1. Bénédicte Boillat Institut für Physik Universität Basel The + (1232) Magnetic Moment

2. GOALS Use of the reaction channel γp Δ + Δ + γ' pπ 0 γ' and determination of: ● Asymmetries (lin + circ) ● Cross Sections ● angular diff. cross sections ● energy diff. cross sections ● Asymmetries (lin + circ)

3. THE ANALYSIS ● Best the 3 possible - pairs determined with χ 2 test on invariant π 0 mass ● Random background substraction based on the time between tagger and the π 00 ● Work on 4 clusters events 1 o Identification of the reaction channel: p ∆+∆+ '∆ + 'p0'p0 'p'p ● One of the clusters must be a proton :m p Є [930;940] MeV

4. The Cuts ● 115 MeV < m π 0 < 155 MeV ● -20'000 MeV 2 < MM π 0 p 2 < 20'000 MeV 2 ● -50 MeV < energie balance < 50 MeV ● Angle γ1γ2, γ1γ', γ2γ' > 30 o ● cosinus angle(vec proton (MWPC)vec proton (NaI) ● t γ1γ2 ● 325 MeV < E beam < 475 MeV ● θ γ' > 12 o real data simulations ● 910 MeV < MM π 0 γ' < 970 MeV Proton Calibration in Simulations Proton Calibration in Simulations

5. 2 differential cross sections: a) On the angle of the radiative photon ': b ) On the energy of the radiative photon ': 2 o Elaboration of Cross Sections:

6. ● N e :Number of electron coming from MAMI. -----> Scalers ● tagg :Tagging efficiency, obtained by specific measurements ● / X : Decay branching ratio: 0 ->2 / total = 0.988 ● N p :Target area density: ● X TAPS+CB : Detectors efficiency from simulations COLD/WARM dimensions? COLD/WARM dimensions?

7. Preliminary Results Energy diff cross sections: a) E= 325-375 MeV

8. Preliminary Results Energy diff cross sections: a) E= 375-425 MeV

9. Preliminary Results Energy diff cross sections: a) E= 425-475 MeV

10. Preliminary Results Angular diff cross sections: a) E= 325-375 MeV

11. Preliminary Results Angular diff cross sections: a) E= 375-425 MeV

12. Preliminary Results Angular diff cross sections: a) E= 425-475 MeV

13. All parts of Cross Sections implemented Satisfactory Channel indentification Next Improvements: ● in Simulations -> generals stuff -> TAPS PID -> proton calibration ● Asymmetries CONCLUSION & OUTLOOK