The 2015 Nobel Prize in Physics was given on October 6 to Takaaki Kajita of the Superkamiokande experiment and to Arthur McDonald of the Sudbury Neutrino Observatory. The work at both those sites is thoroughly discussed in The Cosmos (see Section 12.7, p. 322-325) about the solar-neutrino experiment.
By showing definitively that a mix of the three types of neutrinos reaches the Earth, combining the knowledge that only electron-neutrinos leave the Sun shows that neutrinos change in type en route. Only if neutrinos have mass can such changes take place, so the discovery is a major challenge to the Standard Model of particle physics.
This is the third Nobel Prize for neutrino research. Half the 1995 Nobel Prize went Fred Reines for the discovery of neutrinos in an atomic-reactor beam (his co-discoverer, Clyde Cowan, having died before the prize was given, making him ineligible). Half the 2002 Nobel Prize went to Ray Davis, who ran the chlorine version of the neutrino experiment at the Homestake Mine, and Masatoshi Koshiba, who was in charge of Kamiokande (the Neutrino Detection Experiment [NDE] in the Kamioka mine in Japan). John Bahcall from the Institute for Advanced Study, who had done the bulk of the theoretical work involved, was omitted from the prize, unfortunately (again, as the prize is not awarded posthumously).
Links: 2015 Nobel Prize in Physics at the Royal Swedish Academy of Sciences; Dennis Overbye’s analysis for the NY Times (including a discussion of the next investigations via The Deep Underground Neutrino Experiment, DUNE).
Robert Wilson and Arno Penzias accidentally discovered the afterglow of the big bang in 1964. Their now-famous horn antenna, built for Bell Labs in New Jersey, was supposed to be picking up the radio waves emitted by galaxy clusters and supernova remnants. But it recorded a temperature that was 3.5 kelvin hotter than it should have been, no matter where they pointed it (see Section 19.2a, p. 511).
Credit: © Roger Ressmeyer/CORBIS
We now know this was caused by the first photons to be released after the big bang, which still pervade the cosmos as radio waves. These days, Wilson keeps a sound recording of those waves on his cellphone (see audio link), as New Scientist magazine discovered when they interviewed him at a celebration marking half a century since the discovery.
Robert Wilson is now at the Harvard Smithsonian Center for Astrophysics. In 1978, he and Arno Penzias shared the Nobel prize in physics with Pyotr Kapitsa.
Links: the interview; the background hiss of the big bang audio (both via New Scientist).
François Englert and Peter W. Higgs have been awarded the 2013 Nobel Prize in Physics “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, at CERN’s Large Hadron Collider.” The announcement by the ATLAS and CMS experiments took place on July 4 last year. (See Figure 19-15, p. 523.)
Credit: Vince Higgs
The Brout-Englert-Higgs (BEH) mechanism was first proposed in 1964 in two papers published independently, the first by Belgian physicists Robert Brout (now deceased) and François Englert, and the second by British physicist Peter Higgs. Among other things, it explains the mechanism that endows fundamental particles with mass. A third paper by Americans Gerald Guralnik and Carl Hagen with their British colleague Tom Kibble contributed to the development of the new idea, which now forms an essential part of the Standard Model of particle physics. As was pointed out by Higgs, a key prediction of the idea is the existence of a massive particle of a new type, dubbed the Higgs boson, which was discovered by the ATLAS and CMS experiments at CERN in 2012.
The Standard Model describes the fundamental particles from which we, and all the visible matter in the Universe, are made, along with the interactions that govern their behavior. It’s a remarkably successful theory that has been thoroughly tested by experiment over many years. Until last year, the BEH mechanism was the last remaining piece of the model to be experimentally verified. Now that the Higgs has been found, experiments at CERN are eagerly looking for physics “beyond the Standard Model”.
Links: the CERN press release, a Higgs boson poster courtesy of the Institute of Physics; an introductory cartoon explaining the Higgs field, courtesy of the New York Times; and Sean Carroll’s op-ed article, also in the New York Times.