neutrino astronomy!– However, low fluxes at ZeV (1/km2/century) necessitate neutrino targets of
scale 100-1000 km3
• “Conventional” technology: PMT’s (AMANDA, Baikal, Antares, IceCube, Nestor, NEMO, SuperK) limited by absorption/scattering length of PMT photons (~40 m)
• Radio attenuation length in-ice2 km (DATA!); acoustic attenuation length estimated at 10 km!! (SPATS measurements this year)
measure radio-wavelength rather than optical-wavelength portion of Cherenkov radiation: “Radio Ice Cerenkov Experiment”
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Radio Detection of High Energy Neutrinos
Neutrino collision
Receivers (Rx)
Cones are +/- 3dB
Neutrino enters ice
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RICE-AMANDA-SPASE (South Pole)
RICERICE
SPASE
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17 in-ice half-wave ‘fat’ dipole antennas (400 MHz)
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Effective Volume Systematics:
Signal Strength
Transfer Function
Re(epsilon) (=n)
Im(epsilon) (=Latt)
Birefringence
System Total Gain
Livetime
Software Cuts
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Diffuse Neutrino Search (1999-2005)
Phys.Rev. D73 (2006) 082002
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No UHE neutrinos yet observed compare
with theoretical predictions for how
many neutrinos RICE should have observed,
given sensitivity of experiment and radio
transmission properties of ice
GZK nu models
Diffuse GRB flux
Two representative models: ESS/WB. Both bootstrap from observed charged CR spectrum and estimate neutrino flux (WB assumes all UHECR’s from GRB’s)
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Caution on presentation
• RICE uses a 95% CL upper limit convention– (vs. conventional 90% CL upper limit convention)
• ESS GZK-flux depends on several parameters– RICE upper limits based on most conservative (I.e., lowest flux –
not typical)
• Upper limits as a function of energy are largely for presentation only – sans energy resolution, only integral matters!
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Volumosity? Voluminosity? Your model x our exposure
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During RICE livetime, approximately 120 GRB’s in southern hemisphere w/ `nearly’ complete info. Only 5 with redshift information:
Astro-ph/0605480 (accepted Astropart. Phys.)
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RICE acceptance favors neutrinos incident along horizon at near-glancing angles
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From photon flux to neutrino flux
• Assume photon flux from decay; relate photon flux to neutrino flux (from + decay) via Waxman-Bahcall.
Note: Limits generally weak (preferentially high-redshift sample)
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The future VISION
• South Polar ice is unique!– Optical clarityIceCube (TeV threshold)
– Radio clarityRICE (10 PeV threshold)
– Purest water on planet & high hydrostatic pressureno impurities or defects in ice latticeclear propagation of acoustic wavesacoustic detection of sound wave produced by neutrino interactions! (EeV threshold)
• South Pole is only place that can support all three neutrino detection technologies
• 2006-2010: During bulk of IceCube hole drilling, co-deploy radio & acoustic modules into IceCube holes– 1 km deployment scale x10 over current RICE
• >2010: Dedicated hole-drilling (much cheaper holes!) for acoustic&radio over 10 km deployment scale
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GZK detections / hybrid dector (c. 2010)
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KU
The Askaryan UnderIce Radio Array = THE BRIGHT, SHINING FUTURE!
•Develop technology for larger radio array
•Further map out the radio properties of South Pole Ice
•Build intermediate detector with improved effective volume over RICE
06-07: codeploy with IceCube in 3-4 holes.
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•spare attachment points on IceCube cable (1450m, 2450m, center of the string, an additional breakout could be added a 1400m for minimal cost) could accommodate a “DRM”
•additional connectors added to pressure sphere would connect each of four antennas to form a cluster
•grouping antennas in clusters at 10m separation, gives enough timing difference to distinguish backgrounds, thereby allowing a drop in thresholds
•antenna calibration unit provided calibration and ice property studies
•signal conditioning and amplification happen at the front end, signal is digitized and triggers formed in DRM
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Separate cable taped to IceCube cable would allow deployment at shallow depths where rf tranparency is highest
Same paradigm as 05-06 deployment--shown to work
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Search for highly ionizing magnetic monopoles in Antarctic ice (Daniel Hogan, KU UG)
• Relativistic magnetic monopole generates photon swarm.
• Weizsäcker-Williams energy spectrum:
Jackson, 1963, etc.
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Energy Loss in Earth: ionization+brem+pair production+ photonuclear
Razzaque et al., 2002
3/1
242 183ln
137
4
ZA
rzZNE
dx
dE eo
rad
1
2ln4
22222
I
mvzmcr
A
ZN
dx
dEeo
ion
Check total energy loss against mmc package (dima chirkin) and also seckel, weiler&wick calculation
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Energy Loss in Earth
• Chord Length through Earth:
• Loses energy as z=1/(2α) electric charge
sin
2sin rl
r
θ
lr
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Preliminary monopole flux limits (+/- x2)