ULTRA-HIGH ENERGY NEUTRINO SEARCH WITH THE ASKARYAN RADIO ARRAY - PowerPoint PPT Presentation

ULTRA-HIGH ENERGY NEUTRINO SEARCH WITH THE ASKARYAN RADIO ARRAY PoS(ICRC2017)966 Ming-Yuan Lu for the ARA collaboration Wisconsin IceCube Particle Astrophysics Center, Madison, WI, USA 35 th International Cosmic Ray Conference, Busan, Korea July 12-20 2017 1 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Neutrino-Cosmic Ray Connection • Neutrinos are produced when cosmic rays interact with ambient matter/radiation field p γ → p π 0 n π + 2 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Cosmogenic Neutrinos Ultra-high energy (UHE) cosmic • rays observed with energies up to 10 20 eV Photohadronic interaction • between UHE cosmic rays > 10 19.5 eV and CMB photons: Energy (eV) 10 18 10 19 10 20 This is the Greisen-Zatsepin- • Kuzmin (GZK) process – 
 a ‘guaranteed’ UHE neutrino flux 3 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Radio Detection • Estimated cosmogenic neutrino event rate: ~< 1/km 3 /yr • Requires ~100km 2 of detector effective area The Askaryan Effect ~20% charge asymmetry Peak emission 0.1~1GHz P ~ N e 2 ~ E 2 Highly polarized broadband signal Confirmed detection in ice, SLAC 2006 (Phys. Rev. Lett. 99:171101) 4 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

ARA Detection Principle Detection method Full ARA37 covers ~100km 2
 Most cost-effective for determining cosmic neutrino flux > 10 17 eV New stations 2017-18 5 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

The ARA Detector Each station is an autonomous detector 450MHz notch filter removes SP comms Vpol Hpol Antenna requirements:
 1. Broadband Deployed ~40m away from 150~850MHz station center.
 2. Azimuthal Allow in-situ calibration symmetry 3. Fit in the hole 6 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

ARA Data Analysis ~10TB data/yr/station • Filter:
 • - Dominated by thermal triggers – a thermal rejection of 10 -10 is needed to bring thermal events to ten times less than expected signal - Remove corrupted data (faulty electronics), anthropogenic sources Events that survive filters will be reconstructed
 • - Interaction vertex (direction, distance)
 - Neutrino kinematic parameters (momentum four-vector) We will introduce 3 filter techniques and 1 reconstruction method • Simulated 10 18 eV on- cone event 1.2km away ARA02 Vpol calibration pulser 7 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Interferometric Reconstruction For reconstruction, set of delays N A N A • Σ ( � dt ⋅ v i ( t + τ i ( � )) v j ( t + τ j ( � 1 T ∫ ∑ ∑ P r ) = r r )) associated with each point in the sky Z L T 0 i = 1 j = 1 is computed. Cross correlation values are computed per these delays and summed Delays are calculated with Radiospline • – B-Spline interpolation of tabulated raytraced arrival (Beheler-Amass et al., PoS(ICRC2017)1054) Radiospline accounts for geometric • optics in ice of changing index of staHon Ice Surface refraction Only Vpols are used in reconstruction • (for now). An n-channel filter of 3/8 200m channels with V peak > nσ noise is applied. Only these channels are used in 5000m reconstruction. n (threshold) determind by 1% thermal • rejection on 10% unblinded RF events layer 8 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Calibration Sources No physics background – artificial signals for calibration
 • - Local calibration pulsers
 - Radio transmitters on IceCube string 1 & 22 (deep pulser)
 - Rooftop pulser from IC Lab
 ARA3 run8311 evt12472 - Mobile surface pulser -5 Deep pulser 0.25 Local calibration pulser -10 0.2 -15 S1 1450m Pulser Coherence ] ° 0.15 Zenith [ S22 1450m Pulser -20 0.1 -25 S1 2450m Pulser 0.05 -30 -35 0 250 245 240 235 230 225 220 Azimuth [ ] ° For calibration and ice properties inferred by 
 deep pulser data – Kelley et al. PoS(ICRC2017)1030 9 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Simulation reconstruction • Data set: 10 18 eV neutrino vertices randomly scattered around an ARA station, up to 5km 3 10 3 Mean: -0.13 10 Mean: -0.0059 RMS: 1.30 RMS: 0.31 2 10 Gaus. Fit Count 2 Gaus. Fit Count 10 : 0.0049 µ µ : -0.0044 10 : 0.35 σ σ : 0.29 10 1 -10 -5 0 5 10 -30 -20 -10 0 10 20 30 Reco Zenith - True Zenith [ ] Reco Azimuth - True Azimuth [ ] ° ° Cumulative ratio 1 -1 10 10 -8 rejection:
 -2 10 0.1082 Noise expo log(E/eV)=16 log(E/eV)=17 -3 10 log(E/eV)=18 log(E/eV)=19 log(E/eV)=20 -4 10 log(E/eV)=21 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 10 Coherence [arb. unit] UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Other Filters – Waveform RMS method - Wavefrom RMS: wavefront RMS" is an estimator for how closely the arrival time differences agree with each other - Hit time is determined by power threshold crossing with 5ns integration - Compare the hit times in similar pairs of antennas (e.g. vertically aligned pairs) by finding the RMS of the delays in each pair - Threshold and RMS cut are tunable parameters θ A,i 1 t 1 t 3 0.8 = Face RMS Cut Efficiency = Time Sequence 0.6 Quality Parameter θ A,ii Cut 0.4 t 2 t 4 0.2 = A-type pairs 0 0 5 10 15 20 25 30 = B-type pairs 3 rd Highest Vpeak/RMS for all channels 11 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Other Filters – Surface filter events [a.u.] 0.1 above-ice radio sources - Minimum arrival angle:
 in-ice ν -interactions A2: ~35° 0.08 A3: ~40°
 - The signal arrival angle is 0.06 reconstructed with a plane wave fit using the timing from 4-hit 0.04 combinations, then averaged over combinations 0.02 - Zenith resolution: 2.5° 0 0 20 40 60 80 100 120 140 160 180 zenith angle [degrees] 12 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Summary Multiple filters are being • characterized. Can be -2 10 ] -1 combined to maximize sr IceCube (2015) Auger (2015) -1 sensitivity s -3 10 ANITA II (2010) ARA (2016) -2 UHE neutrino search will be ) [GeV cm • IceCube (2016) ARA 2 Stations '13-'15 (Trig. Lev.) carried out on
 -4 10 ARA 200 Stations 5yr (Trig. Lev.) ARA2: 28.2 month
 ARA3: 27.2 month ν F(E -5 10 Radiospline reconstruction • 2 ν E readily accounts for ray- Kotera et al. (2011) -6 Ahlers & Halzen (2012) 10 bending, and can reach ~<1° p @ 100EeV: 100% vertex resolution p @ 100EeV: 10% -7 10 p @ 100EeV: 1% Going forward, optimization • study shows 25%-30% -8 sensitivity increase in larger 10 station geometry* -9 Phased array approach will 10 • allow triggering at lower energy thresholds** -10 10 16 17 18 19 20 10 10 10 10 10 6 ARA stations at the end of • E [eV] ν this coming Pole season *: PoS(ICRC2017)938 **:P. Allison et al, these proceedings 13 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Backup slide 14 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Askaryan Signal Modelling DetecHon in silica sand (Phys. Rev. LeW. (2001) 86.2802) DetecHon in rock salt (Phys. Rev. D72(2005) 032002 DetecHon in ice, SLAC (Phys. Rev. LeW (2007). 99:171101) UHE Neutrino Search with ARA, ICRC2017, 15 M.-Y. Lu

