Strange particle production in p + p collisions at √s = 200 GeV

We present strange particle spectra and yields measured at midrapidity in √s = 200 GeV proton-proton (p + p) collisions at the BNL Relativistic Heavy Ion Collider (RHIC). We find that the previously observed universal transverse mass (m T ≡ √ pT 2>/sup> + m 2 ) scaling of hadron production in p + p collisions seems to break down at higher m T and that there is a difference in the shape of the m T spectrum between baryons and mesons. We observe midrapidity antibaryon to baryon ratios near unity for Λ and Ξ baryons and no dependence of the ratio on transverse momentum, indicating that our data do not yet reach the quark-jet dominated region. We show the dependence of the mean transverse momentum ⟨p T ⟩ on measured charged particle multiplicity and on particle mass and infer that these trends are consistent with gluon-jet dominated particle production. The data are compared with previous measurements made at the CERN Super Proton Synchrotron and Intersecting Storage Rings and in Fermilab experiments and with leading-order and next-to-leading-order string fragmentation model predictions. We infer from these comparisons that the spectral shapes and particle yields from p + p collisions at RHIC energies have large contributions from gluon jets rather than from quark jets.