1. Liguang Tang Department of Physics, Hampton University & Jefferson National Laboratory (JLAB) July 31 & Aug. 1, 2009, OCPA6 Satellite Meeting on Hadron Physics, Lanzhou University

2.  Baryonic interaction B-B is the important nuclear force that builds the “foundation of world”; - Neutron Stars - Astronomical Scale - Neutron Stars - H H (1p) He  (  - 2p, 2n) C  C (3  )  Fully understand B-B beyond basic N-N ( p and n ) interaction is essential

3. ,  0 (uds) n (udd) p + (uud)  + (uus)  - (dds)  - (dss)  0 (uss) S Q I S = 0 S = -1 S = -2 I 3 = -1 I 3 = +1/2 I 3 = -1/2 I 3 = +1 I 3 = 0 Nucleon (N) Hyperon (Y) S - Strangeness I - Isospin

4.  Our current knowledge is limited at N-N level.  Study Y-N and Y-Y interactions is important for an unified description of B-B interaction and a gate way to include additional flavors   -N interaction is the most fundamental one  The appearance of Y’s in the core of neutron stars is now believed important to stabilize the mass and density  Unfortunately, Y beam does not exist because of the short lifetime of hyperons, among which  has the longest lifetime because it decays via weak interactions only,  = 2.6  10 -10 sec. Direct scattering experiment is almost impossible.

5.  A nucleus with one or more nucleons replaced by hyperon, , , …  A  -hypernucleus is the nucleus with either a neutron or proton being replaced by a  hyperon  Since first hypernucleus found 50 some years ago, hypernuclei have been used as rich laboratory to study YN and YY interactions Discovery of the first hypernucleus by pionic decay in emulsion produced by cosmic rays, Marian Danysz and Jerzy Pniewski, 1952

6.  Sufficient long lifetime, g.s.  -hypernucleus decays only weakly via    N or  N  NN, thus mass spectroscopy with narrow states (~100 keV) exists  Description of a  -hypernucleus within two-body frame work – Nuclear Core (Particle hole)   (particle): 11 C or 11 B Core 3/2 - 1/2 - 5/2 - & 3/2 - 7/2 + & 5/2 + (Few example states)S P    12  C or 12  B g.s. (deeply bound)    12  C or 12  B core excitations    12  C or 12  B substitution states (Example of the lowest mass states)

7.  Two-body effective  -Nucleus potential (Effective theory) : V ΛN (r) = V c (r) + V s (r)(S Λ  S N ) + V Λ (r)(L N  S Λ ) + V N (r)(L Λ  S N ) + V T (r)S 12  The right  -N and  -Nucleus models must correctly describe the mass spectroscopy (  binding energies, excitations, spin/parities, …)  A novel feature of  -hypernuclei  Short range interactions  Change of core structures (Isomerism?) (Isomerism?)  Glue-like role of  (shrinkage of nuclear size) (shrinkage of nuclear size)  Drip line limit  No Pauli blocking to   Probe the nuclear interior  Baryonic property change  N Important for  N &  -Nucleus Int.

8. AA  n A -- K-K- (K,  ) Reaction  Low momentum transfer  Higher production cross section  Substitutional, low spin, & natural parity states  Harder to produce deeply bound states AA  n A ++ K+K+ ( , K) Reaction  High momentum transfer  Lower production cross section  Deeply bound, high spin, & natural parity states AA   p A e e’e’ K+K+ (e, e’K) Reaction  High momentum transfer  Small production cross section  Deeply bound, highest possible spin, & unnatural parity states  Neutron rich hypernuclei CERN  BNL  KEK & DA  NE  J-PARC (Near Future) CEBAF at JLAB (MAMI-C Near Future)

9. Hotchi et al., PRC 64 (2001) 044302 Hasegawa et. al., PRC 53 (1996)1210 KEK E140a Textbook example of single-particle orbits in nucleus (limited resolution: ~1.5 MeV) Energy Resolution BNL: 3 MeV(FWHM) 12  C KEK336: 2 MeV(FWHM) KEK E369 : 1.45 MeV(FWHM) High Yield Rate  single particle states   -nuclear potential depth = -30 MeV  V  N < V NN Precision on Mass

10. Continuous Electron Beam Accelerator Facility (CEBAF) A B C MCC North Linac +400MeV South Linac +400MeV Injector FEL East Arc West Arc Hypernuclear Physics (e, e’ K + ) reaction Hyperon Physics Electro- & photo-production CW Beam (1 – 5 passes) 2 ns pulse separation 1.67 ps pulse width ~10 -7 emittance I max  100  A

