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Hypernuclear Physics at J-PARC

Hypernuclear Physics at J-PARC. Dept. of Physics, Tohoku University H. Tamura. 1. Introduction 2. S=-1 2.1 g spectroscopy of hypernuclei 2.2 n-rich L hypernuclei 3. S=-2 3.1 X hypernuclear spectroscopy 3.2 LL hypernuclei 4. Experimental apparatus 5. Other plans 6. Summary.

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Hypernuclear Physics at J-PARC

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  1. Hypernuclear Physics at J-PARC Dept. of Physics, Tohoku University H. Tamura

  2. 1.Introduction 2. S=-1 2.1g spectroscopy of hypernuclei 2.2n-rich L hypernuclei 3. S=-2 3.1X hypernuclear spectroscopy 3.2LL hypernuclei 4. Experimental apparatus 5. Other plans 6. Summary Contents

  3. 1. Introduction

  4. Nu ~ Nd ~ Ns Strangeness in neutron stars ( r > 3 - 4 r0 ) Strange hadronic matter (A → ∞) Strangeness LL, X Hypernuclei Z L, S Hypernuclei -2 N n-rich nuclei -1 Lower density 0 World of matter made of u, d, s quarks “Stable” Higher density ３-dimensional nuclear chart by M. Kaneta inspired by HYP06 conference poster

  5. Motivation of Hypernuclear Physics • Extending “Nuclear Chart” in 3D space • Hyperons stabilize nuclei -> extend n/p drip lines • Toward multi-strange systems -> high density nuclear matter • Baryon-Baryon interaction • Unified picture of baryon-baryon interactions • Understand short-range nuclear forces in terms of quarks • Necessary to understand high density nuclear matter and strangeness mixing in neutron stars • Impurity effects in nuclear structure • Changes of size/shape, symmetry, cluster/shell structure,.. • Nuclear medium effects of baryons • Probed by hyperons free from Pauli effect

  6. PRC 64 (2001) 044302 J-PARC will answer -> UL = - 30 MeV(c.f. UN = -50 MeV) What we know about YN, YY interactions Established SuggestedUnknown • 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=1/2,S=0) <- 4SHe Strongly repulsive in average?<- 28Si (p-,K+) spectrum How large is the repulsive (T=3/2,S=1) channel? • XN Weakly attractive??<- 12C (K-,K+) spectrum Isospin dependence??? • LL Weakly attractive <- 6LLHe LL-XN-SS coupling force ??? • LS, SS, XL, XS, XX Unknown at all ???

  7. r0 n star ストレンジネス・クォーク星の可能性 南冠座の天体 RX J1856.5-3754 カシオペア座の天体3C58 西暦1181年に起きた超新星爆発のときにできたパルサーと考えられている。その温度が予想よりも低い。 [Credit: NASA/SAO/CXC/J.Drake et al.] 直径が12km弱しかなく、中性子星より密度が高い。 Credit: NASA/SAO/CXC/P.Slane et al. High density matter in neutron star core Large neutron Fermi energy -> Hyperons appear Baryon fraction: very sensitive to YN, YY interactions -> maximum mass, cooling speed Hypernuclear data -> realistic calculations possible - We need XN int., LL int., KN int. (K condensate?), LN p-wave force, NNN and YNN force, … 帆座超新星残骸 かに座超新星残骸 存在比率 密度

  8. 2. S=-1

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

  10. 2.1 S=-1g spectroscopy of L hypernuclei

  11. Hypernuclear g-ray data since 1998 (p+,K+ g) at KEK-PS (K-, p- g) at BNL-AGS using Ge array “Hyperball” NaI array (13LC) “Table of Hyper-Isotopes” EPJ A33 (2007) 243 PRC 77 (2008) 054315

  12. D =∫V (r) |u(r)|2 r2dr, r = r -r sL pN • Two-body LN effective interaction D SL SN T p-shell: 5 radial integrals for sL pN w.f. s Well know from UL = - 30 MeV - V LN spin-dependent interactions • Low-lying levels of L hypernuclei Level spacing: Linear combination of D, SL, SN, T Millener’s approach

