We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
Published online by Cambridge University Press: 05 August 2012
Matter is made up of two kinds of elementary particle, quarks and leptons, each having six varieties divided into two groups of three:
Quarks
up, charmed, top (all three have charge +2/3;)
down, strange, bottom (all three have charge -1/3;)
Leptons
electron, muon, tauon (all three have charge -1)
neutrinoe, neutrinoμ, neutrinoτ (all three have charge 0).
The three neutrinos are not interchangeable; they are distinguished by indices
Usual matter
matter we are familiar with is made up only of:
the up quark, the down quark, and the electron; in particular:
the proton is made up of three quarks: up, up, down (charge +1),
the neutron is made up of three quarks: up, down, down (charge 0).
Mesons
elusive particles made of 1 quark and 1 antiquark; the 6 types of quarks make 36 types of mesons.
Forces of nature
Four types of force of different symmetries occur among matter particles; these forces are carried by particles of a new kind:
(1) electromagnetism, carried by the photon (light, X-rays, γ rays, etc.)
(2) the weak force is carried by three particles: W+, W- and Z0
(3) the strong force is carried by eight ‘colors’ of gluons
(4) gravitation is carried by the graviton
The standard model unifies electromagnetism and the weak force, as if the three particles W+, W- and Z0 were actually heavy photons.
The existence of the top quark had been predicted for a score of years; it was finally observed in 1994, completing the list of elementary particles.
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.
