1 / 24

Capabilities of a Hybrid Optical-Radio-Acoustic Neutrino Detector at the South Pole

Capabilities of a Hybrid Optical-Radio-Acoustic Neutrino Detector at the South Pole. Justin Vandenbroucke Sebastian B öse r Rolf Nahnhauer Dave Besson Buford Price ARENA Workshop, DESY-Zeuthen, May 19, 2005. The goal.

tiana
Download Presentation

Capabilities of a Hybrid Optical-Radio-Acoustic Neutrino Detector at the South Pole

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Capabilities of a Hybrid Optical-Radio-Acoustic Neutrino Detector at the South Pole Justin Vandenbroucke Sebastian Böser Rolf Nahnhauer Dave Besson Buford Price ARENA Workshop, DESY-Zeuthen, May 19, 2005

  2. The goal • ~EeV neutrinos, particularly GZK neutrinos, could be a valuable source for astro- and particle physics • IceCube or Auger could detect ~1 GZK neutrino per year, but • 10-100 GZK events (eg 10 yrs @ 10/yr) would give a quantitative measurement including energy, angular, and temporal distributions allowing tests of cosmic ray production models and new physics [cross section measurements! See A. Connolly’s talk] • Other projects (e.g. ANITA, SalSA, …) are actively seeking this goal.Should IceCube also seek it? • If acoustic ice properties are measured to be as good as predicted [S. Boeser’s talk], proceed from a South Pole Acoustic Test Setup to a hybrid detector (IceCube + Acoustic + Radio EeV Neutrino Array)

  3. Why a hybrid extension to IceCube (in addition to ANITA, SalSA et al)? • Like Auger and detectors at accelerators, use >1 technique monitoring the same interaction region • Difficult to reach 10 GZK events/yr with optical alone • No (?) scattering for radio and acoustic • At ~EeV, radio and acoustic methods could outdo optical • Detecting events in coincidence between 2-3 methods more convincing than detections with one method alone • Coincident events allow calibration/cross-check of the radio and acoustic methods with the optical method • Hybrid reconstruction gives superior energy and direction resolution than with one method, or allows reconstruction of coincident events that cannot be reconstructed with one method alone • Extended IceCube could be a sensitive neutrino telescope at all cosmic energies? • [Halzen & Hooper “IceCube Plus” JCAP 01 (2004) 002]

  4. EeV fluxes • Z-burst and topological defect models predict large EeV fluxes but are observationally disfavored • The GZK flux is a fairly conservative EeV source • Optimize the hybrid detector for a high rate of events from the Engel, Seckel, Stanev (ESS) GZK flux model, but • Do not only seek GZK events. Measure whatever is there at ~EeV and design to detect events over a wide energy range • Then the IceCube Observatory measures the neutrino spectrum over ~10 orders of magnitude!

  5. The ESS GZK flux model zmax = 8, n = 3 Unclear which  to use (unclear effect on star formation rate) For now use the lower rate

  6. Simulation of hybrid-detector GZK event rate (first pass: keep it simple) • Assume exactly the 2 downgoing neutrinos make it to the detector, independent of energy, within our 1016 - 1020 eV range • For radio and acoustic: assume the LPM effect completely washes out signal from EM component of e CC events, so • For all flavors and both CC and NC we detect only the hadronic shower, with • Esh = 0.2E for all events, independent of energy • Generate incident directions uniformly in downward 2, and vertices uniformly in a fiducial cylinder • At each of a set of discrete energies, expose each of the 3 detector components to the same set of Monte Carlo events

  7. An example hybrid array Optical: 80 IceCube + 13 IceCube-Plus holes at a 1 km radius Radio/Acoustic: 91 holes, 1 km spacing; ~5 radio + ~200 acoustic receivers per hole

  8. Optical simulation • Check Halzen & Hooper’s rate estimate with standard simulation tools; run a common event set through optical, radio, and acoustic simulations • For now, only simulate the muon channel (showers in progress) • Use standard AMANDA simulation tools: muon propagation, ice properties, detector response • Define a coincidence to be hits at 2 out of 5 neighboring modules on one string within 1000 ns • Require 10 coincidences in the entire array within 2.5 s • For optical-only events, require > 182 channels hit (a muon energy cut proxy) to reject atmospheric background • Do not apply Nch requirement when seeking coincidence with radio or acoustic

  9. Radio simulationUsing RICE MC - see D. Besson’s talk • Dipole antennas in pairs to resolve up-down ambiguity • 30% bandwidth, center frequency = 300 MHz in air • Effective height = length/ • Radio absorption model: based on measurements by Besson, Barwick, & Gorham (accepted by J. Glac.) • Trigger: require 3 pairs in coincidence • Use full radio MC

  10. Interlude Notes on acoustic neutrino detection in ice Reminder: Signal ~10x higher than water [P.B. Price] Noise >10x lower? [limited by sensor self-noise, not ambient?]

