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Study of  - production reaction π – p → ηn in the near-threshold region

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

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Study of  - production reaction π – p → ηn in the near-threshold region

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

  2. 1. PNPI synchrocyclotron -channel (Gatchina, Russia) • ΔP/P=1,5% (FWHM) • 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 mesonspectrometer cell • Individual crystal size 6060300 mm3 (16Xo) • 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 mesonspectrometer characteristics Energy:M  6% Angle:1m  1 Time: 10 nsec

  9. 8. Trigger D1 andD2 – the sum of dynode signals from central parts of each calorimeters

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

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

  12. 11. DCS calculation Nη– number of produced and registratedη-mesons at solid angle2cosc.m.(cosc.m.=0.2), N-– number of ––mesons drop on target А – setup acceptance, Br – branching ratio of  decay Np–number of hydrogen nucleus per cm2 of the target

  13. 12. η-mesons counts and acceptance

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

  15. 14. Data fit with Legendre polynomial expansion

  16. 15. ai coefficient ratios

  17. Conclusion and outlook • Neutral meson spectrometer was designed and created in PNPI, it has good angle and energy resolution • Measurements of DCS of  –pηn reaction were made with high precision at three momenta 700 , 710 , 720 MeV/c • It is shown that at 700 MeV/c the DCS angular dependence is isotropic, indicating the S-wave character of the -production process • At higher momenta a significant D-wavecontribution has led to the anisotropic angular dependence resulting in bowl-like shape • Further improve our data with kinematical fit • Combined analysis of ηphotoproduction and π-production on protons will improve determination of coupling constants of D13(1520) and S11(1535) resonances • Adding our results to the world database and providing a new PWA solution

  18. Kinematic fit

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