1. Study of  -production reaction π – p → ηn in the near-threshold region Experiment object: Precision data on  – p  ηn reaction DCS measurement Contents: 1.Experiment and setup 2.Neutral meson spectrometer characteristics 3.Experimental data processing 4.Experimental results and conclusion Dr.Bayadilov D., Meson Physics Laboratory, PNPI

2. 1. PNPI synchrocyclotron  -channel (Gatchina, Russia) 1.ΔP/P=1,5% (FWHM) 2.δP/P=±0,5%

3. 2. Experimental setup at PNPI synchrocyclotron  -channel (Gatchina, Russia)

4. 3. Experimental setup scheme

5. 4. Experimental setup

6. 5. Neutral meson spectrometer cell Individual crystal size 60  60  300 mm 3 (16X o ) Photomultiplier type – FEU-97 (  55 mm) PM supply – special high voltage multiplier Dynode signals are used in trigger logic

7. 6. Individual crystal energy calibration a) Cosmic rays; b) Electrons

8. 7. Neutral meson spectrometer characteristics Energy:  M   6% Angle:  1m  1  Time:   10 nsec

9. 8. Trigger D1 and D2 – the sum of dynode signals from central parts of each calorimeters

10. 9. E  2 vs. E  1 distribution for  – momentum 720 MeV/с

11. 10. Monte Carlo simulation. E  2 vs. E  1 distribution for  – momentum 720 MeV/с

12. 11. DCS calculation N η – number of produced and registrated η-mesons at solid angle 2  cos  c.m. (  cos  c.m. =0.2), N  - – number of  – –mesons drop on target А – setup acceptance, Br – branching ratio of  decay N p –number of hydrogen nucleus per cm 2 of the target

13. 12. η-mesons counts and acceptance

14. 13. DCS of  – p  ηn reaction in C.M. (preliminary)

15. 14. Data fit with Legendre polynomial expansion

16. 15. a i coefficient ratios

17. 1)Neutral meson spectrometer was designed and created in PNPI, it has good angle and energy resolution 2)Measurements of DCS of  – p  ηn reaction were made with high precision at three momenta 700, 710, 720 MeV/c 3)It is shown that at 700 MeV/c the DCS angular dependence is isotropic, indicating the S-wave character of the  -production process 4)At higher momenta a significant D-wave contribution has led to the anisotropic angular dependence resulting in bowl-like shape 5)Further improve our data with kinematical fit 6)Combined analysis of η photoproduction and π-production on protons will improve determination of coupling constants of D 13 (1520) and S 11 (1535) resonances 7)Adding our results to the world database and providing a new PWA solution Conclusion and outlook

18. Kinematic fit