1. ANITA: Results from ANITA-lite test flight and warming up for this year’s ANITA flight Amy Connolly for the ANITA Collaboration International Tau Neutrino Workshop Beijing, China April 26 th, 2006

2. ANITA (ANtarctic Impulsive Transient Antenna) Each flight ~15 days – or more 32 quad- ridged horn antennas, dual- polarization, with 10 ± cant Downgoing - not seen by payload Upcoming – absorbed in the earth ! ANITA sees “skimmers”.

3. The ANITA Collaboration University of California at Irvine Irvine, California Ohio State University Columbus, Ohio University of Kansas Lawrence, Kansas Washington University in St. Louis St. Louis, Kansas University of Minnesota Minneapolis, Minnesota University of Delaware Newark, Delaware University of California at Los Angeles Los Angeles, California Pennsylvania State University University Park, Pennsylvania University of Hawaii at Manoa Honolulu, Hawaii Jet Propulsion Laboratory Pasadena, California

4. ANITA-lite 2003-2004 Practice run with 2 antennas – piggybacked on TIGER 18 day flight Virtually every subsystem planned for ANITA tested Calibration pulses sent to payload from ~200 km away Payload landed near Mawson Station Australians have helped us retrieve the payload

5. Could verify that a signal comes from the ice Help discern near, far events ! for energy measurement, for example Anita-lite (cont) Angular resolution measured: ANITA-lite:  t)=0.16 ns !  =2.3 ± Full ANITA: expect  t)=0.1 ns →   =1.5°,  =0.5° Flying two antennas with angular separation 22° allowed us the measure ANITA’s angular resolution Compare time of arrival of calibration pulses  t (ns)  0.16 ns Remember that this is resolution on RF direction

6. ANITA Signal Acquisition Trigger: Signal divided into frequency sub bands –Powerful rejection against narrow bandwidth backgrounds –Multi-band coincidence allows better noise rejection 8 channels/ antenna Require 3/8 channels fire for antenna to pass L1 trigger Global trigger analyzes information across antennas For Anita-lite, no banding: 4 channels, require 3-fold coincidence

7. Anita-lite Two independent analyses modeled time dependent pulse on measured noise Designed cuts to select Askaryan-like events –# cycles in a waveform –Integrated power –Time coincidence between channels –Reduce noise with cross-correlation analysis Both analyses find analysis efficiency ~50% ANITA-lite strongly constrains Z-burst models ES&S baseline (min) Kalashev, et al., saturate all bounds (max)

8. ANITA Simulation Two major simulation efforts: Hawaii (Gorham) and UCLA (Connolly) Signal in frequency domain, but moving to time domain Secondary interactions included Ray tracing through ice, firn (packed snow near surface) Attenuation lengths are depth and frequency dependent Fresnel coefficients Include surface slope and adding surface roughness All 32 quad ridged horn antennas arranged in 3 layers as they are on the payload Measured antenna response Models 3-level trigger system Weighting accounts for neutrino attenuation through Earth ice [S. Barwick] Complementary simulations being developed – essential!

9. Characterizing ANITA’s Sensitivity Position of Interactions Depth of Interactions meters e  Neutrino Flavor Angle wrt Surface  (°) 10 20 eV 10 18.5 eV 10 20 eV 10 18.5 eV 10 20 eV downgoing 10 20 eV

10. Possibility of Seeing Multi-Pulse Events E =10 18.5 E =10 20.0 Could see multi-pulse events from interaction and subsequent –Decay –Photonuclear interaction –Brem, pair production However, some may escape the earth before second interaction Sensitivity to “multi bangs” is under investigation

11. ANITA not nominally sensitive to -N cross section since –Measure RF direction, not direction –Unless we are lucky, do not expect a large sample of events for a shape analysis However, one recent idea may give us a handle on the -N cross section… Cross Section

12. Reflected Rays Reflected Rays Work by: S. Barwick, F. Wu from University of California at Irvine TIR Micro-black holes at ANITA Energies Could measure cross section from relative rates of direct (far) to reflected (near). [S. Barwick] [S. Barwick & F. Wu] ANITA could (possibly) detect events where a signal is reflected from ice-bedrock interface Signals suffer from extra attenuation through ice and losses at reflection At SM  ’s, reflected rays not significant At large cross-sections, short pathlengths → down-going neutrinos dominate ! reflected rays important  SM 10 100 1000 1 Direct rays Reflected rays Events

13. Uncertainty at ice-bedrock interface being investigated: under-ice topologies, radar reflectivities, use Brealt code to study interfaces quantitatively Skymaps For each balloon position: After a complete trip around the continent, cover all Right Ascensions If we could observe reflected rays, could view more sky! 10% reflected power

14. ANITA Engineering Flight, August 2005 August 29,2005, Ft. Sumner New Mexico –All subsystems represented (two dual-pol. antennas only, to limit landing damage) –8 m tall Gondola performed perfectly –No science possible due to EMI (Cannon AFB in nearby Clovis), but waveform recording worked well –Full ANITA payload now cleared for Antarctica Azimuth to Clovis, deg. Average power

15. Stanford Linear Accelerator Calibration ANITA is going to SLAC for 2 weeks of beam time in End Station A during June 2006 –Full-up system calibration with actual Askaryan impulses from Ice –Uses one of SLAC’s largest experiment halls (End Station A) 250’x200’ w/ 50’ crane –Build 1.6 x 1.6 x 5 m ice cube by stacking blocks, “zamboni” each surface before stacking, refrigerate Will provide amplitude, phase, polarization, temporal, and spectral calibration of the antenna array, including all structure Excellent opportunity to calibrate the simulation Payload will be shipped to Antarctica from California after the SLAC test

16. Summary Anita-lite test flight a success, ruled out Z-burst models Simulations are mature, constantly improving –Valuable tool for testing ideas, assessing sensitivity Engineering flight showed full system working perfectly Full system calibration of the system in June First physics flight at the end of this year Ready for some neutrinos Thank you to the organizers of the conference!

