Congratulations to Leonid Nemenov on his 90th birthday!
Leonid Nemenov has been working at the JINR Laboratory of Nuclear Problems since 1959. He began his career studying pion bremsstrahlung at the DLNP synchrocyclotron, using a liquid-hydrogen bubble chamber. Later his interests focused on the inverse electroproduction of pions in hydrogen (Dubna) and carbon (Gatchina). He obtained the world's first values for the pion form factor in the time-like region at low momentum transfers.
In subsequent years and to the present, L. L. Nemenov's scientific interests have focused on the theoretical and experimental study of elementary relativistic atoms produced during the decay of elementary particles and those formed in inclusive processes. L. L. Nemenov's theoretical work has focused on the decay of neutral pions into positronium and gamma rays, including the study of superpermeability during the passage of ultrarelativistic positronium through matter; the decay of a neutral kaon into an atom consisting of a pion and a muon, and a neutrino; and the production of pion-pion and pion-kaon atoms in inclusive processes.
In experiments carried out by L. L. Nemenov's group in Protvino, ultrarelativistic positroniums were detected, the probability of their formation was measured, the cross-section of the interaction of positronium with carbon was measured, and pion-pion atoms were detected for the first time.
Further studies of pion-pion and pion-kaon atoms to test theoretical predictions of QCD at low energies were conducted within the DIRAC experiment at the CERN PS accelerator. In 1994, Leonid Leonidovich organized a collaboration that created an experimental facility for studying hadronic atoms. Since then, he has been the undisputed leader of this experiment. To date, more than 20,000 pion-pion atoms have been detected, allowing pion-pion scattering lengths to be determined with an accuracy of better than 5%. The DIRAC experiment made the first observation of pion-kaon atoms and measured their lifetimes. Long-lived states of a pion-pion atom with a lifetime four orders of magnitude longer than that of the ground state of the atom were also observed for the first time.
Over 67 years of scientific activity, Leonid Leonidovich Nemenov has become an author or co-author of more than 160 scientific papers. He supervised 12 candidate dissertations. His work was awarded the JINR Prize four times. For his extensive scientific and public service, L. L. Nemenov was awarded the Medal of the Order "For Merit to the Fatherland", 2nd class.
We sincerely congratulate Leonid Leonidovich on his anniversary and wish him good health, lively spirit, prosperity, and happiness!
Photo from the JINR archive.
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