Rolf Hagedorn 1919-2003

Rolf Hagedorn, who introduced the concept that hadronic matter has a melting point, died on March 9 2003.
After studies in Göttingen he came to CERN in Geneva in 1954 as an accelerator theorist. He joined the CERN Theory Group after its transfer in 1957 from Copenhagen to Geneva and he was a senior physicist in the Division when he retired in 1984.
He continued his research after retirement, and up to very recently he made pertinent contributions in developments in the field of relativistic heavy ion collisions.
As an accelerator physicist he developed the theoretical predictions for the particle spectra initially observed when the CERN PS first began operation, which was important for the optimisation of secondary beams. He then developed the statistical theory of meson production in considerable detail up to very high energies. It was a consequence of these studies that he found that one should expect a limiting temperature in hadronic collisions, the Hagedorn temperature. This picture has had a major impact on theoretical thinking and on our understanding of the properties of hot hadronic matter, which is important now in the heavy ion program. Since the picture is applicable to any exponentially rising particle mass spectrum it is also influencing the development of string theories.
Among contributions to CERN, Hagedorn developed one of the earliest user-friendly interactive computing programs for algebraic manipulations, the SIGMA.
Rolf Hagedorn was a person of the highest scientific integrity and standards of reasoning. He was always willing to help colleagues and his comments were usually penetrating and deep.

He will be much missed by friends and colleagues.