Tiny proton collisions might be creating miniature droplets of the primordial soup that filled the early universe.
April 23, 2026
Original Paper
Sequential Y(nS) suppression in high-multiplicity pp collisions: the experimental case for an early, globally correlated medium
arXiv · 2604.17657
The Takeaway
Quark-gluon plasma is a trillion-degree fluid that existed moments after the Big Bang and is usually made by smashing heavy gold or lead ions together. New data shows that simple proton-proton collisions are suppressing certain heavy particles in a way that only a plasma can explain. Standard models of particle physics cannot account for this suppression using normal hadronic or string-based theories. This suggests that even the smallest collisions can create a globally correlated medium of free-roaming quarks. This finding forces physicists to rethink the minimum conditions required to melt the fabric of matter. It means the primordial soup is much easier to cook than anyone suspected.
From the abstract
The multiplicity-dependent suppression of $\Upsilon(n\mathrm{S})$ states measured by CMS in $pp$ at $\sqrt s=7\,$TeV \cite{CMS2020}, and of $\psi(2S)\big/J/\psi$ measured by LHCb at $\sqrt s=13\,$TeV \cite{LHCb2024}, is subjected to four multi-differential tests: \emph{cone isolation}, \emph{azimuthal sectors}, \emph{transverse sphericity}, and \emph{prompt vs. non-prompt}. Cone and sphericity close a \emph{scissors constraint}: the local reading of the Comover Interaction Model is in tension wi