1. Results from polarization studies of radio signals induced by cosmic rays
Harm Schoorlemmer,
for the Pierre Auger Collaboration
H. Schoorlemmer
RADBOUD UNIVERSITY NIJMEGEN

2. Motivation
The polarization of the radiation reveals the nature of the emission mechanism(s)
Take back home message: The polarization of the radiation reveals the nature of the emission mechanism(s) Two sketches of the direction of the e field for a given position with respect two the shower axis.
K. Werner, O. Scholten, Astroparticle phys, 2008
H. Schoorlemmer
ARENA 2010

3. Motivation Initial study REAS3 v x B Data
Initial study. Expect an angular dependence on the zenith angel from a geo magnetic model. Compared is reas3 simulations, a v x B model and data. Might see a trend, not very clear, but encouriging dig a bit deeper in polarization effects.
H. Schoorlemmer
ARENA 2010

4. Outline Setup & Data Introduction Geomagnetic Charge excess
Conclusions & Outlook
H. Schoorlemmer
ARENA 2010

5. Setup and Data 3 antennas, 100m separated
Thunderstorm monitor
Setup and Data
3 antennas, 100m separated
triggered by an external particle detector
From May 2007 until May 2008, 495 events were recorded in coincidence with the Pierre Auger surface detector
Particle detector
H. Schoorlemmer
ARENA 2010

6. Conventions
H. Schoorlemmer
ARENA 2010

7. Setup and Data Software package Radio Offline (Poster Daniël Fraenkel)
Cables
Amplifiers
Filters
Digitizer
2 LPDA:
MHz
North – South &
East - West
Software package
Radio Offline
(Poster Daniël Fraenkel)
Data set in this presentation: taken with two of the 3 antennas, because at the other position we where testing different types of antenna’s.
Of this whole setup we have a software package which simulates the response. This is important, because in this way we can compare simulation with the measurements.
400 MHz sampling
H. Schoorlemmer
ARENA 2010

8. Polarization Introduction
The measurement is the projection of the electric field in the horizontal plane
4 modes
2 linear
2 circular
Full description with the Stokes parameters
One can define several observables that depend on the polarization
H. Schoorlemmer
ARENA 2010

9. Signal window East - West North - South FWHM Noise
FWHM of total power I
East - West
North - South
FWHM
Noise
H. Schoorlemmer
ARENA 2010

10. Polarization Geomagnetic
Polarization depends only on direction of shower particles
If only effect, strong linear polarization
K. Werner, O. Scholten, Astroparticle phys, 2008
H. Schoorlemmer
ARENA 2010

11. Polarization Geomagnetic1) SNR > 5
Bad period
Normal conditions
SNR > 5
1) See also next talk by Benoit Revenu
H. Schoorlemmer
ARENA 2010

12. Polarization Charge excess1)
Contribution predicted by MGMR2) & REAS33)
Different polarization from pure geomagnetic model
G.A. Askaryan, Sov. Phys. JETP, 1962
K.D. de Vries, O. Scholten et al, Astroparticle Physics (submitted)
M.Ludwig, T. Huege, Astroparticle Physics (submitted)
K. Werner, O. Scholten, Astroparticle phys, 2008
H. Schoorlemmer
ARENA 2010

13. Polarization
Charge excess
Rotate coordinate system to cancel geomagnetic component in one direction
Define a sensitive variable
vs.
(N =#samples in signal window (FWHM))
H. Schoorlemmer
ARENA 2010

14. Polarization SNR > 5 MGMR Charge excess (MGMR) Data Bad Period
H. Schoorlemmer
ARENA 2010

15. Polarization SNR > 5 Charge excess (MGMR) Bad period
Normal conditions
H. Schoorlemmer
ARENA 2010

16. Polarization SNR > 5 Charge excess (REAS3) REAS3 Data Bad Period
H. Schoorlemmer
ARENA 2010

17. Polarization SNR > 5 Charge excess (REAS3) REAS3 Data Bad Period
H. Schoorlemmer
ARENA 2010

18. Polarization SNR > 5 Charge excess (REAS3) Bad period
Normal conditions
H. Schoorlemmer
ARENA 2010

19. Conclusions Polarization analysis shows:
Geomagnetic emission mechanism confirmed
Data shows features of additional emission mechanisms
First hint of charge excess
H. Schoorlemmer
ARENA 2010

20. Outlook More data with higher precision
More than two antennas per event
Better reconstructed shower parameters from surface and fluorescence detectors
See talk by Stefan Fliescher
H. Schoorlemmer
ARENA 2010

21. Back-up Charge excess Compare with simulations
Randomize in the uncertainty from the surface detector reconstructed shower parameters
Take into account that the uncertainties are correlated
Generate 100 showers with CORSIKA to include shower-to- shower fluctuations (QGSJET-II and UrQMD)
H. Schoorlemmer
ARENA 2010

22. Back-up Data: Propagation of the noise to the parameters
Uncertainty charge excess plot
Data: Propagation of the noise to the parameters
Simulations: Spread in values from 100 simulation within the uncertainties of the surface detector reconstructed parameters. Including shower to shower fluctuations (CORSIKA)
H. Schoorlemmer
ARENA 2010

23. Back-up Use auger reconstruction to find the radio pulse
Selection criteria
Use auger reconstruction to find the radio pulse
Apply a SNR cut based on the total power in the horizontal plane
H. Schoorlemmer
ARENA 2010

24. Back-up Uncertainties: Uncertainties plot2 RMS of in the FWHM window
H. Schoorlemmer
ARENA 2010

25. Back-up SNR > 5 Without bad period events H. Schoorlemmer
ARENA 2010

26. Back-up SNR > 5 Without bad period events H. Schoorlemmer
ARENA 2010

27. Back-up Complex electric field using a Hilbert transform
Stokes parameters
Complex electric field using a Hilbert transform
4 – components:
H. Schoorlemmer
ARENA 2010

28. Back-up
REAS3
H. Schoorlemmer
ARENA 2010

29. Back-up
MGMR vs REAS3
MGMR
REAS3
H. Schoorlemmer
ARENA 2010

30. Back - up
MGMR vs. REAS3
H. Schoorlemmer
ARENA 2010

31. Back-up Uncertainties / cuts geo plot 1 Selection criteria:
SNR cut in East -West or North – South for data and simulation
Direction reconstruction within 20° of standard auger reconstruction
Cut on simulation rejects 6 out of 21 data points
Uncertainties
Data:
REAS3: rms of 30 noise simulations
v x B: none
H. Schoorlemmer
ARENA 2010