EuNPC2015

The CLAS experiment at CEBAF at Jefferson Laboratory investigates photon scattering on the proton with high intensities. The analysis presented in this talk focuses on the reaction γp → pπ + π − η to investigate excitations of η mesons. The observed η as well as the η(1295) and η(1405) decay preferably to π + π − η. The main goal is to improve the present knowledge of these states. Based on...

The Quark Model has predicted meson spectroscopy with great success. However, the nature of some light unflavored mesons is not fully determined yet. The case of f0(980) is particularly puzzling. Its nature remains debatable: it may be a 4-quark state or a KK molecule, rather than a simple q-qbar pair. While f2(1270) is better known, there are suggestions that it could be an intermediate state...

The study of η-decays allows to probe symmetry-breaking phenomena, to test theoretical calculations and to explore the anomalous sector of QCD. In order to perform those studies two data samples have been acquired with the WASA-at-COSY facility at Forschungszentrum Juelich. A proton beam is accelerated within the COSY storage ring towards a liquid deuterium or a liquid hydrogen pellet target...

One important step in understanding the baryon spectrum is a precise knowledge of the excited states and their decays. In order to extract the contributing resonances from experimental data a partial wave analysis needs to be performed. To resolve ambiguities, the measurement of polarization observables is indispensable. In the regime of high mass baryon resonances multi-meson final states are...

The BESIII experiment has accumulated a large sample of J/psi, psi' and psi(3770) data set. Through these charmonium radiative and hadronic decays, we can explore the light hadron spectroscopies. In this talk, we will report our recent results on the properties of the X states, such as X(1835) and X(p pbar), study of J/psi radiative decays (J/psi → γKKη , γπ+π-η', γπ0π0). In addition, we also...

The goal of the COMPASS experiment at CERN is to study the structure and dynamics of hadrons. The two-stage spectrometer has a good acceptance over a wide kinematic range for charged as well as neutral particles and thus allows to access a large range of reactions. Light mesons are studied with negative (mostly π-) and positive (p, π+) hadron beams with a momentum of 190 GeV/c. The spectrum of...

To investigate important aspects for the upcoming PANDA experiment, partial wave analyses (PWA) of antiproton-proton annihilation processes are carried out using data from the Crystal Barrel (LEAR) experiment. A coupled channel analysis of the three reactions resulting in the final states K+K-π0, π0π0η and π0ηη at a beam momentum of 900 MeV/c is currently in progress. Preliminary results on...

We calculate electron-positron pair production in pion-nucleon and pion-nucleus collisions. We derive the elementary cross sections in an effective field theory approach. We use these cross sections in a transport model to study π-nucleus reactions. We study the effect of the interference term (which is destructive in pi+ n and constructive in pi- p collisions) of the ρ and ω mesons on the...