ANITA: Hunting for Ultra-High Energy Neutrinos in Antarctica Ryan - PowerPoint PPT Presentation

ANITA: Hunting for Ultra-High Energy Neutrinos in Antarctica Ryan Nichol

Outline • Timeline – From Austria in 1912 to Antarctica in 2006/8 • Motivation – For Astronomers, Astrophysicists and Particle Physicists • Detection – Problem of size – Askaryan effect • ANITA – Why Antarctica – Detector Concept – Results • Future Prospects 2

Brief scientific timeline leading to ANITA Wilson and Wolfgang Pauli Penzias discover does “something the cosmic very bad”... he microwave postulates the background neutrino 1930 1965 1912 1962 Victor Hess Gurgen Askaryan discovers hypothesises cosmic rays, by coherent radio flying balloons emission from up to 3 miles particle cascades above Austria in dielectric media 3

Kamiokande, IMB ANITA-I launches and Baksan detect from Williams Field neutrinos from a in Antarctica nearby supernova 1987 2006 1966 1998 Super-Kamiokande Greisen, discover neutrinos Zatsepin & have mass. Using Kuzmin predict neutrinos produced the end of the by cosmic rays in cosmic ray the atmosphere spectrum 4

Why? 5

Why Ultra-High Energy Neutrinos? The Pretty Pictures Argument For Astronomers For Astrophysicsts Infrared X-Ray Neutrinos? Radio Optical Neutrinos can probe the distances and !"#$%&'&%('%)*"+,-)." /&'01%(%&*'%+ 21-+#"3'0-+($4."* energies that other particles can’t reach. The Particle 6

Aside -- The GZK Effect • Greisen-Zatsepin- Kuzmin (GZK) calculated cosmic rays above 10 19.5 eV should be slowed by CMB within 50MPc. p + ϒ CMB → Δ * → n + π + ➘ µ + + ν µ Auger 2007 ICRC Results ➘ e + + ν µ + ν e • Have Auger detected the GZK cut-off? 7

GZK Effect in Pictures + = “Guaranteed” Neutrino “Beam”! ν GZK Neutrinos Point Back to original proton p source 8 50Mpc Radius

Particle Physics with 300TeV (CoM) Neutrino Beam • Neutrino-nucleon cross Anchordoqui et al: hep-ph/0605086 section in new regime Large extra dimensions – Large extra dimensions Std. model – Micro blackholes GZK ! • Neutrino mixing: – z=1 is v. long baseline Anchordoqui et al. Astro-ph/0307228 9 Table from David Saltzberg

Case Study: SN1987A • 20-some neutrinos • Scientific output including – Neutrino mass limits – Supernova mechanics – + lots more 100 Annual Citations (from SPIRES) of SN 1987A Papers 90 80 70 Plots stolen from 60 Georg Raflett 50 40 30 20 10 0 10 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005

How can you do it? 11

A Problem of Size • Some Numbers: ~1 GZK neutrinos/km 2 /year @ 10 18 eV the ν-N interaction length ̃ 300km ∴ 0.003 neutrino interactions/km 3 /year • Need a huge detector volume (>>100 km 3 ) to ensure detection • Use naturally occurring medium – Transparent (to some signal) – Possibilities • Air, Ice, Salt, Water, The Moon 12

Possible Detection Methods µ • Optical Cherenkov – Mature field but not optical Incoherent Cerenkov scalable to huge volumes Coherent radio • Radio Cherenkov Cerenkov – Active field best candidate for first detection • Acoustic acoustic – Emerging field, with Coherent much R&D incoming neutrino • Other – Air showers 13

Radio Cherenkov -- The Askaryan Effect • In 1962 Gurgen Askaryan hypothesised coherent radio transmission from EM cascades in a dielectric: Typical Dimensions: e ± or ϒ L ≈ 10 m R Moliere ≈ 10 cm – 20% Negative charge excess: • Compton Scattering: ϒ + e -(rest) ⇒ ϒ + e - • Positron Annihilation: e + + e -(rest) ⇒ ϒ – Excess travelling with, v > c/n • Cherenkov Radiation: dP ∝ ν d ν – For λ > R emission is coherent, so P ∝ E 2shower 14

Experimental Verification • Askaryan effect experimentally confirmed in 2000 From Saltzberg, Gorham, Walz et al PRL 2001 • Use 3.6 tons of silica sand, brem photons to o • Using 3.6 Tonnes of sand – (like a big cat’s litter box) 15 on, 19 th September 2005 11

Also in Ice • ...so we took it to SLAC in summer 2006. • and built a 7.5 tonne block of ice 2 reference volts 1 0 ! 1 raw impulse response ! 2 partially deconvolved ! 3 ! 20 ! 15 ! 10 ! 5 0 5 10 15 20 25 30 time, ns 40 field strength, V/m/MHz 20 0 ! 20 raw RF Cherenkov ! 40 partially deconvolved ! 60 ! 20 ! 15 ! 10 ! 5 0 5 10 15 20 25 30 time, ns 16 From PRL 99, 171101 (2007)

