Experimental Search for Dense Nuclear Bound Systems Mediated by K - Mesons Toshimitsu Yamazaki (RIKEN) * Condensed few-body systems with K - (Kbar cluster): predicted, Akaishi-TY, PRC (2002), TY-Akaishi, PLB (2002) * Antisymmetric Molecular Dynamics calculations Dote et al., strong binding, high densities, exotic shapes, isovector deformation, * 1st evidence: 4 He(K -,n)ppnK -, Oct 2003, Iwasaki et al., KEK * Double-K - nuclei: ppK - K -, ppnK - K - * K - clusters as residues of quark-gluon plasma: Invariant-mass spectroscopy of decay particles, proposed 2003 * Indication for ppnK - from FOPI at GSI * Implications and future scopes Seoul, November , 2003, KIAS-APCTP International Symposium in Astro-Hadron Physics Compact Stars: Quest For New States of Dense Matter

Explore dense nuclear states at T = 0 with K - bound states Cold and dense microscopic nuclear systems a New Paradigm - so far untouched

Quark condensate as a function and T and  M. Lutz, S. Klimt and W. Weise, Nucl. Phys. A542 (1992) 52 T. Hatsuda and T. Kunihiro, PRL 55 (1985) 158

In-medium Hadrons: Brown-Rho scaling (1991) Partial restoration of chiral symmetry m  *(  )/m  = m N * (  ) /m N = m  * (  )/m  = f  * (  ) /f  = [ (  ) / 0 ] 1/2 quark condensate How to measure m  *(  ) in a well-define medium density  ? Invariant-mass spectroscopy applied to decaying X in medium ?! Quasi-invariant mass - disturbances caused by collisions New method: bound-state spectroscopy of X, if narrow X =  - Deeply bound pionic states X = K- Strongly bound kaonic states

Quasi Invariant Mass TY and Y. Akaishi, PLB 453 (1999) 1 Mass of X a hadron in medium or a bound hadron not invariant: no invariant mass Nevertheless, one can construct M inv *=(E 1 +E ) 2 - (P 1 +P ) 2 What does M inv * reflect? ---> not mass but energy-like ---> kinematical shift/broadening because of “ missing medium ”

Collisional shift and broadening TY and Y. Akaishi, PLB 453 (1999) 1 cf. Moessbauer effect  -meson decay in nuclei Nuclear Debye-Waller factor

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

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

Evidence for partial restoration of chiral symmetry in nuclear medium probed by 1s pionic nuclei (2003) b1/b1* = f  *(0.6  0 ) 2 /f  2 = */ 0 ~ 0.65 at  =  0 The 1st clear support for the whole scenario: quantitative agreement with theoretical predictions isoisosoisoisoso Isovector s-wave  N scattering length

KN interaction Before 1997: Confusing situation 1997 KpX experiment at KEK Iwasaki et al. PRL(1997): K - p atom shift:  E 1s “ repulsive ”, Indicating the K - p interaction is strongly attractive Consistent with the view that   (1405): 1s bound state of K - p Atomic ground state is 2s bound state --->> Akaishi-Y constructed KN interaction

Akaishi-TY, PRC (2002) KN interaction derived from coupled-channel calculations Based on empirical data I=0: Extremely attractive

Brown, Lee, Rho & Thorsson, NP A567 (1994) 937

Kaonic Bound States Believed to be non-existing:  > BE However, Akaishi-Yamazaki (2002) predicted: - K - -p interaction so strong - strongly bound states - shrinks nuclei --> deeper bound states - deep enough: the main decay channel KN-->  N closed BE > 100 MeV: narrow bound states High nucleon density:  ~ (4-7)  0 - chiral symmetry restoration? - deconfined quark-gluon phase?

Diagram Kaon Bound System

ppK - bound system - kaonic “hydrogen molecule”

K - potentials and bound states Y. Akaishi and TY, PRC (2002) Narrowing mechanism: E K <  threshold TY and Y. Akaishi, PLB (2002)

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

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?

