Speaker
Description
Motivated by the apparent tension between the absence of jet quenching in small systems and the observation of azimuthal anisotropy in the distribution of high-$p_\perp$ particles, our study (arXiv: 2510.11914) investigates jet formation time ($\tau_f$) as an observable to probe early medium effects in small systems. It was shown that $\tau_f$ is sensitive to the presence of a medium even when there is only a single, very early and very soft interaction that breaks the colour coherence of the partonic system produced in the hard scattering, without inducing any energy loss. Our findings show that the resulting shift in the formation-time distribution due to decoherence is not only potentially measurable, but arises purely from the loss of colour coherence. In other words, jet formation time allows us to disentangle energy loss from coherence breaking, even in cases where both mechanisms would individually produce the same signal in $R_{AA}$. Furthermore, we extend this analysis by progressively introducing energy loss to identify when and how it begins to influence jet formation time. These results suggest that this observable is a powerful probe of medium effects in small collision systems.
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