Although we have tried to trace and contact copyright holders before publication, in some cases this has not been possible. We have no control over, and are not responsible for, the contents of such third party websites. These materials may contain links for third party websites. Designed and typeset by Mike Brain Graphic Design Limited Illustrated by Peter Harper Cover design by Clare Webber and Macmillan Education Cover photograph by Pasieka, Science Photo Library The publishers would like to thank Tim Jackson for his help in developing and editing the manuscript for publication. Design and illustration © Macmillan Publishers Limited 2014 First published 2014 All rights reserved no part of this publication may be reproduced, stored in a retrieval system, transmitted in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publishers. Macmillan Education 4 Crinan Street, London N1 9XW A division of Macmillan Publishers Limited Companies and representatives throughout the world ISBN 978-5-6 AER Text © Helen Jacobs, Novelette McKnight, Stewart McLean, Patrice Piggott-Cumberbatch and Mike Taylor SBA chapter contributed by Graeme Corbin and © Macmillan Publishers Limited. Chemistry For CAPE® Examinations is an independent publication and has not been authorized, sponsored, or otherwise approved by CXC. Any other particle could not produce exactly these traces as it decayed.įor CAPE Examinations Helen Jacobs, Novelette McKnight, Stewart McLean, Patrice Piggot-Cumberbatch, Graeme Corbin, Mike TaylorĬAPE® is a registered trade mark of the Caribbean Examinations Council (CXC). The tracks that you see in the cover picture of this book (a computer visualization of the response of the huge array of detectors in the LHC) are some that can only have come from the decay of the Higgs boson. It was in the LHC on July 4th 2012 that collisions were seen which could only have come from the decay of a Higgs boson. For this you need the apparatus called the Large Hadron Collider (LHC). The only way to ﬁnd it would be to smash two other particles together at speeds near to that of the speed of light. Other calculations showed that such a particle could only exist for, at most, nanoseconds and that it would carry (or be) a large amount of energy. The exchange particle which goes with the mass ﬁeld is called the Higgs boson. Such a particle-cumenergy-packet is called a boson. Some very subtle physics showed that the particle must have a particular property it must behave as though it had no spin. If that is the case, the mass ﬁeld, like any other, must have an exchange particle associated with it. It was this problem which led Professor Higgs and his co-workers to suggest that the whole universe is ﬁlled with a ‘mass ﬁeld’ and that particles interact with that ﬁeld to acquire ‘mass’. Nothing in it makes possible the property that we call mass.

But there is a problem with the standard model. Each one comprises a ﬁeld and an associated exchange particle. These are gravity, electromagnetism, the ‘strong force’ (which holds nuclear particles together) and the ‘weak force’ (responsible for effects such as magnetism). It is the exchange of energy packets which is the ‘force’. If the ball is very heavy the thrower staggers backwards after throwing and so does the catcher. It is like children who throw and catch a ball: as long as they do so, they stay together. But is that really an explanation? Today’s explanation (called the standard model) says that there is a region of space round the magnets (the ‘ﬁeld’) inside which the magnets throw other particles to and fro between each other. Two magnets attract or repel one another, but why and how do they do this? We get round it by saying that there is a magnetic ‘ﬁeld’ between them, with ‘lines of force’ that change shape and produce the attractive or repulsive effect. Another such concept is the idea of ‘action at a distance’.

But this is a concept outside our everyday experience, which we can accept and use but not picture happening. We have also learned that matter and energy are one and the same thing, according to Einstein’s famous equation E = mc2.

We now know that electrons are indeed indivisible, but that protons and neutrons are themselves made up of ‘quarks’: it takes three quarks to make either a proton or a neutron. Then came the discovery of the atomic nucleus, made up of protons and neutrons, and the electrons that surround the nucleus. The Higgs boson In the early 19th century atoms were thought to be the ultimate, indivisible, components of matter.

Helen Jacobs Novelette Sadler-McKnight Stewart McLean Patrice Piggot-Cumberbatch Graeme Corbin Mike Taylor

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