Hyperons in nuclei -- review Hadron2011 June 17, 2011 Munich Hyperons in nuclei -- review Dept. of Physics, Tohoku University H. Tamura

Contents 1. Introduction 2. L hypernuclei 2.1 (p,K+) spectroscopy (incl. n-rich L hypernuclei) 2.2 g spectroscopy of L hypernuclei 2.2. (e,e’K+) spectroscopy of L hypernuclei 3. S-nuclear systems 4. Double strange systems 5. Weak decays of L hypernuclei (FINUDA data) 6. Summary K mesons in nuclei (K- nucleus and K- atoms)

1. Introduction

World of matter made of u, d, s quarks N Z L, S Hypernuclei LL, X Hypernuclei Nu ~ Nd ~ Ns Strangeness in neutron stars ( r > 3 - 4 r0 ) Strange hadronic matter (A → ∞) “Stable” Strangeness -1 -2 Higher density => Baryon-baryon interactions Unified understanding of “extended nuclear force” Understanding of short range parts of nuclear force Test of lattice QCD ３-dimensional nuclear chart by M. Kaneta inspired by HYP06 conference poster

High density matter in neutron stars Large neutron Fermi energy -> Hyperons appear Baryon fraction: sensitive to YN, YY interactions -> Maximum mass, Cooling speed Hypernuclear data -> realistic calculations possible One probable assumption but should be determined by experimets. We still need XN, LL, SN, KN forces, LN p-wave force, NNN and YNN force, … - r0 n star Vela Supernova remnant Nu ~ Nd ~ Ns The heavy n-star (M=1.97 ± 0.04 M◎) can be supported? S’s appear? Kbar appear? Strange hadronic matter exists?

Overview of Strangeness Nuclear Physics Experiments K- or p+/- beams KEK-PS, BNL-AGS => J-PARC L and S hypernuclear spectroscopy, g-spectroscopy of L hypernuclei LL and X hypernuclei [Takahashi], weak decays of L hypernuclei K- nuclei [Fujioka], K- atoms, e- beam Jefferson Lab (Hall A, Hall C), MAMI-C high-res. L hypernuclear spectroscopy, weak decays K- from f DAFNE (FINUDA, SIDDHARTA, AMADEUS) spectroscopy of L hypernuclei [Botta,Bonomi] weak decays of L hypernuclei [Bufalino] K- nuclei, K- atoms [Ishiwatari,Okada], Heavy ion beams GSI (HypHI) Heavy-Ion induced production, lifetimes,.…

2. L hypernuclei 2.1 (p+,K+) spectroscopy incl. n-rich L hypernuclei

Previous (p+,K+) data and LN interaction SKS at KEK-PS p+ n -> L K+ -> Nuclear potential of L UL = - 30 MeV (c.f. UN = -50 MeV) Better resolution is necessary for LN spin-dependent forces, LN-SN force, .. Mass of hypernucleus -BL (MeV) (p,K+) -> (e,e’K+) at JLab g spectroscopy at KEK/BNL, J-PARC Hotchi et al., PRC 64 (2001) 044302

Present Status of L Hypernuclear Spectroscopy (2006) Updated from: O. Hashimoto and H. Tamura, Prog. Part. Nucl. Phys. 57 (2006) 564.

Neutron-rich hypernuclei p- p p -> L n K+ 2-step charge exchange (p-p->p0n, p0p->K+L etc.) Via S- admixture in L hyp. (p- p->S- K+, S- p<->Ln) 10B (p-, K+) 10LLi pp~1.2 GeV/c 11.1±1.9 nb/sr Physics Interest L-S coherent coupling -> LNN attraction important in neutron stars Cross section sensitive to S- admixture in L hyp. n-halo disappear by L ? Akaishi et al., PRL 84 (2000) 3539 Almost no background KEK E521, K6+SKS Saha et al., PRL 94 (2005) 052502 First data on n-rich hypernucleus New data from FINUDA – 6LH suggested by 6Li(K-stop,p+) E. Botta, Monday

2.2 g spectroscopy

Hypernuclear g-ray data Hyperball 1998~ Ge array for hypernuclei Hypernuclear g-ray data CERN (NaI) (p+,K+ g) at KEK-PS (K-, p- g) at BNL-AGS => DE ~ 2 MeV -> 3 keV (FWHM) Observation of hypernuclear fine structure LN spin-dependent interaction Nuclear shrinkage by a L from B(E2)

LN spin-dependent interactions Low-lying levels of L hypernuclei Level spacing: Linear combination of D, SL, SN, T Millener’s approach Two-body LN effective interaction - V D SL SN T p-shell: 5 radial integrals for sL pN w.f. s D =∫V (r) |u (r)|2 r2dr, r = r - r sL pN Well known from UL = - 30 MeV g-ray data => D = 0.33 (0.43 for A=7), SL = -0.01, SN = -0.4, T= 0.03 [MeV] Small spin-dependent forces have been established.