Askaryan Signal PolarizaHon UHE Neutrino Search with ARA, ICRC2017, 16 M.-Y. Lu

LPM Effect & NC/CC InteracHons UHE Neutrino Search with ARA, ICRC2017, 17 M.-Y. Lu

LPM Effect & NC/CC InteracHons UHE Neutrino Search with ARA, ICRC2017, 18 M.-Y. Lu

Radio AWenuaHon In Ice UHE Neutrino Search with ARA, ICRC2017, 19 M.-Y. Lu

Radio AWenuaHon In Ice J. Appl. Phys. 80, 5884 (1996) UHE Neutrino Search with ARA, ICRC2017, 20 M.-Y. Lu

Delays - Raytracing • Ice index of refraction varies with depth. Change is most drastic near surface (firn). As a result, EM waves travel in curved paths – raytracing • Ideal vertex direction/distance reconstruction need to take into Varying Index of Refraction account raytracing effect index of refraction vs. depth 21 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Raytracing and Radiospline Semi-analytic approach to compute ray paths -> Delays computed by this • approach tabulated and fitted with B-Spline Raytrace shadow boundary Depth (m) Distance Target -200 4km -300 Region without -400 Antenna raytrace solutions depth: -500 25m -600 Solution 0 -700 Region with Solution 1 raytrace solutions -800 -900 Source 0 500 1000 1500 2000 2500 3000 3500 4000 Horizontal Distance (m) Region without 0 Depth (m) raytrace solutions Antenna Distance Target -100 depth: 1km 200m -200 -300 Region with raytrace solutions -400 -500 -600 Solution 0 -700 Solution 1 -800 Source 0 100 200 300 400 500 600 700 800 22 Horizontal Distance (m) UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu

Radiospline • Solution: Cartesian coordinates to Cylindrical, multi-step process air antenna source in air? spline (z target , radius) Source table Time firn shadow location tables Delays (z source , radius) ice source in ice? spline source in firn table shadow? No Solution random sources in ice random sources in air Random source/target locations (2.3 GHz Core i7) Faster than raytracer by factor > 500 M. Beydler sample size = 100,000 sources 23 UHE Neutrino Search with ARA, ICRC2017, M.-Y. Lu