Exotic system: Kaonic nuclei the present status and the future development

1. A. Dote （KEK） Y. Akaishi (Nihon univ.) T. Yamazaki (RIKEN) ´ Exotic system: Kaonic nuclei the present status and the future development • Introduction • Exotic properties of K nuclei • Recent experimental results • Strange tribaryons by KEK experiment • ppK- by FINUDA • ppnK- by FOPI • Future developments • Summary and future plans QCDとハドロン物理の新展開 @ KEK, ’06.Mar.1

2. K nuclear state K nuclear state Introduction What are kaonic nuclei (K nuclei)? • K- meson is bound in a nucleus by strong interaction. cf) Kaonic atom K- meson is around a nucleus, bound by Coulomb interaction. • K nuclei can exist as discrete states, • since K- meson is deeply bound below Σπ threshold. KNNN… ΣπNN…

3. Very attractive I=0 KN interaction makes … Deeply bound; Binding energy of K- > 100 MeV Discrete state; Below Σπ threshold ... Deeply bound kaonic nuclei Phenomenological KN potential (AY KN potential) Strongly attractive. • free KN scattering data • 1s level shift of kaonic hydrogen atom • binding energy and width of Λ(1405) = K- + proton Y. Akaishi and T. Yamazaki, PRC 52 (2002) 044005

4. My motivation … Akaishi’s special lecture held in Kyoto university in ’00. 8Be + K- Only one K- meson can drastically change the nuclear structure? Y. Akaishi and T. Yamazaki, PRC 52 (2002) 044005

5. K- Kaonicnucleus normal nucleus ?? ? ? ? ?? ? What kind of structure does A+1 system favor? Exotic features of K nuclei Anti-symmetrized Molecular Dynamics Fully microscopic treatment No assumption on nuclear structure; cluster, deformation … System self-organizes only following energy variation. Normal nucleus p p n n

6. 0p 0s Cooling Shell Cluster Essence of AMD AMD wave function can describe not only shell-model-like structure but also cluster-like one. Gaussian wave packet The structure is determined by only the energy-variation.

7. Single nucleon/kaon wave function + Charge projection of total wave function ☆ Improve AMD for K nuclei mixing

8. We used only central potential as VNN before the discovery of strange tribaryons. Hamiltonian in AMD calculation : effective NN int. Tamagaki potential (OPEG) : effective KN int. AY KN potential Y. Akaishi and T. Yamazaki, PRC 52 (2002) 044005 G-matrix method

9. Isovector deformation Binding energy of K- = 104 MeV Nucleus-K-threshold pppK- (simple AMD) Σπ threshold Width (Σπ, Λπ) Density (/fm^3) 0.0 0.41 0.83 Density (/fm^3) 0.0 0.10 0.20 8BeK- Proton satellite Rrms = 1.42 fm β = 0.55 Central density = 0.76/fm^3 8Be Rrms = 2.46 fm β = 0.63 Central density = 0.10 /fm^3 4.5 normal density AMD studies revealed … • E(K) > 100 MeV for various light nuclei • Drastic change of the structure of 8Be, • isovector deformation in 8BeK- • Highly dense state is formed in K nuclei. • maximum density > 4ρ0 • averaged density 2～4ρ0 • Proton satellite in pppK- A. D., H. Horiuchi, Y. Akaishi and T. Yamazaki, PLB 590 (2004) 51; PRC 70 (2004) 044313.

10. 1.67 1.14 1.78 2.55 2.53 4 fm Single K- meson can interact with limited numbers of nucleons? Saturation of E(K) 4.1ρ0 Various shapes of K nuclei ppnK- pppK- pppnK- 3 fm 8.8ρ0 9.2ρ0 7.6ρ0 6BeK- 9BK- 4 fm 4.1ρ0 5.4ρ0

11. Recent experimental results Various groups are trying to search for deeply bound kaonic nuclei in various way. • T. Suzuki, M.Iwasaki et al; 4He(stopped K-, n or p) @ KEK • H. Fujioka, T. Nagae et al; ppK- @ DAΦNE • Kishimoto et al; 16O(inflight K-, n) 15OK- @ BNL • N.Herrmann et al; • Invariant-mass method (heavy-ion collision) @ GSI • K. Suzuki et al; proton induced reaction @ GSI • J-PARC

12. 4He (stopped K-, n) ppnK- 4He (stopped K-, p) pnnK- pnnK- (T=1) ppnK- (T=0) ppnK- :Strange tribaryon S+(3140) pnnK- :Strange tribaryon S0(3115) Total binding energy = 169 MeV Decay width < 25 MeV Total binding energy = 194 MeV Decay width < 21 MeV arXiv: nucl-ex/0310018 PLB 597, 263 (2004) T. Suzuki, M. Iwasaki et al KEK group • KEK • Stopped K- reaction on 4He target • Missing-mass method (Detecting p or n)

