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Fundamentals Of Physics
Found in: Page 1363

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Short Answer

The A2+ particle and its products decay according to the scheme

A2+ρ0+π+ρ0π++π-π+μ++νμ+e++ν+ν¯π-μ-+ν¯μ-e-+ν+ν¯

(a) What are the final stable decay products? From the evidence, (b) is the A2+ particle, a fermion or a boson and (c) is it a meson or a baryon? (d) What is its baryon number?

(a) The final stable decay products are two electrons, one positron, five neutrinos and four antineutrinos.

(b) The particle is a boson.

(c) The particle is a meson.

(d) The baryon number of the particle is 0.

See the step by step solution

Step by Step Solution

Step 1: Given data

The decay scheme of the particle is as below.

A2+ρ0+π+ρ0π++π-π+μ++νμ+e++ν+ν¯π-μ-+ν¯μ-e-+ν+ν¯

Step 2: Spins of pion and rho-meson 

Quark modeling of the pion and rho classifies the pion as a pseudoscalar meson with zero angular momentum. Quarks have spin 1/2 and the spins are "paired" or anti-aligned. In the rho meson, a vector meson, the angular momentum is j = 2 , indicating parallel rotations.

The pions π+,π- have spin 0 and the rho-meson ρ0 has spin 1.

Step 3: (a) Determining the final decay products of A2+

The A2+ decays to a π+ and a ρ0. The ρ0 decays to a π+ and a π- . Thus A2+ decays to two π+ and one π- .

A π+ decays to μ+ and a neutrino and the μ+ decays to an electron and a neutrino-antineutrino pair. The π- decays to a μ- and an antineutrino and the μ- decays to a positron and a neutrino-antineutrino pair.

Thus the final decay products are,

A2+ρ0+π+ π++π-+π+ μ++ν+μ-+ν¯+μ++ν e++ν+ν¯+ν+e-+ν+ν¯+ν¯+e++ν+ν¯+ν

Thus, the final products are two electrons, one positron, five neutrinos and four antineutrinos.

Step 4: (b) Determining whether  A2+ is a fermion or a boson

The spin of the A2+ is the sum of spins of the pion and the rho-meson. Hence its spin is 0 + 1 = 1 .

Hence, the A2+ is a boson.

Step 5: (c) Determining whether A2+  is a meson or a baryon:

As stated in the previous step, the A2+ is a boson. Baryons are fermions because they have half-integer spins. Since the A2+ is a boson, it is also a meson.

Step 6: (d) Determining the baryon number of  A2+ 

As obtained in the previous step, the A2+ is not a baryon, hence its baryon number is 0.

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