1+ XTZ States within QCD Sum Rules

We present improved estimates of the couplings, masses and mass ratios of the X Q , Z Q and T Q Q q ¯ q ¯ ′ states ( Q ≡ c , b ; q , q ′ ≡ u , d , s ) using (inverse) QCD Laplace sum rules (LSR), their ratios R and double ratios (DRSR), within stability criteria. We conclude that the observed X c ( 3872 ) and Z c ( 3900 ) are tetramoles states (superposition of quasi-degenerated molecule and tetraquark states having similar couplings to the currents) with the predicted masses: M T X c = 3876 ( 44 ) MeV and M T Z c = 3900 ( 42 ) MeV . We also do an extensive analysis of the four-quark nature of different T Q Q q ¯ q ¯ ′ axial-vector states. Then, combining R and DRSR, we reanalyze the observed state X c ( 3872 ) and we obtain a precise prediction of M T c c 1 + = 3886 ( 6 ) MeV . Extending to the beauty sector, we find the results: M T Z b = 10579 ( 99 ) MeV and M X b = 10545 ( 131 ) MeV . Finally, we confront our combined LSR ⊕ DRSR results with the ones from some other approaches (lattices and quark models).