1. Spectroscopic Investigation of  hypernuclei in the wide mass region using the (e,e’K + ) reaction (Extension request of the currently running E01-011 experiment) Osamu Hashimoto Department of Physics, Tohoku University representing the HKS collaboration JLab PAC28 August 24, 2005 P05-115

2. Hyper Collaboration O. Hashimoto (Spokesperson), S.N. Nakamura (Spokesperson), Y. Fujii, M. Kaneta, M. Sumihama, H. Tamura,K. Maeda, H. Kanda, Y. Okayasu, K. Tsukada, A. Matsumura, K.~Nonaka, D. Kawama, N. Maruyama, Y. Miyagi (Tohoku U) S. Kato (Yamagata U) T. Takahashi, Y. Sato, H. Noumi (KEK) T. Motoba (Osaka EC) L. Tang (Spokesperson), O.K. Baker, M. Christy, L. Cole, P. Gueye, C. Keppel, L. Yuan (Hampton U) J. Reinhold (Spokesperson), P. Markowitz, B. Beckford, S. Gullon, C. Vega (FlU) Ed.V. Hungerford, K. Lan, N. Elhayari, N. Klantrains, Y. Li,S. Radeniya (Houston) R. Carlini, R. Ent, H. Fenker, D. Mack, G. Smith, W. Vulcan, S.A. Wood, C. Yan (JLab) N. Simicevic, S. Wells (Louisiana Tech) L. Gan (North Carolina, Wilmington) A. Ahmidouch, S. Danagoulian, A. Gasparian (North Carolina A&T) D. Dehnhard (Minnesota) M. Elaasar(New Orleans) R. Asaturyan, H. Mkrtchyan, A. Margaryan, S. Stepanyan, V. Tadevosyan (Yerevan) D. Androic, T. Petkovic, M. Planinic, M. Furic (Zagreb) T. Angelescu (Bucharest) V.P. Likhachev (Sao Paulo) M. Ahmed (Duke)

3. Outline of the talk 1.Significance of hypernuclear spectroscopy and goals of the proposed experiment 2.(e,e’K + ) spectroscopy and the current status of E01-011 experiment 3. Setup & conditions of the proposed experiment 4. Summary with prospect

4. Significance of hypernuclear spectroscopy and the goals of the proposed experiment

5. 3D Nuclear Chart with the strangeness degree of freedom

6. Single-particle nature of  hypernuclei New degree of freedom  free from Pauli blocking Deeply bound nuclear states Baryon structure in nuclear medium Unique structure of hadronic many-body system Nucleus with a new quantum number Core excited states Glue role of a  hyperon  N interaction Unified view of baryon-baryon interaction in SU(3) Central and spin-dependent  N interaction Singly charged atom Core Nucleus +  Core excitation, A  hyperon in the mean field

7. Nucleon single particle orbits e e’ p

8. Single-particle nature of  hypernuclei New degree of freedom  free from Pauli blocking Deeply bound nuclear states Baryon structure in nuclear medium Unique structure of hadronic many-body system Nucleus with a new quantum number Core excited states Glue role of a  hyperon  N interaction Unified view of baryon-baryon interaction in SU(3) Central and spin-dependent  N interaction Singly charged atom Core Nucleus +  Core excitation, A  hyperon in the mean field

9. YN, YY Interactions and Hypernuclear Structure Free YN, YY interaction Constructed from limited hyperon scattering data (Meson exchange model: Nijmegen, Julich) YN, YY effective interaction in finite nuclei (YN G potential) Hypernuclear properties, spectroscopic information from structure calculation (shell model, cluster model…) Energy levels, Energy splitting, cross sections Polarizations, weak decay widths high quality (high resolution & high statistics) spectroscopy plays a significant role G-matrix calculation

10. Hypernuclear Hamiltonian v  N weak compared to v  H N (Core) : Core nucleus ( Usually hole states) t  :   kinetic energy V  N : effective  N interaction ( Nijmegen, Julich... ) H = H N (Core) + t  +  V  N effective Weaker compared with NN Direct comparison of spectroscopic data with structure calculation Biding energy, energy splitting, cross section, ….

