The Tianshan Radio Experiment
for Neutrino Detection
Olivier Martineau-Huynh
NAOC G&C lunch talk May 28, 2014
Milky Way over 21CM array (Gu Junhua)
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:1311.2044)
• UHE heavy nuclei emmited (= UHECRs)
• Interaction with supernova ejecta
• p+
l + nl (= UHE neutrinos)
Physics with UHE
cosmic neutrinos
• GZK neutrinos
p+gCMB
D+
p+ + n.
p+
l + n l.
Great tool to study UHECRs.
GZK
suppression?
Ahlers et al.,
arxiv:1208.4181
Physics with UHE cosmic neutrinos
• Lots of physics with
neutrinos above 1016eV
– Test of pulsars, AGN, GRBs,
– Test of UHECRs propagation
– Probe distant Universe
–…
• Downside: neutrino
detection challenge + low
flux @ UHE…
Need for cheap / scalable /easily maintainable detector.
Neutrino detection
• Elusive particle
requires dense & large target:
– Ice: detection of shower initiated by n NC interaction
– Ground
ARIANA project
1400m
ICECUBE
1000m
Birth of neutrino astronomy
• IceCube 2012&2013
– Milestone in astronomy&astrophysics but:
– Angular reconstruction for shower events ?
– ~1 event/year above 250TeV.
Neutrino detection
Target = Earth
Extensive air shower
nt
t
Radio detection
Eth ~1017 eV
• Earth + mountains as target for neutrino interaction (AUGER-type)
• Radio detection of subsequent EAS (good at large zenith angles)
EAS radiodetection: principle
•
Bgeo

Acceleration of relativistic charged particles in
the Earth magnetic field (Kahn & Lerche,
1965): geosynchrotron emission
Bgeo

F = qvBgeo
•
Coherent effect
detectable radio emission
(~100ns & 10s µV/m)
+
-
Giant Radio Array for Neutrino Detection
The GRAND project
• 100’000 antennas over
60’000km² would make the
best UHE neutrino observatory.
(sensitivity evaluation TBC by
full MC)
• Major challenge: n
identification over background
Esh=1018eV
q=90°
472 antennas triggered
Radio background
TREND antenna
Reconstrcuted source
position
TREND-50 antennas
radio array:
- 1.5km²
- 220 days data subset
- 1.2 1010 triggers recorded
- 1.4 109 coincidences
~0.2Hz event rate
over TREND-50 array
(physical origin)
Expected EAS trigger rate:
~100 events/day for E>1017 eV
Background rejection is a
key issue for EAS radiodetection.
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 2011.
• Goal: establish possibility for autonomous radio detection of EAS.
TREND-15
(2010)
TREND-50
~1.5 km²
Background rejection
EAS signal
- ~ Plane wavefront.
- Fast drop of amplitude when
moving away from shower axis.
- Random time and direction
Shower axis
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.
Radio cone
EAS signal
Background
TREND-50 EAS candidates
2011-2012 data
(Antennas oriented EW):
396 candidates in 320 live days.
EAS simulation
Proton showers @ 1017eV
(half sky)
90°
90°
60°
60°
30°
30°
West
90°
West
90°
South
90°
South
90°
TREND-50 EAS candidates
Data (norm)
Simu (norm)
Data (norm)
Simu (norm)
• 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 q values)
n - 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
Shower axis
Shower axis
Standard EAS signal:
focused ground patern &
rapid drop of amplitude
n-induced (~horizontal) shower:
no significant variation of amplitude along shower axis
(but OK in lateral direction)
Polarization measurment
• EAS radio emission is polarized: at first order F = qv.Bgeo
Linear polarity, with P  Bgeo & P  shower direction
Shower core
(q=66°, j = 354°)
b ~89° on all antennas
h ~7° on all antennas
Trigerred
antennas
z
b
h
y
P
x
GRAND-proto
•
•
Polarization measurment = powerfull identification tool
for EAS?
Test setup: «GRAND-proto»
– 35 3-polar antennas for a complete polar measurment (h =
atan(Vy/Vx) & b = 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, GRANDproto promising!