Multiplicity dependence of K${}^{\ast }(892{)}^{\pm }$ production in pp collisions at $\sqrt{s}$ = 13 TeV

The first results of K${}^{\ast }$(892)${}^{\pm }$ production at midrapidity ($\mathrm{\mid }y\mathrm{\mid }<0.5$) in pp collisions at $\sqrt{s}=13$ TeV as a function of the event multiplicity are presented. The K${}^{\ast }$(892)${}^{\pm }$ has been reconstructed via its hadronic decay channel K${}^{\ast }$(892)${}^{\pm }\to {\pi }^{\pm }+K_{\mathrm{S}}^0$ using the ALICE detector at the LHC. For each multiplicity class the differential transverse momentum ($p_{\mathrm{T}}$) spectrum, the mean transverse momentum $⟨p_{\mathrm{T}}⟩$, the $p_{\mathrm{T}}$-integrated yield (d$N$/d$y$), and the ratio of the K${}^{\ast }$(892)${}^{\pm }$ to $K_{\mathrm{S}}^0$ yields are reported. These are consistent with previous K${}^{\ast }$(892)${}^0$ resonance results with a higher level of precision. Comparisons with phenomenological models such as PYTHIA6, PYTHIA8, EPOS-LHC, and DIPSY are also discussed. A first evidence of a significant K${}^{\ast }$(892)${}^{\pm }$/$K_{\mathrm{S}}^0$ suppression in pp collisions is observed at a 7$\sigma$ level passing from low to high multiplicity events. The ratios of the $p_{\mathrm{T}}$-differential yields of K${}^{\ast }$(892)${}^{\pm }$ and $K_{\mathrm{S}}^0$ in high and low multiplicity events are also presented along with their double ratio. For $p_{\mathrm{T}}\lesssim 2$ GeV/$c$ this double ratio persists below unity by more than $3\sigma$ suggesting that the suppression affects mainly low $p_{\mathrm{T}}$ resonances. The measured decreasing trend of the K${}^{\ast }$(892)${}^{\pm }$/$K_{\mathrm{S}}^0$ ratio with increasing multiplicity, which in heavy-ion collisions is typically attributed to the rescattering of decay particles of the short-lived resonances, is reproduced by the EPOS-LHC model without the use of hadronic afterburners.