Resonance suppression from color reconnection

Abstract

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 ρ 0 and K Ã , providing an alternative explanation for the K Ã /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 Ã /K and ρ 0 /π 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.

Effect of color reconnection and rope formation on resonance production in p–p collisions in Pythia 8

“…The suppression is similar for both color reconnections -off and color reconnections (0) mode. The enabling of CR leads to the production of a large number of shorter strings, and the effect is more pronounced for the color reconnections (1) scheme [16]. Therefore, the production of massive K * 0 is suppressed compared to kaons in high-multiplicity events, as shorter strings fragment to less massive particles.…”

“…: V,-vol tion were able to describe the observation of strangeness enhancement [11,12], near-side long-range ridge-like correlations [13], and flow-like effects [3] in p-p collisions at LHC energies. In a recent study on p-p collisions using the Pythia 8 generator [15], the QCD-based color reconnection mechanism was able to reproduce the suppression trend in the K * 0 /K ratio as a function of event activity [16]. Color reconnections (CR) refer to the mechanism of formation of hadronizing strings between the outgoing partons regardless of their formation history.…”

“…These ropes have a larger effective string tension and are likely to fragment into more strange quarks and di-quarks, which leads to enhanced production of baryons and strange hadrons [19,20]. The suppression of mesonic resonances using Pythia 8 was attributed to the mechanism of QCD-based color reconnection [16]. The CR lead to the formation of shorter string lengths which are more likely to fragment into less massive particles.…”

η′ production in nucleus-nucleus collisions as a probe of chiral dynamics

“…A residual volume dependency on strangeness seems to scale with multiplicity but reach a plateau for high multiplicity AA collisions [44]. While a suppression has been seen in resonances in high multiplicity events [53], explained either by rescattering [53] or initial state effects [54][55][56], this suppression seems to be specific to some short-lived Regge excitations which are longer lived but also strongly interact with the hadron gas (the Λ(1520) and K * appear suppressed, but the Σ * and Ξ * do not [55,56]). The long-lived and non-strange η ′ , with a comparatively weak in-medium cross-section [29] will thus be less affected by hadronic in-medium rescatterings and will therefore conserve more memory of the production mechanism.…”

Effect of color reconnection and rope formation on resonance production in p$-$p collisions in Pythia 8

“…Recently, the microscopic processes like color reconnections and rope hadronization were able to describe the observation of strangeness enhancement [12,13], near side long-range ridge-like correlations [14], and flow-like effects [3] in p−p collisions at LHC energies. In a recent study done in p−p collisions using the Pythia 8 generator [15], the QCD-based color reconnection mechanism was able to reproduce the suppression trend in K * 0 /K ratio as a function of event activity [11]. Color reconnections refer to the mechanism of formation of hadronizing strings between the outgoing partons regardless of their formation history.…”