1409
Chapter 41
Elementary Particles and the Beginning of the Universe
Conceptual Problems
1
•
Similarities
Differences
Baryons and mesons are hadrons, i.e., they
participate in the strong interaction. Both
are composed of quarks.
Baryons consist of three quarks and are
fermions. Mesons consist of two quarks
and are bosons. Baryons have baryon
number +1 or
−
1. Mesons have baryon
number 0.
2
•
Determine the Concept
The muon is a lepton. It is a spin-½ particle and is a fermion. It
does not participate in strong interactions. It appears to be an elementary particle like the
electron. The pion is a meson. Its spin is 0 and it is a boson. It does participate in strong
interactions and is composed of quarks.
*3
•
Determine the Concept
A decay process involving the strong interaction has a very short
lifetime (
∼
10
−
23
s), whereas decay processes that proceed via the weak interaction have
lifetimes of order 10
−
10
s.
4
•
(
a
) True
(
b
) False. There are two kinds of hadrons-baryons, which have spin
2
1
(or
,
,
2
5
2
3
and so
on), and mesons, which have zero or integral spin.
5
•
False. Mesons have zero or integral spins.
6
•
Determine the Concept
A meson has 2 quarks, a baryon has 3 quarks.
7
•
Determine the Concept
No; from Table 41-2 it is evident that any quark-antiquark
combination always results in an integral or zero charge.

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