Exploring the strong interaction through electroproduction of exotic particles

Quarks are the building blocks of hadronic matter. They can combine into systems of three quarks (baryons) and quark-antiquark (mesons). However, evidence for numerous exotics has been found in the last 50 years, from glueballs and hybrid mesons to tetra- and hexaquarks. These greatly advanced our knowledge of the Strong interaction. This thesis presents three new studies for signatures of exotic and non-exotic particles in electroproduction reactions from nuclear targets. The experimental data used in this thesis work was obtained from the CEBAF Large Acceptance Spectrometer for operation at 12 GeV beam energy (CLAS12). CLAS12 is based in Hall B of Jefferson Laboratory, Newport News, Virginia, where an electron is accelerated and impinged off a stationary target.

The first study is of the reaction channel ep → e′ pX → e′ p(K+K−), which were performed at small electron scattering angles so a quasi-real photon induced the interaction. Angular distribution moments have been produced for the meson resonance X in the hopes of finding possible exotic meson contributions; initial observations are promising, with many structures appearing in the distributions.

A second study is presented with the first-ever extraction of the scaling behaviour of strangeness. An initial estimate for the suppression factor of strange production in electroproduction ( 1/100 ) suggests one reason for the relative paucity of hyperons discovered. Some strange exotic production is expected to have a weak coupling to individual protons or neutrons, so ratios of strange production cross-sections between a proton and a deuteron target were taken. Enhancements seen via production on
deuteron could direct us towards possible new exotics.

The 3rd study focuses on the first constraint on the very strange hexaquark dsss, with the upper limit of the cross-section measured as dσdsss/dMM = 76 ± 2 fb/GeV.