Chapter 1.1: Are Elementary Particles Everlasting?

In the realm of quantum physics, particles can exhibit dual characteristics; they can behave like both particles and waves. For example, photons represent electromagnetic waves, while phonons are sound waves. Thus, we might consider their lifespans in a manner analogous to that of waves.

To understand this, we can look at the behavior of ordinary waves, such as those generated by a vibrating guitar string. The string generates sound waves as it vibrates, but these vibrations do not persist indefinitely. They eventually diminish as the energy transferred to the string dissipates, transforming into the kinetic energy of air molecules and contributing to sound wave propagation. This process, known as dissipation, occurs because the vibrating string interacts with its surroundings.

If particles can be viewed as waves, they too can disperse or ‘decay.’ This notion is central to the Standard Model, which describes various particles and their interactions. According to this framework, certain elementary particles can transform into two to four lighter particles. Though it might seem paradoxical that indivisible particles can decay, in particle physics, ‘decay’ encompasses a broader definition. Rather than breaking into smaller parts, elementary particles convert into different particles, marking the conclusion of their existence.

Chapter 1.2: The Lifespan of Elementary Particles

Physicists categorize particles into two main types: unstable and stable. Unstable particles, such as the Higgs boson, tend to decay rapidly, often within a mere 10^-24 seconds. Conversely, stable particles like electrons either do not decay or do so extremely slowly, potentially existing for durations exceeding the lifespan of our Universe.

Unstable particles have lifespans ranging from 10^-24 seconds to several minutes, while stable particles are theorized to live indefinitely. Interestingly, some hypotheses suggest that certain particles may decay over timeframes far greater than the age of the Universe, yet their decay remains unverified, allowing them to be classified as stable. Therefore, while some elementary particles are indeed mortal, others may potentially endure far beyond the temporal limits of our vast cosmos.

In the video "Sabine Hossenfelder: Can Elementary Particles Decay?", physicist Sabine Hossenfelder delves into the intricacies of particle decay and its implications for our understanding of the universe.

The video titled "Why can elementary particles decay?" further explores the mechanisms behind particle decay and the theoretical frameworks that govern these phenomena.

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