11. Population of excited  hypernuclear states and  hypernuclear spectroscopy neutron or proton  n p  BB BpBp BnBn 208  Pb 207  Tl 207  Pb Weak decay nonmesonic mesonic  Narrow widths < a few 100 keV  -particle nucleon-hole states ~25 MeV Reaction spectroscopy Gamma-ray spectroscopy

12. B  =0  Hypernuclear production (  +,K ＋ ) Stopped (K -,  ) (e,e’K+) ( ,K ＋ ) (p,K ＋ ) Inflight(K -,  ) Hypernuclear Cross section Momentum transfer (MeV/c) mb/sr nb/sr  b/sr 05001000 JLab KEK, BNL BNL, CERN (K -,  - ) (  +,K + )

13. Light hypernuclei (A<~20) Fine structure Baryon-baryon interaction in SU(3)  coupling in large isospin hypernuclei Cluster structure Heavy hypernuclei (A>~50) Single-particle potential Distinguishability of a  hyperon U 0 (r), m  *(r), V  NN,... Neutron star (A ~ 10 57 ) Hyperonization  Softening of EOS ? Superfluidity Hypernuclei in the wide mass range -- toward strange matter -- Short range nature of the  N interaction : no pion exchange meson picture or quark picture ?

14. 12 C(  +,K + ) 12  C spectra by the SKS spectrometer at KEK 12 GeV PS KEK336 2 MeV(FWHM) KEK E369 1.45 MeV(FWHM) Hypernuclear spectroscopy established BNL 3 MeV(FWHM) SKS

15.  Single particle states ->  -nuclear potential  hyperon in heavier nuclei Single-particle orbits in nucleus Hotchi et al., PRC 64 (2001) 044302Hasegawa et. al., PRC 53 (1996)1210KEK E140a Skyrme HF (Yamamoto) DDRH (Lanske) Quark-meson coupling (Saito, Thomas) ……… YLaPb Si

16. Goals of the proposed experiment 51 V(e,e’K + ) 51  Ti reaction –Next heavier  hypernuclei from 28  Al –  binding energies for s,p,d orbits determined –  hypernuclear structure investigated – ls splitting in l=2,3 orbits to b derived If sizable 89 Y(e,e’K + ) 89  Sr reaction – Exploratory run to examine feasibility of (e,e’K+) spectroscopy in heavier hypernuclei 6,7 Li(e,e’K + ) 6,7  He and 10,11 B(e,e’K + ) 10,11  Be – Precision hypernuclear structure in neutron-rich  hypernuclei – LS coupling effect changing isospins with neutron number

17. (e,e’K+) spectroscopy and E01-011 status

18. The (e,e’K + ) reaction for hypernuclear spectroscopy Proton to    Neutron rich  hypernuclei Large angular momentum transfer Spin-flip amplitude   Hyperon production reactions for spectroscopy  Z = 0  Z = -1 comment neutron to  proton to  (  +,K + ) (  -,K 0 ) stretched, high-spin large momentum transfer In-flight (K -,  - ) in-flight (K -,  0 ) substitutional stopped (K -,  - ) stopped (K -,  0 ) large momentum transfer (e,e'K 0 ) (e,e'K + ) spin-flip (  K 0 ) ( ,K + ) & large momentum transfer Higher energy resolution & First (e,e ’ K + ) spectroscopy  E89-009 (SOS + ENGE) A few 100 keV achievable Only at JLab

19. What limited the E89-009 experiment ? Energy resolution –The kaon arm limited hypernuclear mass resolution Hypernuclear yield rates –High accidental background rate due to Brems electrons –Solid angle of the kaon arm (SOS) limited detection efficiency (1) A high-resolution large-solid-angle kaon spectrometer (HKS) (2) New experimental configuration “Tilt method”

20. Tilt method and optimization of the tilt angle Side view Singles rate of the e-arm 200 MHz  < a few MHz even with 5  Target thickness and 50  Beam intensity

