Measurements from high-energy collisions lead to better understanding of why meson particles disappear

For several years, physicists at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), USA, have studied an unusual state of matter called the quark–gluon plasma, which they believe mimics the hot, dense particle soup that existed immediately after the big bang. Now, the PHENIX collaboration at RHIC reports findings about a particle called the J/ψ meson that will help physicists distinguish the properties of the quark–gluon plasma (QGP) from those of normal matter.