Strange antiparticles pop out of RHIC’s quark-gluon plasma
// March 4th, 2010 // No Comments » // Tech News
So far, the LHC has been spending its time ramming protons together, leaving Brookhaven’s Relativistic Heavy Ion Collider (RHIC) the king of the hill when it comes to smashing larger atomic nuclei. When the nuclei of gold atoms collide within RHIC, their components dissolve into a high-energy state called a quark-gluon plasma (the LHC will eventually smash lead atoms to similar effect). A paper in today’s Science describes some of the more exotic items that briefly emerge from the wreckage: the antiparticle equivalent of Deuterium, with strange quarks replacing some of the more familiar ones. The paper itself is a mindbending trip through families of particles that are similar to our familiar protons and neutrons (termed nucleons), but have at least one of their quarks replaced by a heavier, strange version, resulting in what’s termed a hyperon (four of these, Λ, Σ, Ξ, and Ω, have been observed). In the brief periods that the quark-gluon plasma exists, particles and antiparticles are equally probable, leading to a large collection of heavy and light nuclei and anti-nuclei. It also leads to some fantastic sentences, like the following: “Hypernuclei bring a third dimension into play, based on the strangeness quantum number of the nucleus, thus allowing the territory of antinuclei with nonzero strangeness.” The paper focuses on the hypertritons, atomic nuclei that consist of a proton, a neutron, and a Λ hyperon. RHIC has now produced around 200 hypertritons/antihypertritons, which survive for a couple hundred picoseconds. That’s enough to determine that they are probably being formed in the same way a standard atomic nucleus is, by the condensation of their component nucleons and hyperons. In fact, they were formed in similar numbers to their less-strange equivalents, 3 He and its antiparticle equivalent. The authors take that as an indication that, at the energies produced by RHIC, strange quarks are present in equivalent numbers to their more mundane counterparts, meaning that further collisions will provide us some indication of their binding interactions, which may help shape the interior of neutron stars. So, they’re gearing up to go for another round of collisions that will produce an order of magnitude more of these (literally) strange nuclei. Science , 2009. DOI: 10.1126/science.1183980 Read the comments on this post
