Benchmarking the Non-flow Contributions to the Elliptic Flow Parameter (v₂) in Proton-Proton Collisions

This manuscript reports on the elliptic flow parameter, v₂, in proton-proton (p-p) collisions using PYTHIA8 event generator simulations. The typical Event Plane (EP) method v₂(EP) besides the algorithm used for the real data analysis has been adopted to measure the v₂ of particles composed of different quark flavors. The v₂ of the aforementioned particles was measured at the center of mass energy √S_NN = 200 GeV and √S_NN = 13 TeV. The pseudorapidity gap techniques, theoretically defined as |Δη| = |η_particle - η_EP|, between the particle of interest and the soft particles, p_ₜ ≤ 2 GeV/c, used for the event plane determinations, have been implemented in the current measurements. The v₂^π^±,π⁰, v₂J/ψ,Υ, K, D, B, and the v₂^γdir show similar pattern dependence on the transverse momentum for the same |Δη|, at both √S_NN = 200 GeV and √S_NN = 13 TeV. At each center-of-mass energy, the v₂^γdir ≤ v₂J/ψ, Υ, K, D, B ≤ v₂^π^±,π⁰ for similar |Δη|. The measured v₂ shows slightly higher values at smaller √S_NN for particles of similar |Δη|, particularly at small |Δη|. The measured v₂ for all particles shows systematic decreases with increasing the |Δη| gaps as expected. Since PYTHIA8 does not include final state interactions, the reported v₂(EP) is mainly due to the non-flow contributions which should be subtracted from the signal in the real data analysis that uses the same event plane determination algorithm.