Mean transverse mass of hadrons in proton–proton reactions

An energy dependence of the mean transverse mass 〈mT〉〈mT〉 at mid-rapidity in proton–proton (p+pp+p) reactions is studied within the ultra-relativistic quantum molecular dynamics (UrQMD). The UrQMD model predicts a nonmonotonous dependence of 〈mT〉〈mT〉 on collision energy for several hadron species: for π+π+, p  , K+K+, and Λ   the mean transverse mass has a maximum at the center of mass energy region 5≤s≤8 GeV. These results are a consequence of an interplay of two contributions: 1) excitations and decays of the baryonic resonances N⁎N⁎ and Δ; 2) excitations and decays of the baryonic strings. The UrQMD results do not show any nonmonotonous dependence of 〈mT〉〈mT〉 on s for π−π−, K−K−, and antiprotons. Whether a nonmonotonous dependence of 〈mT〉〈mT〉 at mid-rapidity on the collision energy for π+π+, p  , K+K+, and Λ   is relevant for real p+pp+p interactions will be soon checked experimentally by the NA61/SHINE Collaboration.