EXOTIC ATOMS/NUCLEIT. 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 SpectroscopyToshimitsu 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 States1s 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 nucleiSeki-Masutani relation
Double-scattering effect
Pionic Bound States Probe Nuclear Surface
Overlapping density:
maximum at
The density-dependent potential parameter:
is transposed to
€
S(r) = ρ(r) | Φ (n,l) |2 r 2
€
b1(ρ(r)) =b1
( free )
1−α ρ(r)
€
b1* =
b1( free )
1−α ρeff
€
ρ(r) ⇒ ρeff ≈ 0.60 ρ (0)
in 205Pb
Sn(d,3He) spectraK. Suzuki et al., PRL (2003)
PIONIC NUCLEI as a unique indicator of Chiral Symmetry Restoration
in the nuclear mediumFundamental 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 breakingQCD vacuum is subject to change: partial restoration of chiral symmetryHOW to prove or disprove this scenario? As in superconductors Pion decay constant in medium ---> Isovector pion-N interaction
b1(free) /b1*(ρ) -->>
B1s and 1s in Sn Isotopes
Pionic Bound States as an Indicator of Chiral Symmetry Restoration
Isovector s-wave interaction --->> pion decay constant in the
mediumWeise (2000, 2001)Kienle and TY (2001)
Best probe: Pionic 1s inheavy nuclei
GSI experiment on pionic 115Sn, 119Sn, 123Sn K. Suzuki et al. (2002)
Evidence for partial restoration of chiral symmetry in nuclear medium probed by 1s pionic nuclei (2003)
isoisoso
Isovector s-wave N scattering length
Hadron Bound States
Nuclear excited states with strangeness S = -1as Feshbach resonances
p, n(940)
: stable Hypernuclei: Many observed,,
Hypernuclei: Unstable: conversio
n Exception: 4
He405: K-p bound stateK-N(1433)
K- nuclear bound states?
Akaishi KN PotentialY. 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
3He ---> 3HeK- shrinkage !!
Antisymmetric Molecular Dynamics Method
IsovectorDeformation Dote et al.
Very exotic systemskaonic 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-,-) (-,K0) (+,K+) (,K0) Q -1 0 +1 targetp * +, +*[n] - * +, +* d pnK- ppK- -3He ppnK- pppK- -4He ppnnK- pppnK- ppppK-
Experimental SearchM. Iwasaki et al., at KEK
4He (stopped K-, n)K- 3He
-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 1520 + p + n +…. ---> K- + p + p + n
+…
• ---> K- bound state +
Predicted (K-,-) Spectra Y. Akaishi
How about ppK-K-, ppnK-K- ??
total B.E. = 221 MeVcentral density = 3.01 fm-3
rmsR= 0.69 fm
ppnK-K-
total B.E. = 118 MeVcentral density = 1.50 fm-3
rmsR= 0.72 fm
total B.E. = 6.0 MeVcentral density = 0.14 fm-3
rmsR= 1.59 fm
Double kaonic nucleus // ppnK-K- //
ppnK- ppn
Density [fm-3]0.0 1.5 3.0
Density [fm-3]0.00 0.75 1.50
Density [fm-3]0.00 0.07 0.14
4 fm 4 fm 4 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 incompressibilityis 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: Minv
2 = (E1 + E2 +..)2 - (P1 + P2 + ..)2
Search for K- cluster fragments in HI reactionshigh-density environment provided by HI fireball
Invariant mass spectroscopy for their decaysK-pp --> + p, K-ppn --> + d
Kbar cluster decay in the freeze-out phaseK (=10 fm/c) > freeze-out
FOPI from Kusche (PhD) 1999
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