7.3 The Structure of Matter

Electron capture is one of the ways a nucleus attains stability.

In this process, a proton in the nucleus ‘captures’ an inner-shell electron. While the mass number is unchanged, the atomic number decreases by 1, and a highly energetic particle is released.

At the quark level, only some are directly involved in this process. Those which are not are sometimes called ‘spectator quarks’.

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A similar process known as muon capture is being investigated for use in the disposal of highly radioactive waste. A highly energetic muon beam causes muons to be captured by protons in the nuclei of the radioactive isotopes in order to convert them into more stable isotopes.

 is a baryon with a quark structure of .

A proposed particle interaction involving the  baryon is:

 is part of a family of baryons called Sigma baryons. They are all strange particles.

Determine the quark combination of the  baryon. Clearly show your working

The virtual photon mediates the electromagnetic force.

It is called a ‘virtual’ photon because it is not detectable in a laboratory.

The unfinished Feynman diagram shows the interaction between a proton and an anti-neutrino. 

(c)        Complete the Feynman diagram.

The neutron-neutrino interaction can be expressed in a similar way to the Feynman diagram in part (c).

The Feynmann diagrams show two electroweak interactions between electrons. One of the exchange particles is a photon.

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The discovery of the Higgs Boson marked a huge accomplishment for particle physicists.

It was first hypothesised by Peter Higgs and his team in 1964 and then discovered by a large collaborative effort at the CERN particle physics laboratory much later in 2012.