370 research outputs found
Saturating Cronin effect in ultrarelativistic proton-nucleus collisions
Pion and photon production cross sections are analyzed in proton-proton and proton-nucleus collisions at energies 20 GeV < s^1/2 < 60 GeV. We separate the proton-proton and nuclear contributions to transverse-momentum broadening and suggest a new mechanism for the nuclear enhancement in the high transverse-momentum region
Multiple scattering and -broadening at RHIC energies
In ultrarelativistic heavy-ion collisions, in the 2 GeV 6 GeV transverse momentum region, the soft and semi-hard multiple scattering of the incoming nucleons in the nuclear medium results in the broadening of the expected hadronic (e.g. pion) spectra relative to proton-proton () collisions. Thus, higher transverse-momentum regions are populated than in collisions. In a perturbative QCD based calculation we include the intrinsic transverse momentum () of the partons in the nucleon (determined from collisions), augmented by the extra broadening obtained via a systematic analysis of proton-nucleus () collisions in the energy range 17 39 AGeV. The original polynomial spectra are modified, and a nearly exponential spectrum appears in the region 2 GeV. At present RHIC energies (130 AGeV), the slope of the calculated spectra is reminiscent of that of fluid-dynamical descriptions, but lacks any thermal origin. We determine and discuss the size of the modifications originating in multiple scattering, which lead to this state of affairs
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