18. Since ANITA is near the threshold of GZK neutrino detection –Necessary to reduce systematics as much as possible –Make the most of our data set Requires detailed simulation of –Noise, Signal, and Trigger response in the time domain Simulating noise may prevent having to sacrifice some of the data for an “unblinded” sample May help to understand efficiency for multi-pulse events –Surface roughness May affect properties of the signal Region of sensitivity Keys to Improving Sensitivity

19. Moving Trigger Simulation from Frequency Domain to Time Domain Amy Connolly and Stephen Hoover, graduate student Currently, simulations model the trigger using only the frequency profile: –Integrate total peak voltage read by each channel in frequency domain –Pick a noise voltage from Gaussian distribution, add to signal –Compare that signal + noise to RMS noise in each channel –Threshold = 2.3 x V RMS True system integrates signal in time domain –We have begun to build tools for a time domain simulation

20. What Narrow-Band Noise Looks Like in the Time Domain Essentially, the noise (at ~center frequency f 0 ) is acting as a carrier, to the “signal” (the bandwidth) Noise only (no signal) in the band from 350 to 450 MHz: Plot by Stephen Hoover 1/BW # of wiggles/envelope ¼ f 0 / BW a Simulation Generated by summing sin waves flat in frequency within the band, with random phases

21. Properties of Noise Sampled at Small Time Intervals The envelopes sampled at small intervals follow a Rician distribution But instantaneous voltage sampled at small intervals follows a Gaussian a (Volts) V (Volts) Pure noise Noise + Signal (Signal=2 V RMS noise ) Pure noise Noise + Signal (Signal=2 V RMS noise ) Arbitrary Units

22. ANITA Trigger Integrates Over a Longer Time Interval Model the tunnel diode as an integrator with exponential response (  =3.75 ns) Deadtime once a trigger is generated is 50 ns (flight system will have 12 ns) Find good agreement with lab measurements Encouraged by this, we are proceeding to model the tunnel diode’s response to an Askaryan signal Tunnel Diode Output Single Channel Trigger Rate Model Measurements

23. Modeling the Time-Dependent Pulse Theorists calculate frequency-dependent electric field and cone width of signal emitted from the interaction (J. Alvarez- Muniz, et al., Phys.Rev.D62:063001,2000; J. Alvarez-Muniz, et al., Phys.Lett.B411:218-224,1997) Creating efficiency curves for signals + noise at the payload Will test time domain simulation against SLAC calibration data Take Fourier transform of frequency profile to find V(t)

24. Surface roughness & sastrugi But: Google images are a highly biased sample! Slide by Peter Gorham, University of Hawaii

25. Traverse data on sastrugi Wavelengths in ANITA’s band are ~30 cm to 1.5 m Verticle feature size ~ wavelength Lateral feature size ~ few wavelengths

26. Studying the Effect of Surface Roughness on Signal Transmission Brian Daub, Erik Everson, Mark Harrison, Martin Griswold (undergraduates), Amy Connolly and David Saltzberg We have scaled down the problem to lab-bench size Purchased diffusers with various “grits” Use lens to make ~2 o divergence Measure transmission vs. incident angle Laser, white light

27. Roughness of Diffusers GritAve. Height (  ) Ave. Separation 4004.43 10002.82.5 15001.11.5 Measured feature sizes with high power microscope Within order of magnitude of 632 nm laser, but we’d like to go finer 1000 grit

28. Features of Transmission from Rough Surfaces Signal is diffused over ~ § 10 deg. –Narrower at smaller angles of incidence Transmission tends toward the normal –Closer to specular at smaller angles of incidence Incident angle on diffusing surface = 39°,Grit 1500 Angle off specular (deg.) Normalized Power Towards the normal Grit 1500 shows feature sizes closest to wavelengths measured with ANITA ANITA sensitive to events near TIR Total internal reflection (TIR) glass! air at 42° “Specular” ray: follows Snell’s law

29. Guided by Measurements, Simulating Impact of Roughness Balloon observes not just one “ray” but many Sum intensity measured by balloon With roughness, a signal would contain contributions across a section of the Cerenkov cone

30. Some Observations Regarding Roughness and ANITA Spreading out of the transmitted signal will clearly reduce the observed signal for events where the specular ray sits at the peak of the Cherenkov cone Ability to observe an entire section of the Cherenkov cone increases sensitivity to events where specular is off-peak Offset of transmission peak toward the normal may increase our sensitivity to events closer to the balloon Roughness may allow us to observe events that would have been TIR (Nieto-Vesperinas,Sanchez-Gil, J.Opt.Soc.Am.A/Vol.9,No.3/March 1992) Plan to transmit from a borehole to receivers on surface, ANITA payload- measure effect of roughness to compare Ordered rounded glass to get to higher incident angles Begun to grind our own diffusers to get to finer grits and closer to the level of Antarctic roughness