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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. Result of previous experiment E471 for Indication of strange trybaryon S+ (T=0) More 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 >8)

  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 K - Target region Target cell Reaction time of z Degrader & Al cap T0ADC (a.u.) K - Stop kaon selection region Unit :100ps z Blue : cut by stop kaon selection Red : remainder after stop kaon selection T0ADC (a.u.)

  8. VDC Stopping kaon selection by reaction time Target cell Reaction time of BLC Beam direction Stop kaon 100ps In-flight

  9. Separation for NC 1/beta NC ADC (MeVee) Background level ~ 7MeVee

  10. S/N Improvement Previous result (E471) Present preliminary result (E549) 3 MeVee Improvement 5 MeVee 10 MeVee Even 5MeVee threshold, S/N ratio is about 10:1

  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 We can say neutron momentum scale is reasonable. 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 ~185MeV/c

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

  14. Semi-inclusive neutron momentum distribution Accidental neutron Previous result (E471) 1/beta NC ADC (MeVee) threshold Blue : Accidental neutron Red : After rejecting accidental neutron With 10 MeVee threshold Very preliminary Only about 5% of E549 data was used

  15. summary • Neutron S/N ratio is much improved. • Now, 1/beta resolution is comparable with previous E471 result. • Neutron statistics is much 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. Beam direction cosine distribution of Decay particle by VDC chamber In-flight decay stop decay

  18. Semi-inclusive Neutron momentum with 7MeVee threshold

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