Particle Physics Questions

Q13.

Helium is the second most abundant element in the universe.

The most common isotope of helium is

A nucleus of this isotope has a rest energy of 3728 MeV.

In 2011, at the Relativistic Heavy Ion Collider, anti-helium nuclei were produced.

Nuclei of anti-helium are made up of antiprotons and antineutrons.

It is suggested that an antineutron can decay to form an antiproton in a process similar to β– decay.

In one particular collision between an anti-helium nucleus and a helium nucleus, the nuclei are annihilated and two photons are formed.

(a) State what is meant by 'isotopes'.

[2 marks]

(b) Explain why two photons are formed instead of a single photon when a helium nucleus annihilates with the anti-helium nucleus.

[2 marks]

[4 marks]

(d) Complete this equation for the possible decay of an antineutron.

[2 marks]

(e) Name the interaction would be responsible for such a decay.

[1 mark]

(Total 11 marks)