7. The following diagram gives information on the Standard Model of fundamental particles - Scottish Highers Physics - Question 7 - 2017

This statement is correct because baryons are a specific subclass of hadrons that are made up of three quarks. While all baryons, such as protons and neutrons, are hadrons (which encompass any particles formed from quarks), there are other types of hadrons known as mesons, which are made from quark-antiquark pairs. Thus, while every baryon qualifies as a hadron, not every hadron can be classified as a baryon.

The charge of the strange quark can be calculated based on the relationship that the total charge of the sigma particle is obtained from its quark content. Given that the charge of the up quark is (\frac{2}{3} e) and the charges of the other quarks must yield the observed charge of the sigma particles, the charge on a strange quark is found to be (-\frac{1}{3} e).

The force that holds the quarks together in the sigma (Σ) particle is known as the strong nuclear force. This fundamental force is responsible for binding quarks together to form protons, neutrons, and other hadrons.

The boson associated with the strong nuclear force is known as the gluon. Gluons act as the exchange particles for the strong force, facilitating the interaction between quarks within hadrons.

To find the mean lifetime of the Σ⁻ particle as measured by the stationary observer, we can use time dilation due to relativistic effects. The formula for time dilation is:

$t' = \frac{t}{\sqrt{1 - \frac{v^2}{c^2}}}$

Where:

• (t) is the proper lifetime in the particle's rest frame (1.5 × 10⁻¹⁸ s),
• (v) is the speed of the particle (0.9c),
• (c) is the speed of light.

Plugging the values, we get:

$t' = \frac{1.5 \times 10^{-18}}{\sqrt{1 - (0.9)^2}} = \frac{1.5 \times 10^{-18}}{\sqrt{1 - 0.81}} = \frac{1.5 \times 10^{-18}}{\sqrt{0.19}} \approx 3.4 \times 10^{-18} \text{ s}$

Thus, the mean lifetime of the Σ⁻ particle as measured by the observer is approximately 3.4 × 10⁻¹⁸ seconds.