# M2: Accomplishments of ﬁrst funding period

• Construction and operation of a new end-point tagging spectrometer
A new spectrometer that allows the energy tagging of bremsstrahlung at high photon energies of 10–150 MeV below the electron beam energy was constructed and successfully used in two running periods.
• Precise measurement of the $$\mathbf{\gamma p\to\omega p}$$ and $$\mathbf{\gamma p \to\eta^\prime p}$$ cross sections
The reactions $$\gamma p\to\omega p$$ with $$\omega\to\pi^0\gamma$$ and $$\gamma p\to\eta^\prime p$$ with $$\eta^\prime\to\gamma\gamma ,\eta\pi^0\pi^0$$ were measured with the Crystal Ball detector at MAMI with unprecedented accuracy. The results for $$\omega$$ production are submitted for publication. The analysis of the $$\eta^\prime$$ cross section is almost ﬁnished. A publication is planned in 2015.
• Simulation of a possible WASA at MAMI setup
Evaluate performance of a possible WASA detector setup at the A2 photon beam line for current and future experimental program. Extensive simulation program performed with major contributions from project M2.
• Upgrade of the DAQ system of the CB detector
A major upgrade of the running DAQ system was performed with main contributions from the projects M2 and S3. The readout rate was increased by a factor 4-5 compared to 2012 with much higher stability and reliability of the whole system.
• Construction of a new forward trigger detector
A new hodoscope that allows us to select forward scattered proton from the $$\gamma p\to\eta^\prime p$$ reaction at trigger level has been designed and constructed. The commissioning of the detector with beam will done in Nov./Dec. 2014.
• New slow control and HV system for the CB detector
A new slow control system based on the EPICS toolkit was developed and installed. The increased reliability and stability greatly contribute to higher data taking efﬁciency. In addition, a new high voltage distribution system for the CB photomultipliers was built, installed, and successfully commissioned. The new HV system is designed to set and monitor each individual channel separately, greatly improving the uniformity in energy response. Both projects were performed with major contributions from project M2.
• Measurement of the decays $$\mathbf{\eta^\prime\to\omega\gamma ,\eta^\prime\to\eta\pi^0\pi^0}$$ and $$\mathbf{\omega\to\eta\gamma}$$ long data taking in 2014.
Data analysis will start in 2015.
• Measurement of the decay $$\mathbf{D0\to K0~SK^+K^-}$$ at BESIII
Branching fraction measurement and ﬂavour-dependent amplitude analysis of this ﬁnal state close to complete. Publication is foreseen for 2015.
• Quantum corrections to chiral anomaly
1. Calculation of vector vector axial-vector current (V V A) vertex at $$O(p^6)$$ in $$SU(3)_L \times SU(3)_R$$ chiral perturbation with all legs off shell
2. Connection with $$\pi^0\gamma^\ast\gamma^\ast$$ and $$\eta\gamma^\ast\gamma^\ast$$ vertices using LSZ reduction formalism tested
3. Anomalous Ward identity tested
• $$\mathbf{\eta-\eta^\prime}$$ mixing
Derivation of an expression for $$\eta-\eta^\prime$$ mixing at next-to-next-to-leading-order in large-$$N_c~U(3)_L~\times~U(3)_R$$ chiral perturbation theory
• Workshop on Light Meson Dynamics (February 10-12, 2014)
Mini-proceedings available as arXiv:1403.6380 [hep-ph]