Classification of particles: hadrons and leptons

A positive pion collides with a neutron and the following interaction is observed:

Σ⁰ is a neutral sigma particle with a strangeness of −1

The interaction can be used to deduce the classifications of the Σ⁰.

Identify the classifications of each particle in Table 1. Tick (✓) the appropriate boxes for each particle.

A conservation rule predicts that the following interaction cannot occur:

State the conservation rule. Go on to explain your answer.

One way in which neutral pions decay is

Compare the rest energies of the particles involved in this decay.

The decay of the neutral pion leads to the production of further gamma photons.

Explain why.

The Standard Model is a theory that classifies elementary particles. Evidence for the theory has been collected since about 1950. However, the term Standard Model has only been used since 1973.

Suggest why progress in particle physics is slow.

The neutral lambda particle Λ⁰ is a baryon with a strangeness of −1

One possible decay for a Λ⁰ is

Deduce the quark structure of a Λ⁰.

State and explain which interaction is involved in this decay.

An antiparticle of the neutral lambda particle decays into a neutral pion and particle X

Identify X.

The rest energy of a Λ⁰ is equal to the energy of a photon with a frequency

Determine, in MeV, the rest energy of a Λ⁰.

The discovery of particles such as the Λ⁰ is made by large international research teams.

Suggest one reason for this.

Which statement about muons is correct?

Which statement is correct?

Cosmic rays are high-energy particles that come from space. Most of these particles are protons. There are other particles in cosmic rays, including atomic nuclei.

Table 1 gives the data for one particular nucleus X.

Determine the number of neutrons in nucleus X.

Calculate the speed of X. Ignore relativistic effects.

A pion (π⁺) and a kaon (K⁺) are produced when cosmic rays interact with the upper

atmosphere.

The π⁺ decays to produce a positron and an electron neutrino.

Show how the conservation laws apply to this decay.

The K⁺ decays to produce an anti-muon and a muon neutrino.

Explain how strangeness applies in this decay.

Write an equation for a K⁺ decay that involves only hadrons.

The gravitational force is one of the four fundamental forces. The ticks in the table match particles with the other fundamental forces.

In which row is the particle matched to the only other fundamental forces it experiences?

A muon and an electron are travelling at the same speed.

Which row gives the particle with the greater kinetic energy and the particle with the longer de Broglie wavelength?

Determine whether the following reaction is a possible decay for the neutral pion π⁰.

State the two possible quark configurations of a π⁰.

^{0 0} A student suggests that the kaon K and the anti-kaon K are the same particle.

Discuss whether this suggestion is correct.

The nucleus is held together by a force. It was predicted that a particle exists that is responsible for this force. The particle itself must experience this force.

The particle would have a rest energy between that of an electron and half that of a nucleon.

Discuss whether a kaon, a muon and a pion each have the properties of the predicted particle.

Information about these three particles is in the Data and Formulae Booklet.

The ⁰ baryon, composed of the quark combination uds, is produced through the strong interaction between a ⁺ meson and a neutron.

What is the quark composition of X ?