CERN's ALICE experiment challenges a long-standing theory of how gluons behave inside atomic nuclei
A peer-reviewed CERN ALICE measurement, published in Physical Review Letters, finds a pattern in gluon behavior inside atomic nuclei that conventional nuclear-shadowing theory doesn't fully explain.
The ALICE Collaboration at CERN's Large Hadron Collider measured incoherent J/psi particle production inside lead nuclei across collision energies of 20 to 633 billion electron volts, probing structures down to 0.2 femtometers - about a quarter the size of a proton. At the smallest scales, particle production was suppressed more than the long-standing 'nuclear shadowing' theory predicts, a result with roughly three-sigma statistical significance. University of Kansas physicist Daniel Tapia Takaki, who helped lead the study, says the pattern is consistent with a different phenomenon called gluon saturation. Three-sigma is treated by physicists as evidence, not the five-sigma threshold typically required to call something a confirmed discovery. Published in Physical Review Letters.