Exotic Mesons in QCD Sum Rules

by Dr Hüseyin Dag (TUM - Theoretische Physik (T39))

Monday 19 Nov 2018, 14:15 → 15:45 Europe/Berlin

3344 (TUM - Physics Department - Garching)

In QCD, due to the running coupling constant, non-perturbative techniques are required to determine the properties of hadrons. QCD sum rules is one of the successful techniques, which enables us to calculate the correlation functions in terms of either hadronic or quark gluon degrees of freedoms, including non-perturbative contributions with the help of operator product expansion. In the case of conventional hadrons, it is applied widely and successfully to estimate the masses, couplings, decay widths, etc.

In the last two decades, several excited states were observed above the quarkonium thresholds, which could not be explained well by quark-antiquark, or three-quark composites, mostly due to their masses, widths and decay properties. In the literature, these states are assumed to be good candidates for exotic tetraquark or pentaquark states. Even though, studying these states within QCD sum rules is a bit risky due to the nature of the continuum at higher energies, properties of these exotic states are widely studied by using the QCD sum rules approach.In this talk, some QCD sum rule studies in the exotic meson sector will be reviewed. As an example, the application of QCD sum rules to the state X(4140) and its possible partners will be discussed. Moreover, the technique will be modified to estimate the properties of excitations of the aforementioned states.