[...]... Taking that difference in binding energy of proton and neutron into account the decay of a neutron in a nucleus is usually impossible While the mass of the neutron is larger than the sum of the masses of a proton and an electron, the margin is small (about 0.7 MeV) The difference in binding energies of neutron and proton may (and often will) be more than this small margin and in those cases neutrons in. .. was Bohr’s, answering Einstein using arguments from Einstein’s own theory of gravitation Even if Bohr had the last word, Einstein never wavered from his point of view It should be mentioned that Bohr started his work leading to his model at Manchester, where Rutherford provided much inspiration Bohr’s famous trilogy of 1913, explaining many facts, in particular certain spectral lines of hydrogen (Balmer... be something you could understand at the end of Act One But no We understand many things about particles and their interactions, but this and other mysteries make it very clear that we are nowhere close to a full understanding And, most important: we still do not understand gravity and its interplay with quantum mechanics This book has been set up as follows Chapter 1 contains some preliminaries: atoms,... neutrons and quarks are introduced, as well as photons and antiparticles Furthermore there is an introductory discussion of mass and energy, followed by a description of the notion of an event, central in particle physics The Chapter closes with down-to-earth type subjects such 4 E L E M E N TA R Y PA R T I C L E P H Y S I C S as units used and particle naming We begin in Chapter 2 by introducing the... event anything is possible An important observation can be made here Looking at neutron decay we see the following: initially there is a neutron That particle disappears, and three new particles appear, namely a proton, an electron and an antineutrino Thus in particle reactions particles disappear and new particles are created This is very important, as this phenomenon, the creation of particles, is... before, the neutron contains one up quark and two down quarks What actually happens is that one of the down quarks decays into an up quark, an electron and an antineutrino The change of a down quark into an up quark transforms a neutron into a proton In the figure the antineutrino, being an antiparticle, is represented by a ball with a thin black rim e d u d d u u N ν P As an interesting aside: neutrons... the actors, the elementary particles and their interactions Forces are understood today as due to the interchange of particles, and therefore we will use the word ‘interactions’ rather than the word ‘forces’ The ensemble of particles and forces described in Chapter 2 is known as the Standard Model In Chapter 3 some very elementary concepts of quantum mechanics shall be discussed, and in Chapter 4 some... astonishing things: why did he not discover quantum theory? Knowing all about the wave theory of light and having introduced the concept of the photon, he never fused these concepts into one theory According to Pais, Einstein pondered about this problem in a most intensive way in the period 1905–1910 It seems so straightforward now, yet he missed it 18 Papers that changed the world: Einstein’s photon... one could write electron and that would mean a positron And also, to make the point once again, positron means an electron This convention will be used throughout this book 20 Paul Dirac (1902–1984) He succeeded in combining quantum mechanics and the theory of relativity in 1928, and introduced in 1929 the idea of an antiparticle (although not the name, introduced by de Broglie in 1934) Unfortunately... registered in some way From these tracks one must try to reconstruct what happened, and looking at many such cases an understanding can be achieved Thus there is no rigorously fixed behaviour for unstable particles For example, the neutron is an unstable particle that on the average lives for about 10 minutes It decays into a proton, an electron and a neutrinoc (in fact, in today’s parlance, an antineutrino) . Folder:Chapter-FM: Library of Congress Cataloging -in- Publication Data Veltman, Martinus. Facts and mysteries in elementary particle physics / Martinus J.G. Veltman. p. cm. Includes index. ISBN 981-238-148-1 ISBN. 53 2.7 Families and Forces 55 v contents.p65 06/30/2004, 12:15 PM5 vi ELEMENTARY PARTICLE PHYSICS 2.8 The Spin 2 1 Particles 62 2.9 The Spin 1 and 2 Particles 68 2.10 Forces and Interactions 69 2.11. central in particle physics. The Chapter closes with down-to-earth type subjects such introduction.p65 06/30/2004, 12:15 PM3 4 ELEMENTARY PARTICLE PHYSICS as units used and particle naming. We begin