ANITA: Results from ANITA- ANITA: Results from ANITA- lite test flight and warming lite test flight and warming up for this year’s ANITA up for this year’s ANITA flight flight Amy Connolly for the ANITA Collaboration International Tau Neutrino Workshop Beijing, China April 26 th , 2006
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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.
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ANITA: Results from ANITA-lite test ANITA: Results from ANITA-lite test flight and warming up for this year’s flight and warming up for this year’s
ANITA flightANITA flight
Amy Connollyfor the ANITA Collaboration
International Tau Neutrino WorkshopBeijing, ChinaApril 26th, 2006
• 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
Anita-liteAnita-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
ES&S baseline (min)Kalashev, et al., saturate all bounds (max)
ANITA SimulationANITA 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!
• 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
• 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
Reflected RaysReflected RaysWork 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 10001
Direct rays
Reflected rays
Eve
nts
Uncertainty at ice-bedrock interface being investigated: under-ice topologies, radar reflectivities, use Brealt code to study interfaces quantitatively
SkymapsSkymapsFor 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
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.A
vera
ge p
ow
er
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
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!
• 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 SensitivityKeys to Improving Sensitivity
Moving Trigger Simulation from Frequency Domain to Time DomainAmy 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 VRMS
• True system integrates signal in time domain – We have begun to build tools for a time domain simulation
What Narrow-Band Noise Looks Like in the Time Domain
Essentially, the noise (at ~center frequency f0) 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 f0 / BW
a
Simulation
Generated by summing sin waves flat in frequency within the band, with random phases
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 VRMS
noise)
Pure noise
Noise + Signal(Signal=2 VRMS
noise)
Arb
itrar
y U
nits
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 SingleChannel Trigger Rate
Model
Measurements
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)
Surface roughness & sastrugi
• But: Google images are a highly biased sample!
Slide by Peter Gorham, University of Hawaii
Traverse data on sastrugiWavelengths in ANITA’s band are~30 cm to 1.5 m
Verticle feature size ~ wavelength
Lateral feature size ~ few wavelengths
Studying the Effect of Surface Roughness on Signal TransmissionBrian 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 ~2o divergence• Measure transmission vs. incident angle• Laser, white light
Roughness of Diffusers
Grit Ave. Height ()
Ave.
Separation
400 4.4 3
1000 2.8 2.5
1500 1.1 1.5
• Measured feature sizes with high power microscope
• Within order of magnitude of 632 nm laser, but we’d like to go finer
1000 grit 1000 grit
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
Grit 1500, 70 Deg.
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
-40 -30 -20 -10 0 10 20 30 40
Angle off Specular
Norm
aliz
ed P
ower
Incident angle on diffusing surface = 39° ,Grit 1500
Angle off specular (deg.)
Nor
mal
ized
Pow
er
Towards the normal
Grit 1500 shows feature sizes closest to wavelengths measured with ANITA
ANITA sensitive to events near TIRTotal internal reflection (TIR) glass! air at 42°“Specular” ray: follows Snell’s law
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
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 anglesBegun to grind our own diffusers to get to finer grits and closer to the level of Antarctic roughness