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Scaling properties of high p_T inclusive hadron production

S. J. Brodsky·H. J. Pirner·J. Raufeisen
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Abstract

We analyze the scaling properties of inclusive hadron production in proton-proton and in heavy ion collisions from fixed target to collider energies. At large transverse momentum p_T, the invariant cross section exhibits a power-like behavior Ed^3σ/d^3p\propto p_T^{-n} at fixed transverse x, x_T=2p_T/\sqrt{s}, and fixed center-of-mass scattering angle θ_{cm}. Knowledge of the exponent n allows one to draw conclusions about the production mechanisms of hadrons, which are poorly known, even at high p_T. We find that high-p_T hadrons are produced by different mechanisms at fixed-target and collider energies. For pions, higher-twist subprocesses where the pion is produced directly dominate at fixed target energy, while leading-twist partonic scattering plus fragmentation is the most important mechanism at collider energies. High-p_T baryons on the other hand appear to be produced by higher-twist mechanisms at all available energies. The higher-twist mechanism of direct proton production can be verified experimentally by testing whether high p_T protons are produced as single hadrons without accompanying secondaries. In addition, we find that medium-induced gluon radiation in heavy ion collisions can violate scaling.

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S. J. Brodsky, H. J. Pirner, J. Raufeisen. 2005-12-21. Scaling properties of high p_T inclusive hadron production. https://doi.org/10.1016/j.physletb.2006.03.079

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