Richard Phillips Feynman

A Parametrization of the Properties of Quark Jets

A model is analyzed that provides a parametrization of the properties of the jet of mesons generated by a fast outgoing quark. It is assumed that the meson that contains the original quark leaves momentum and flavor to a remaining jet in which the particles are distributed (except for scaling of the energy and possible changes of flavor) like those of the original jet. One function, the probability f(η) that the remaining jet has a fraction η of the momentum of the original jet, is chosen (as a parabola) so the final distribution of charged hadrons agrees with data from lepton experiments. All the properties of quark jets are determined from f(η) and three parameters; the degree that SU(3) is broken in the formation of new quark-antiquark pairs (s[bar]s is taken as half as likely as uu[bar]), the spin nature of the primary mesons (assumed to be vector and pseudoscalar with equal probability), and the mean transverse momentum given to these primary mesons. Monte Carlo methods are used to generate typical jets. Analytic approximations are also given. Many features of quark jets are examined. The distribution of momentum of various hadrons D_q^h(z), the properties of the hadrons of largest momentum in the jet, correlations, rapidity-gap distribution of charge and of transverse momentum are some of the subjects discussed. The appearance of the jets to an instrument sensitive only to particles above some minimum momentum is also described. Although the model is probably not a true description of the physical mechanism responsible for quark jets, many predictions of the model seem quite reasonable, possibly much like real quark jets (except that the possibility of the emission of baryons is disregarded). The purpose of this work is to provide a model useful in the design of experiments in which quark jets may be observed, and further to provide a standard to facilitate the comparison of lepton-generated jets with the high-p⊥ jets found in hadron collisions.

Quantum mechanical computers

The physical limitations, due to quantum mechanics, on the functioning of computers are analyzed.

There's plenty of room at the bottom [data storage]

The problem of manipulating and controlling things on a small scale is discussed. The question of how to write the entire 24 volumes of the Encyclopaedia Britannica on the head of a pin is examined. The question of how to read it is also discussed, focusing on the need to make the electron microscope more powerful. Other aspects of miniaturization and of making things on a small scale are discussed, including miniaturizing the computer, miniaturization by evaporation, problems of lubrication, and rearranging atoms.<<ETX>>

Chapter II Application of Quantum Mechanics to Liquid Helium

Publisher Summary The aim of this chapter is to describe the physical ideas that have been suggested to explain the behavior of helium, which can most easily be related to the properties of the Schriidinger equation. Since the discovery of liquid helium, considerable progress has been made in understanding its behavior from first principles. Some of the properties are more easily understood than others. The most difficult of these concern the resistance to flow above critical velocity. Liquid helium exhibits quantum mechanical properties on a large scale in a manner somewhat differently than do other substances. No other substance remains liquid to a temperature low enough to exhibit the effects. Classically at absolute zero all motion stops, but quantum mechanically this is not so. In fact the most mobile substance known is one at absolute zero, where on the older concepts one should expect hard crystals. Helium stays liquid, as London has shown, because the inter-atomic forces are very weak and the quantum zero point motion is large enough, since the atomic mass is small, to keep it fluid even at absolute zero.

What Do You Care What Other People Think?: Further Adventures of a Curious Character

A scientist and physicist, one of the greatest of the 20th century, and winner of the Nobel Prize, Richard Feynman worked on the atomic bomb and revealed the cause of the Challenger disaster. Before his death earlier this year, he worked with his friend Ralph Leighton to prepare this manuscript, his last literary legacy. Illustrated.

Correlations among particles and jets produced with large transverse momenta

We continue to investigate consequences of the assumption that the high transverse momentum particles seen in hadron-hadron collisions are produced by a single, hard, large-angle elastic scattering of quarks; one from the target and one from the beam. A large p⊥ event consists of four jets (collection of hadrons moving in roughly the same direction). The two outgoing quarks fragment into two jets of hadrons with roughly equal and opposite transverse momentum. The other two jets have small transverse momentum and result from the break up of the beam and target hadrons. We compare the model with existing data on the correlations among particles on the same and opposite (away) side of a large p⊥ trigger. If we allow the quarks within the initial hadrons to have a large mean transverse momentum, 〈k⊥〉_(h→q), then good agreement with data is found. We have taken 〈k⊥〉_(h→q) = 500 MeV; however, even larger values are suggested by certain ISR experiments. A large cross section for producing a jet (quark) is predicted. For instance, σ(pp → jet + X)/σ(pp → π^0 + X) = 370 at x⊥ = 0.4 and θ_(c.m.) = 90°. This is consistent with a recent FNAL jet trigger experiment. Predictions for future FNAL and ISR experiments are made.

Dispersion of the neutron emission in U-235 fission☆

Equations are developed which allow the calculation of the average number of neutrons per U{sup 235} fission from experimental measurements. Experimental methods are described, the results of which give a value of (7.8{+-}0.6){sup 1/2} neutrons per U{sup 235} thermal fission. (D.E.B.)

The meaning of it all : thoughts of a citizen-scientist

Many appreciate Richard P. Feynmans contributions to twentieth-century physics, but few realize how engaged he was with the world around himhow deeply and thoughtfully he considered the religious, political, and social issues of his day. Now, a wonderful bookbased on a previously unpublished, three-part public lecture he gave at the University of Washington in 1963shows us this other side of Feynman, as he expounds on the inherent conflict between science and religion, peoples distrust of politicians, and our universal fascination with flying saucers, faith healing, and mental telepathy. Here we see Feynman in top form: nearly bursting into a Navajo war chant, then pressing for an overhaul of the English language (if you want to know why Johnny cant read, just look at the spelling of friend); and, finally, ruminating on the death of his first wife from tuberculosis. This is quintessential Feynmanreflective, amusing, and ever enlightening.

The behavior of hadron collisions at extreme energies

There are several reasons to be interested in this problem of very high energy hadron scattering. Firstly, most theoretical inventions are based on analysis of simple collisions, in which only a small number of particles come out. But it is at once realized that questions of unitarity, the asymptotic behavior for high energy in dispersion integrals, etc, require some ansatz be made for the higher energy collisions, in order to close the infinite hierarchy of equations which result. Secondly, experiments at high energies usually yield many particles, and only by selecting the rare collision can we find those about which the theorist has been speaking. For the highly multiple inelastic collisions (to which the major part of the inelastic cross section is due) so many variables are involved that it is not known how to organize or present this data. Any theoretical suggestion (even if it proves to be not quite right) suggests a way that this vast amount of data may be analyzed. For this reason I shall present here some preliminary speculations on how these collisions might behave even though I have not yet analyzed them as fully as I would like.

An Outsider's Inside View of the Challenger Inquiry

A few days after the Challenger accident, on a Friday, I got a call from William Graham, who was the acting director of NASA. Mr. Graham had been a student of mine—at Caltech, and also at the Hughes Aircraft Company, where I gave a series of lectures—and thought maybe I would be of some use to the investigation. When I heard it would be in Washington, my immediate reaction was not to do it. I have a principle of not going anywhere near Washington or having anything to do with government. In the course of diagnosing the technical causes of the Challenger space shuttle disaster, the author also formed some impressions of NASA and became acquainted with some of the pitfalls of participation in an official investigation.