The quark combination of a particle is sū - AQA - A-Level Physics - Question 12 - 2021 - Paper 1
Question 12
The quark combination of a particle is sū.
Which is true for this particle?
A It has a baryon number of 1
B It has a charge of −1.6 × 10−19 C.
C It is a pion.
D It... show full transcript
Worked Solution & Example Answer:The quark combination of a particle is sū - AQA - A-Level Physics - Question 12 - 2021 - Paper 1
Step 1
A It has a baryon number of 1
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Answer
The baryon number is defined as the total number of baryons in the system minus the total number of antibaryons. The particle formed by the quark combination sū consists of a strange (s) quark and an up (u) quark, which is a meson rather than a baryon. As mesons have a baryon number of 0, this statement is false.
Step 2
B It has a charge of −1.6 × 10−19 C.
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Answer
The quark combination sū consists of an up quark (charge + rac{2}{3} e) and a strange quark (charge - rac{1}{3} e). The total charge is:
+ rac{2}{3} e - rac{1}{3} e = + rac{1}{3} e
Since the electron charge is approximately −1.6 × 10−19 C, the charge of the particle is + rac{1}{3} e, which does not equal -1.6 × 10−19 C. Hence, this statement is false.
Step 3
C It is a pion.
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Answer
A pion, or pi meson, is a type of meson consisting of a quark and an antiquark. Given the quark combination sū indicates the presence of an up and strange quark, this particle does not conform to the characteristics of a pion. Therefore, this statement is false.
Step 4
D It has a strangeness of −1/3
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Answer
Strangeness is defined as the number of strange quarks present minus the number of anti-strange quarks. Here, the strange quark makes the strangeness −1, which indicates that it indeed carries a strangeness value of −1. Hence, this statement is true.
