Milky Way over 21CM array (Gu Junhua) The Tianshan Radio Experiment for Neutrino Detection Olivier Martineau-Huynh NAOC G&C lunch talk May 28, 2014

Physics with UHE cosmic neutrinos UHE neutrinos as a tool to study violent phenomena in the Universe – One example: young extragalactic pulsars (Ke Fang et al., arXiv: ) UHE heavy nuclei emmited (= UHECRs) Interaction with supernova ejecta  + l + l  (= UHE neutrinos)

Physics with UHE cosmic neutrinos GZK neutrinos Ahlers et al., arxiv: GZK suppression? p+  CMB  +  + + n.  + l + l  Great tool to study UHECRs.

Physics with UHE cosmic neutrinos Lots of physics with neutrinos above eV – Test of pulsars, AGN, GRBs, – Test of UHECRs propagation – Probe distant Universe – … Downside: neutrino detection challenge + low UHE… Need for cheap / scalable /easily maintainable detector.

Neutrino detection Elusive particle requires dense & large target: – Ice: detection of shower initiated by NC interaction – Ground 1000m 1400m ICECUBE ARIANA project

Birth of neutrino astronomy IceCube 2012&2013 – Milestone in astronomy&astrophysics but: – Angular reconstruction for shower events ? – ~1 event/year above 250TeV.

  Earth + mountains as target for neutrino interaction (AUGER-type) Radio detection of subsequent EAS (good at large zenith angles) Extensive air shower Radio detection E th ~10 17 eV Neutrino detection Target = Earth

EAS radiodetection: principle B geo  + - F = qv  B geo Acceleration of relativistic charged particles in the Earth magnetic field (Kahn & Lerche, 1965): geosynchrotron emission  B geo Coherent effect detectable radio emission (~100ns & 10s µV/m)

Giant Radio Array for Neutrino Detection 100’000 antennas over 60’000km² would make the best UHE neutrino observatory. (sensitivity evaluation TBC by full MC) Major challenge: identification over background E sh =10 18 eV  =90° 472 antennas triggered The GRAND project

Radio background TREND antenna TREND-50 antennas radio array: - 1.5km² days data subset triggers recorded coincidences ~0.2Hz event rate over TREND-50 array (physical origin) Expected EAS trigger rate: ~100 events/day for E>10 17 eV Background rejection is a key issue for EAS radio- detection. Reconstrcuted source position Background sources: HV lines, radio emiters, train, cars, planes, thunderstorms…

Autonomous EAS radio-detection with the TREND-50 setup 50 antennas deployed in summer-automn 2010, total surface ~1.5km². Stable operation since January Goal: establish possibility for autonomous radio detection of EAS. TREND-50 ~1.5 km² TREND-15 (2010)

Background rejection EAS signal Background Shower axis Radio cone EAS signal -~ Plane wavefront. -Fast drop of amplitude when moving away from shower axis. -Random time and direction Background: Close source: - Spherical wavefront -Fast drop of amplitude when moving away from source. Distant source: -~ Plane wavefront -~ Constant amplitude Both: correlated in time & direction.

TREND-50 EAS candidates EAS simulation Proton eV (half sky) West 90° 30° 60° 90° data (Antennas oriented EW): 396 candidates in 320 live days. South 90° West 90° 30° 60° 90° South 90°

TREND-50 EAS candidates Good match between data & EAS simulation: TREND-50 was able to identify EAS with limited background contamination. Still a preliminary result: Simulation statistics to be increased. Analysis cuts to be applied to simulated data. If they remain, discepencies to be understood (e.g. large  values) Data (norm) Simu (norm) Data (norm) Simu (norm)

- induced shower radiodetection Identification of standard EAS OK statistically (TREND-50). Neutrino detection: – Very bad Signal/Noise ratio: TREND-50 ID method not reliable enough. – Looking for horizontal showers: amplitude pattern at ground not as specific as for standard ones Standard EAS signal: focused ground patern & rapid drop of amplitude -induced (~horizontal) shower: no significant variation of amplitude along shower axis (but OK in lateral direction) Shower axis

Polarization measurment EAS radio emission is polarized: at first order F = qv.B geo Linear polarity, with P  B geo & P  shower direction Shower core (  =66°,  = 354°) Trigerred antennas x y z P    ~7° on all antennas  ~89° on all antennas

GRAND-proto Polarization measurment = powerfull identification tool for EAS? Test setup: «GRAND-proto» – 35 3-polar antennas for a complete polar measurment (  = atan(Vy/Vx) &  = atan(Vz/Vplan). – 6 antennas in test at present. – 21 scintillators for EAS offline validation (IHEP) – Full setup in summer 2015.

Conclusion Neutrinos are a powerfull tool for astrophysics (violent phenomena multi-messenger approach) Giant radio arrays could be the most adequate instrument for their detection. Main challenge: background rejection TREND-50 results (very) encouraging, GRAND- proto promising!