Conservation laws in particle interactions

This question is about an isotope of titanium that only decays by electron capture.

Complete Figure 1 to show the quark change that occurs during electron capture. Label the incoming and outgoing particles and the exchange particle.

In some circumstances, a nucleus of this isotope can exist with no orbiting electrons.

Explain why a neutral atom of this isotope is less stable than a nucleus that has no orbiting electrons.

A nucleus of this isotope of titanium has a proton number of 22 and a specific charge

Determine the number of neutrons in this nucleus.

The following equation represents a strong interaction between particle X and a proton.

What is the quark configuration of X ?

In β − decay:

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.

The diagram represents a quark change in which an electron antineutrino is produced.

Carbon-14 d ys into nitrogen-14 with the release of a beta (β⁻) particle and an

State the change of quark character in β⁻ decay.

Figure 2 shows the distribution of kinetic energies of β⁻ particles from the decay of carbon-14.

Explain how Figure 2 supports the existence of the antineutrino.

The existence of the antineutrino was confirmed by experiments in which antineutrinos interact with protons. The equation for this interaction is:

Identify particle X.

The positron released in this interaction is annihilated when it encounters an electron. A pair of gamma photons is then produced. Particle X can be absorbed by a nucleus. This produces another gamma ray. Table 1 contains data for three gamma photons detected during an antineutrino–proton interaction experiment.

Deduce which of the three gamma photons could have been produced by positron annihilation.

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.

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.

125 131 Two isotopes of iodine are I and I. 53 53

Determine, for these two isotopes, the difference between the constituents of the nuclei.

131 – A₅₃ I nuclide undergoes beta (β) decay to form a xenon nuclide.

State the nucleon number of the xenon nuclide.

125 A₅₃ I nuclide decays by electron capture to form a tellurium nuclide.

State two differences between the constituents of the iodine nucleus and the tellurium nucleus it decays into.

Internal conversion is a process in which a nucleus in an excited state can release its excess energy. In internal conversion all of the excess energy is transferred from the nucleus to an orbital electron through the electromagnetic force. This orbital electron is ejected from the atom.

The tellurium nucleus formed in question 01.3 is in an excited state and can undergo internal conversion.

Discuss three differences between internal conversion and beta (β^–) decay.

The process of beta plus (β⁺) decay can be represented by

Which row identifies particles X and Y ?

The decay is represented by this equation:

Complete the equation to show the decay by filling in the gaps.

Explain which fundamental interaction is responsible for the decay in question 01.1.

One decay mechanism for the decay of results in the argon nucleus having an excess energy of 1.46 MeV. It loses this energy by emitting a single gamma photon.

Calculate the wavelength of the photon released by the argon nucleus.

The potassium isotope can also decay by a second decay process to form a

Suggest how the emissions from a nucleus of decaying potassium can be used to confirm which decay process is occurring.