# Prize Recipient

## Heinrich Wahl University of Ferrara/CERN

Citation:

"For leadership in the series of experiments that resulted in a multitude of precision measurements of properties of neutral K mesons, most notably the discovery of direct CP violation."

Background:

Studies of physics at the University of München, the Swiss Technical Highschool (ETH) in Zürich, and at the University of Hamburg. Doctoral Degree in 1967 from the University of Hamburg on nuclear resonance fluorescence in Li6. Experiments on high energy photoproduction of mesons at the German Electron-Synchroton Laboratory DESY in Hamburg. The 1970 Physics Prize of the German Physical Society was awarded for these results to the research group F35 at DESY.

Since 1969 Research Staff at the European Laboratory for Particle Physics CERN in Geneva. Investigations of neutral kaon and hyperon decays at the CERN PS until 1974. Precision measurements of various parameters in the neutral kaon system, in particular the CP violating two pion decay amplitude, its phase and the charge asymmetry in semileptonic decays.

Experimental investigations of high energy neutrino interactions at the CERN SPS (WA1 experiment, 1974-83). This included the measurement of charged-current structure functions and their comparison with QCD, the first precise measurement of the Weinberg angle, evidence for right-handed couplings in weak neutral current interactions, and the clarification of the origin of multimuon events in neutrino interactions.

Experiment on CP violation at the CERN SPS accelerator, primarily to search for direct CP violation in neutral kaon decays and to determine its strength (NA31 experiment, 1981-93). First observation and measurement of direct CP violation. A new approach followed to determine direct CP violation more precisely (NA48 experiment, 1990-2002). Confirmation of the 1988 and 1993 NA31 results on direct CP violation in 1999. The 2005 High Energy Particle Physics prize of the European Physical Society was awarded jointly to Heinrich Wahl, and to the NA31 collaboration, for these challenging experiments on direct CP violation.

At present Professor of Physics at the University of Ferrara.

Selection Committee:

Ian Shipsey (Chair), Bob Cousins (12/06), Pier Oddone (2006 Recipient)(12/06), Al Goshaw (V. Chair)(12/07), David Macfarlane (12/07)