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## Seminare im Jahr 2018

#### Seminare in früheren Jahren

 Neutrinoless double beta decay in effective field theory Dozent/Speaker: Dr. Jordy de Vries (NIKHEF, Amsterdam) Termin/Date: Di. 13.02.2018, 16:15 - 17:45 Ort/Location: NB 6/173 Übersicht/Abstract: Next-generation neutrinoless double-beta decay experiments aim to discover lepton-number violation in order to shed light on the nature of neutrino masses. A non-zero signal would have profound implications by demonstrating the existence of elementary Majorana particles and possibly pointing towards a solution of matter-antimatter asymmetry in the universe. However, the interpretation of the experimental signal (or lack thereof) requires care. First of all, a single nonzero measurement would indicate lepton-number violation but will not identify the underlying source. Second, complicated hadronic and nuclear input is required to connect the experimental data to a fundamental description of lepton-number violation. In this talk, I will use effective field theories to describe neutrinoless double-beta decay processes. In particular, I will apply the Standard Model effective field theory and chiral effective field theory to bridge the gap between high-energy models of lepton-number violation to neutrinoless double-beta decay experiments. Few-neutron resonance study using transition operators Dozent/Speaker: Dr. Arnoldas Deltuva (Vilnius University) Termin/Date: Do. 01.02.2018, 16:15 - 17:45 Ort/Location: NB 6/173 Übersicht/Abstract: Existing bound-state type calculations of few-neutron resonances yield contradicting results. A direct study of the three- and four-neutron continuum using rigorous scattering equations with realistic potentials and search for possible resonances is aimed. Faddeev-type integral equations for transition operators are solved in the momentum-space partial-wave framework. The evolution of resonances is studied by enhancing the strength of the two-neutron interaction in partial waves with nonzero orbital momentum. Calculated few-neutron transition operators exhibit resonant behavior for sufficiently large enhancement factors; pole trajectories in the complex-energy energy plane are extracted from their energy dependence. However, the resonant behavior completely disappears for the physical interaction strength. Production of tensor glueball in reaction $\gamma\gamma\rightarrow G_2\pi^0$ Dozent/Speaker: Dr. N. Kivel (Universität Mainz) Termin/Date: Do. 11.01.2018, 16:15 - 17:45 Ort/Location: NB 6/173 Übersicht/Abstract: We studied production of tensor glueball in the reaction $\gamma\gamma\rightarrow G_2\pi^0$ at large energy and large scattering angles. The scattering amplitude is computed within the collinear factorisation framework that allows us to estimate the cross section. We obtained that if the value of the tensor gluon coupling is not too small $f^T_g\sim 100$~MeV then the cross section can be measured in the future BELLE-II experiment.