Flashy Ice 17

ANITA 18

The ANITA Collaboration • • University of Hawaii at Manoa University of Kansas Honolulu, Hawaii, USA Lawrence, Kansas, USA • • University of California at Irvine University of Minnesota Irvine, California, USA Minneapolis, Minnesota, USA • • University of California at Los The Ohio State University Angeles Columbus, Ohio, USA Los Angeles, California, USA • Stanford Linear Accelerator • University College London Center London, UK Menlo Park, California, USA • • University of Delaware National Taiwan University Newark, Delaware Taipei, Taiwan • • Jet Propulsion Laboratory Washington University in St. Louis Pasadena, California, USA St. Louis, Missouri, USA 19

Why Antarctica? • It is the coldest, driest, windiest place on Earth • But... – Lots of Ice • Despite our best efforts • Over 4km thick in places – Also: • The only continent exclusively dedicated to scientific research • No indigenous (human) population – So relatively free of manmade noise 20 Ice depth data from BEDMAP consortium

ANITA • The ANtarctic Impulsive Transient Antenna – A balloon borne experiment • 32 dual polarization antennas • Altitude of 37km (120,000 ft) • Horizon at 700km • Over 1 million km 3 of ice visible 21

ANITA Electronics and Trigger • Need a low power (only solar energy), 90 channel, GHz bandwidth oscilloscope. L1 - Antenna L2 - Cluster L3 - Global • Split trigger and waveform paths • Use multiple frequency bands for trigger • ‘Buffer’ waveform data in switched capacitor array • Only digitise when we have a trigger 22

Up, up and away • The Balloon – Just 0.02mm thick – Takes 100 million litres of helium (and several hours) to fill 23

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The First Flight • Lasted 35 days (the record is 42) – Three and a half sort of polar orbits – Recorded over 8 million triggers • Maybe 1 or 2 neutrinos Fits inside the balloon at altitude 26

What Goes Up... • The Landing: – Initiated by detonating small explosive to separate from balloon – Descend gently on a parachute to the ground – Release parachute to prevent dragging • In 2006, BLAST was dragged for 100 miles (ending up in a crevice) • A few years ago one was dropped from 5000 feet Photos from Dana Braun 27

Event Display 28

Event Reconstruction Cross-Correlated Waveforms AB"F) A4) Calibration pulse Sum of x-corrs 10 7 map 0 29 from A. Romero Wolf, Neutrino 2008

Borehole Calibration 0.2 deg in Elevation 0.8 deg in Azimuth ~150km Reconstructed event locations To Payload Pulser Ross ice shelf 25 m 30 Broadband antenna

ANITA-I -- Initial High Threshold Analysis • ~19K events (9.6K V- Pol & 10K H-Pol) are impulsive and reconstruct to Ant. ice • Exclude all repeating locations (H, V, H+V) • Exclude single events within 50km of known sites “Camp” = any human-made installation, active or not 31

ANITA-I -- Initial High Threshold Analysis • ~19K events (9.6K V- Pol & 10K H-Pol) are impulsive and reconstruct to Ant. ice • Exclude all repeating locations (H, V, H+V) • Exclude single events within 50km of known sites • After these cuts: – 0 V-Pol (no Askaryan like neutrino signals) “Camp” = any human-made installation, active or not – 6 H-Pol 32

Horizontal Polarisation?? • Askaryan signals strongly favour vertical polarisation – Only top of Cherenkov cone escapes TIR at surface – Fresnel coefficients transmit more V-pol than H-pol • Reflections from above the horizon sources would favour H-pol over V-pol at the balloon • H-pol events are not neutrinos but could be: – Radio signals from cosmic ray air shower 33

ANITA-I Results • ANITA-I limit has begun to constrain some of the highest (less likely) GZK models. • ANITA-II (launched in Dec. 2008) with much improved sensitivity compared to ANITA-I 34 From PRL 103, 051103 (2009)

ANITA-II Improvements • New front end amplification system – Lower system temperature by ~40K • Active direction trigger mask to blank out noise from camps and stations – Improve efficiency by ~20% (lower thresholds) • Switch to vertical polarisation trigger – Improve sensitivity by ~30% • Add third antenna (drop-down) ring – Improve sensitivity by ~30% • Net improvement: – Factor of 1.7 in threshold --> x3 in event rate – Up to 30% in exposure (flight path dependent) – Up to 40% in livetime 35 – Total factor > 5 in neutrino event rate

ANITA-II • Launched Dec 2008 • Terminated after 30 days at float • Little victories – Better flight path – Over 27 million events – Over 100,000 Taylor Dome pulses • Data fully recovered – Two students spent a week camping out at crash site 36