11.  Established: High precision mass spectroscopy of  -hypernuclei with wide mass range. (Hall C program will be shown as an example)  Proposing: High precision decay pion spectroscopy for light and exotic  -hypernuclei

12.  E89-009 (Phase I, 2000) – Feasibility  Existing equipment  Common Splitter – Aims to high yield  Zero degree tagging on e’ Splitter ENGE Spectrometer (e’) Mom. resolution: 5×10 -4 FWHM Solid angle acceptance: 1.6msr SOS spectrometer (K + ) Mom. resolution: 6×10 -4 FWHM Solid angleacceptance : 5msr Central angle: 2 degrees High accidental background  Low luminosity  Low yield Sub-MeV resolution – 800 keV FWHM) First mass spectroscopy on 12  B using the (e, e’K + ) reaction T. Miyoshi, et al., Phys. Rev. Lett. Vol.90, No.23, 232502 (2003) L. Yuan, et al., Phys. Rev. C, Vol. 73, 044607 (2006)

13.  E01-011/HKS (Phase II, 2005) – First upgrade  Replaced SOS by HKS w/ new KID system  Tilted Enge (7.5 o ) with a small vertical shift K+K+ e’ Electron beam To beam dump HKS Mom. Resolution: 2x10 -4 FWHM Solid angle acceptance: 15msr Tilted Enge Mom. Resolution: 5x10 -4 FWHM Scattering angle:  4.5 o E e =1850 MeV w=1494 MeV Electron single rate reduction factor – 0.7x10 -5 Allowed higher luminosity – 200 times higher Physics yield rate increase – 10 times Energy resolution improvement –  450 keV FWHM Hypernuclei: 7  He, 12  B, 28  Al, …

14.  e Beam 2.4 GeV e’ K+K+ Tilted HES Mom. Resolution: 2x10 -4 FWHM Angular acceptance:  10msr  E05-011/HKS-HES (Phase III, 2009) – Second upgrade  Replaced Enge by new HES spectrometer for the electron arm HKS Remain the same 10 times more physics yield rate than HKS (100 HNSS) Further improvement on resolution (~350 keV) and precision Hypernuclei: 6,7  He, 9  Li, 10,11  Be, 12  B, 28  Al, 52  V, 89  Sr

15. K+K+ _ D K+K+ 1.2GeV/c Local Beam Dump E89-009 12 Λ B spectrum ~800 keV FWHM HNSS in 2000 ss pp Phase I in Hall C HKS 2005 12 C(e, e’K + ) 12  B, Phase II in Hall C  s (2 - /1 - )  p (3 + /2 + ’s) B  (MeV) Counts (150 keV/bin) Accidentals Core Ex. States ~450 keV FWHM K+K+ _ D K+K+ 1.2GeV/c Local Beam Dump E89-009 12 Λ B spectrum ~800 keV FWHM HNSS in 2000 ss pp Phase I in Hall C E94-107 in Hall A (2003 & 04)  s (2 - /1 - )  p (3 + /2 + ’s) Core Ex. States Red line: Fit to the data Blue line: Theoretica l curve: Sagay Saclay-Lyon (SLA) used for the elementary K- Λ electroproduction on proton. (Hypernuclear wave function obtained by M.Sotona and J.Millener) M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007) ~635 keV FWHM (  +,K + ) 12  C

16.  1 st observation of 7  He G.S.  n n 6 He core E. Hiyama, et al., PRC53 2078 (1996)  7 Li(e, e’K + ) 7  He (n-rich) HKS JLAB Counts (200 keV/bin) Accidentals B  (MeV) ss Sotona HKS (Hall C) 2005

17. B  (MeV) 28 Si(e, e’K + ) 28  Al HKS JLAB Counts (150 keV/bin) 28  Al ss pp dd Accidentals  1 st observation of 28  Al  ~400 keV FWHM resol.  Clean observation of the shell structures KEK E140a SKS 28 Si(  ,K + ) 28  Si Motoba with full (sd) n wave function Peak B  (MeV) E x (MeV) Errors (St. Sys.) #1 -17.820 0.0 ± 0.027 ± 0.135 #2 -6.912 10.910 ± 0.033 ± 0.113 #3 1.360 19.180 ± 0.042 ± 0.105 HKS (Hall C) 2005

