Marian Danysz (1909 - 1983)

The most important scientific achievement of Marian Danysz was created amid the murmur of conversations and the scent of freshly brewed coffee, in the haze of cigarette smoke, and was the result of collaboration with Jerzy Pniewski.

Warsaw scientists, analyzing traces of cosmic radiation particles recorded in a block of photographic emulsion, discovered a hypernucleus, that is, an atomic nucleus that, in addition to protons and neutrons, contains at least one hyperon. In this case, it was the Λ hyperon. This was a bold hypothesis. At the time, no one suspected that the recently discovered particle, the hyperon, could be a component of the atomic nucleus. However, subsequent observations confirmed the validity of the Polish scientists' idea. This discovery initiated a new field of physics—studying hypernuclei. Nobel archives contain information that Danysz and Pniewski were repeatedly nominated for the Nobel Prize for this discovery.

For nearly two years, Danysz worked in Bristol at the laboratory of Cecil Frank Powell (1903-1969). During his stay, the English scientist was awarded the Nobel Prize in Physics "for the development of the photographic method of studying nuclear processes and his discoveries related to mesons produced by this method." Powell used blocks of light-sensitive photographic emulsion, which could be divided into layers. Radiation particles passing through the emulsion left a trace on it. To increase the chances of registering cosmic radiation, the emulsion was taken high above the Earth's surface. Danysz, who returned to Warsaw in May 1952, brought with him a block of emulsion exposed during a stratospheric balloon flight. Danysz persuaded Pniewski to collaborate, with whom he had developed closer ties during their six-month stay in Liverpool. After splitting the block of emulsion, the individual layers were examined under a microscope. In the evening of September 19, during such a review, Danysz's exclamation "Look at this strange beast!" was heard. His attention was drawn to an image of a "double star." The first star marked the point where a high-energy cosmic radiation particle collided with an atomic nucleus in the emulsion. It was a burst of linear tracks emanating from the collision point. Each of them had been left by a fragment of the broken nucleus. One of them unexpectedly split into four parts, forming a second star. This meant that the fragment that left this trace had undergone further decay. Explaining the cause of this trace consumed the scientists. Twice a day, they went to the recently opened café Niespodzianka, located near the Institute of Physics on Hoża Street in Warsaw. They rejected various ideas until only one explanation remained— the observed trace had to come from an atomic nucleus containing, in addition to protons and neutrons, a Λ hyperon. This was the first observation of a hypernucleus in the world. The scientists' work, published in the prestigious journal The Philosophical Magazine, soon led to reports of other observations of hypernuclei. It was one of the greatest successes of post-war Polish physics. Two years later, M. Gell-Mann (1929-2019) and A. Pais (1918-2000), as well as independently K. Nishijima (1926-2009), demonstrated that hyperons possess a peculiar property called "strangeness." This property explained their long lifespan before decay and confirmed the correctness of the conclusion drawn by Danysz and Pniewski.

A hypernucleus is an atomic nucleus in which at least one nucleon (proton or neutron) has been replaced by a hyperon. Nucleons also have an internal structure. Both the proton and neutron are made of three quarks: the proton consists of two d quarks and one u quark, while the neutron is composed of two u quarks and one d quark. Quarks are currently recognized as one of the fundamental elements of the structure of matter. In addition to the u (up) and d (down) quarks, there are also the s (strange), c (charming), b (bottom), and t (top) quarks. This classification was not yet known when Danysz and Pniewski observed the first hypernucleus. A hyperon is a particle made of three quarks, which contains a strange quark. The Λ hyperon is a particle made of u, d, and s quarks.

Soon after this discovery, the scientists' paths diverged for several years. Danysz became the deputy director of the Joint Institute for Nuclear Research in Dubna, spending most of his time in the Soviet Union. Pniewski, on the other hand, became consumed with administrative duties after being appointed director of the Institute of Physics. In the late 1950s, the scientists, along with a group of young physicists, many of whom later became professors at Warsaw universities, returned to research on hypernuclei and made further discoveries. In 1959, they obtained the best estimate at the time of the mass of the Λ hyperon. In 1962, they initiated hypernuclear spectroscopy, that is, the study of hypernuclei in excited states. In the same year, they discovered the first double hypernucleus containing two Λ hyperons. This discovery involved hypernuclei produced in an accelerator that accelerated particles to high energies. Their collaborator, Jerzy Zakrzewski (1932-2008), was the first to notice the trace that turned out to be the trace of a double hypernucleus. Observing a double hypernucleus was very difficult to capture. For nearly 30 years, besides Warsaw, only one similar case had been observed at the American laboratory at Brookhaven. Further studies of hypernuclei were most often carried out by large international teams using the largest particle accelerators.

