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Osamu Hashimoto Department of Physics, Tohoku University representing the HKS collaboration

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

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Osamu Hashimoto Department of Physics, Tohoku University representing the HKS collaboration

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

  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 • Significance of hypernuclear spectroscopy and goals of the proposed experiment • (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 spectroscopyandthe goals of the proposed experiment

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

  6. Single-particle nature of L hypernuclei Core Nucleus + L Singly charged atom A L hyperon in the mean field • 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 L hyperon • LN interaction • Unified view of baryon-baryon interaction in SU(3) • Central and spin-dependent LN interaction Core excitation,

  7. e’ e p Nucleon single particle orbits

  8. Single-particle nature of L hypernuclei Core Nucleus + L Singly charged atom A L hyperon in the mean field • 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 L hyperon • LN interaction • Unified view of baryon-baryon interaction in SU(3) • Central and spin-dependent LN interaction Core excitation,

  9. YN, YY Interactions and Hypernuclear Structure Free YN, YY interaction Constructed from limited hyperon scattering data (Meson exchange model: Nijmegen, Julich) G-matrix calculation 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

  10. Population of excited L hypernuclear statesand L hypernuclear spectroscopy L-particle nucleon-hole states neutron or proton L ~25 MeV BL p Narrow widths < a few 100 keV p Reaction spectroscopy Bp n Bn 207LTl g 207LPb 208LPb Gamma-ray spectroscopy Weak decay nonmesonic mesonic

  11. BL=0 L Hypernuclear production (K-,p-) Inflight(K-,p) BNL, CERN mb/sr (p+,K+) Stopped (K-,p) KEK, BNL Hypernuclear Cross section mb/sr (p+,K＋) JLab (e,e’K+) (g,K＋) (p+,K+) nb/sr (p,K＋) 0 500 1000 Momentum transfer (MeV/c)

  12. Hypernuclei in the wide mass range -- toward strange matter -- • Short range nature of the LN interaction : no pion exchange • meson picture or quark picture ? • Light hypernuclei (A<~20) • Fine structure • Baryon-baryon interaction in SU(3) • LScoupling in large isospin hypernuclei • Cluster structure • Heavy hypernuclei (A>~50) • Single-particle potential • Distinguishability of a L hyperon • U0(r), mL*(r), VLNN, ... • Neutron star (A ~ 1057 ) • Hyperonization  Softening of EOS ? • Superfluidity

  13. 12C(p+,K+) 12LC spectraby the SKS spectrometer at KEK 12 GeV PS BNL 3 MeV(FWHM) SKS SKS KEK E369 1.45 MeV(FWHM) Hypernuclear spectroscopy established KEK336 2 MeV(FWHM)

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

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

  16. (e,e’K+) spectroscopy andE01-011 status

  17. L Hyperon production reactions for spectroscopy DZ = 0 DZ = -1 comment neutron to L proton to L (p+,K+) ( p-,K0) stretched, high-spin large momentum transfer In-flight (K-,p-) in-flight (K-,p0) substitutional stopped (K-,p-) stopped (K-,p0) large momentum transfer (e,e'K0) (e,e'K+) spin-flip (g,K0) (g,K+) & large momentum transfer The (e,e’K+) reaction for hypernuclear spectroscopy • Proton to L  Neutron rich L hypernuclei • Large angular momentum transfer • Spin-flip amplitude & Higher energy resolution A few 100 keV achievable First (e,e’K+) spectroscopy  E89-009 (SOS + ENGE) Only at JLab

  18. 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”

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

  20. The HKS spectrometer system for E01-011 High resolution Kaon Spectrometer (HKS) 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 % Tilt method for the electron arm

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

  22. Expected singles rates Ie = 30 mA, 100 mg/cm2 Measured values at E89-009 Ie = 0.66 mA, 22 mg/cm2 Greater hadron rates High rejection efficiencies against pions and protons are required

  23. Yield comparison of E01-011 and E89-009

  24. Beam currents, singles rates & trigger rates E01-011 Tilt method proved to work !!

  25. coincidence time (ns) p K p Kaon PID E01-011 HKS singles events HKS-ENGE coincidence events btof – btrack

  26. p(e,e’K+)L/S0 reactions E89-009 experiment E01-011 experiment Improved! 12C(e,e’K+) quasi-free Accidental 210 Lambda’s 1390 Lambdas

  27. (1-,2-) (2+,3+) 90 80 (1-,0-) 70 (2-,1-) 60 50 40 -15 -10 -5 0 5 10 15 12LB spectrum ( 12C target ) E01-011 E89-009 < 1MeV (FWHM) 1 month ds/dW nb/sr/0.3 MeV Preliminary Hypernuclear excitation (300 keV/bin) -BL(MeV) 12LBg.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)

  28. 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

  29. HKS-HES hypernuclear spectrometer system New Splitter

  30. Acceptable energy windows of HKS systemwith ENGE or HES ENGE HES Acceptable Central Energy (GeV) 0.3 0.4 0.6 0.8 1 Ee’ (GeV) 1.8 1.9 2.0 2.2 2.4 2.5 2.1 Ee at Hall (GeV) Etop2pass (GeV) 4.4 4.55 5.0 6.0 Etop1pass (GeV) 9.45 10.3 10.8 12.0

  31. 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

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

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

  34. Expected Energy Resolution <~400 keV(FWHM) expected

  35. Expected hypernuclear production ratesin the (e,e’K+) reaction Calculated hypernuclear cross sections Hypernuclear production rates (Target thickness 100 mg/cm2) Motoba, Sotona

  36. 51LTi and 51LV spectra KEK SKS data Simulation

  37. Evolution of (e,e’K+) spectroscopy 2000 2004-2005 2005 200? ( ) expected * ENGE spectrometer to be used for a 1.8 GeV beam

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

  39. Requested beam time

  40. 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 L hypernuclei (51V target) and light L hypernuclei(6,7Li or10,11B 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 3rd generation (e,e’K+) hypernuclear spectroscopy even with 6 GeV and 12 GeV operation.

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