Melvin Schwartz was born in 1932. He grew up in New York City in the Great Depression and went to the Bronx High School of Science. His interest in physics began there at the age of 12. He began undergraduate work at Columbia University in 1949, where Nobel Prize laureate Isidor I. Rabi was the head of the physics department. He provided the research setting for six Nobel Prize-winning projects during those 13 years, as well as hosting about a half dozen future laureates, either as students or as post-doctoral researchers. Schwartz stayed at Columbia for his graduate work and became an Assistant Professor there in 1958. He became an Associate Professor in 1960 and a Professor in 1963.
In 1966, after 17 years at Columbia, he moved west to Stanford University, where a new accelerator was just being completed. There, he was involved in research investigating the charge asymmetry in the decay of long-lived neutral kaons and another project which produced and detected relativistic hydrogen-like atoms made up of a pion and a muon.
He became president of Digital Pathways in the 1970s, and he still holds that position. In addition, he became Associate Director, High Energy and Nuclear Physics, at Brookhaven National Laboratory in 1991.
He shared the 1988 Nobel Prize in Physics with Leon Max Lederman and Jack Steinberger, with whom he did the prize-winning research to develop the neutrino beam method and the demonstration of the doublet structure of the leptons through the discovery of the muon neutrino (see Press Release).
The following press release from the Royal Swedish Academy of Sciences describes Schwartz's work:
The work now rewarded was carried out in the 1960s. It led to discoveries that opened entirely new opportunities for research into the innermost structure and dynamics of matter. Two great obstacles to further progress in research into weak forces - one of nature's four basic forces - were removed by the prizewinning work. One of the obstacles was that there was previously no method for the experimental study of weak forces at high energies. The other was theoretically more fundamental, and was overcome by the three researchers' discovery that there are at least two kinds of neutrino. One belongs with the electron, the other with the muon. The muon is a relatively heavy, charged elementary particle which was discovered in cosmic radiation during the 1930s. The view, now accepted, of the paired grouping of elementary particles has its roots in the prizewinner's discovery.
Neutrinos are almost ghostlike constituents of matter. They can pass unaffected through any wall, in fact all matter is transparent to them. During the conversion of atomic nuclei at the centre of the sun, enormous quantities of neutrinos (which belong to the electron family) are produced. They pass through the whole sun virtually unhindered and stream continually from its surface in all directions. Every human being is penetrated by sun neutrinos at a rate of several billion per square centimetre per second, day and night, without leaving any noticeable trace. Neutrinos are inoffensive. They have no electrical charge and they travel at the speed of light, or nearly. Whether they are weightless or have a finite but small mass is one of today's unsolved problems.
The contribution now awarded consisted among other things of transforming the ghostly neutrino into an active tool of research. As well as in cosmic radiation, neutrinos, which belong to the moon family, can be produced in a multistep process in particle accelerators, and this is what the prizewinners utilized. Suitable accelerators exist in some few laboratories throughout the world. Since all matter is transparent to neutrinos, it is difficult to measure their action. Neutrinos are, however, not wholly inactive. In very rare cases a neutrino can score a random direct hit or, more correctly, a near-miss, on a quark, a pointlike particle within a nucleon (proton or neutron) in the nucleus of an atom or on a similarly infinitesimal electron in the outer shell of an atom. The rarity of such direct hits implies that a single neutrino of moderate energy would be able to pass unhindered through a wall of lead of a thickness measured in light-years. In neutrino experiments the rarity of the reactions is compensated for by the intensity of the neutrino beam. Even in the first experiment, the number of neutrinos was counted in hundreds of billions. The probability of a hit also increases with the energy of the neutrinos. The method of the prizewinners makes it possible to achieve very high energies, limited only by the performance of the proton accelerator. Neutrino beams can reveal the hard inner parts of a proton in a way not dissimilar to that in which X-rays reveal a person's skeleton.
When the neutrino beam method was invented by the Columbia team at the beginning of the 1960s the quark concept was still unknown, and the method has only later become important in quark research. Also of later date is the experimental discovery of an entirely new way for a neutrino to interact with an electron or a quark in which it retains its own identity after impact. The classical way of reacting implied that the neutrino was converted into an electrically charged lepton (electron or muon), and this was the reaction utilised by the prizewinners.