Ultra-high energy cosmic ray research with the Pierre Auger Observatory: operation, data analysis and interpretation

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics


The Pierre Auger Observatory is a 3000 square kilometre detector array in Argentina that was designed and constructed to record showers of secondary particles, induced by ultra-high energy (UHE) cosmic rays in the atmosphere. The rate of these cosmic rays is as low as 1 particle per square kilometre per century, and, 40 years after their discovery, it is still unknown what their origin is, how they gain their huge energies and what they actually are. The Pierre Auger Observatory will measure UHE cosmic rays with unprecedented precision and statistics to answer exactly these questions. The size of the experiment was chosen to catch about 30 UHE particle per year, and two complementary techniques are used for good precision and particle identification. The Leeds and Oxford groups bring a broad range of experience to the international Collaboration which comprises about 250 physicists from 17 countries.


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Abraham J (2010) The fluorescence detector of the Pierre Auger Observatory in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Abraham J (2010) Trigger and aperture of the surface detector array of the Pierre Auger Observatory in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Description We confirmed that the flux of ultrahigh energy cosmic rays is suppressed at very high energies (exceeding 5 x 10^{19} eV) ... as had been predicted in 1966 by Greisen, Zatsepin & Kuzmin shortly after the cosmic microwave background radiation was discovered. They noted that such high energy particles would interact with this universal radiation and undergro severe energy losses. The calculation was based on Einstein's theory of special relativity, hence there was much surprise when the AGASA experiment in Japan claimed that there is no such effect. Hence the definitive measurements by the Pierre Auger Observatory essentially confirmed that Lorentz invariance holds true up to the highest energies accessible in Nature.

Moreover according to the theory the highest energy particles observed should originate from relatively nearby (since they cannot propagate too far through the background radiation without losing all their energy). Accordingly we undertook a search for correlations between the arrival directions of the highest energy particles and the positions of nearby active galactic nuclei (supermassive black holes in the centres of galaxies which have long been suspected of being able to accelerate such particles). Interestingly a correlation was seen although not strong enough to be definitive.

Thus astronomy with high energy cosmic rays has still not proved possible, nevertheless the Pierre Auger Observatory clarified crucial questions and set the agenda for all subsequent work in the field.
Exploitation Route Our findings have been used to plan further experiments studying very high energy cosmic rays such as the Telescope Array (http://www.telescopearray.org/) and JEM-EUSO on the International Space Station (http://jemeuso.riken.jp/en/). They have also determined the strategy of experiments searching for high energy neutrinos e.g. IceCube (http://icecube.wisc.edu/) and KM3NeT (http://www.km3net.org/).
Sectors Digital/Communication/Information Technologies (including Software),Education

URL https://www.auger.org/
Description The Auger project has also led to the creation of a company in Yorkshire. Dr Paul Clark of the School of Electronic and Electrical Engineering at the University of Leeds and his two students have spun-out a business to exploit the cellular data-networking technology they developed for gathering information at the observatory and which is now used to enhance railway safety (http://commsdesign.ltd.uk/).
First Year Of Impact 2005
Sector Digital/Communication/Information Technologies (including Software),Education
Impact Types Cultural,Economic