21. Maximum momentum 1.2 GeV/c Dispersion 4.7 cm/% Momentum resolution 2 x 10 -4 (FWHM) Solid angle 30 msr w/o splitter 16 msr w splitter Momentum acceptance 12.5 % The HKS spectrometer system for E01-011 Tilt method for the electron arm High resolution Kaon Spectrometer (HKS)

22. E01-011 setup in Hall C ENGE HKS Tilted ENGE

23. Expected singles rates Target HKSENGE e + (kHz)  + (kHz) K + (kHz) p (kHz) e - (kHz)  - (kHz) 12 C -4200.381501,0002.8 28 Si -4200.321301,9602.8 51 V -4100.291202,6503.0 E89-009 12 C 1001.4<1 Hz0.14200,000- SOSENGE I e = 30  A, 100 mg/cm 2 High rejection efficiencies against pions and protons are required Measured values at E89-009 I e = 0.66  A, 22 mg/cm 2 Greater hadron rates

24. Yield comparison of E01-011 and E89-009 ItemE01-011E89-009 Gain factor Virtual photon flux per electron(x10 -4 ) 0.240.05 Target thickness(mg/cm 2 )100224.5 Scattered electron momentum acceptance(MeV/c) 1901201.6 Kaon survival rate0.350.40.88 Solid angle of K arm (msr)1653.2 Beam current (  A) 300.6645 Estimated yield ( 12  B gr :counts/h) 41 (expected) 0.9 (measured) 46

25. Beam currents, singles rates & trigger rates E01-011 Target Beam current (  A) COIN Trigger rate (Hz) HKS singles rate (kHz) ENGE singles rate (kHz) CH 2 (5 mm) 1.5883.4590 12 C (100 mg/cm 2 ) 242909.5980 28 Si (65 mg/cm 2 ) 123777.01040 Tilt method proved to work !!

26.  p K Kaon PID E01-011 coincidence time (ns)  tof –  track HKS singles eventsHKS-ENGE coincidence events

27. p(e,e’K + )  0 reactions 12 C(e,e’K + ) quasi-free Accidental E89-009 experimentE01-011 experiment Improved! 210 Lambda’s 1390 Lambdas

28. -15051015-5-10 (2+,3+)(1-,2-) (1-,0-) (2-,1-) 40 50 60 70 80 90 12  B spectrum ( 12 C target ) 12  B g.s ~ 600 counts (~20 /hr) <1 MeV (FWHM)  400 keV vs. E89-009 Hall C ~ 165 counts with ~750 keV (~0.9 /hr) E94-107 Hall A ~ 600 counts with ~800 keV (~3 /hr) Preliminary Hypernuclear excitation (300 keV/bin) d  /d  nb/sr/0.3 MeV -B  (MeV) 1 month E01-011 E89-009 < 1MeV (FWHM)

29. Proposed experimental setup & conditions Basically similar to those of E01-011 except for the new High-resolution electron spectrometer and some improvement based on the E01-011 experience

30. HKS-HES hypernuclear spectrometer system New Splitter

31. High resolution electron spectrometer (HES) --- widen acceptable beam energy window --- compatible with 6, 12 GeV operation P K (GeV/c) E  * (GeV/c) Ee (GeV/c) Ee’ (GeV/c E89-009 & E01-011 1.21.51.80.3 E94-1071.92.24.01.8 HES Option 1.21.5 2.1 - 2.5 0.6 – 1.0 HKSE  dependence 6 GeV 12 GeV Beam energy and spectrometer conditions ( ENGE is used as an electron spectrometer when the beam energy is 1.8 GeV )

32. E top 1 pass (GeV) E top 2pass (GeV) Acceptable energy windows of HKS system with ENGE or HES 10.4 0.3 0.60.8 E e’ (GeV) 2.51.81.9 E e at Hall (GeV) Acceptable Central Energy (GeV) HES ENGE 2.02.22.4 4.44.555.06.0 9.4510.310.812.0 2.1

33. Basic specification of HES Configuration DQQD horizontal 50 degree bend Central momentum 0.6 – 1.0 GeV/c Momentum acceptance > 200 MeV/c Momentum resolution 2 x 10 -4 Electron detection angle horizontal : 0 degrees vertical : < 10 degrees Solid angle > 10 msr Maximum D magnetic field 1.6 T

