Strange particle production in proton–proton collisions at $\sqrt{s}=0.9$ $\mbox {${\rm TeV}$}$ with ALICE at the LHC: The ALICE Collaboration

The production of mesons containing strange quarks ( $\mbox {$\mathrm {K0}_{S}}$}$ , phi ) 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 plus or minus 0.002(stat.) plus or minus 0.006(sys t.) for $\mbox {$\mathrm {K0}_{S}}$}$ and 0.021 plus or minus 0.004(stat.) plus or minus 0.003(sys t.) for phi . For baryons, we find dN/dy=0.048 plus or minus 0.001( stat.) plus or minus 0.004(syst.) for $\mbox {$\mathrm {\Lambda }$}$ , 0.047 plus or minus 0.002(stat.) plus or minus 0.005(sys t.) for $\mbox {$\overline {\mathrm {\Lambda }}$}$ and 0.0101 plus or minus 0.0020(stat.) plus or minus 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.