Strange particle production in proton–proton collisions at with ALICE at the LHC

The production of mesons containing strange quarks ($$\mbox {$$\mathrm {K^{0}_{S}} $$}$$ , φ) and both singly and doubly strange baryons ($$\mbox {$$\mathrm {\Lambda } $$}$$ , $$\mbox {$$\overline {\mathrm {\Lambda }} $$}$$ , and $$\mbox {$$\mathrm {\Xi ^{-}+\overline {\Xi }^{+}} $$}$$ ) are measured at mid-rapidity in pp collisions at $$\sqrt{s}$$ = 0.9 $${\rm TeV}$$ with the ALICE experiment at the LHC. The results are obtained from the analysis of about 250 k minimum bias events recorded in 2009. Measurements of yields (dN/dy) and transverse momentum spectra at mid-rapidity for inelastic pp collisions are presented. For mesons, we report yields (〈dN/dy〉) of 0.184±0.002(stat.)±0.006(syst.) for $$\mbox {$$\mathrm {K^{0}_{S}} $$}$$ and 0.021±0.004(stat.)±0.003(syst.) for φ. For baryons, we find 〈dN/dy〉=0.048±0.001(stat.)±0.004(syst.) for $$\mbox {$$\mathrm {\Lambda } $$}$$ , 0.047±0.002(stat.)±0.005(syst.) for $$\mbox {$$\overline {\mathrm {\Lambda }} $$}$$ and 0.0101±0.0020(stat.)±0.0009(syst.) for $$\mbox {$$\mathrm {\Xi ^{-}+\overline {\Xi }^{+}} $$}$$ . The results are also compared with predictions for identified particle spectra from QCD-inspired models and provide a baseline for comparisons with both future pp measurements at higher energies and heavy-ion collisions.