of the nuclear matter in heavy-ion collisions as its nuclear refractive index, the density of partons, their free path length and energy loss.

Asymmetry of in-medium resonances.
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Another specific feature of low-energy Cherenkov effect is that it leads to the somewhat unusual particle content within the ring.

[**Prediction 2.**]{} Masses of Cherenkov states are less than in-vacuum meson masses. This leads to the asymmetry of decay spectra of resonances with increased role of low masses.

[**Proposal 2.**]{} Plot the mass distribution of $\pi ^+\pi ^-$, $\mu ^+\mu ^-$, $e^+e^-$-pairs near resonance peaks.

Apart from the ordinary Breit-Wigner shape of the cross section for resonance production, the dilepton mass spectrum would acquire the additional term proportional to $\Delta n$ (that is typical for Cherenkov effects) at masses below the resonance peak [@dnec]. Therefore its excess (e.g., near the $\rho $-meson [^4]) can be described by the following formula $$\frac{dN_{ll}}{dM}=\frac {A}{(m_{\rho }^2-M^2)^2+M^2\Gamma ^2}
\left(1+w\frac{m_{\rho }^2-M^2}{M^2 }\theta (m_{\rho}-M)\right).    \label{ll}$$ Here $M$ is the total c.m.s. energy of two colliding objects (the dilepton mass), $m_{\rho }$=775 MeV is the in-vacuum $\rho $-meson mass. The first term corresponds to the Breit-Wigner cross section. According to the optical theorem it is proportional to the imaginary 