  13. DE = -0.04D + 2.46SL+ 0.99T DE = 1.29D + 2.17SL - 2.38T 3/2+ 3/2- 2+ 1- 43 keV 7/2+ 5/2+ 3+ 471 keV 5/2+ -310 keV DE = 0.70SN 3/2+ 1+ 0+ 1/2+ 1- 692 keV 1/2- 6Li 1/2+ 26 keV 8Be 15O 0- DE = 1.44 D + 0.05SL- 0.27T DE = - 0.38 D+ 1.38SL+ 7.85T 7LLi 9LBe 16LO Determination of the spin-dependent force parameters PRC 73 (’06) 012501 D ,SL, T: consistent D = 0.4 MeV SN = - 0.4 MeV SL = - 0.01 MeV T = 0.03 MeV PRL 86 (’00) 5963 PRL 88 (’02) 082501 PRL 93 (2004) 232501 -> Test and improve baryon-baryon interaction models (meson exchange/ quark models)

  14. (K-,p- ) r (sL-dN) > r (sL-pN) sensitive to interaction range and exchanging meson mass ?? Very large CSB !? Not theoretically understood. BL(MeV) E13 (Tamura et al.)g-ray spectroscopy of light L hypernuclei (K-,p-) reaction (pK=1.5 GeV/c) at K1.8 line using SKS + Hyperball-J (developed for higher counting rate) • Further study of LN interaction • LN-SN coupling and three body force • Charge symmetry breaking (Ln≠Lp?) • Radial dependence (Interaction range) 4LHe, 10LB, 11LB, 19LF • gL in a nucleus from spin-flip B(M1) 7LLi

  15. eh mq= 2mqc ~100% Doppler Shift Attenuation Method : gc in s-orbit g factor of L in nucleus mL in nucleus -> medium effect of baryons mq : Const. quark mass • Direct measurement extremely difficult (tL ~ 0.1-- 0.2 ns) • B(M1) of L-spin-flip M1 transition -> gL reduction of mass -> enhancement of m?? applied to “hypernuclear shrinkage” in 7LLi from B(E2) : PRL 86 (’01)1982 -> Precise B(M1) measurement (~5%) of 7LLiat J-PARC

  16. 2.2 S=-1 n-rich hypernuclei

  17. Search for n-rich hypernucleiby (Stopped K-, p+) 9LHe 6LH 12LBe 7LH 16LC Only upper limit Background from Sigma decay

  18. L-S coherent coupling Akaishi et al., PRL 84 (2000) 3539 Neutron-rich hypernucleus (KEK E521, K6+SKS) Physics Interest • L-S coherent coupling -> more bound? • Behavior of n-halo with a L • Production mechanism? • 2-step charge exch. • (p-p->p0n, p0p->K+L etc.) • S- admixture • (p- p->S- K+, S- p->Ln) p- p p -> L n K+ pp~1.2 GeV/c 10B (p-, K+) 10LLi 11.1±1.9 nb/sr Almost no background Saha et al., PRL 94 (2005) 052502 First data on n-rich hypernucleus

  19. E10 (Sakaguchi et al.)Study on Neutron-Rich Hypernuclei NCX: (K-,p-), (p+,K+) reaction Produce neutron-rich hypernuclei by the double charge-exchange (DCX) reaction L-hypernuclei SCX: (e,e’K+), (K-,p0), (p-,K0) reaction DCX: (K-,p+),(p-,K+)reaction NCX ordinary nuclei SCX this study DCX Akaishi: Glue-like role of L (BL=4.4 MeV) + LNN coherent coupling ( +1.4 MeV) 6LH p 5H n n n L n p n n n n unbound “Hyperheavy hydrogen”: deeply bound

  20. 3.1 S= -2 X-hypernuclei

  21. -> Take a similar spectrum for (K-,K+) reaction E05 (Nagae et al.)X-hypernuclear spectroscopy by (K-,K+) K- p -> X- K+ 1st priority • First spectroscopic study of S=-2 systems in (K-,K+) reaction • First step to multi-strangeness baryon systems • XN Interaction • Attractive or repulsive? How large? <- X-nuclear potential depth • Isospin dependence ? <- Different targets • XN-LL coupling force? • <- Xp→LLconversionwidth <- X and LL hypernuclear mixing states

  22. Previous data on XN interaction(BNL AGS E855) PK=1.8 GeV/c ΔM=9.9 MeV/c2 (FWHM) for p(K−,K+)Ξ− −20 < EΞ < 0 MeV 89±14 nb/sr θ< 8° 42± 5 nb/sr θ<14° VΞ = -14 MeV?