34. Splitter, HKS, HES geometry HKS HES New Splitter 0.6 GeV/c 1.0 GeV/c Splitter TOSCA calculation

35. HES mechanical design For 600 MeV/c For 1000 MeV/c

36. Expected Energy Resolution Item Contribution to the resolution (keV, FWHM) Target 7 Li 12 C 51 V 89 Y HKS momentum 190 ( 500 for SOS) Beam momentum< 180 Enge or HES momentum 93 K + angle2301523620 Target thickness< 170< 180< 148< 138 Overall< 400< 360< 320< 310 <~400 keV(FWHM) expected

37. Expected hypernuclear production rates in the (e,e’K + ) reaction Target Beam Intensity (  A) Counts per 100nb/sr /hour Q-free K+ in HKS(Hz) 12 C3048340 28 Si3021288 51 V3011228 Target Hypernucle us  orbital Cross section (nb/sr) 12 C 12  B s1/2112 p3/279 p1/245 28 Si 28  Al s1/256 p3/295 p1/257 d5/2131 d3/2111 51 V 51  Ti s1/218 p3/241 p1/226 d5/252 d3/248 1s1/216 f7/232 f5/238 Calculated hypernuclear cross sections (Target thickness 100 mg/cm 2 ) Hypernuclear production rates Motoba, Sotona

38. 51  Ti and 51  V spectra KEK SKS data Simulation

39. 50 22 Ti and 51 23 V

40. Evolution of (e,e’K + ) spectroscopy E89-009E94-107E01-011P05-115* Configuration SOS+ENGE +Splitter HRS+HRS +Septum HKS+ENGE +Splitter HKS+HES +New splitter Beam intensity (  A) on 12 C 0.661002430 thickness (mg/cm 2 )22100 Hypernuclear yield (12  B gr : /hr) 0.92-320 ~ (40)(> 40) Resolution (keV)750-900~ 800(3-400) Beam energy (GeV)1.7-1.841.82.0 - 2.4* pK (central : GeV)1.21.91.2 Pe (central: GeV )0.32.20.30.6 – 1.0  K (degree) 0-761-13  e (degree) 064.5< 4.5 ( ) expected * ENGE spectrometer to be used for a 1.8 GeV beam 20002004-20052005200?

41. Roadmap of (e,e’K + ) hypernuclear spectroscopy Light  hypernuclear spectroscopy –  N interaction,  coupling p shell hypernuclei 6,7 Li, 9 Be, 10,11 B, 12 C, 13 C, 16 O targets s shell hypernuclei 3,4 He targets Medium to heavy hypernuclear spectroscopy –A  binding in the mean field, quark picture vs. conventional picture 28 Si, 51 V, (Cr)  89 Y  208 Pb ? targets Coincidence experiment – weak decay --- fission – proton, neutron and pion emission HKS as a “strangeness tagger” HES as a “virtual photon tagger” Complimentary to spectroscopy with hadronic beams at J-PARC

42. Requested beam time TargetHypernucleus# of days# of hours Spectrometer commissioning & calibration 4(8)96(192) Data taking 6,7 Li, 10,11 B 6,7  He, 10,11  Be 5120 51 V 51  Ti 14336 89 Y 89  Sr 5120 Subtotal for data taking 24576 Grand total 28(32)672(768)

43. Summary Precision hypernuclear spectroscopy by the (e,e’K+) reaction plays an essential role in the investigation of hadronic may-body systems that contain “strangeness”. Physics goal of the proposed experiment is two-fold; spectroscopy of heavier  hypernuclei ( 51 V target) and light  hypernuclei( 6,7 Li or 10,11 B targets). A high resolution electron spectrometer (HES) is under construction at TOHOKU as a part of the HKS-HES hypernuclear spectrometer system. It will be shipped to JLab at the end of 2006. The HKS-HES spectrometer system allows us to conduct the proposed 3 rd generation (e,e’K+) hypernuclear spectroscopy even with 6 GeV and 12 GeV operation.