Abstract
We present studies that show how multi-parton interaction and color reconnection affect the hadro-chemistry in proton-proton (pp) collisions with special focus on the production of resonances using the PYTHIA8 event generator. We find that color reconnection suppresses the relative production of meson resonances such as $\rho_{0}$ and K*, providing an alternative explanation for the K*/K decrease observed in proton-proton collisions as a function of multiplicity by the ALICE collaboration. Detailed studies of the underlying mechanism causing meson resonance suppression indicate that color reconnection leads to shorter, less energetic strings whose fragmentation is less likely to produce more massive hadrons for a given quark content, therefore reducing ratios such as K*/K and $\rho_0/\pi$ in high-multiplicity pp collisions. In addition, we have also studied the effects of allowing string junctions to form and found that these may also contribute to resonance suppression.
Highlights
In heavy-ion experiments, observables are studied as a function of collision centrality, defined by the measured event charged particle multiplicity, to evaluate the dependence with system size and are compared to elementary proton-proton collisions that is used as reference data, since no effects from the quark-gluon plasma are expected in such small systems
In order to isolate the effect of color reconnection (CR) on the KÃ/K ratio, we study the dependence on the number of partonic interactions (NPI) as shown in Fig. 2, represented by the square symbols, where the black symbols represents the ratio for no CR, and the blue symbols represent the ratio for when the various CR algorithms are turned on
We have studied the effects of CR on yields as a function of transverse momentum, and have found that the suppression caused by CR for events with large NPI concentrates in the low pT region, and affects both the yields of KÃ and K, but the suppression is more pronounced for the KÃ, leading to the decrease observed in the pT-integrated KÃ/K ratio
Summary
The University of Texas at Austin, Austin, Texas, 78712, USA (Received 20 July 2017; published 12 February 2018). We present studies that show how multi-parton interaction and color reconnection affect the hadrochemistry in proton-proton (pp) collisions with special focus on the production of resonances using the PYTHIA8 event generator. We find that color reconnection suppresses the relative production of meson resonances such as ρ0 and KÃ, providing an alternative explanation for the KÃ/K decrease observed in proton-proton collisions as a function of multiplicity by the ALICE collaboration. Detailed studies of the underlying mechanism causing meson resonance suppression indicate that color reconnection leads to shorter, less energetic strings whose fragmentation is less likely to produce more massive hadrons for a given quark content, reducing ratios such as KÃ/K and ρ0/π in high-multiplicity pp collisions. We have studied the effects of allowing string junctions to form and found that these may contribute to resonance suppression
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