  23. Expected 12C (K-,K+) 12XBe Spectrum ΔEmeas. = 3 MeVFWHM pX VΞ= -20MeV VΞ= -14MeV [counts/0.5MeV] sX • Precision: • Peak Position: 0.1 - 0.3 MeV • Width: 0.2 - 1 MeV -BΞ [MeV]

  24. 3.2 S=-2LL hypernuclei (and X- atoms)

  25. p L n DBLL =1.01±0.20 +0.18 MeV - 0.11 A golden event of LL Hypernuclei Nagara event The first well-identified double L hypernucleus event “Triple magic nucleus” p(0s)2 n(0s)2L(0s)2 produced from K- p -> X- K+ reaction Mass -> Interaction betweenL-L is weekly attractive. Takahashi et al., PRL 87 (2001) 212502 KEK E377 Emulsion-counter hybrid method ~103 stopped X- PRL 87 (2001) 212502

  26. E03 (Tanida et al.)X- atomic X rays by (K-,K+)X- on Fe target “LL”-> S-p decay event E07 (Nakazawa, Imai, Tamura et al.)S=-2 Systems with Emulsion-Counter Hybrid Method Measure tracks by counters • Ten times more events of LL hypernuclei >104 stopped X-, ~102LL hypernuclei • Details of LL interaction strength • L-L correlation (H dibaryon-like state) • in nucleus from “LL”-> S-p decay • Measure X- -atomic X-rays with Hyperball-J • Shift and width of X-rays -> X-nuclear potential • Stopped X- events identified from emulsion

  27. Experimental Apparatus K1.8

  28. Hadron Hall X hypernuclei LLhypernuclei X-atomic X rays g spectroscopy n-rich Lhypernuclei Q+ search w nucleus SKS Beam Dump K- nucleus bound states K- atomic X rays h, f nucleus K1.8 (Fall,2009~) KL Handron Hall K1.8BR (Dec.2008~) • Production • target (T1) K1.1 (when?) 30 (→ 50) GeV primary beam g spectroscopy S hypernuclei YN scattering Q+ nucleus K0.8 (when?)

  29. SKS spectrometer(SksMinus) An Example of Setup (E13) p- SKS superconducting magnet 1.4 GeV/c Hyperball-J K- 1.5 GeV/c K1.8 beamline spectrometer

  30. SKS spectrometer Modified SKS magnet • Disassembled Jan.15-30 • Under modification of cooling system • Assemble at J-PARC site (2008 Sep.-Oct.) 1.4 GeV/c SksPlus for (K-,K+) • Additional magnet produced using an old iron yoke

  31. Double-sided Si Strip Detector Almost same as PS-E373 Setup of E07 KURAMA spectrometer (existing) # Beam :K- (1.7GeV/c), 3 x 105K-/spill withK-/p- > 6 at K1.8 beam-line (~20% of 9mA) # Trigger :(K-, K+) => 104 X- stopping events (more than 10 times higher statistics than E373) Hyperball-J Faster emulsion scanning system

  32. 5. Other plans • High resolution (~0.2 MeV) (p±,K+) spectroscopy for (n-rich) L, S hypernuclei (Noumi) • Weak decay of L hypernuclei (Bhang) • g spectroscopy of heavy L hypernuclei and n-rich L hypernuclei (Tamura) • Light S hypernuclear systems (Tamura) • SN, LN, (XN) scattering experiments (Ieiri, Miwa)

  33. 6. Summary • Hypernuclear physics is one of the most important physics subjects at the J-PARC Hadron Hall. • g spectroscopy of hypernuclei using Hyperball-J will further investigate LN interactions. Nuclear medium effect can be also studied from in-medium gL. • n-rich L hypernuclei to be studied at J-PARC will extend the hypernuclear chart and clarify the LN-SN mixing. • X hypernuclear data will provide the strength of XN interaction for the first time. • Many LL hypernuclear samples will be found, establishing the LL interaction, and revealing a possible LL correlation.

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