## Willy van Neerven, 1947-2007

photograph courtesy DESYWilhelmus Lodewijk Godefridus Adrianus Maria (Willy) van Neerven died on February 15th 2007. He was associate professor at the Instituut-Lorentz of Leiden University and held a special professorship at the Vrije Universiteit Amsterdam, working as a theoretical particle physicist.

Willy was born at Weert in The Netherlands on May 3rd 1947. He received his PhD at Nijmegen University in 1975, carrying out thesis studies under the supervision of R.P. Van Royen and J.J. de Swart. As a post-doctoral fellow and during long-term visits he worked at CERN, NIKHEF, Dortmund University, ETH Zürich, Tallahassee, YITP Stony Brook and DESY. From his early years on at CERN and NIKHEF he performed groundbreaking calculations within perturbative Quantum Field Theory. He was involved in the development of important aspects of Quantum Electrodynamics, Quantum Chromodynamics and the Standard Model. He developed specific calculation technologies and performed a large number of complete calculations at the one- and two-loop level, including those with different mass scales and polarized initial states.

Willy played a leading role in the calculation of the 2-loop QED-corrections for LEP, which were instrumental in establishing all precision measurements at the Z-peak. His pioneering work on the QCD-Wilson coefficients for the deeply inelastic structure functions, also including those for heavy flavors, formed a milestone in QCD and was instrumental for interpreting the experimental data at HERA. He performed one of the first calculations of the polarized next-to-leading order anomalous dimensions. His work in collider physics covered the celebrated 2-loop calculations of the cross sections for the Drell-Yan process and for Higgs-production, which are of central importance for the physics at the TEVATRON and LHC. He also calculated the next-to-leading QCD corrections to the top quark cross section. Without his efforts much of the precision analysis of the data would not have been possible.

Willy was a driven teacher to the benefit of both his students and collaborators. He was equipped with a fabulous encyclopedic knowledge of many facets of quantum field theory, but also of scientific literature often down to the volume number as well as of historic facts down to dates. We all remember conversations with him, especially during walks where he enjoyed a good cigar; besides being pleasant they offered a great way to analyze current scienctific problems with his collaborators. In his reasoning he was strict but not dogmatic at all. His aim was to understand a physics problem to the very end, whenever possible. Willy understood physics thoroughly as quantitative science and therefore only accepted theories which could be tested by experiment. He will be greatly missed by friends and colleagues alike.

P. van Baal, J. Blümlein, P. Mulders, A. Schellekens, J. Smith, J. Vermaseren

published in Cern Courier, April 2007.