The Standard Model explains how the basic building blocks of matter interact, governed by four fundamental forces - Scottish Highers Physics - Question 6 - 2022

The K+ particle is composed of an up quark and an anti-strange quark.

The fundamental force involved in the decay of kaons is the weak nuclear force.

To find the time taken for the pion to travel 30.0 m at 0.95c:

Using the formula: $t = \frac{d}{v}$

Where:

• $d = 30.0\,m$
• $v = 0.95 \times 3 \times 10^8\, m/s$

Calculating: $t = \frac{30.0}{0.95 \times 3 \times 10^8} \approx 1.053 \times 10^{-7}\, s = 105.3 \text{ ns}$

In the pion's frame of reference, the distance between the detectors can be calculated using:

$d' = d \sqrt{1 - \frac{v^2}{c^2}}$

Substituting:

• $d = 30.0\,m$
• $v = 0.95c$

So, $d' = 30.0 \sqrt{1 - (0.95)^2} \approx 30.0 \sqrt{0.0975} \approx 9.37\,m$

The greater number of pions detected at the second detector can be explained by the effects of time dilation. Pions have a mean lifetime of 26 ns in their own frame of reference. However, due to relativistic effects, from the stationary observer's point of view, the pions appear to live longer because they are moving close to the speed of light. This increased observed lifetime leads to more pions being detected at the second detector than would normally be expected without considering relativistic effects.

The analogy of the Standard Model as a set of children's building blocks effectively illustrates the concept of fundamental particles as the basic components of matter. Just as different shapes and sizes of blocks can combine in various ways to build complex structures, various fundamental particles interact and combine to form the diverse matter observed in the universe. This analogy helps simplify complex physics concepts, making them more accessible and relatable.