重玻色子为何不稳定？重子构成WIMP模型稳定性问题咨询

Hey there! Let's work through your questions tied to your dark matter research—great to see you digging into these foundational stability arguments.

Your conclusion that WIMPs (Weakly Interacting Massive Particles) can't be baryonic is fully supported by the stability constraint you highlighted. Here's a more detailed breakdown:

• Baryons (protons, neutrons, and their composite counterparts) lack the long-term stability required for dark matter candidates. While protons have an experimentally measured half-life far exceeding the universe's age, the Standard Model predicts proton decay in the long run, and even without that, baryonic systems can't avoid annihilation or decay over cosmic timescales.
• For WIMPs to explain the observed dark matter abundance, they must be thermally stable: their decay or annihilation rate has to be low enough that they persist from the early universe to today. Baryonic particles simply can't meet this requirement—their interactions via the strong or weak forces ensure they'd be depleted long before now, ruling out baryonic WIMPs as a viable model.

Heavy bosons (including Standard Model particles like W/Z bosons, or hypothetical heavy scalar bosons) are unstable due to two core quantum field theory principles:

1. Mass-Energy Conservation: A heavy boson carries significant rest mass energy. As long as there exists a set of lighter particles that satisfy all conservation laws (charge, baryon number, lepton number, etc.), the heavy boson will decay into those lighter particles to minimize total energy. This is a fundamental driver of particle decay.
2. Coupling Strength: Most heavy bosons interact via the weak or strong nuclear forces, which have relatively high coupling constants. This leads to a large decay width (a measure of decay probability), resulting in an extremely short lifetime. For example, the W boson has a lifetime of ~10⁻²⁵ seconds—way too brief to contribute to dark matter, which requires particles that persist for the entire cosmic timeline.

• A quick exception note: The Higgs boson is a unique case, but even it decays rapidly into lighter particles (like W boson pairs, quark pairs, or leptons) thanks to its couplings to other Standard Model particles.

内容的提问来源于stack exchange，提问作者Heberty O. A.