exotic atoms/nuclei t. yamazaki, riken

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