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An \(\eta^{0}\) meson at rest decays into three \(\pi\) mesons. (a) What are the allowed combinations of \(\pi^{0}, \pi^{+}\), and \(\pi^{-}\) as decay products? (b) Find the total kinetic energy of the \(\pi\) mesons.

Short Answer

Expert verified
The possible combinations of \( \pi^{0}, \pi^{+} \), and \( \pi^{-} \) as decay products are either three \( \pi^{0} \) or one of each \( \pi^{0}, \pi^{+} \), and \( \pi^{-} \). The total kinetic energy of the \( \pi \) mesons is zero for either case.

Step by step solution

01

Determine Possible Decay Pathways

The eta meson \( \eta^{0} \) has a neutral charge. As such, the sum of the charges of the decay particles must also be neutral. There are two possibilities for this: 3 \( \pi^{0} \) which are all neutral, or 1 \( \pi^{+} \), 1 \( \pi^{-} \), and 1 \( \pi^{0} \), where the positive and negative charges cancel out.
02

Apply Energy Conservation for the First Possibility

For the possibility of the eta meson decaying into three neutral pions, the total energy of the eta meson before the decay equals the sum of the kinetic energy of the three pions after the decay. Let \( m_{\eta} \) be the rest mass of the eta meson and \( m_{\pi} \) the rest mass of a pion, and \( KE_{\pi} \) the kinetic energy of one pion. From the conservation of energy we know that \( m_{\eta} = 3 m_{\pi} + 3 KE_{\pi} \). Since the pions are at rest before the decay, their initial kinetic energy (and therefore their final kinetic energy) is zero, making the total kinetic energy also zero.
03

Apply Energy Conservation for the Second Possibility

For the possibility of the eta meson decaying into a \( \pi^{+} \), a \( \pi^{-} \), and a \( \pi^{0} \), we apply the conservation of energy similarly. We get the same equation, \( m_{\eta} = 3 m_{\pi} + 3 KE_{\pi} \). These pions also start at rest, so their final kinetic energy is again zero, making the total kinetic energy also zero.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Meson Decay
Meson decay is a fascinating event in particle physics where a meson, such as the \( \eta^0 \), transforms into other particles. When it comes to the \( \eta^0 \) meson, it can decay into combinations of \( \pi \)-mesons. The decay possibilities are dictated by certain conservation laws. For the \( \eta^0 \), which is uncharged, the decay products can either be three \( \pi^0 \) mesons, which are neutral; or one \( \pi^+ \), one \( \pi^- \), and one \( \pi^0 \). The specific combination of particles depends on the conservation of charge neutrality, as the net charge needs to remain zero, which we will explore in the next sections. Meson decay processes help physicists understand the fundamental forces that govern particle interactions, including the strengths of the weak force involved in such decays. Exploring these interactions provides insight into the behavior and characteristics of subatomic particles.
Conservation of Energy
Conservation of energy is a key principle in physics, stating that energy cannot be created or destroyed, only transformed. In the case of \( \eta^0 \) meson decay, the initial energy is solely the rest energy of the meson. One of the fundamental laws applied when the meson decays is that the sum of the energies of the decay products must equal the initial rest energy of the meson. Thus the equation:
  • Initial energy (\( E_{initial} = m_{\eta} \).
  • Final energy (\( E_{final} = \sum KE_{\pi} + \sum m_{\pi} c^{2} \).
In our scenario, the particles decay while initially at rest, meaning many of the energy terms vanish, leading to zero kinetic energy post-decay. Nonetheless, the law remains unbroken, illustrating how energy conservation steers the decay pathway outcomes.
Charge Neutrality
Charge neutrality is another cornerstone concept that dictates the behavior of particles during a decay process. The \( \eta^0 \) meson, being electrically neutral, requires its decay products to be charge-neutral as well. Therefore, when the \( \eta^0 \) meson decays, one option is to produce three \( \pi^0 \) mesons. These mesons have no charge, naturally complying with the charge neutrality requirement. Alternatively, the decay could result in a \( \pi^+ \), a \( \pi^- \), and a \( \pi^0 \). Here, the positive charge of the \( \pi^+ \) and the negative charge of the \( \pi^- \) balances out to neutral, maintaining the overall charge neutrality. This balance ensures particles obey the fundamental vessel of charge conservation, a rule integrally tied to the electromagnetic force.
Kinetic Energy Calculation
Calculating kinetic energy in particle decay scenarios involves understanding that the system's total energy must be conserved. In the case of \( \eta^0 \) meson decay at rest, all decay products should equate in energy to the initial energy of the meson. However, when these decay products start at rest, their initial kinetic energy is nonexistent. Here's the breakdown:
  • Initial kinetic energy is zero because the mesons are at rest.
  • The rest mass energies of the decay products total to match the rest mass energy of the \( \eta^0 \) meson.
  • No additional kinetic energy is imparted, due to the decay products maintaining a resting state post-decay.
Hence, the total kinetic energy calculated for this decay scenario simplifies to zero, perfectly illustrating energy distribution when dynamics are balanced perfectly by the constraints described.

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Most popular questions from this chapter

(a) A high-energy beam of alpha particles collides with a stationary helium gas target. What must the total energy of a beam particle be if the available energy in the collision is \(16.0 \mathrm{GeV} ?\) (b) If the alpha particles instead interact in a colliding-beam experiment, what must the energy of each beam be to produce the same available energy?

The \(\mathrm{K}^{0}\) meson has rest energy \(497.7 \mathrm{MeV}\). A \(\mathrm{K}^{0}\) meson moving in the \(+x\) -direction with kinetic energy \(225 \mathrm{MeV}\) decays into a \(\pi^{+}\) and a \(\pi^{-}\), which move off at equal angles above and below the \(+x\) -axis. Calculate the kinetic energy of the \(\pi^{+}\) and the angle it makes with the \(+x\) -axis. Use relativistic expressions for energy and momentum.

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Determine the electric charge, baryon number, strangeness quantum number, and charm quantum number for the following quark combinations: (a) \(u d s ;(b) c \bar{u} ;(c) d d d ;\) and \((d) d \bar{c} .\) Explain your reasoning.

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