Dependence of the $\Upsilon$(nS) production ratios on charged particle multiplicity in pp collisions at $\sqrt{s}=7~\mathrm{TeV}$

The ratios of the cross section of the $\Upsilon$(nS) mesons with $|y|<1.2$ are studied as a function of the number of charged particles with $p_{T}>0.4~\mathrm{GeV}$ and $|\eta|<2.4$ produced in pp collisions at $\sqrt{s}=7~\mathrm{TeV}$. Evidence of a decrease of the ratios between the higher and the lower mass states is observed, that is more pronounced at lower $p_{T}$. For $\Upsilon$(nS) mesons of transverse momentum greater than $7~\mathrm{GeV}$, this effect is studied as a function of the underlying event sphericity, and of the distribution of charged particles with respect to the $\Upsilon$(nS) direction.