ANITA: Results from ANITAlite test flight and warming up for this years ANITA flight

1
ANITA Results from ANITA-lite test flight and
warming up for this years ANITA flight
Amy Connolly for the ANITA Collaboration Interna
tional Tau Neutrino Workshop Beijing, China April
26th, 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
Anita-lite (cont)

• Flying two antennas with angular separation 22
  allowed us the measure ANITAs angular resolution
• Compare time of arrival of calibration pulses

?0.16 ns
Angular resolution measured ANITA-lite ?(?
t)0.16 ns ! ?(??)2.3 Full ANITA expect ?
(?t)0.1 ns ? ?(? ?)1.5, ?(??)0.5
? t (ns)

• Could verify that a signal comes from the ice
• Help discern near, far events ! for energy
  measurement, for example

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

ESS 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

Complementary simulations being developed
essential!
S. Barwick
9
Characterizing ANITAs Sensitivity
Position of Interactions
1020 eV
Depth of Interactions
1018.5 eV
1020 eV
Angle wrt Surface
Neutrino Flavor
1020 eV
meters
1018.5 eV
downgoing
1018.5 eV
1020 eV
m
t
?? ()
e
10
Possibility of Seeing Multi-Pulse Events

• Could see multi-pulse events from ? interaction
  and subsequent
• Decay
• Photonuclear interaction
• Brem, pair production
• However, some may escape the earth before second
  interaction

E?1018.5
E?1020.0
Sensitivity to multi bangs is under
investigation
11
Cross Section

• ANITA not nominally sensitive to n-N cross
  section since
• Measure RF direction, not n 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-N cross section

12
Reflected RaysWork by S. Barwick, F. Wu from
University of California at Irvine

• ANITA could (possibly) detect events where a
  signal is reflected from ice-bedrock interface

• At large cross-sections, short pathlengths ?
  down-going neutrinos dominate ! reflected rays
  important

S. Barwick F. Wu
Direct rays
Events
Micro-black holes at
ANITA Energies
S. Barwick
Reflected rays

• Signals suffer from extra attenuation through
  ice and losses at reflection
• At SM ? s, reflected rays not significant

1
100
10
1000
?/?SM

• Could measure cross section from relative rates
  of direct (far) to reflected (near).

13
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
Uncertainty at ice-bedrock interface being
investigated under-ice topologies, radar
reflectivities, use Brealt code to study
interfaces quantitatively
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

Average power
Azimuth to Clovis, deg.
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 SLACs largest experiment halls (End
  Station A) 250x200 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!
17
(No Transcript)
18
Keys to Improving Sensitivity

• 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

19
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

20
What Narrow-Band Noise Looks Like in the Time
Domain
Noise only (no signal) in the band from 350 to
450 MHz
Simulation
Generated by summing sin waves flat in frequency
within the band, with random phases
1/BW
a
of wiggles/envelope ¼ f0 / BW
Plot by Stephen Hoover
Essentially, the noise (at center frequency f0)
is acting as a carrier, to the signal (the
bandwidth)
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
Pure noise
Pure noise
Noise Signal
Arbitrary Units
(Signal2 VRMSnoise)
Noise Signal
(Signal2 VRMSnoise)
a (Volts)
V (Volts)
22
ANITA Trigger Integrates Over a Longer Time
Interval

• Model the tunnel diode as an integrator with
  exponential response (t3.75 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 diodes 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.D62063001,2000 J. Alvarez-Muniz, et
  al., Phys.Lett.B411218-224,1997)

Take Fourier transform of frequency profile to
find V(t)

• Creating efficiency curves for signals noise at
  the payload
• Will test time domain simulation against SLAC
  calibration data

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 ANITAs 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 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

27
Roughness of Diffusers
1000 grit
1000 grit

• Measured feature sizes with high power microscope
• Within order of magnitude of 632 nm laser, but
  wed like to go finer

28
Features of Transmission from Rough Surfaces
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
Snells law

• 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

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