Revised Observation of “Hypernuclear Fine Structure” BNL E930　 (AGS D6 line + Hyperball) 9Be (K-, p- g) 9LBe 16O (K-, p- g) 16LO 43±5 keV 26.1±2.0 keV Eg (keV) Eg (keV) MeV MeV SL = -0.01 MeV T = 0.03 MeV PRL 88 (2002) 082501 PRL 93 (2004) 232501 consistent with Quark Cluster Model consistent with Meson Exch. Model

mL in nucleus -> medium effect of baryons g factor of L in nucleus mL in nucleus -> medium effect of baryons Can be investigated using a L in 0s orbit mq reduction by chiral sym. rest. -> mB enhances ?? mB looks OK with mq= eh 2mqc mq: constituent quark mass Direct measurement of mL in nucleus extremely difficult (t ~ 0.1-- 0.2 ns) B(M1) of L-spin-flip M1 transition -> gL in s-orbit gc Doppler Shift Attenuation Method : ~100% Applied to “hypernuclear shrinkage” in 7LLi from B(E2) : PRL 86 (’01)1982 Prelim. data for 7LLi(3/2+->1/2+) (E930, M.Ukai) gL = -1.1 +0.6 mN -0.4 => J-PARC E13: ~ 5% accuracy for B(M1) gL(free) = -1.226 mN

2.3 (e,e’K+) spectroscopy

Characteristic features of (e,e’K+) experiments at JLab Sub MeV resolution  High quality primary e beam Proton to L  Neutron rich L hypernuclei Mirror to those by (p+,K+) Large angular momentum transfer  Stretched states (similar to (p+,K+)) Spin-flip amplitude  Unnatural parity states Calibration by p(e,eK+) S, L -> Absolute mass scale -> Fine structure of bound and unbound states -> Accurate BL values

Improvement of Resolution preliminary 12C(p+,K+)12LC @ KEK-PS PRC 64 (2001) 044302 DE = 2 MeV (FWHM) 12C(e,e’K+)12LB @ JLab Hall A DE ~ 0.65 MeV (FWHM) PRL 99 (2007) 052501 12C(e,e’K+)12LB @ JLab Hall C DE ~ 0.5 MeV (FWHM)

Dedicated spectrometer at Hall C ENGE HKS Splitter Electron beam To beam dump Target Dp/p = 4×10-4 (FWHM) Recently replaced to new spectrometers e’ 0.3 GeV/c e 1.8 GeV Took data for 7LHe, 9LLi, 10LBe, 12LB , 32LAl, 52LV

A new test of charge symmetry breaking (K-,p- ) => Ln≠Lp very large CSB? Tests by non-emulsion methods awaited #1 9 events ?? Juric et al. NP B52 (1973) 1 g ray calc. by Hiyama Tamura et al. PRL 84 (2000) 5963 T=0 T=1 7Li(e,e’K+)7LHe Hall C Absolute mass scale well calibrated via H(e,e’K+)L,S0 prelim. -5.68±0.03±0.22 7Li(e,e’K+)7LHe

3. S-nuclear systems

The only S-nuclear bound state so far observed No S bound states peaks in other S hypernuclei Substitutional (DL=0) state: n(s1/2)-1L(s1/21) T=1/2, 3/2 S=0 4SHe T=3/2 only S=0 Large spin-isospin dependence (I,S) = (3/2,0), (1/2,1) attractive (3/2,1), (1/2,0) repulsive -- Consistent with meson exchange models How about spin-isospin averaged potential? S in neutron stars? BNL-AGS, Nagae et al., PRL 80 (1995) 1605

S--28Si Nuclear potential (KEK E438) 28Si (p-,K+) at 1.2GeV/ with SKS Strong repulsion coming from Pauli effect between quarks? Quark Cluster Model Lattice QCD SN (I,S) = (3/2,1) V0 ~ -10 MeV W0 ~ -10 MeV S’s never appear in n-stars? High statistics S+p/ S-p scattering experiment planned at J-PARC Noumi et al., PRL 87(2002) 072301 Strongly repulsive potential (U~ +30 MeV) How repulsive are (I,S) = (3/2,1), (1/2,0) channels?

4. Double strange nuclear systems

LL hypernuclei via emulsion+counter hybrid method (KEK E373) Nakazawa (Hyp-X conf.) Nagara event Mikage event DBLL= 3.82 ±1.72 MeV #8 6 He (unique and accurate) LL 6 He LL DBLL= 0.67±0.17 MeV 11 Be LL Hida event Demachi-yanagi event 10 Be* (w/ theoretical help) LL DBLL= -1.52 ±0.15 + 3.0 cf. Ex = 3.0 DBLL= 2.27 ±1.23 MeV

LL interaction strength Nagara event Well-identified double L hypernucleus event L n p produced from K- p -> X K+ reaction Mass -> DBLL = 0.67±0.17 MeV Interaction between LL is weekly attractive Bound H dibaryon does not exist. Takahashi et al., PRL 87 (2001) 212502 Takahashi et al., PRL 87 (2001) 212502 => ~10 times more LL hypernuclear events X hypernuclear spectroscopy, X atomic X-rays at J-PARC

