Study of -production reaction π–p → ηn

in the near-threshold region

Experiment object:

Precision data on –pηn reaction DCS measurement

Contents:

1. Experiment and setup2. Neutral meson spectrometer characteristics

3. Experimental data processing4. Experimental results and conclusion

Dr.Bayadilov D., Meson Physics Laboratory, PNPI

1. PNPI synchrocyclotron -channel (Gatchina, Russia)

1. ΔP/P=1,5% (FWHM)2. δP/P=±0,5%

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

3. Experimental setup scheme

4. Experimental setup

5. Neutral meson spectrometer cell

• Individual crystal size 6060300 mm3 (16Xo)• Photomultiplier type – FEU-97 ( 55 mm)• PM supply – special high voltage multiplier• Dynode signals are used in trigger logic

6. Individual crystal energy calibration

a) Cosmic rays; b) Electrons

7. Neutral meson spectrometer characteristics

Energy: M 6%

Angle: 1m 1

Time: 10 nsec

8. Trigger

D1 and D2 – the sum of dynode signals from central parts of each calorimeters

9. E2 vs. E1

distribution for – momentum 720 MeV/с

10. Monte Carlo simulation. E2 vs. E1distribution for – momentum 720 MeV/с

11. DCS calculation

,cos2 ..

..

mcp

mc

BrNAN

N

d

d

Nη – number of produced and registrated η-mesons

at solid angle 2cosc.m. (cosc.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

12. η-mesons counts and acceptance

13. DCS of –pηn reaction in C.M.(preliminary)

14. Data fit with Legendre polynomial expansion

)(cos)(cos ..22

..110

..mcmc

mc

PaPaad

d

15. ai coefficient ratios

1) Neutral meson spectrometer was designed and created in PNPI, it has good angle and energy resolution

2) Measurements of DCS of –pηn 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 fit6) Combined analysis of η photoproduction and π-production on

protons will improve determination of coupling constants of D13(1520) and S11(1535) resonances

7) Adding our results to the world database and providing a new PWA solution

Conclusion and outlook

Kinematic fit