R. M. Albuquerque, F. Fanomezana, S. Narison, A. Rabemananjara
We estimate the masses of the 1-- and 0++ heavy four-quark and molecule states by combining exponential Laplace (LSR) and finite energy (FESR) sum rules known perturbatively to lowest order (LO) in \alpha_s but including non-perturbative terms up to the complete dimension-six condensate contributions. This approach allows to fix unambiguously and more precisely the value of the QCD continuum threshold (often taken ad hoc) at which the optimal result is extracted. We use double ratio of sum rules (DRSR) for determining the SU(3) breakings terms. We also study the effects of the heavy quark mass definitions on these LO results. The SU(3) mass-splittings of about (70 -- 110) MeV and the ones of about (250-300) MeV between the lowest ground states and their 1st radial excitations are (almost) heavy-flavour independent. The mass predictions summarized in Table 4 are compared with the ones in the literature (when available) and with the three Y_c(4260, 4360, 4660) and \Y_b(10890) 1-- experimental candidates. We conclude (to this order approximation) that the lowest observed state cannot be a pure four-quark nor a pure molecule but may result from their mixings. Our predictions can be further tested at LHC_b and in some other hadron factories.
View original:
http://arxiv.org/abs/1204.1236
No comments:
Post a Comment