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Decay widths for $\rho$ meson is $149 MeV$ while for the $\phi$ meson it is $4MeV$. Why is there such a difference?

I know that the phi meson decays primarily to $K \bar K$ states as the $\pi^+ \pi^- \pi^0$ states are OZI suppressed. The $\rho$ meson decays predominantly to $\pi^+\pi^-$ via strong interaction.

Is OZI suppression the culprit?

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Here is the phi mass 1019.445±0.020 MeV/c2. Here is the K mass 493.667±0.013 MeV/c2 , times two 987

1019-987~32 MeV/c2 are left over to be shared as kinetic energy of the two kaons.

It is a matter of phase space. The two pions of the rho are ~280 MeV/c, leaving a lot of phase space to facilitate the decay, i.e. give larger probability because of larger integration scope. enter image description here

In a e+e-scattering experiment: the probability of generating light quarks at a given energy is higher than heavy quarks to make up the phi, because of phase space.

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  • $\begingroup$ I don't see why the phase space argument answers the question. The fact that the phase space is small for the $\phi$ to decay into 2 kaons is an argument to explain why this partial decay width is small. It doesn't explain why the total decay width of the $\phi$ is small. One should explain why in spite of such a small phase space, this decay channel remains the one having the largest branching ratio. $\endgroup$
    – Paganini
    Commented Jun 15, 2015 at 14:27
  • $\begingroup$ @Paganini The phi is made up with the strange antistrange pair of quarks, therefore kaons . The other decay mode of e+e- is 10^-4 branching ratio to K+K- journals.aps.org/prl/abstract/10.1103/PhysRevLett.21.1504 $\endgroup$
    – anna v
    Commented Jun 15, 2015 at 15:35
  • $\begingroup$ ok, thanks. I thought the $\phi$ meson was a more complicated objects made of a superposition of $u\bar{u}, d\bar{d}, s\bar{s}$. If it's only $s\bar{s}$, then your explanation is clear. $\endgroup$
    – Paganini
    Commented Jun 15, 2015 at 18:44
  • $\begingroup$ @anna-v Can you explain why is mean lifetime of rho meson is shorter compared to mean life time of K meson, in a simple way? $\endgroup$
    – Aman
    Commented Jul 3, 2022 at 17:18
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    $\begingroup$ @Aman Look at the quark content of the rho meson, they are unflavored so rho can decay through the strong interaction to pions, prectically 100%, see pdg.lbl.gov/2015/tables/contents_tables_mesons.html . Kaons have strangeness and to decay the weak interaction has to be involved, because there are no other lower mass strange mesons to which it could decay by the strong interaction withoug violating strangeness conservations. $\endgroup$
    – anna v
    Commented Jul 3, 2022 at 18:48

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