CERN ALICE Finds 3-Sigma Gluon Saturation Signal in Lead Nuclei
Updated
Updated · The Brighter Side of News · Aug 12
CERN ALICE Finds 3-Sigma Gluon Saturation Signal in Lead Nuclei
3 articles · Updated · The Brighter Side of News · Aug 12
Summary
ALICE measured suppressed J/ψ production at the smallest scales inside lead nuclei, a pattern that points to gluon saturation rather than standard nuclear shadowing.
Using Run 2 lead-ion data, the experiment tracked incoherent J/ψ photonuclear production across 20 to 633 GeV and resolutions from 0.6 to 0.2 femtometers—the first multidimensional measurement spanning both energy and momentum transfer.
At the highest momentum transfer and energy, the normalized cross-section ratio was 0.52 ± 0.13, differing from unity by more than three standard deviations after the rise in production flattened.
Above 100 GeV, a leading-twist shadowing model missed the new data by more than 3 sigma in lower momentum-transfer ranges and more than 4 sigma in the highest range, while two saturation-based models stayed much closer.
The result gives physicists a sharper probe of how gluons organize collectively inside nuclei, though ALICE said more high-energy, large-momentum-transfer data are still needed to pin down the mechanism.