Extraction of flow-modulated background in π0–hadron triggered correlations using a moving average method

Two-particle azimuthal correlations between high-transverse-momentum neutral pion trigger particles and associated charged particles are studied in proton–proton (pp) and Pb–Pb collisions at the Large Hadron Collider. The analysis is performed for trigger particles with 8 < \:pTᵗʳⁱᵍ < 16GeV/c and associated particles in the range 0.5 < \:pTᵃˢˢᵒᶜ < 6GeV/c. Per-trigger normalized correlation functions are constructed within the pseudorapidity interval |Δ η|< 0.8. Complete experimental data are taken from published ALICE paper and referenced in text. Several variants of the ZYAM method are used to determine the flat background level in pp correlations. For Pb– Pb collisions, where collective flow contributes to the correlation structure, a moving-average smoothing procedure is applied to suppress jet contributions and extract the flow-modulated background. The resulting distributions are fitted using a Fourier expansion to obtain the anisotropic flow coefficients Vn ( \:pTᵃˢˢᵒᶜ , \:pTᵗʳⁱᵍ ) up to the fifth harmonic. The extracted coefficients are compared with previously published measurements from ALICE and ATLAS. After background subtraction, near-side and away-side jet yields are determined by integrating the correlation function in the regions |Δ ϕ|< 0.7and |Δϕ − π |< 1.1, respectively, while jet widths are obtained from Gaussian fits centered at Δϕ = 0and Δϕ = .The nuclear modification factor is calculated as the ratio of Pb–Pb to pp per-trigger yields. The results indicate suppression of the away-side yield at high \:pTᵃˢˢᵒᶜ , consistent with parton energy loss in the hot and dense medium, and an enhancement at lower \:pTᵃˢˢᵒᶜ , which may be related to medium-induced gluon radiation and other medium response effects. A moderate near-side enhancement is also observed, potentially reflecting modifications of the jet fragmentation process in the medium.