All-charm tetraquarks.pdf

All-charm tetraquarks Richard J. Lloyd and James P. Vary Iowa State University, Department of Physics and Astronomy We investigate four-body states with only charm quarks. Working in a large but finite oscillator basis, we present a net binding analysis to determine if the resulting states are stable against breakup into a pair of cc mesons. We find several close-lying bound states in the two models we examine. 12.39.Jh, 12.39.Pn, 12.39.Mk Introduction The spectrum of multiquark states has been investigated for three decades, but very little in the way of quantitative results for the spectrum of all-charm tetraquarks, 22 cc , has been published. Iwasaki1 provides the first treatment that argues bound states of 22 cc exist and estimates their mass. His argument is based on a string model of hadrons and a generalized OZI rule to establish the plausibility of 22 cc exotics. The best value for the charm quark mass of 1.5 GeV (in 1975) was used to estimate the mass of the tetraquark bound state in the neighborhood of 6 GeV (or 6.2 GeV if the ?/J was used). A number of other approaches to multiquark models exist in the literature. Jaffe2, using an early version of the bag model, made predictions for tetraquark spectroscopy of the type 22 qq with q a light quark (lighter than charm). In a similar vein, Schaffner-Beilich and Vischer3 give impressive systematic treatments of charmlets (systems with at least one charm quark plus lighter quarks) but do not treat 22 cc . In addition to the bag model, many variants of a wide class of potential models are used to describe multiquark states. Successful models founded upon the work of Isgur and Weinstein4 tended to confirm the earlier prediction of Jaffe, and identified the ? ?9800a and ? ?9800f as molecular states of four quarks, for example (see especially Isgur and Godfrey5 ). Models in the spirit of Karl and Ericson6 employ a pion exchange potential to investigate hadronic