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Ch 44: Particle Physics and Cosmology
Young & Freedman Calc - University Physics 15th Edition
Young & Freedman Calc15th EditionUniversity PhysicsISBN: 9780135159552Not the one you use?Change textbook
Chapter 43, Problem 21

If a Σ+Σ^+ at rest decays into a proton and a π0π^0, what is the total kinetic energy of the decay products?

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1
Identify the conservation laws applicable to the problem: Conservation of energy and conservation of momentum. Since the Σ^+ is initially at rest, the total momentum of the decay products must also be zero.
Write the energy conservation equation: The rest energy of the Σ^+ particle is equal to the sum of the rest energies of the proton and π^0, plus the total kinetic energy of the decay products. Use the equation: EΣ=Ep+Eπ+Ktotal, where EΣ is the rest energy of Σ^+, Ep and Eπ are the rest energies of the proton and π^0, respectively, and Ktotal is the total kinetic energy.
Determine the rest energies of the particles using their masses and the equation E=mc2. The mass of Σ^+, proton, and π^0 can be found in a particle physics reference table.
Apply the conservation of momentum: Since the Σ^+ is at rest, the proton and π^0 must move in opposite directions with equal and opposite momenta. Use the relationship between momentum and kinetic energy: K=p22m, where p is the momentum and m is the mass of the particle.
Combine the energy and momentum conservation equations to solve for the total kinetic energy of the decay products. This involves substituting the rest energies and solving for Ktotal.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Conservation of Energy

In any physical process, the total energy before and after the event must remain constant. In the case of particle decay, the rest mass energy of the initial particle (Σ^+) is converted into the kinetic energy of the decay products (proton and π^0). This principle allows us to calculate the kinetic energy of the products by considering the mass-energy equivalence given by Einstein's equation, E=mc².
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Rest Mass Energy

Rest mass energy is the energy contained in a particle due to its mass when it is at rest. For the Σ^+ particle, this energy can be calculated using its mass and the speed of light. When the particle decays, this rest mass energy is transformed into the kinetic energy of the resulting particles, which is crucial for determining the total kinetic energy of the decay products.
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Kinetic Energy of Particles

Kinetic energy is the energy that an object possesses due to its motion. In particle physics, the kinetic energy of decay products can be calculated using the formula KE = 1/2 mv² for non-relativistic speeds or using relativistic equations when speeds approach the speed of light. Understanding how to calculate the kinetic energy of the proton and π^0 after the decay is essential for solving the problem.
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Related Practice
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You work for a start-up company that is planning to use antiproton annihilation to produce radioactive isotopes for medical applications. One way to produce antiprotons is by the reaction p+pp+p+p+pˉp + p → p + p + p + p̄ in proton-proton collisions. You first consider a colliding-beam experiment in which the two proton beams have equal kinetic energies. To produce an antiproton via this reaction, what is the required minimum kinetic energy of the protons in each beam?

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Textbook Question

How much energy is released when a µµ^- muon at rest decays into an electron and two neutrinos? Neglect the small masses of the neutrinos.

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Textbook Question

A K+K^+ meson at rest decays into two pp mesons. What are the allowed combinations of π0π^0 , π+π^+, and ππ^- as decay products?

Textbook Question

What is the total kinetic energy of the decay products when an upsilon particle at rest decays to r++rr^+ + r^-?

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Textbook Question

In which of the following reactions or decays is strangeness conserved? In each case, explain your reasoning.

(a) K++μ++νμK^{+}+\(\mu\)^{+}+\(\nu\)_{\(\mu\)}

(b) n+K+p+π0n+K^{+}\(\to\) p+\(\pi\)^0

(c) K++Kπ0+π0K^{+}+K^{-}\(\to\]\pi\)^0+\(\pi\)^0

(d) p+KΛ0+π0p+K^{-}\(\to\]\Lambda\)^0+\(\pi\)^0