The European Physical Society (EPS) has recognized four individuals and a collaboration for their work on charge-parity (CP) violation, gamma-ray astronomy, cosmology and outreach activities. Heinrich Wahl, formerly of CERN, and the NA31 collaboration share the 2005 High Energy and Particle Physics Prize for their work on CP violation at CERN. Mathieu de Naurois of IN2P3 in France receives the Young Physicist Prize, Matias Zaldarriaga of Harvard University wins the Gribov Medal, and Dave Barney of CERN and Peter Kalmus of Queen Mary, University of London, share the Outreach Prize.
Wahl was the spokesperson for the NA31 Collaboration, which saw the first evidence for direct CP violation in the decays of neutral K mesons. CP violation is thought to be the reason why the universe is made of matter, even though equal amounts of matter and antimatter should have been created in the Big Bang. CP violation means that the laws of physics change slightly when particles are replaced by their antiparticles and all three directions in space are reversed. Indirect CP violation was first seen in 1964, and the experiment led to James Cronin and Val Fitch sharing the Nobel Prize in 1980.
De Naurois is recognized for his work on two gamma-ray experiments: CELESTE and HESS. The CELESTE telescope in the French Pyrénées detects gamma rays in the 50 GeV range by measuring “Cerenkov radiation” (short flashes of blue light that are produced when gamma rays are absorbed in the air). The HESS telescope in Namibia gathers Cerenkov radiation with four telescopes, which it then uses to create images of astronomical objects. De Naurois developed a new method to analyse Cerenkov images of atmospheric “showers”, which allowed HESS to detect new gamma-ray sources near the centre of our galaxy.
Zaldarriaga is rewarded for his theoretical contributions to cosmology that are important for theories of fundamental interactions. His contributions include devising a new method for calculating fluctuations in the cosmic microwave background (CMB) — the radiation left over from the Big Bang — which has helped put constraints on various cosmological models. He has also worked on the polarization of the CMB and gravitational lensing.
Barney and Kalmus have been recognized for communicating results of particle physics experiments to the public. The prizes will be awarded at the EPS High Energy Physics meeting in Portugal next week.
