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Experimental study of strange tribaryons in the reaction

Experimental study of strange tribaryons in the reaction. Heejoong Yim Seoul National University For E549 collaboration. KEK-PS E549 Collaboration.

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Experimental study of strange tribaryons in the reaction

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  1. Experimental study of strange tribaryons in the reaction Heejoong Yim Seoul National University For E549 collaboration

  2. KEK-PS E549 Collaboration H. Bhang, J. Chiba, S. Choi, H. Fukuda, T. Hanaki, R. S. Hayano, M. Iio, T. Ishikawa, M. Iwai, S. Ishimoto, T. Ishiwatari, K. Itahashi, M. Iwasaki, P. Kienle, J. Kim, Y. Matsuda, H. Ohnishi, S. Okada, H. Outa, M. Sato, S. Suzuki, T. Suzuki, D. Tomono, E. Widmann, T. Yamazaki, H. Yim

  3. Difference between and nucl-ex/0310018 No structure at around 3140 MeV/c2 on the proton spectrum T=0 higher statistics with better resolution is required to confirm the peak structure.

  4. KEK PS-E549 experiment • Further study of S0 state in the 4He(K-stop, p) reaction - 4He(K-stop, p) spectroscopy (1) Determinationwidthwith high resolution E471 upper limit  E549 finite value (2)Inclusivespectroscopy of S0 Formation rate K- + 4He → S0[T=1] + p | 1/2 -1/2 > |1 -1> + |1/2 1/2> K- + 4He → S+[T=1] + n | 1/2 -1/2 > |1 0> + |1/2 -1/2> Statistics x 20 (3) Search for excited state Formation ratio = 2:1 • Search for other kind of strange tribaryon in the 4He(K-stop, n) - 4He(K-stop, n) spectroscopy (1) Study of isospin dependence (T=0,1 state) (2) Confirmation of S+ (T=0) (statistics ~3 times higher)

  5. TC T0 BLC VDC TC NC NC

  6. TOF analysis for neutral particles • TNC-TT0 • Determine vertex point TOFtarget->vertex • Tkaon_flight

  7. Stopping kaon selection by T0 ADC VDC K - Target region Target cell z Target cell BLC Beam direction T0ADC (a.u.) K - Stop kaon selection region z T0ADC (a.u.)

  8. Z-vertex correction for kaon flight time from T0 to it’s stop σ~380ps σ~295ps

  9. Separation for NC 1/beta NC ADC (MeVee)

  10. S/N Improvement Previous result (E471) Present preliminary result (E549) 3 MeVee Improvement 5 MeVee 10 MeVee S/N ratio is much improved.

  11. NC time calibration and resolution Previous result (E471) The resolution variation on ADC energy range (10 MeVee threshold) Present E549 result (very preliminary) MeVee σ~0.040 Now the resolution is comparable with E471 result. But, TOF analysis is still progressing. So, the resolution will be more improved. 10 MeVee threshold

  12. Check of neutron TOF analysis using Σ decay Monochromatic neutron source from is expected in the stopped K- reaction at 185 MeV/c 3MeVee threshold & 1 charged hit on TC & 1 charged hit on the opposite NC arm 3MeVee threshold & 1 charged hit on the opposite NC arm ~185MeV/c We can say neutron momentum scale is reasonable. ~185MeV/c

  13. Particle identification by TC Previous TC setup (E471) Present TC setup (E549) TC_D layer TC_C layer Upgrade TC_B layer TC_thick layer TC_A layer TC_thin layer TC_thin MeVee/cm dE/dx of TC_A (a.u.) (a.u.) TC_thick MeVee/cm

  14. Semi-inclusive neutron momentum distribution Present result (E549) Previous result (E471) 7 MeVee threshold Very preliminary 10 MeVee threshold Very preliminary

  15. summary • Neutron S/N ratio is much improved. • Now, missing mass resolution is comparable with previous E471 result. • Neutron statistics is increased. • Analysis is in progress.

  16. Vertex image by VDC and BLC tracking Carbon degrader Al cap Target cell z (mm) y y z x

  17. Degrader & Al cap

  18. Result of previous experiment E471 for Indication of strange trybaryon S+ (T=0)

  19. Reaction time of Stopping kaon selection by reaction time Reaction time of 100ps Unit :100ps Blue : cut by stop kaon selection Red : remainder after stop kaon selection

  20. Beam direction cosine distribution of Decay particle by VDC chamber In-flight decay stop decay

  21. 7MeVee

  22. PID by TC (2) Stop event Passing through event

  23. Accidental neutron Blue : Accidental neutron Red : After rejecting accidental neutron With 10 MeVee threshold 1/beta Very preliminary NC ADC (MeVee) threshold

  24. Cell structure of VDC

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