Investigating the Role of Coherence Effects on Jet Quenching in Pb-Pb Collisions at $\sqrt{s_{NN}} =2.76$ TeV using Jet Substructure

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We report measurements of two jet shapes, the ratio of 2-Subjettiness to 1-Subjettiness ($\it{\tau_{2}}/\it{\tau_{1}}$) and the opening angle between the two axes of the 2-Subjettiness jet shape, which is obtained by reclustering the jet with the exclusive-$\it{k}_{T}$ algorithm~\cite{kT} and undoing the final clustering step.

• The aim of this measurement is to explore a possible change in the rate of 2-pronged objects in Pb-Pb compared to pp due to colour coherence.
• Coherence effects~\cite{ColourCoherence} relate to the ability of the medium to resolve a jet's substructure, which has an impact on the energy loss magnitude and mechanism of the traversing jet.
• In both collision systems charged jets are found with the anti-$\it{k}_{T}$ algorithm~\cite{Anti-kT}, a resolution parameter of $\it{R}=$0.4\ and a constituent cut off of $0.15$ GeV.