Antisymmetrized Molecular Dynamics Dote, Horiuchi, Akaishi, TY (2002) Ab initio - No assumption on the structure - Structure: dynamically produced no shell model, no cluster model KN: AY interaction: empirically based NN: Tamagaki interaction ~ 600 MeV

3 He ---> 3 HeK - shrinkage !! Antisymmetric Molecular Dynamics Method Isovector Deformation Dote et al. 2002

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 -

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

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

KEK Experimental Result Iwasaki et al. October 16, He(stopped K -, n) ppnK - Observed B K ~ 170 MeV  K ~ 25 MeV Predicted (Akaishi 2002) B K ~120 MeV + 25 MeV (relativistic, etc)  K  ~ 30 MeV Observed Yield much smaller than expected

Observation of K - ppn < Pr ediction < Reltivistic correction etc. << Observed

How about ppK - K -, ppnK - K - ?? T. Y.,A. Dote,Y. Akaishi, 2003 “Kaonic hydrogen molecule” Strange di-proton Jaffe’s H di-baryon? uud-us-us-uud not uuddss -

3 He K - ppn  (0)=0.14  (0)~1.5 B = 20 MeV B ~118 MeV K - K - ppn  (0)~3.0 B~221 MeV Single-K - Double-K -

3 He K - ppnK - K - ppn How to produce? Supression?

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 emitted K and bound K: brothers deep trapping centers

Cooling/expanding cf. Lee-Wick density isomer Mini-QCD Ball (Tachibana)

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

Search for K - clusters as residues in heavy-ion reactions High density medium accommodated in QGP fire balls Deep self-trapping centers of K - produced in fire balls Freeze-out phase Invariant-mass spectroscopy for decay fragments Single-K - ppK - --->  + p ppnK - --->  + d ppnnK - --->  + t pppnK - --->  + 3 He Double-K - ppK - K - --->  +  pppK - K - --->  +    pppnK - K - --->  +   d

Yield: Prediction by chemical equilibrium model: A. Andronic and P. Braun-Munzinger, priv.comm., 16/10/03 Observed Combinatorial background R = S/N = BR (Kppn -->  d) Y Kppn /(Y  Y d ) ~ Y  ~ 0.15, Y d ~ 2 BR (Kppn->  d) ~0.1 (assumed) Thus, Observed : Y Kppn ~ Prediction: Y Kppn ~ 0.01

SIS 100/300 SIS AGS CERN SPS optimum production of baryons with strange quarks maximum compression in heavy-ion collisions threshold for strange quarks threshold for antiprotons threshold for charm quarks ion energy [AGeV] nuclear matter density (blue curve) Rel.production of strange quarks (red curve) GSI SIS : Ideal Place

A. Andronic and P. Braun-Munzinger, priv.comm., 17/10/ >> SIS100/300: best place

Prospect Invavriant mass spectroscopy with  in heavy-ion reactions: promising Yield esimate by Braun-Munzinger’s group Search for single-K - and double-K - Once found, they become probes for dynamics involving QGP and fleeze-out phase: yields, shifts/broadening More experiments at FOPI:  +t for K - ppnn,  + 3 He for K - pppn,…

Strangeness at high nuclear densities Nuclear incompressibility is overcome by the Strong K - p attraction At high density K - matter [K - p] + [K - p] + …+ n +… may be more stable Schematic Spontaneously, dynamically organized high density without the aid of gravity!

Chiral Symmetry Restoration In-medium Tomozawa-Weinberg relation T  N (-)* (  ) =  /2f  * (  ) 2 = m  /2f  2 x 1/(1-    ) f  (  )* 2 / f  2 = 1 - (   /m  2 f  2 )  ~  /  0   isovector s-wave  -N interaction      * (  )  m K /f K *(  ) 2 = m  /f  2 x 1/(1-    ) f  (  )* 2 /f  2 = 1 - (   /m  2 f  2 )  ~  /  0 strongly bound K - nuclei

Hadrons in Nuclear Matter [GeV] /0/0 K/N=1/2 K/N=1 K/N=3/ p =uud av. K =us - - Tuning B Kppn (obs) = 173 MeV B Kppn (calc) =138 MeV  B = 35 MeV --->> enhanced KN in medium by 17% T KN *(  ) =T KN /(1 -  ) Against “ strong ” decay s/ud cross-over density decreases to ~ 7  0

Kaonic Nuclei - mini strange matter Very strong K - - p attraction deep discrete bound states: predicted B K ~ 100 MeV * Highly excited resonance states * In-medium KN interactions modified? chiral symmetry? * Dense nuclear systems formed Possibly, Quark-Gluon phase at T = 0 Colour Super * Precursor to kaon condensation; strange matter * Nuclear dynamics under extreme conditions