18. p e’ e 12 C K+K+  12  B g.s. 12 C g.s.  - Weak mesonic two body decay 1-1- 0.0 2-2- ~150 keV Ground state doublet of 12  B B  and  Direct Production Example:

19. p e’ e 12 C  12  B * K+K+ 4 He  - Weak mesonic two body decay (~10 -10 s) Access to variety of light and exotic hypernuclei, some of which cannot be produced or measured precisely by other means    4H4H Fragmentation (<10 -16 s) Fragmentation Process Example:

20. e e’ ** K+K+  p A (A-1) Quasi-free  production (Continuum) e e’ ** K+K+  p A Y (A-1) Production of Hyperfragment (Continuum) N e e’ ** K+K+  p AaAa (A a -1) Production of Hyperfragment (Continuum) AbAb N Y (A b -1) e e’ ** K+K+  p A YAYA Direct production of Hypernuclei Background A rich source of a variety of light hypernuclei for new findings and discoveries 2B decay pion is used as the tool

21.  High precision on ground state light hypernuclei  Resolution: ~130 keV FWHM; mass precision : < ± 30 keV  Precise  binding energy  Charge symmetry breaking  Linkage between structures of hypernuclei and nuclei  Determining ground state spin/parity  Search for Isomeric low lying states ( Isomerism )  Study the drip line limit on  -hypernuclei, such as heavy hyper-hydrogen: 6  H, 7  H, and 8  H  Medium modification of baryon property

22. Figure 6. Schematic top view of the experimental configuration for the JLAB hypernuclear decay pion spectroscopy experiment (Hall A). Hall Z-axis To Hall Dump K+K+ -- 22mg/cm 2 64mg/cm 2 To a local photon dump HES 94 – 140 MeV/c 2.3 GeV 1.2 GeV/c

23. Beam energy~2.3 GeV Luminosity (beam current  target thickness)60  A  64 mg/cm 2 Target thickness toward HES22 mg/cm 2 Target tilt angle20 o Average energy shift due to target straggling loss~40 keV Momentum resolution due to target straggling61 keV/c (r.m.s.) Experimental targetsPhase-I: 7 Li; -II: 9 Be; and -III: 12 C HKS central angle (horizontal)6o6o HKS momentum and acceptanceP o = 1.2 GeV/c and ±12.5% HKS solid angle acceptance12 msr HKS (K + ) momentum resolution 2  10 -4 FWHM HKS scattering angle resolution2.5 mr FWHM HKS production time resolution130 ps (r.m.s.) HES central angle (horizontal)110 o HES momentum and acceptanceP o = 116 MeV/c and ±20% HES solid angle acceptance20 msr Detection efficiency80%  - survival rate ~32% Decay pion acceptance0.16% HES (  - ) mom. resolution w/ extended “beam spot”6  10 -4 FWHM HES scattering angle resolution6 mr FWHM HES decay time resolution100 ps (r.m.s.) Overall decay pion momentum resolution165 keV/c FWHM Absolute energy scale precision~ ±20 keV

24. Quasi-free   p +  - (all) Within the HES acceptances

25. Example: 4  He  3 He + p +  - P  Acceptance

26. Breakup ModeQ value (MeV)  - Decay P  (MeV/c)Width (keV/c) FWHM 7  He- 7 Li +  - 114.61165 p + 6  H-23.503 (B  =5.1) 6 He +  - 133.47165 n + 6  He-3.409 6 Li +  - 108.39165 d + 5  H-23.011 (B  =4.1) 5 He +  - 133.42~900 * 3 H + 4  H-16.995 4 He +  - 132.95165 4 H + 3  H-26.981 3 He +  - 114.29165 Two-Body decay – 6 possible hypernuclei Breakup ModeQ value (MeV)  - Decay P  max (MeV/c) – cut off d + 5  H-23.011 (B  =4.1) 4 He + n +  - 139.27 * 2n + 5  He-3.567 4 He + p +  - 102.42 3n + 4  He-24.868 3 He + p +  - 103.15 Three-Body decay – Background

27. Breakup ModeQ value (MeV)  - Decay P  (MeV/c)Width (keV/c) FWHM 9  Li- 9 Be +  - 121.18165 p + 8  He-13.817 8 Li +  - 116.40165 n + 8  Li-3.756 8 Be +  - 124.12165 2p + 7  H-40.328 (B  =6.1) 7 He +  - 135.17~270 * d + 7  He-12.568 7 Li +  - 114.61165 § 2n + 7  Li-12.218 7 Be +  - 108.02165 3 He + 6  H-29.608 (B  =5.1) 6 He +  - 133.47165 § 3 H + 6  He-9.745 6 Li +  - 108.39165 § 3n + 6  Li-18.957 6 Be +  - 100.58~220 **  + 5  H -11.749 (B  =4.1) 5 He +  - 133.42~900 *§ n +  + 4  H -12.005 4 He +  - 132.95165 § 6 He + 3  H-18.183 3 He +  - 114.29165 § Two-Body decay – 6 additional hypernuclei

