Ten-year-old Pierre Auger Observatory to resume with improved detectors
Pierre Auger, the observatory for cosmic particles in Argentina, will receive new, improved detectors. From 14 to 16 November, an event took place at Auger to celebrate the achievements of the first 10 years and to discuss the plans for the next decade. Dutch participants at the international research project are making a significant contribution to the new 'Scintillator Surface Detector', one of the most important new components. With this, the researchers hope to be able to measure the exact properties of the high-energy cosmic radiation that reaches Earth.
The Pierre Auger Observatory in the province of Mendoza, Argentina, is the most important measurement installation for research into cosmic radiation, which is caused by charged particles from space. More than 500 scientists from 16 different countries are working on the question as to where in the cosmos the highest energy particles originate. Since measurements started in 2005, more than 220 young scientists have based their PhD theses on measurements from Auger.
A Dutch Auger group has been active since 2005. This is a collaboration between Nikhef and KVI-CART, in which researchers from the Institute for Mathematics, Astrophysics and Particle Physics at Radboud University also participate. The group has a prominent role in the analysis and interpretation of the data, especially in determining the types of particles that constitute the cosmic radiation with the highest energy. Dutch scientists are also playing an important role in the planned improvements.
New detector shield
The new 'Scintillator Surface Detector' adds a new detection layer that, together with the existing detector, can measure the difference between electrons and muons. When an ultrahigh energy cosmic particle collides with the atmosphere, an avalanche of secondary particles is created, consisting of muons, electrons and atomic particles. Atomic particles rarely reach the Earth ' s surface. The muons mainly originate from the initial collisions in the atmosphere, whereas electrons are created later in the particle avalanche. Using the separate information about muons and electrons, it can be established what type of nucleus the incoming cosmic particle had. This information is vital for elucidating where in the cosmos these particles originated. It is also important for discovering the exact physical processes that take place during the ultrahigh energy collisions of these particles in the atmosphere. The energy level involved is hundreds of times greater than the most powerful particle collider ever made by humans on Earth, the LHC at CERN.
Endpoint found, theory fails
One of the most important results from Auger is the irrefutable confirmation of a maximum energy for cosmic particles. This had been predicted, but the prediction about the composition of the particles at the maximum energy was found to be incorrect. Consequently, the rest of the explanation also became doubtful. A correct interpretation can only be established if a new aspect is added to the measurement, namely the derivation of the exact properties of the highest energy cosmic radiation.
After careful planning and research, Auger will significantly improve the detectors of the observatory in order to achieve this. Following this upgrade, the observatory will once again be able to perform observations for another ten years to answer this new question and other questions that still remain. To mark this milestone, a large event was held at the observatory from 14 to 16 November. The successes already achieved and the new challenges to be faced were presented, and the new agreement for the observatory was signed.
Further information
Sijbrand de Jong, Nikhef programme leader cosmic radiation and Professor of Experimental Physics at Radboud University, +31 6 20 40 36 89.
Further information about the event held from 14 to 16 November is available on the Auger website.