Karen Avetovich Ter-Martirosyan (1922-2005)

Karen Avetovich Ter-Martirosyan, who died on 19 November 2005, was an outstanding theoretician. He spent most of his scientific career at the Institute of Theoretical and Experimental Physics (ITEP) in Moscow, where during five decades, he made remarkable contributions to our understanding of high-energy physics phenomena. He also created new trends in the theory of strong interactions, and founded the Elementary Particle Physics chair of the Moscow Institute of Physics and Technology and the Laboratory of Hadron Physics at ITEP.

Born in Tbilisi, Karen graduated from Tbilisi State University in 1943 and, after two years of teaching physics at the Tbilisi Railroad Institute, started postgraduate studies at the Leningrad Physico-Technical Institute (now the A F Ioffe Physico-Technical Institute in St Petersburg). He completed his candidate's (PhD) thesis under the supervision of Yakov Frenkel and in 1949 accepted a position in the Theory Division, where he met Lev Landau. Their very active working relationship continued in Moscow, when Karen moved in 1955 to join the Theory Division of ITEP led by Isaak Pomeranchuk. Two years later Karen received the Doctor of Science (professor's) degree in theoretical physics.

In his scientific work, Karen frequently selected problems that others had not worked on and gave correct, straightforward and useful solutions. He attacked each problem in his own way, which soon became the standard way.

In 1952 he created a theory of the Coulomb excitation of atomic nuclei, which led to the discovery of nonsphericity in certain heavy nuclei. Soon after, in 1952-54, he solved the quantum-mechanical three-body problem with a point-like interaction; the Skornyakov-Ter- Martirosyan equation was later generalized by L Faddeev and became a major tool in nuclear and atomic physics. In quantum field theory he formulated, together with I Dyatlov and V Sudakov, the method of parquet equations for summing planar diagrams.

Karen invested a tremendous amount of effort in the theory of high-energy hadron interactions. In the 1960s, together with Vladimir Gribov and Pomeranchuk, he developed the theory of branch points in the complex angular-momentum plane. He also discovered processes with multi-reggeon kinematics and set down the theoretical description of rising cross-sections. Together with A Migdal and A Polyakov he developed a theory of critical and supercritical pomerons. In these investigations of high-energy interactions, a profound theoretical understanding comes together with the analysis of the bulk of experimental data from the new big accelerators, including the rise of total cross-sections. For self-consistency, theory had to comprise multi-particle processes as well, and Karen created a theory of the hadron multiplicity distribution at high energy.

In the 1980s Karen developed a model of quark-gluon string production and fragmentation, which became the basis for a realistic theory of particle production in hadron-hadron and hadron-nuclear collisions. It provided a high-precision description of all available experimental hadron-inclusive spectra and to this day remains the valid phenomenological theory of hadron interactions at high energy, naturally incorporating ideas in QCD.

Karen received his most recent honour in 1999 with the award of the Pomeranchuk Prize, and in 2000 he was elected a corresponding member of Russian Academy of Sciences. B-meson physics and Standard Model extensions were a recent major focus of his interest, and his last talk at the ITEP seminar, in 2005, concerned neutrino physics.

A gifted teacher, Karen loved teaching and his students, to whom he was available no matter how busy he was, loved him. Karen and M Voloshin co-authored the textbook Gauge Theory of Elementary Particle Interactions, which remains a delight and inspiration to students and established theorists alike.

Never short on new insights, Karen did much to launch international contacts for Soviet physics. It was on his initiative that the ITEP Theory Division began collaborations with Oxford and Orsay, and in the 1960s he organized famous International Schools in Nor-Hamberd and Yerevan in Armenia.

Karen remained active and surrounded by talented young physicists until his last days. Perhaps his most lasting legacy will be in the many scientists who struggled to meet his exacting standards and who now populate elite research centres worldwide.

His friends from ITEP and from CERN.

The Hadronic Shower Simulation Workshop will take place on 6-8 September at the Fermi National Accelerator Laboratory. The aim for the workshop is to bring together world experts in a collaborative effort that will lead to a better understanding and simulation of hadronic showers for hadron calorimetry at the ILC and Large Hadron Collider, neutrino fluxes and atmospheric showers. For further information and details about registration (deadline 28 August) see http://conferences.fnal.gov/hss06/.