28. Breakup ModeQ value (MeV)  - Decay P  (MeV/c)Width (keV/c) FWHM 12  B- 12 C +  - 115.49165 p + 11  Be-12.280 (B  =10.5) 11 B +  - 109.66165 n + 11  B-12.765 11 C +  - 105.99165 2p + 10  Li-32.908 (B  =12.3) 10 Be +  - 119.78165 d + 10  Be-18.264 10 B +  - 104.31165 2n + 10  B-22.544 10 C +  - 95.84165 3p + 9  He-48.534 (B  =7.8) 9 Li +  - 117.83165 3 He + 9  Li-30.237 9 Be +  - 121.18165 § 3 H + 9  Be-16.072 9 B +  - 96.88165 * 3n + 9  B-41.713 9 C +  - 96.71165 4p + 8  H-68.937 (B  =7.1) 8 He +  - 137.15165 4 Li + 8  He-46.961 8 Li +  - 116.40165 §  + 8  Li -14.444 8 Be +  - 124.12165 § 4 H + 8  Be-37.659 8 B +  - 97.09165 4n + 8  B-56.317 (B  =6.7) 8 C +  - 97.21365 ** p + 4 Li + 7  H-73.473 (B  =6.1) 7 He +  - 135.17~270 *§ 5 Li + 7  He-26.436 7 Li +  - 114.61165 § 5 He + 7  Li-25.782 7 Be +  - 108.02165 § 6 Be + 6  H-48.317 (B  =5.1) 6 He +  - 133.47165 § 6 Li + 6  He-24.186 6 Li +  - 108.39165 § 6 He + 6  Li-27.663 6 Be +  - 100.58~220 **§ 7 Be + 5  H-44.499 (B  =4.1) 5 He +  - 133.42~900 *§ 2  + 4  H -22.693 4 He +  - 132.95165 § 9 Be + 3  H-27.244 3 He +  - 114.29165 § Two-Body decay – 12 additional hypernuclei

29. (a) 2-B decay from 7  He and its continuum (Phase I: 7 Li target) 1/2 + HES P Max HES P Min 0 2 ExEx ExEx 0 2 4H4H 0+0+ 7  He 1/2 + 3/2 + 5/2 + 3H3H 6  He 1- ?1- ? 6H6H 5H5H 90.010 0.0 11 0.0 12 0.0 13 0.0 14 0.0  - Momentum (MeV/c) 3B background (b) 3B background 2 0 ExEx 1 0 ExEx 1 0 ExEx 1 0 ExEx 2-2- 3/2 + 5/2 + 1/2 + 9  Li 8  He J p =? 1-1- 8  Li 7H7H 1/2 + 3/2 + 7  Li 1- ?1- ? 6  Li Additions from 9  Li and its continuum (Phase II: 9 Be target) (c) Additions from 12  B and its continuum (Phase III: 12 C target) 12  B 1-1- 11  Be 11  B 10  Li 10  Be 5/2 + J p =? 10  B J p =? 9  He J p =? 9  Be 1/2 + 9  B J p =? 8H8H 8  Be 8B8B 3B background J p =? Illustration of Decay Pion Spectroscopy A p 1 2 34 5 678 910 1112 1 2 3 4 5 6 3H3H 4H4H 5H5H 6H6H 7H7H 8H8H 6  He 7  He 8  He 9  He 6  Li 7  Li 8  Li 9  Li 10  Li 11  Be 9  Be 10  Be 8  Be 11  B 9B9B 10  B 8B8B 12  B Light Hypernuclei to Be Investigated Previously measured Mirror pairs

30.  High quality and high intensity CW CEBAF beam at JLAB made high precision hypernuclear programs possible  Electroproduced hypernuclei are neutron rich and have complementary features to those produced by mesonic beams. Together with J-PARC’s new programs, as well as those at other facilities around world, the hypernuclear physics will have great achievement in the next couple of decades  The mass spectroscopy program will continue beyond JLAB 12 GeV upgrade  The new decay pion spectroscopy program will start a new frontier