Nucleons in heavy ion collisions are half as big as previously expected

To study atomic nuclei and subatomic particles, scientists use the Large Hadron Collider (LHC) to collide heavy ions--atomic nuclei completely stripped of their surrounding electrons. In these collisions, the quarks and gluons that normally make up nucleons (protons and neutrons) melt into a new state of matter called a quark-gluon plasma (QGP).