  11. Sound velocity profile in South Pole ice Sound channel ridge measured in firn (J. Weihaupt) Firn (uncompactified snow) in top 200 m: Vsound increasing with density refraction. Rcurvature ~200 m! predicted in bulk (using IceCube-measured temperature profile and A. Gow temperature coefficient) - measure with SPATS?

  12. Acoustic ray traces 1 m depth: Only downward ~10° penetrate source in firn 10 m depth: Only downward ~40° penetrate source in bulk

  13. Strong refraction in firn Acoustic: upward Radio: downward [D. Besson] Signals always bend toward minimum propagation speed, but: Sound abhors vacuum [c =0] Radio adores vacuum [c = 3e8 m/s]

  14. Predicted depth (temperature)-dependent acoustic absorption at ~10 kHz See P.B. Price’s talk: absorption frequency-independent but temperature (depth)-dependent In simulation, integrate over absorption from source to receiver

  15. Acoustic detection contours in ice Contours for Pthr = 9 mPa: raw discriminator, no filter

  16. Acoustic event rate depends on threshold (noise level) and hole spacing Trigger: ≥ 3 strings hit ESS GZK events per year: Need low-noise sensors (DESY) and low-noise ice (South Pole?) Frequency filtering may lower effective noise level For hybrid MC, set threshold at 9 mPa = a few sigma

  17. Acoustic neutrino direction and vertex reconstruction - With 3 strings hit, it’s easy: - Fit a plane to hit receivers. - Upward normal points to neutrino source. - Within that plane, only 2D vertex reconstruction is necessary, done by intersecting 2 hyperbola determined by 3 arrival times.

  18. Acoustic angular resolution Resolution due to pancake thickness: expose array (0.5 km hole spacing) to isotropic 1019 eV  flux, determine hit receiver, fit plane to hit receivers, compare plane normal with true MC neutrino direction: Result (not including noise hits):

  19. Hybrid reconstruction • Typical UHE vertices are outside the optical detector - optical might measure muon energy at detector but needs muon energy at vertex and doesn’t know the vertex • Get the vertex from radio/acoustic shower detection. Combining them gives good energy and pointing resolution • Very little radio or acoustic scattering - hits are always prompt and timing information straightforward • So hybrid sets of 4 receivers hit (e.g. 3+1, 2+2, 2+1+1) may be sufficient for vertex reconstruction using time differences of arrival • Different radiation patterns between the methods leads to non-degenerate hit geometry for good reconstruction • Not a problem that timing resolutions are different:

  20. Can we combine acoustic and radio timestamps on equal footing? Problem: Acoustic timing resolution (pulse width) ~10 us. Radio ~ few ns Can we combine them for reconstruction? Yes! [R. Porrata]: convert times to distances using respective signal speeds. Then they have the same resolution and the analytical TDOA matrix equations (with SVD) can be used. Verification with simulated hybrid event set in progress…

  21. Optical, radio, acoustic independent effective volumes Preliminary!

  22. Coincident effective volumes Preliminary! RA, AO, ORA curves in preparation

  23. Event rates • cf. Halzen & Hooper IceCube-Plus muon rate: 1.2 • These results depend on a wide parameter space: • - Acoustic ice properties and noise level • Optimizing the array (eg hierarchical spacing such as adding R/A receivers to the optical holes) could increase rates • Adding the optical shower channel will increase rates. • First results are encouraging

  24. O(91) radio/acoustic strings for a fraction of the IceCube cost? • Holes: ~3 times smaller in diameter and ~1.5 km deep • Don LeBar (Ice Coring and Drilling Services) drilling estimate: $33k per km hole length after $400k drill upgrade (cf. SalSA ~$600k/hole) • Sensors: simpler than PMT’s • Cables and DAQ: Only ~5 radio channels per string (optical fiber). ~200 acoustic modules per string, but: • Cable channel reduction: Send acoustic signals to local in-ice DAQ module (eg 16 sensor modules per DAQ module) which builds triggers and sends to surface • Acoustic bandwidth and timing requirements are easy (csound ~10-5 clight!) • Acoustic data bandwidth per string = 0.1-1 Gbit, could fit on a single ethernet cable per string

More Related