Speaker
Description
In two-particle angular correlation measurements, jets give rise to a near-side peak formed by particles associated with a higher $p_\mathrm{T}$ trigger particle. Measurements of these correlations as a function of pseudorapidity and azimuthal differences are used to extract the centrality and $p_\mathrm{T}$ dependence of the shape of the near-side peak in the $p_\mathrm{T} $ range $3 < p_\mathrm{T,\,trig} < 16$ GeV and $1.5 < p_\mathrm{T,\,asso} < 8$ GeV in lead-lead (PbPb) and proton-proton collisions at $\sqrt{s_\mathrm{NN} $= 5.02 TeV. A combined fit of the near-side peak and long-range correlations is applied to the data. By disentangling short-range correlations from long-range contributions, we quantify the variance of the near-side peak, which exhibits significant broadening in the longitudinal direction from peripheral to central PbPb collisions, particularly pronounced for low-$p_\mathrm{T} particles. This broadening phenomenon diminishes above $p_\mathrm{T} = 4$ GeV. In contrast, the width of the peak in the azimuthal direction remains nearly constant across centrality. Additionally, we observe a longitudinal asymmetry on the near-side peak, which increases towards forward rapidity compared to mid rapidity, attributed to jet-medium interactions in PbPb collisions. This rapidity asymmetry phenomenon is more pronounced in the high $p_\mathrm{T,\,trig}$ between 4.0--16.0 GeV , and low $p_\mathrm{T,\,asso}$ between 1.5--4.0 GeV.
| Category | Experiment |
|---|---|
| Collaboration | CMS |
