Olivier Martineau, LPNHE Paris – IN2P3 – CNRSVLVnT 2015 workshopRome, September 14, 2015

Proposal for a Giant Radio Array for Neutrino Detection

Kumiko Kotera

GRAND neutrino detection principle

nt

t

• Earth + mountains as target for neutrino interaction Fargion et al, arxiv:0002.453, Bertou et al., arxiv:0104.452• Radio detection of subsequent EAS (good at large zenith angles)

on a HUGE array [ o(100’000km²) ]

Extensive air shower

Radio detectionEth ~1017 eV

A giant radio array on ground for UHE neutrino

detection?

• GRAND workshop, LPNHE, Paris, Feb 2015 https://indico.in2p3.fr/event/10976/

• 35 participants from the field (UHE CRs, g and n, air shower radio detection, …) & conex topics.

• Main output: be ambitious! GRAND worth if we aim at guaranteed detection of cosmogenic neutrinos.

Pure Iron No source evolution

Mixed compositionSource evolution

Kotera et al., arxiv:1009.1382

Iron rich, low Emax

No source evolution Ahlers et al., arxiv:1208.4181

Cosmogenic neutrinos fluxes

• Cosmogenic neutrinos fluxes @ EeV energies primarly depend on UHECRs chemical composition & source evolution.

• Combinaison with PeV measurments explains Gal/Extragal transition.

Cosmogenic neutrinos are a great tool to study UHECRs!

• Sensitivity = 3 10-11 GeV/cm²/s/sr would allow to test all models & provide ~100 n/year for most reasonable models.

• … what would it take to achieve this sensitivity?

GRAND proposal: people involved

• Tianshan Radio Experiment for Neutrino Detection (TREND): French IN2P3 & Chinese CAS collaboration for air shower autonomous radio-detection; ~15 researchers + engineers.

• Kumiko Kotera @ IAP Paris (phenomenology)• Krijn de Vries @ VUB Brussels (radio simulations)• Jaime Alvarez-Muniz + Washington Carvalho @

Santiago di Compostella (radio simulations)• Charles Timmermans @ NIKHEF (AUGER-AERA)• Others in Sweden (Chad Finley), USA, France

• Anybody interested is welcome!ICRC proceedings, arXiv:1508.01919

GRAND neutrino sensitivity study

• End-to-end MC simulation being setup:

Neutrino simulation : from the nt trajectory to the t decay products.Custom 1D simulation scheme. Written in C++. External dependencies : Pythia6.4 and TAUOLA /FORTRAN. Scattering is neglected.

Radio E-field computation : from the t decay products to the radio E field. Codes: ZhAires (arxiv:1107.1189) & EVA.

Work in progress... Issues:- Simulations of very inclined showers- Ground reflexion effects- Huge CPU requests!

Antenna response computation: from the radio E-field to theantenna current/voltage response. NEC code.

GRAND n sensitivity preliminary study - Layout

Toy setup: 60’000 antennas deployed over 220x270km² in Tianshan mountains (Western China), site of the TREND & 21CMA experiments.

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Nor

thin

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Tianshan mountains

60’000km²

Urumqi

UlastaiBeijing

GRAND n sensitivity preliminary study - Principle

E>3 1016eV

5km120km

W=1-10°

• MC down to t decay (En in 1017 - 1021 eV, q in [85-95°])

• Simplified criteria for subsequent shower detection:– Antenna fired if:

• in direct view of shower• in a light cone of few degs

(W=f(E), [1-10°])• Tau decay point distant by [5,120]

kms.

– Detection if :• one cluster of 8+ antennas fired.• Shower energy > 3 1016 eV /

1017eV

GRAND n sensitivity preliminary study - Results

3.1017 eV3.1018 eV

3.1019eV3.1020eV

DownwardGoing(mountains)

UpwardGoing

(Earth)

• ~ Horizontal trajectories.• Mountains are sizable tragets.• Earth becomes opaque at higher energies

60000km² simulation setup:factor 3 to 10 better

sensitivity compared to ARA in 1017-1019eV En range.

GRAND

Eth=3.1016eV

Eth=1017eV

Nb of triggers/antenna

GRAND 200’000km² layout

• « Hotspots » with event rates well above average (large slopes facing distant mountain range).

• Possible strategy: deploy sub-arrays on hotspots only [size = o(10’000km²)?]. Total detection area x3 (~200’000km²) may result in x10 in sensitivity.

• Sub-arrays could be separated by large distances… and very well be on different continents!

• Strategy to be validated/refined through complete MC study.

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60’000km²

GRAND n sensitivity preliminary study - Results

3.1017 eV3.1018 eV

3.1019eV3.1020eV

DownwardGoing(mountains)

UpwardGoing

(Earth)

• ~ Horizontal trajectories.• Mountains are sizable tragets.• Earth becomes opaque at higher energies

GRAND 200’000km² full array at 3 10-11 Gev/cm²/s/sr (?)

To be confirmed!

GRAND

Eth=3.1016eV

Eth=1017eV

GRAND challenge: technical aspects

• How realistic/affordable is it to deploy, run & maintain a 200’000 antennas array?

• Possible answer: keep it as basic as possible!– Basic (analog) trigger (T0) on transient signal.

– Record 4 words/trigger [Max amplitude x 3 channels + trig time by GPS]

– Rely on commercial solutions for electronics & data transfer.

– <1W & <200$ / antenna probably achievable.

– … Possibly not as crazy as it first sounds!

1.5m5kg

Antennas are ridiculously basic detectors .

Science case definition will interfer![see later]

GRAND challenge: background rejection

• Atmospheric neutrinos– Negligeable above 1016 eV.

• HE muons from UHECRs showers– Back of the enveloppe calculation based

on Chirkin (hep-ph/0407078): 3 10-6 decays/year over full array above 1016 eV.

• (Misreconstructed) standard cosmic ray showers– Cut 1° below horizon (mountains )

• 1° 5s for 0.2° angular resolution 5 10-7 suppression factor

• Affects marginaly detection efficiency: <10%

– Discrimination on young (neutrinos) vs old (CRs) showers (?)

0.2° angular resolution at worst for st = 3ns8 antennas triggering

ICECUBEarxiv:1405.5303

GRAND challenge: background rejection

Terrestrial background

3 108 events/year (?)

TREND project (2009-2014):~10Hz coinc rate for 1.5km²

arXiv:1007.4359

Neutrino signal: 0-100 events/year

Rejection factor:R~109

• Discriminating parameters: Trigger pattern at ground? Polarisation?

AUGER, arXiv:1402.3677v2

GRANDproto

• Hybrid setup with 35 3-polar antennas + 24 scintillators.

• Target: (standard) air showers coming from North with 40°<q<70° & 1017eV<E<1018eV.

• Principle: select radio candidates from polar info, use scintillator array as a cross-check => qualitative determination of rejection factor.

• Deployment on-going, to be completed before june 2016.

• Proposal to perform similar tests @ AUGER-AERA.

Other science with GRAND

• n sensitivity + angular resolution <0.1° would open the door for neutrino astronomy @ VHE.

• Huge effective area + performances for EAS reconstruction: great tool for UHECR physics above 1019eV.

• Epoch of reionization (?)• Fast Radio Bursts (?)

• Choices will necessarily impact detector design.

Science case to be defined in more details! Work in progress.

60000km² setup

GRAND 200’000km² setup

Conclusion

• GRAND could be a great tool for VHE astronomy.• GRAND proposal being set-up (science case + neutrino sensitivity)• Possible (?) timeline: – mid-2016: proposal completed– 2019: engeneering array (o(1000km²))– 2022: GRAND

• Join us!