5. Weak decays of L hypernuclei (New FINUDA data)

S.Bufalino - HADRON2011, June 13-17 München S.Bufalino, Monday Mesonic weak decays (FINUDA) p- energy spectra and decay rates were measured for 15O: 1/2-gs & sd (~6 MeV) Agnello PLB 681 (2009) 139 L->pp- decay in nuclei spin-parity assignment pion optical potential L wavefunciton in nucleus present data T. Motoba PTPS 117 (1994) 477 previous data A.Gal NPA 828 (2009) 72 A S.Bufalino - HADRON2011, June 13-17 München T. Motoba NPA 489 (1988) 683. Jp (15LNg.s.) = 3/2+ strong nuclear structure effects A

Non Mesonic Weak Decay (FINUDA) S.Bufalino, Monday Non Mesonic Weak Decay (FINUDA) Spectra contain LN->NN, FSI, and 　　　　LNN->NNN (2N-induced nonmesonic decay) 15 MeV NPA 804 (2008),151 NPA 804 (2008),151 NPA 804 (2008),151 K-np background subtracted GNM G2 = Gn/Gp+ 1 + G2/Gp G2/Gp = 0.24 ± 0.10 M. Kim et al., PRL 103 (2009) 182502: 　 0.29 ± 0.13 12LC M.Agnello et al., PLB 685 (2010) 247

6. Summary (p-,K+) spectroscopy for L hypernuclei Neutron-rich10LLi observed. Will be used to investigate LNN force. g-spectroscopy of L hypernuclei: Almost all p-shell data accumulated and spin-dependent LN interactions well determined. gL to be measured from B(M1). (e,e’K+) spectroscopy of L hypernuclei at JLab: Resolution improved to ~ 0.5 MeV (FWHM). New test of LN charge symmetry breaking. S-nuclear systems: strong repulsive potential observed. 6LLHe event revealed LL force weakly attractive. Mesonic and nonmesonic weak decay (LNN->NNN) data from FINUDA. Further progress in strangeness nuclear physics is expected at J-PARC, JLab, DAFNE, GSI, FAIR.

Summary for the YN, YY interactions Established Suggested Unknown LN 　　Attractive (~ 2/3 of NN force) <- LZ L-single particle orbit data 　　Very small LS force, small spin-spin/ tensor forces <- LZ p-shell g-ray data etc. 　 LN-SN coupling force <- s-shell L hypernuclei 　　 p-wave force? Charge symmetry breaking (Lp≠Ln)? SN Strong isospin dependence (attractive for T=3/2,S=0 and T=1/2,S=1) <- 4SHe Strongly repulsive in average <- 28Si (p-,K+) spectrum How large is the repulsive (T=3/2,S=1) channel? LL Weakly attractive <- 6LLHe LL-XN-SS coupling force ? XN Weakly attractive? <- 12C (K-,K+) spectrum Isospin dependence? LS, SS, XL, XS, XX; WN Unknown at all ?? J-PARC will answer

Thank you for your warmhearted supports and encouragement to Japan, particularly to Tohoku University (Sendai) and J-PARC/KEK. We are recovering everything back and going forward.

Summary for the YN, YY interactions PRC 64 (2001) 044302 -> UL = - 30 MeV Summary for the YN, YY interactions Established Suggested Unknown KEK E373 : Nagara event LN 　　Attractive (~ 2/3 of NN force) <- LZ L-single particle orbit data 　　Very small LS force, small spin-spin/ tensor forces <- LZ p-shell g-ray data etc. 　 LN-SN coupling force <- s-shell L hypernuclei 　　 p-wave force? Charge symmetry breaking (Lp≠Ln)?? SN Strong isospin dependence (attractive for T=3/2,S=0 and T=1/2,S=1) <- 4SHe Strongly repulsive in average <- 28Si (p-,K+) spectrum How large is the repulsive (T=3/2,S=1) channel? LL Weakly attractive <- 6LLHe LL-XN-SS coupling force ??? XN Weakly attractive?? <- 12C (K-,K+) spectrum Isospin dependence??? LS, SS, XL, XS, XX; WN Unknown at all ??? J-PARC will answer g-ray data BNL E930

How to extend S=-1 nuclear chart? 6LH “hyperheavy hydrogen” 9LHe J-PARC E10 deeply bound by additional binding (+1.4 MeV) from LNN force (Akaishi) target nuclei (e,e’K+) single charge exchange (p+ ,K+) (K-, p-) (p- ,K+) double charge exchange p- p p -> L n K+ 2-step charge exchange (p-p->p0n, p0p->K+L etc.) Via S- admixture in L hypernuclei (p- p->S- K+, S- p<->Ln)

Motivation Baryon-baryon interactions Unified understanding of “extended nuclear force” Understanding of short range parts of nuclear force Test of lattice QCD  High density nuclear matter in neutron stars Nuclear medium effects using hyperons gL in nucleus Impurity effect to nuclear structure Shrinkage, Change of deformation, Dissaperance of halo and cluster structure,…