Title of the PosterM2: Meson Dynamics

Principal Investigators: N. Berger, M. Fritsch, W. Gradl, S. Scherer

Role within the CRC

The duality between a better knowledge of the internal structure and the dynamics of hadrons and its relevance and impact in different fields is the central and connecting goal of the CRC1044. In this project the spectroscopy and dynamic investigations of light and heavy mesons connect the perturbative description of the strong interaction at high energies which describes the interaction in terms of quarks and gluons with the non-perturbative description at the low-energy regime where mesons and baryons are the degrees of freedom.

Physics Program of the Second Funding Period (2016 – 2019)

Effective Field Theory: ● Description of anomalous processes in chiral EFT including vector mesons

Dirac constraint analysis

Investigation of various vector-meson approaches (vector, tensor, massive Yang-Mills formulation) to study VPγ interactions

Development of power-counting scheme (complex-mass scheme)

● Quantum corrections to chiral anomaly

Investigation of more complex processes such as η(’) → π+π-γ and η(’) → π+π-γγ

Light Mesons: ● η, ω and η’ decays with A2 @ MAMI Amplitude analysis η' → 3π0 Study decays ω → ηγ and ω → π0 e+e-

● Light hadron dynamics in charmonium decays Study difference between J/ψ → π+π-π0 and ψ’ → π+π-π0 (ρπ puzzle)

Study effects of ππ rescattering

Develop and test amplitude analysis methods across channels and with various models

Heavy Mesons: ● Global analysis of exotic charmonium states Interrelationship of Y and Z+ states Simultaneous amplitude analysis of the channels Y → J/ψ π+π- and Y → DD*

● Search for exotic charmonium isospin singlets Isospin singlet decaying to J/ψη to the Zc(3900) triplet Isospin singlet decaying to ηcη

● Search for exotic charm states Inclusive analyses of the D and D+ recoil spectra

Big Questions

● What is the interplay of dynamical symmetry breaking, explicit symmetry breaking by the quark masses, and the chiral anomaly? How does it affect the dynamics of light mesons? What role do light meson (rescattering) dynamics play in heavy meson decays?

● What is the nature of the bound states of the strong force? When does the quark-antiquark picture of mesons break down? Are there exotic states like tetraquarks, molecules, hybrids, and glueballs and how do they interrelate?

Achievements of the First Funding Period

A2 @ MAMI: ● Commissioning of end-point tagger, upgrade of DAQ system, successful η’ data taking ● First results on γp → η’p cross section ● Construction of forward PID and trigger detector BESIII: ● Amplitude analysis of D0 → KS K+ K-

Theory: ● Vector form factor of the pion in chiral effective field theory ● η-η’ mixing in large-Nc chiral perturbation theory ● Effective field theories for vector particles and constraint analysis

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