Jefferson Lab in the News
Four Experiments Give Evidence of an Exotic Baryon With Five Quarks
Figure 1
At the corners of the antidecuplet of baryons predicted by Dmitri Diakonov, Victor Petrov, and Maxim Polyakov are three exotic states that require five valence quarks (shown in red) and their decay modes. The recently discovered positive-strangeness baryon near 1540 MeV is tentatively identified with the predicted .+(1530). The numbers in parentheses are the predicted masses (in MeV) of the charge multiplets for each value of the strangeness.
Figure 2
The strongest evidence to date for the exotic, positive-strangeness .+ baryon is the 5.3-standard-deviation peak (fitted with the red curve) centered at 1542 1 5 MeV in this K+n invariant-mass distribution from a Jefferson Lab experiment in which K+K-pairs were photoproduced on a deuterium target. The blue curve is a fitted estimate of the background, and the dashed histogram indicates collisions excluded because they produced a .0 baryon.