Danysz embarked on his scientific path more than 20 years before the discovery of the hypernucleus. In 1930, he began volunteering at the Radiology Laboratory, which was operating under the auspices of the Warsaw Scientific Society, a laboratory whose first director was his father. At that time, it was led by his father’s former collaborator, Ludwik Wertenstein (1887-1945). In 1934, shortly after the discovery of artificial radioactivity by Irene (1897-1956) and Fryderyk (1900-1958), Danysz and Michał Żyw (1905-1943) began experiments in which they irradiated targets made of various materials with alpha particles. They were astonished to find that, regardless of the target material, the half-life of the resulting radiation was similar. One evening, the researchers concluded that the common factor in their experiments was the irradiation of the targets placed in the air. They spent the entire night in the laboratory testing different hypotheses. By morning, they were convinced that the source of the radiation was an unknown radioactive isotope of fluorine. Years later, Danysz recalled his emotions related to this event: "I remember that when I left the laboratory in the morning, I was deeply impressed by the possibility of such a dialogue with nature, of asking questions, receiving answers, and that in the course of a single night, one could solve a problem, confirm or reject this or that hypothesis." At the Radiology Laboratory, Danysz was also involved in the discovery of a new isotope of scandium and in research that led to the discovery of inelastic neutron scattering.

Biography

Marian Danysz was born on March 17, 1909, in Paris. In his family, scientific work was highly esteemed. His grandfather, Jan Danysz (1860-1928), was a microbiologist and an employee of the Pasteur Institute in Paris. His father, Jan Kazimierz Danysz (1884-1914), was a student of Piotr Curie (1859-1906) and an assistant to Marie Curie-Skłodowska (1867-1934). When a radiology laboratory was opened in Warsaw in 1913, which was headed by the Polish Nobel laureate, Danysz became her deputy and managed the daily operations of the laboratory. In 1914, as a reserve officer and a French citizen, he was called to military service and was killed in November 1914.

Marian Danysz followed in his father’s footsteps. Although he held French citizenship until the end of World War II, he lived and studied in Warsaw. After completing high school at the Stefan Batory Gymnasium in 1928, he began studies at the Warsaw University of Technology. It was not until 1938 that he received his degree as an electrical engineer.

In 1937, he began working in his field of education at the Warsaw State Institute of Telecommunications. There, he developed a new model of a night vision device, for which he received an award from the Minister of Posts and Telegraphs.

Immediately after the war, Danysz became a lecturer in electrical engineering at the Wawelberg and Rotwand Higher State School, and in 1947, he started working as an assistant at the Department of Experimental Physics at the University of Warsaw. When he began working at the Institute of Physics, he had not yet completed his physics studies, but for his achievements in this field, related to his work at the Radiology Laboratory of the Warsaw Scientific Society (TNW), he was exceptionally granted the title of Master of Science. Fulfilling formal requirements necessary for obtaining further academic degrees was not Danysz’s strength. Although his scientific career was filled with outstanding achievements, he never submitted either a doctoral or habilitation thesis. He remained affiliated with the Warsaw university until the end of his scientific career.

The then-director and founder of the University of Warsaw's Institute of Physics, Stefan Pieńkowski (1883-1953), sought to provide his assistants with opportunities for scientific development. Therefore, in 1949, Danysz went on a research stay in England. He spent several months in Liverpool and then in Bristol, where he worked under the guidance of Cecil Powell. He returned to Poland in 1952.

In 1954, Danysz was appointed an extraordinary professor. He combined his work at the university with activities at the Institute of Nuclear Research in Świerk, where he first headed the Cosmic Ray Laboratory (in 1955) and later the Department of High-Energy Physics. Another significant distinction was his serving as the deputy director of one of the most important scientific institutions in the so-called People’s Democracies (countries under the influence of the Soviet Union), the Joint Institute for Nuclear Research (JINR) in Dubna, from 1956 to 1960. In the 1960s, he was also a member of the Scientific Council of JINR. He held a similar position as Poland's representative in the Scientific Council at CERN, where he worked as a visiting professor from 1970 to 1972. The opportunity for Polish scientists to conduct research at this largest European center for particle physics was the result of Poland gaining observer status in the CERN Council, thanks to the efforts and international contacts of Danysz and the Kraków physicist Marian Mięsowicz (1907-1992).

For his scientific achievements, Danysz was honored with many awards. In 1963, he was granted the title of full professor. He was a member of the Polish Academy of Learning (since 1960) and a corresponding member of the Academy of Sciences in Heidelberg. In 1969, he received the Smoluchowski Medal, the highest distinction awarded by the Polish Physical Society. After retiring in 1977, the University of Warsaw awarded him the title of Doctor Honoris Causa. He was also a knight of the highest state orders—the Order of the Banner of Work and the Commander’s Cross with Star of the Order of Polonia Restituta.

Marian Danysz was highly regarded by his colleagues for both his scientific achievements and physical intuition, as well as his personality. In science, he was primarily interested in the essence of the physical phenomenon he was studying, paying less attention to details. One of his passions was fast driving. The Dutch physicist and future CERN director, Leon van Hove (1924-1990), once remarked that when he got out of the coach driven by Danysz, which they had driven from Warsaw to Mazury, looking somewhat pale, he said that Danysz had a very interesting way of driving: he always waited for each maneuver until the situation on the road became interesting! His colleagues also called him "Tysiącpięćset" (from the initials MD – M-1000, D-500).

He passed away in Warsaw on February 9, 1983.