13. ppK- Total binding energy = 115 MeV Decay width = 67 MeV PRL 94, 212303 (2005) Strong correlation between emitted p and Λ (back-to-back) Invariant mass of p and Λ H. Fujioka, T. Nagae et al FINUDA group • e+e- collider DAΦNE, FINUDA spectrometer • K- absorbtion at rest on various nuclei • Invariant-mass method

14. Invariant mass of d and Λ ppnK- Total binding energy = ～150 MeV Decay width = 100 MeV ? N. Herrmann et al FOPI group • GSI • Heavy-ion collision Ni+Ni @ 1.93 A GeV • Invariant-mass method Preliminary !

15. Summary of present status

16. Experimental results are more deeply bound than ours. Summary of present status

17. Jπ=1/2-, T=0 (0s)3 Jπ=3/2+, T=1 (0s)2(0p) • Isobaric analog state of pppK- • Large energy gain • by KN interaction • Additional energy gain • by NN-LS interaction • 14% enhanced KN interaction • NN-LS interaction is important in pnnK-. Experimental results are more deeply bound than ours. Summary of present status B.E. = 177 MeV B.E. = 187 MeV

18. Nucleon configuration of pnnK- p n n P K- K- K0 ppnK- pnnK- T=0 T=1 (0s)3 (0s)3 (0s)2(0p) I=0 KN I=1 KN 1 / 2 1 / 2 1 / 6 5 / 6 2 / 3 1 / 3

19. Summary of present status Decay width is consistent?

20. Summary of present status Consistent? Especially, decay width.

21. Summary of present status Unobserved states can be found by each other experiment? ??? ??? ??? ??? ???

22. 2, Using more theoretical KN interaction • Energy- and density-dependence • I=1 P-wave interaction • … Attractive below Σ(1385). • … Large contribution at high density? Additional attraction to deeply bound kaonic nuclei 3, Mystery of two-body absorption (KNN --> YN) … large decay width at high density K nuclei can survive? Future developments Theory 1, Short-range repulsive core part of NN interaction The repulsive core part of the effective NN potential derived by G-matrix method is too much smoothed out for the study of kaonic nuclei? “Beyond the conventional nuclear physics” 4, The study from the view point of quarks; Quark matter or not?

23. Possible by measuring the momentum correlation of three particles emitted in the decay NNNK → N+N+Λ P. Kienle, Y. Akaishi and T. Yamazaki, Phys.Lett.B632, 187 (2006) Future developments Experiment 1, More experiments to confirm the existence of kaonic nuclei 2, Determine Jπ of , especially, strange tribaryons 3, Dense or not?

24. Summary • Kaonic nuclei have interesting properties! The AMD study with AY KN interaction showed … • K- is deeply bound by ～100 MeV • and forms highly dense state. • Strange structures appear in K nuclei. • Drastic change of 8Be structure, • Isovector deformation in 8BeK-, • Proton satellite in pppK-. • Observed strange tribaryons, ppnK- and pnnK-, can be understood … • 14% enhanced KN interaction and NN-LS force • pnnK- : (0s)2(0p) configuration Jπ=3/2+, T=1 • ppnK- : (0s)3 configuration Jπ=1/2-, T=0

25. Summary • Various experimental results are now reported. They indicate the evidence of deeply bound kaonic nuclei. But comparing with each other, there seems to be some inconsistency between them. In particular in decay width. KEK; narrow FINUDA and FOPI; broad Need more experiments!

26. Future plans • Study K nuclei from the viewpoint of quarks Collaborate with Y. Kanada-En’yo and O. Morimatsu - - - Λ(1405) = qqq-qq, ppK- = 7qq, ppnK- = 10qq (undeca-quarks state) • Study more various K nuclei Many experiments will start, or started. • T. Suzuki, Iwasaki et al; 4He(stopped K-, n or p) @ KEK • Fujioka, Nagae et al; ppK- @ DAΦNE • Kishimoto et al; 16O(inflight K-, n) 15OK- @BNL • Herrmann et al; Invariant-mass method (heavy-ion collision) @ GSI • K. Suzuki et al; proton induced reaction @ GSI • J-PARC • Other type of KN interaction? I=1 p-wave KN interaction… suggested by S. Wycech et al. nucl-th/0501019 Collaborate with W. Weise • Apply our wave function to the study of reaction Dense or not?(S. Hirenzaki and J. Yamagata) • Double K nuclei?

27. Λ（１４０５） KN interaction Chiral symmetry restoration Kaonic atom Kaon condensation Cold and Dense Interesting structure … Nuclear structure (Strange) Quark matter K nuclei…Exotic system ! Kaonic nucleus … related to various fields!!