Missing: Antimatter


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 Prof. Yosef Nir


Looking at certain pictures, we get the feeling something is missing. Prof. Yosef Nir, Dean of the Weizmann Institute’s Faculty of Physics, looks at the picture of matter in the universe and sees that “something” simply isn’t there. This mystery has wide-ranging implications, as this matter makes up everything from humans to remote galaxies.

The Standard Model of elementary particles divides matter particles into two groups: leptons (electrons and neutrinos) and quarks (the particles that make up protons and neutrons). Opposite this “picture” of matter is the parallel system of antimatter, which has the same types of particles, only with the opposite charges. Thus if the “regular” electron has a negative charge, its antimatter “twin” equals it in everything except that its electric charge is positive.

One would expect the universe to have equal quantities of matter and antimatter, yet the antimatter disappeared in the first few fractions of a second of the universe’s existence. Why did it vanish and how? That’s one of the questions investigated by Nir. His research focuses, among other things, on neutrinos, which only in the past few years were discovered to have mass. This finding might lead to the solution of the antimatter mystery.


Why Israel? Why Weizmann?

“I was born and raised in Israel. Just as I’m part of Israel, so it is part of me. During my army service as a helicopter pilot I got to know Israel’s beauty from up close. In my 22 years at the Weizmann Institute – 5 as a student and 17 as a faculty member – I’ve seen that the joy of research here is greater than in some of the best research institutions in the world.”

“I chose to be photographed in Tel Aviv, the city that brought together my mother, a daughter of Polish communists, and my father, who came from a bourgeois Austrian family. It’s a city of culture and openness that pulsates with life around the clock.”


Prof. Yosef Nir is the incumbent of the Amos de-Shalit Chair of Theoretical Physics.