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

ANITA ANITA (ANtarctic Impulsive Transient Antenna)(ANtarctic Impulsive Transient Antenna)

Each flight ~15 days –

or more

32 quad-ridged horn antennas, dual-polarization, with 10± cant

Downgoing - not seen by payloadUpcoming – absorbed in the earth

! ANITA sees “skimmers”.

The ANITA Collaboration University of California at Irvine

Irvine, California

Ohio State UniversityColumbus, Ohio

University of KansasLawrence, Kansas

Washington University in St. LouisSt. Louis, Kansas

University of MinnesotaMinneapolis, Minnesota

University of DelawareNewark, Delaware

University of California at Los AngelesLos Angeles, California

Pennsylvania State UniversityUniversity Park, Pennsylvania

University of Hawaii at ManoaHonolulu, Hawaii

Jet Propulsion LaboratoryPasadena, California

ANITA-lite 2003-2004ANITA-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

• Could verify that a signal comes from the ice

• Help discern near, far events ! for energy measurement, for example

Anita-lite (cont)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

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

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

• Both analyses find analysis efficiency ~50%• ANITA-lite strongly constrains Z-burst

models

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!

Characterizing ANITA’s Characterizing ANITA’s SensitivitySensitivity

Position of Interactions Depth of

Interactions

meters

e

NeutrinoFlavor

AnglewrtSurface

(°)

1020 eV

1018.5 eV 1020 eV

1018.5 eV

1018.5 eV

1020 eV

downgoing

1020 eV

Possibility of Seeing Multi-Pulse Events

E=1018.5

E=1020.0

• 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

• 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