Sea-Level Cosmic-Ray Mass Spectrum in the Interval30me−2000me

In nuclear emulsion stacks exposed to sea-level cosmic radiation under 180 g ${\mathrm{cm}}^{-2\mathrm{}}$ of iron, no evidence for mass values in the regions $30m_e$ to $100m_e$ and $400m_e$ to $900m_e$ was found. If such particles do exist, their intensity relative to that of $\mu$ mesons stopping in the same range interval must be as follows: for $30m_e$ to $100m_e$, ≤0.13%; for $400m_e$ to $900m_e$, ≤0.04%.