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Stability of the proton

AS Level Notes

Garfield Graphics included with kind permission from PAWS Inc. All Rights Reserved.LOJ Feb 2004

Stability of the proton and neutron

• Decay of the Proton • A free proton (one outside a nucleus) has long been

considered to be a stable particle, but recent developments of grand unification models have suggested that it might decay with a half-life of about 1031 years.

• WOW! 10,000,000,000,000,000,000,000,000,000,000 years!

• Particle Physicists are trying to prove that this is indeed the case.

• The decay of the proton is associated with a quark transformation in which an "up" quark is converted to a "down" quark by the weak interaction .

Garfield Graphics included with kind permission from PAWS Inc. All Rights Reserved.LOJ Feb 2004

Proton Decay

• The decay of the proton is associated with a quark transformation in which an "up" quark is converted to a "down" quark by the weak interaction .

Garfield Graphics included with kind permission from PAWS Inc. All Rights Reserved.LOJ Feb 2004

Decay of the Neutron

• A free proton is virtually stable but a free neutron is comparitively very UNstable.

• It will decay with a half-life of about 10.3 minutes but it is considerably more stable if combined into a nucleus.

Garfield Graphics included with kind permission from PAWS Inc. All Rights Reserved.LOJ Feb 2004

Neutron Decay

• The decay of the neutron involves the weak interaction as indicated in the Feynman diagrams you know.

Garfield Graphics included with kind permission from PAWS Inc. All Rights Reserved.LOJ Feb 2004

Neutron Decay

• The decay of the neutron is associated with a quark transformation in which a "down" quark is converted to an "up" quark by the weak interaction.