EXOTIC ATOMS/NUCLEI T. Yamazaki, RIKEN Yukawa mesons (1935) Anderson PR51(1937), Nishina PR52(1937): muon Tomonaga-Araki, PR58(1940): mesonic atom formation Fermi-Teller (1947) Strong-interaction shifts of pion: Jenkins et al. (1966) Ericson-Ericson (1966), Tomozawa-Weinberg (1966) Deeply bound pions: Toki-Yamazaki (1988) First observation (1996)

Exotic Resonance States of Antiprotons, Pions and Kaons in Atomic and Nuclear Systems Toshimitsu Yamazaki, RIKEN Hadronic systems --> strong nuclear absorption --> short-lived, no discrete states Exceptions: long-lived, discrete states in continuum: Energy spacing >Width --> High-precision spectroscopy Feshbach resonances: Bound states of X - embedded in continuum Exotic atoms/nuclei Negative pions Negative kaons Antiprotons

Hadron-Nucleus Bound-State Spectroscopy Toshimitsu Yamazaki (RIKEN) Explore Chiral Symmetry Restoration in Nuclear Media Brown-Rho scaling: HOW TO MEASURE In-medium hadron masses and interactions in well defined states and densities?? POPULAR METHODS: Invariant-mass spectroscopy for decay particles in continuum medium NEW METHOD: Bound-state spectroscopy: IF hadron bound states exist with narrow widths? How? Suppression mechanisms for nuclear absorption? Pionic Nuclei (1988 -): observed (1996,1998,2001), matured Kaonic Nuclei (2000 -): predicted, no observation yet

Deeply Bound Pionic States 1s pionic states in heavy (N>Z) nuclei Shallow pionic atoms: Last orbital: ~1-10 keV Deeply bound states: ~ 0.5 MeV ~ 5 MeV Still discrete states!! Coulomb attraction + Strong Interaction Repulsion ----->> Halo like pionic states (absorption suppressed) E. Friedman and G. Soff (1985) H. Toki et al. (1988): --->> pion transfer reactions First success: (d, 3He) at GSI

New Frontiers of Exotic Atoms/Nuclei From outside to inside * atomic states of X radiative transitions from outer orbitals * terminated cascade From inside to outside * nuclear resonance states * still bound states of X EXOTIC ATOMS/NUCLEI

Pion-Nucleus Potential Parameters s-wave p-wave Light 1s states in symmetric nuclei Seki-Masutani relation Double-scattering effect

Pionic Bound States Probe Nuclear Surface Overlapping density: maximum at The density-dependent potential parameter: is transposed to

  in 205 Pb

Sn(d, 3 He) spectra K. Suzuki et al., PRL (2003)

PIONIC NUCLEI as a unique indicator of Chiral Symmetry Restoration in the nuclear medium Fundamental building blocks: Nuclei: protons (938 MeV) + neutrons (940 MeV) + virtual mesons (pion: 140 MeV; etc.) Hadrons: quarks + gluons: u (~ 5 MeV), d (~ 8 MeV), s (~ 150 MeV) Surprising discrepancies -->> ascribed to quark condensate in QCD vacuum: order parameter of chiral symmetry breaking QCD vacuum is subject to change: partial restoration of chiral symmetry HOW to prove or disprove this scenario? As in superconductors Pion decay constant in medium ---> Isovector pion-N interaction b 1 (free) /b 1 *(  ) -->>

B 1s and  1s in Sn Isotopes

Pionic Bound States as an Indicator of Chiral Symmetry Restoration Isovector s-wave interaction --->> pion decay constant in the medium Weise (2000, 2001) Kienle and TY (2001) Best probe: Pionic 1s in heavy nuclei GSI experiment on pionic 115 Sn, 119 Sn, 123 Sn K. Suzuki et al. (2002)

Evidence for partial restoration of chiral symmetry in nuclear medium probed by 1s pionic nuclei (2003) isoisosoisoisoso Isovector s-wave  N scattering length

Hadron Bound States

Nuclear excited states with strangeness S = -1 as Feshbach resonances  p , n (940)   : stable  Hypernuclei: Many observed   ,   ,       Hypernuclei: Unstable:  conversion Exception: 4  He   405  : K-p bound state K - N (1433) K - nuclear bound states?

Akaishi KN Potential Y. Akaishi and TY, PRC (2002)

Diagram Kaon Bound System

ppK - bound system - kaonic hydrogen nuclear molecule

K - potentials and bound states Y. Akaishi and TY, PRC (2002) TY and Y. Akaishi, PLB (2002)

Shrinkage effect: Competition between K-p attraction and nuclear incompressibility

3 He ---> 3 HeK - shrinkage !! Antisymmetric Molecular Dynamics Method Isovector Deformation Dote et al.

Very exotic systems kaonic tri-protons kaonic tetra-protons

Kaonic Be-8: Contracted Alpha Cluster Dote et al. (2002)

(K,  ) and ( ,K) reactions for various K - bound systems * Large q: good for large internal momentum * Varieties (K -,  -) (  -,K 0 ) (  +,K + ) (  ,K 0 )  Q target p   *  +,  + * [n] -   *  +,  + * d pnK - ppK He ppnK - pppK He ppnnK - pppnK - ppppK -

Experimental Search M. Iwasaki et al., at KEK 4 He (stopped K -, n)K - 3 He

  -doorway and   -compound mechanisms T. Yamazaki and Y. Akaishi, PLB 535 (2002) 70 Hepp et al., N.P. B 115 (1976) 82

K - Compound Nuclei  p + n +…. ---> K - + p + p + n +… ---> K - bound state +  

Predicted (K -,  - ) Spectra Y. Akaishi

How about ppK - K -, ppnK - K - ??

total B.E. = 221 MeV central density = 3.01 fm -3 rmsR= 0.69 fm ppnK - K - total B.E. = 118 MeV central density = 1.50 fm -3 rmsR= 0.72 fm total B.E. = 6.0 MeV central density = 0.14 fm -3 rmsR= 1.59 fm Double kaonic nucleus // ppnK - K - // ppnK - ppn Density [fm -3 ] Density [fm -3 ] Density [fm -3 ] fm

Kaonic Nuclei - Future Scope Very strong K - - p attraction Very deep discrete states: predicted B K ~ 100 MeV Highly excited resonance states In-medium KN interactions modified? Dense nuclear systems formed Possibly, Quark-Gluon phase at T = 0 Kaon condensation; strange matter Nuclear dynamics under extreme conditions

Strangeness at high nuclear densities The nuclear incompressibility is overcome by the Strong K- p attraction At high density K- matter [K - p] + [K - p] + …+ n +… may be more stable

Spectroscopy ** Entrance channel spectroscopy Direct reactions : A+a --> X + b Missing-mass spectroscopy ** Decay channel spectroscopy Compound reactions --> X + anything X --> x1 + x2 + … Invariant-mass spectroscopy: M inv 2 = (E 1 + E 2 +..) 2 - (P 1 + P 2 +..) 2

Search for K - cluster fragments in HI reactions high-density environment provided by HI fireball Invariant mass spectroscopy for their decays K - pp -->  + p, K - ppn -->  + d

Kbar cluster decay in the freeze-out phase  K (=10 fm/c) >  freeze-out

FOPI from Kusche (PhD) 1999

Search for K- clusters as residues in heavy-ion reactions High density medium accommodated in fire balls Deep self-trapping centers in fire balls Freeze-out phase Invariant mass spectroscopy for fragments ppK - --->  + p ppnK - --->  + d