Heavy-Quark Symmetry Implies Stable Heavy Tetraquark Mesons Q_{i}Q_{j}q[over ¯]_{k}q[over ¯]_{l}.

For very heavy quarks Q, relations derived from heavy-quark symmetry predict the existence of novel narrow doubly heavy tetraquark states of the form Q_{i}Q_{j}q[over ¯]_{k}q[over ¯]_{l} (subscripts label flavors), where q designates a light quark. By evaluating finite-mass corrections, we predict that double-beauty states composed of bbu[over ¯]d[over ¯], bbu[over ¯]s[over ¯], and bbd[over ¯]s[over ¯] will be stable against strong decays, whereas the double-charm states ccq[over ¯]_{k}q[over ¯]_{l}, mixed beauty+charm states bcq[over ¯]_{k}q[over ¯]_{l}, and heavier bbq[over ¯]_{k}q[over ¯]_{l} states will dissociate into pairs of heavy-light mesons. Observation of a new double-beauty state through its weak decays would establish the existence of tetraquarks and illuminate the role of heavy color-antitriplet diquarks as hadron constituents.

Technicolor explanation for the CDF Wjj excess.

We propose that the 3.2σ excess at ~150 GeV in the dijet mass spectrum of W+jets reported by CDF is the technipion πT of low-scale technicolor. Its relatively large cross section is due to production of a narrow Wjj resonance, the technirho, which decays to WπT. We discuss ways to enhance and strengthen the technicolor hypothesis and suggest companion searches at the Tevatron and LHC.

B-meson gateways to missing charmonium levels.

We outline a coherent strategy for exploring the four remaining narrow charmonium states [eta(')(c)(2(1)S0), h(c)(1(1)P1), eta(c2)(1(1)D2), and psi(2)(1(3)D2)] expected to lie below charm threshold. Produced in B-meson decays, these levels should be identifiable now via striking radiative transitions among charmonium levels and in exclusive final states of kaons and pions. Their production and decay rates will provide much needed new tests for theoretical descriptions of heavy quarkonia.