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Photoproduction of L(1405)/S(1385)

Photoproduction of L(1405)/S(1385). M. Niiyama. TPC data w/ CH2 and carbon target. g p  K + S(1385)  K + L p 0  K + p p - p 0. g p  K + L(1405)  K + S  p ∓  K + p + p - n. Physics Motivation structure of Λ*(1405).

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Photoproduction of L(1405)/S(1385)

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  1. Photoproduction of L(1405)/S(1385) M. Niiyama TPC data w/ CH2 and carbon target. g p  K+ S(1385)  K+L p0 K+pp-p0 g p  K+ L(1405)  K+S p∓ K+ p+p-n

  2. Physics Motivationstructure of Λ*(1405) • To measure in medium modification of the lineshape of L(1405) • First, measure the production cross section from free proton in CH2 E. Oset et al.

  3. High voltage plane Drift field cage 700mm Beam Target holder Wire & pad plane E // B TPC Active volume (cylindrical shape) 700 mm in length 400 mm in diameter

  4. Outline • The mass difference between L(1405) and S(1385) is too small to be separated by missing mass mm(K+). • Detect decay products and distinguish these two hyperon resonances. • Measure the production ratio L(1405) / S(1385) • using TPC data • Extract the absolute value of L(1405) and S(1385) from liquid hydrogen target with the input of measured production ratio. g p  K+ S(1385)  K+L p0 K+pp-p0 g p  K+ L(1405)  K+S p∓ K+ p+p-n

  5. spectrum of S(1385) in 2 Egbins g p  K+ S(1385)  K+L p0 K+pp-p0

  6. Spectrum of L(1405)comparison with Ahn-san’s measurement at LEPS

  7. Angular distribution of p from L(1405) decay. (angle Kp in CM) This work Ahn-san’s measurement

  8. spectrum of L(1405) in 2 Egbins g p  K+ L(1405)  K+S p∓ K+ p+p-n

  9. Ratio of L(1405)/S(1385) in 2 Eg bins 1.5<Eg<2.0 GeV 0.54±0.17 2.0<Eg<2.4 GeV 0.084±0.076 2.0<Eg<2.4 GeV 1.5<Eg<2.0 GeV t nor q^2 doesn’t change. Eg dependence should be due to the other reason. |t| GeV^2 |q|^2 (GeV/c^2

  10. Absolute value of the differential cross section Fit to MM(K+) spectrum of liq. H2 data with the input of production ratio of L(1405) /S(1385) S(1385) L(1405)

  11. Summary We have measured the ratio of L(1405)/S(1385). The absolute value is obtained using LH2 data. The production cross section of L(1405) decreases in higher photon energy region. It seems not due to t-dependence or q^2-dependence. It should be due to the other production mechanism.

  12. L(1405), S(1385) in 2 tbins MC g p  K+ S(1385)

  13. spectrum of L(1405) in 2 tbins

  14. mm(K) for L tagged eventsin 2 tbins |t|<0.22 |t|>0.22

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