Quark masses, hyperfine interaction and pentaquarks

by Marek Karliner (Cambridge Univ. & Tel Aviv Univ.)

Friday 12 Dec 2003, 14:00 → 15:00 Europe/Zurich

TH Auditorium (CERN)

We propose a model for the recently discovered Θ⁺ exotic KN resonance as a novel kind of a pentaquark with an unusual colour structure: a \\bar{3}_c ud diquark, coupled to \\bar{3}_c ud\\bar {s} triquark in a relative P-wave. The state has J^P = 1/2⁺, I = 0 and lies in the antidecuplet of SU(3)_f. A rough mass estimate of this pentaquark is close to experiment. We also discuss other related pentaquarks: a dd ss \\bar {u} exotic Ξ, and the anticharmed exotic baryon Θ_c with quark content uudd \\bar {c}. We expect that Θ_c is an isosinglet with J^P = 1/2^- and estimate its mass at 2985 ± 50 MeV. We also discuss another possible exotic baryon resonance containing heavy quarks, the Θ_b⁺, a uudd \\bar {b} state, and estimate m_{Θb⁺}= 6398 ± 50 MeV. These states should appear as unexpectedly narrow peaks in D^-p, \\bar{D}⁰ n, B⁰ p and B⁺n mass distributions. H.J. Lipkin and M. Karliner, hep-ph/0307243 and hep-ph/0307343.