20th_IPhO_1989 - Problems of the 20th International Physics...

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Unformatted text preview: Problems of the 20th International Physics Olympiad 1 (Warsaw, 1989) Waldemar Gorzkowski Institute of Physics, Polish Academy of Sciences, Warsaw, Poland 2 Abstract The article contains problems given at the 20 th International Physics Olympiad (1989) and their solutions. The 20 th IPhO was the third IPhO organized in Warsaw, Poland. Logo The emblem of the XX International Physics Olympiad contains a picture that is a historical record of the first hypernuclear event observed and interpreted in Warsaw by M. Danysz and J. Pniewski 3 . The collision of a high-energy particle with a heavy nucleus was registered in nuclear emulsion. Tracks of the secondary particles emitted in the event, seen in the picture (upper star), consist of tracks due to fast pions (thin tracks) and to much slower fragments of the target nucleus (black tracks). The black track connecting the upper star (greater) with the lower star (smaller) in the figure is due to a hypernuclear fragment, in this case due to a part of the primary nucleus containing an unstable hyperon instead of a nucleon. Hyperfragments (hypernuclei) are a new kind of matter in which the nuclei contain not only protons and neutrons but also some other heavy particles. In the event observed above the hyperon , bound with nucleon, decays like a free particle through a week (slow) process only. This fact strongly suggested the existence of a new quantum number that could explain suppression of the decay, even in presence of nucleons. Indeed, this was one of the observations that, 30 months later, led to the concept of strangeness. Introduction Theoretical problems (including solutions and marking schemes) were prepared especially for the 20 th IPhO by Waldemar Gorzkowski. The experimental problem (including the solution and marking scheme) was prepared especially for this Olympiad by Andrzej Kotlicki. The problems were refereed independently (and many times) by at least two persons 1 This article has been sent for publication in Physics Competitions in October 2003 2 e-mail: gorzk@ifpan.edu.pl 3 M. Danysz and J. Pniewski, Bull. Acad. Polon. Sci. , 3(1) 42 (1952) and Phil. Mag. , 44 , 348 (1953). Later the same physicists, Danysz and Pniewski, discovered the first case of a nucleus with two hyperons (double hyperfragment). after any change was made in the text to avoid unexpected difficulties at the competition. This work was done by: First Problem: Andrzej Szadkowski, Andrzej Szymacha, Wodzimierz Ungier Second Problem: Andrzej Szadkowski, Andrzej Szymacha, Wodzimierz Ungier, Stanisaw Woronowicz Third Problem: Andrzej Rajca, Andrzej Szymacha, Wodzimierz Ungier Experimental Problem: Krzysztof Korona, Anna Lipniacka, Jerzy usakowski, Bruno Sikora Several English versions of the texts of the problems were given to the English- speaking students. As far as I know it happened for the first time (at present it is typical). The original English version was accepted (as a version for the students) by the leaders of the...
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This note was uploaded on 11/08/2011 for the course PHYS 0000 taught by Professor Na during the Spring '11 term at Rensselaer Polytechnic Institute.

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20th_IPhO_1989 - Problems of the 20th International Physics...

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