The production rates and the transverse momentum distribution of strange hadrons at mid-rapidity ($$\left| y\right| &lt; 0.5$$ <math><mrow><mfenced><mi>y</mi></mfenced><mo>&lt;</mo><mn>0.5</mn></mrow></math> ) are measured in proton-proton collisions at $$\sqrt{s}$$ <math><msqrt><mi>s</mi></msqrt></math>  = 13 TeV as a function of the charged particle multiplicity, using the ALICE detector at the LHC. The production rates of $$\mathrm{K}^{0}_{S}$$ <math><msubsup><mrow><mi>K</mi></mrow><mi>S</mi><mn>0</mn></msubsup></math> , $$\Lambda $$ <math><mi>Λ</mi></math> , $$\Xi $$ <math><mi>Ξ</mi></math> , and $$\Omega $$ <math><mi>Ω</mi></math>  increase with the multiplicity faster than what is reported for inclusive charged particles. The increase is found to be more pronounced for hadrons with a larger strangeness content. Possible auto-correlations between the charged particles and the strange hadrons are evaluated by measuring the event-activity with charged particle multiplicity estimators covering different pseudorapidity regions. When comparing to lower energy results, the yields of strange hadrons are found to depend only on the mid-rapidity charged particle multiplicity. Several features of the data are reproduced qualitatively by general purpose QCD Monte Carlo models that take into account the effect of densely-packed QCD strings in high multiplicity collisions. However, none of the tested models reproduce the data quantitatively. This work corroborates and extends the ALICE findings on strangeness production in proton-proton collisions at 7 TeV.

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Multiplicity dependence of (multi-)strange hadron production in proton-proton collisions at $$\sqrt{s}$$ <math><msqrt><mi>s</mi></msqrt></math>  = 13 TeV