546 10 Particle Physics – II
10.10 Show that (a)ρ→η+πis forbidden as a decay through strong interaction.
(b)ω→η+πis forbidden as an electro-magnetic or strong decay.
10.11 (a) Theρ^0 andK^0 mesons both decay predominantly toπ++π−. Explain
why the mean lifetime of theρ^0 is 10−^23 s, while that ofK^0 is 0. 89 ×
10 −^10 s.
(b) TheΔ^0 and theΛboth decay to proton andπ−meson. Explain why the
Δ^0 meson lifetime is∼ 10 −^23 s while that ofΛis 2. 6 × 10 −^10 s.
10.12 State and give reasons for the following decay modes of theρ-meson
(Jp= 1 −,I=1) which are allowed by the strong or electromagnetic inter-
action
(a)ρ^0 →π+π−
(b)ρ^0 →π^0 π^0
(c)ρ^0 →η^0 π^0
(d)ρ^0 →π^0 γ
10.13 Conventionally nucleon is given positive parity. What does one say about
deuteron’s parity and the intrinsic parities of u and d-quarks?
10.14 Which of the following hyperon decays are allowed in lowest order weak
interactions?
(a)Ξ^0 →Σ−+e++νe
(b)Ξ^0 →p+π−+π^0
(c)Ω−→Ξ^0 +e−+νe
(d)Ω−→Ξ−+π++π−
10.15 Explain how the parity of K−meson has been determined.
10.16 (a) Briefly define the following terms giving two examples of each:
(i) Hadron
(ii) Lepton
(iii) Baryon
(iv) Meson
(b) Aπ^0 meson at rest decays into two photons of equal energy. What is the
wavelength (in m) of the photons? [The mass of theπ^0 is 135 MeV/c^2 ]
[University of London]10.2.2 StrongInteractions.................................
10.17 (a) TheΔ++Resonance has a full width ofΓ=120 MeV. How far on aver-
age would such a particle of energy 200 GeV travel before decaying?
(b) Given that the width for W-boson decay is less than 6.5 MeV, estimate the
limit for the corresponding lifetime.
10.18 Analyze the pion – proton scattering data in terms of isospin amplitudes a 1 / 2
and a 3 / 2 for the reactions: