SKS (K - ,K + ) X J-PARC Project - PowerPoint PPT Presentation

SKS を用いた (K - ,K + ) 反応による X ハイパー核分光 永江 知文 J-PARC Project Office

Day-1 experiments n L06: New generation spectroscopy of Hadron Many-Body Systems with Strangeness S =-2 and -1 n X hypernuclei spectroscopy n Hypernuclear gamma-ray spectroscopy n L10: Study of Dense K Nuclear Systems

Strangeness Nuclear Physics

S=-2 Hypernuclear Spectroscopy n X hypernuclei/ LL hypernuclei n only several events of LL hypernuclei reported n X hypernuclear spectroscopy ? n a mixed states of X , LL , and H states ? K. Ikeda et al., Prog. Theor. Phys. 91 (1994) 74 n n need high intensity beams at 50-GeV PS n (K - ,K + ) reaction at 1.8 GeV/c ex. 208 Pb(K - ,K + ) with 2 g/cm 2 thick target Æ ~6 events/MeV/day n H dibaryon (ssuudd, I=J=0) n no evidence so far n m H >2223.7 MeV(very close to 2m L ) n S=-3 W - nuclei, charmed-hypernuclei etc.

S=-2 Systems

(K - ,K + ) Spectroscopy n High momentum transfer ~500 MeV/c n Preference to spin-stretched states like ( π + ,K + ) reaction n Simple excitation spectra n Coulomb-Assisted bound states

( π + ,K + ) Spectroscopy n Success at BNL Textbook Example ! n ∆E~3 MeV n Up to 89 L Y

X hypernuclei potential ? n L , S - , X - , K - in Neutron Star Core ? 2 m B = m B + k F n Chemical Potential: + U ( k F ) 2 m B U S <0, U X <0 U S >0, U X <0 U S >0, U X >0

Issues in X A potential n A -dependence of X A potential depth n Strong p-wave attraction n X- 207 Tl > 2x X- 11 B n Isospin dependence n How strong is the Lane term ? n X - p- X 0 n mixing n Width and XN-LL coupling

Particle Mixing

Entrance to the S=-2 World n Doorway Reaction: K - +p Æ K + + X - at 1.8 GeV/c

Experimental hall (Phase 1) Toward Phase 2 : l Extension of the hall to 100 m l Addition of target T2 on A-line and secondary lines l Installation of primary lines of B (with target Tx) and C

SKS@K1.8

(K - ,K + ) Spectroscopy of X -Hypernuclei

Energy Resolution n 2 MeV FWHM resolution 2 + b K - 2 + D E straggling D E 2 = b K + 2 ¥ D p K + 2 ¥ D p K - 2 D p / p K - = 2 ¥ 10 - 4 D p / p K + = (0.96 ± 0.13) ¥ 10 - 4 p K + (0.092 ± 0.007)(%) 1.89 2 + 0.31 2 + 0.5 2 = 2 MeV FWHM \D E ~ n Limited by the SKS resolution n Widths of the X bound state < 1 MeV?

Yield Estimation n 50 msr, 2g/cm 2 -thick Pb Y = I Beam ¥ 2 g / cm 2 /208 g ¥ N A ¥ d s d W ¥ DW¥ f decay ¥ f eff = 10 7 ¥ (2/208) ¥ 6.02 ¥ 10 23 ¥ 0.1 ¥ 10 - 30 ¥ 0.05 ¥ 0.5 ¥ 0.5 events / sec @ 6 events / MeV / day

n Coulomb-Assisted bound states n Large momentum transfer ~500 MeV/c n ~6 events/MeV/day

Summary n Spectroscopy of X- Hypernuclei in the (K - ,K + ) reaction n Our initial goal: Potential depth, mass number dependence n Beam line & Spectrometer should be optimized further n Spectroscopy of LL -Hypernuclei in the (K - ,K + ) reaction n Next step n Study of excited levels