11 July 1924 - Birth of César Lattes, co-discoverer of the meson pi o pion

Cesare Mansueto Guilio Lattes, known as César Lattes, was one of the most brilliant Brazilian scientists of his generation. At the age of just 23, together with the English scientist Cecil Frank Powell and the Italian Giuseppe Occhialini, he discovered a particle inside the atomic nucleus that ensures the cohesion of the atom: the pi meson.

Lattes was born in the Brazilian city of Curitiba on 11 July 1924. The son of Italian immigrants, he began his studies in his hometown. He then moved to São Paulo where he attended high school at the Instituto Médio Dante Alighierei. He later studied physics and mathematics at the University of São Paulo where he graduated at the age of 19.

At the time, scientists around the world were wondering how protons were held together in the nucleus of the atom. His interest in these questions led him to move to England, where he worked at the Bristol University Laboratory with Giuseppe Occhialini and Cecil Powell (Nobel Prize in Physics in 1950). Together they discovered a new atomic particle, the pi meson or pion, which decays into a new type of particle, the meson or muon. This marked the beginning of a new area of research: particle physics.

In 1947, to pursue his main line of research into the "study of cosmic rays", Lattes set off for Chacaltaya, one of the highest peaks in the Bolivian Alps, where the rays from space were most intense. There, at an altitude of over 5,000 meters, he exposed photographic plates to the action of cosmic rays, and experimentally proved the existence of heavy mesons or pions.

A year later, at the University of California, he succeeded in producing the meson artificially by accelerating alpha particles in the cyclotron.

In 1949, Lattes returned to Brazil as a professor at the University of São Paulo and also took up the position of professor and researcher at the Federal University of Rio de Janeiro. He was one of the founders of the Brazilian Centre for Physical Research, set up in Rio de Janeiro in the same year.

Between 1955 and 1957, he remained in the United States before returning to Brazil to take up the post of Director of the Physics Department at the University of São Paulo. At that time, he joined the Brazilian Academy of Sciences.

In 1969, Brazilian and Japanese scientists under his supervision determined the mass of the "fireballs", a phenomenon caused by the intense collision of extremely high-energy particles, which were supposed to be clouds of mesons.

Lattes retired in 1986, the year he received the title of doctor honoris causa and professor emeritus of his university. He died in São Paulo of a heart attack on 8 March 2005.

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