The existence and properties of the sigma meson have been controversial for almost six
decades, despite playing a central role in the spontaneous chiral symmetry of QCD or in the …

A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the
confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of …

Glueballs, hybrids and multiquark states are predicted as bound states in models guided by
quantum chromo dynamics (QCD), by QCD sum rules or QCD on a lattice. Estimates for the …

In the past years there has been a revival of hadron spectroscopy. Many interesting new
hadron states were discovered experimentally, some of which do not fit easily into the quark …

We review our investigations devoted to the analysis of the resonances Zc (3900), Zc (4430),
Zc (4100), X (4140), X (4274), α1 (1420), Y (4660), X (2100), X (2239), and Y (2175) …

The hadronic charmless B decays into a scalar meson and a pseudoscalar meson are
studied within the framework of QCD factorization. Based on the QCD sum rule method, we …

We use QCD spectral sum rules to test the nature of the meson X (3872), assumed to be an
exotic four-quark (cc¯ qq¯) state with J PC= 1++. For definiteness, we work with the diquark …

In this article, we distinguish the charge conjunctions of the interpolating currents, calculate
the contributions of the vacuum condensates up to dimension 10 in a consistent way in the …

We use QCD sum rules to study the possible existence of QQ− u¯ d¯ mesons, assumed to
be a state with JP= 1+. For definiteness, we work with a current with an axial heavy diquark …

In this article, we take the point of view that Y (2175) be a tetraquark state which consists of
color octet constituents, and calculate its mass and decay constant within the framework of …