The form factors of γ * N → ∆(1600) transition is calculated within the light-cone sum rules assuming that ∆ + (1600) is the first radial excitation of ∆(1232). The Q 2 dependence of theare studied. Finally, our predictions oñ G M (Q 2 ),G E (Q 2 ), andG C (Q 2 ) are compared with the results of other theoretical approaches.

In this work the properties of the axial-tensor K2(1820) meson in a hot medium are investigated. The mass and the decay constant of this state are calculated via thermal QCD sum rules considering QCD condensates up to dimension five. Our analysis show that both mass and decay constant stay almost monotonous up to certain temperatures and then they diminish with increasing temperature. The mass and decay constant estimated at zero temperature are in good agreement with the present experimental data and theoretical estimations.

In this work, we chose three molecular and three diquark-antidiquark currents with the quark content ccss and J P C = 0 ++ , 1 ++ , 2 ++ , and estimated the masses and the meson coupling constants of the ground states coupling to these currents in the framework of QCD sum rules. In operator product expansion, we considered the terms including dimension eight, and we performed pole contribution tests carefully. According to our results, all of these currents couple to the ground states with degenerate masses which are in 10 MeV vicinity of X(4140). Therefore, with a QCD sum rules analysis, it is not possible to conclude that X(4140) has a dominant molecular or diquarkantidiquark content. However, there may be three states degenerate in mass, with positive charge conjugation and different isospins. sD * s molecule, however Refs. [21,22] claim the opposite with similar currents. In Refs. [21,22], using scalar and axial vector tetraquark currents, the authors calculated masses of the ground states but the results were incompatible with X(4140). However with a similar axial vector diquarkantidiquark current, a mass close to recent results of LHCb was predicted in [25]. These inconsistencies in between the predictions of QCD sum rules studies, and with the LHCb results, motivated us to perform a complete QCD sum rules investigation with the aim of contributing to this unconcluded topic.