1-+ light exotic mesons in QCD

We systematically re-examine the extraction of the masses and Couplings of the 1(-+) hybrid, four-quark and molecule mesons from QCD spectral sum rules (QSSR). To NLO for the perturbative and power corrections, the hybrid mass is M-H = 1.81(6) GeV and M-H <= 2.2(2) GeV from the positivity of the spectral function. In the same way, but to LO, the four-quark state mass is M-4q = 1.70(4) GeV and M-4q <= 2.4(1) GeV, while the molecule mass is 1.3(1) GeV. The observed pi(1)(1400) and pi(1)(1600) could be explained by a two-component mixing with the set of input masses (1.2-1.3; 1.70-1.74) GeV and with a mixing angle theta similar or equal to -(11.7 +/- 2.2)degrees, which slightly favours a molecule/four-quark mixing, and which eventually suggests that the pi(1)(2015) is mostly an hybrid meson. Isospin and non-exotic partners of the previous states and some of their radial excitations are also expected to be found in the energy region around 2 GeV. Further tests of this phenomenological scenario are required. (C) 2009 Elsevier B.V. All rights reserved.