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for the next generation (e,e’K + ) hypernuclear experiment, JLab E05-115

The design of a H igh resolution E lectron S pectrometer ( HES ). for the next generation (e,e’K + ) hypernuclear experiment, JLab E05-115. Department of Physics, Tohoku Univ. Japan D. Kawama for the JLab E05-115 Collaboration. Outline.

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for the next generation (e,e’K + ) hypernuclear experiment, JLab E05-115

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  1. The design of a High resolutionElectron Spectrometer (HES) for the next generation (e,e’K+) hypernuclear experiment, JLab E05-115 Department of Physics, Tohoku Univ. Japan D. Kawama for the JLab E05-115 Collaboration 18th Indian-Summer School

  2. Outline • Hypernuclear Spectroscopy via (e,e’K+) and its history • Backgrounds in scattered electron side • The setup for E05-115 experiment • Design of Splitter Magnet • Expected performance of HES • Summary & Future 18th Indian-Summer School

  3. Hypernuclaer Spectroscopy via (e,e’K+) (e,e’K+) reaction e’ e γ* K+ p Λ • Merit of (e,e’K+) reaction • Excitation of deeply-bound state • Easy to create neutron-rich or mirror hypernuclei • (compared to (π+,K+) or (K-,π-) reaction) • Spin-flip and non-flip events are equally generated at very forward angle • Good energy resolution because of using electron primary beam Using electron beam of CEBAF (Jefferson Lab), energy resolution should be ofsub-MeV 18th Indian-Summer School

  4. Purpose of E05-115 experiment • Core excited states • LS splitting Provide the important Λ hypernuclear information Spectroscopic study of Λ hypernuclei via (e,e’K+) Experimental requirement • Spectroscopy of Medium-heavy hypernucleai (52ΛV, 51ΛTi, 89ΛSr) • High resolution ( < 400keV in FWHM ) • High statistics (~10/hour/(100nb/sr)) for 51V target Need New Spectrometer (=HES) 18th Indian-Summer School

  5. The history of hypernulear spectroscopy via (e,e’K+) @ JLab-HallC HKS K+ ENGE e’ Splitter 1.8GeV electron Our (e,e’K+) experiment and Spectromters • 2000 1st experiment, target : 12C • using existing spectrometer in HallC • 2005 2nd experiment, target : 12C, 28Si • newly-constructed HKSand • Tilted ENGE-Spectrometer • ~2008 3rd experiment, target : 51V, 89Y • Accepted as E05-115 in PAC28 • HKS and newHES under construction • Limited energy resolution • A lot of backgrounds in e’ side 2004 E94-107 at JLab-HallA • HKS (High resolution Kaon Spectrometer) : • 1.05<p<1.35[GeV], ⊿p/p~2・10-4 • To avoid e- backgrounds, we tilted ENGE (Tilt method) Main theme of this presentation The picture of E01-011 Setup 18th Indian-Summer School

  6. HKS-Enge Setup (2nd Exp.) 1.2GeV/c K+ 0.3 GeV/c e’ keep in mind this picture… 18th Indian-Summer School

  7. HES-HKS Setup (3rd Exp.) under construction in Japan 1.2GeV K+ 0.5-1.0GeV e’ HKS HES Splitter 2.0-2.5GeV e- Beam • new Splitter • (very big) • new HES • HKS is same as 2nd Exp. 18th Indian-Summer School

  8. About Tilt Method Signal Background Spectrometer(Enge or HES) One of the difficult points in (e,e’K+) → many e- background bremsstrahlung, moller scattering how to avoid? → Tilt Enge (2nd Exp.) or HES (3rd Exp.) → Reduced Background Ratio → Good Signal/Noise Ratio 1st experiment CH2 target 2nd experiment CH2 target Preliminaly S/N~1 S/N~4 S/N was improved! Tilt Method worked excellently 18th Indian-Summer School

  9. Experimental Condition 18th Indian-Summer School

  10. Expected performance of HES MC simulation : Geant4 condition : Ein=2.5GeV, target density=100mg/cm2 w/ assumption of HKS ⊿p/p=2.0e-4 and solid angle=8msr considering K+ decay, HES 7.9deg tilt Λ yield means the count rate/(100nb/sr) ~10 time larger Λ yield 18th Indian-Summer School

  11. History of our 12ΛB Spectrum improvement 1st Experiment (E89-009) 3rd Experiment (E05-115) 292hr count simulation 24hr 2nd Experiment (E01-001) 90hr Preliminaly Excitation Energy(MeV) 18th Indian-Summer School

  12. Summary & Future • The3rd generation (e,e’K+) hypernuclear spectroscopy with HES is planned. • 10 times larger yield with HES is expected than ENGE. • New detector (larger Drift Chamber, Hodoscopes) design is being considered. • HES is now under construction to be shipped to JLab in 2007. reference : Miyoshi et. al. Phys. Rev. Lett. 90, 232502 (2003) 18th Indian-Summer School

  13. JLab E05–115 collaborators in proposal 87 people from 19 institutes Dept. of Phys. Tohoku Univ. D.Kawama, Y. Fujii, O. Hashimoto, H. Kanda, M. Kaneta, K. Maeda, N. Maruyama, A. Matsumura, S.N. Nakamura, K. Nonaka, Y. Okayasu, M. Sumihama, H. Tamura, K. Tsukada, Y. Miyagi Dept. of Phys. Hampton Univ. O.K. Baker, L. Cole, M. Christy, P. Gueye, C. Jayalath, C. Keppel, S. Malace, E.K. Segbefia, L. Tang, V. Tvaskis, L. Yuan Dept. of Phys. Florida International Univ. A. Acha, W. Boeglin, L. Kramer, P. Markowitz, N. Perez, B. Raue, J. Reinhold, R. Rivera Dept. of Phys. Yamagata Univ. S. Kato Institute of Particle and Nuclear Physics High Energy Accel. Res. Org. (KEK) H. Noumi, Y. Sato, T. Takahashi Laboratory of Phys. Osaka Electro-Comm. Univ. T. Motoba Dept. of Phys. Univ. of Houston Ed. V. Hungerford, K.J. Lan, Y. Li, N. Elhayari, S. Randeniya, N. Klantrains Thomas Jefferson National Accel. Facility P. Bosted, R. Carlini, V. Dharmawardane, R. Ent, H. Fenker, D. Gaskell, M. Jones, D. Mack, J. Roche, G. Smith, W. Vulcan, S. Wood, C. Yan Yerevan Physics Institute R. Asaturyan, H. Mkrtchyan, A. Margaryan, S. Stepanyan, V. Tadevosyan Nuclear Physics InstituteLanzhou Univ. X. Chen, B. Hu, S. Hu, Y. Song, W. Luo, B. Wang Dept. of Physics / Applied Phys. Univ. of Zagreb D. Androic, M. Furic, T. Petkovic, M. Planinic, T. Seva Dept. of Phys. North Carolina A&T State Univ. A. Ahmidouch, S. Danagoulian, A. Gasparian Dept. of Phys. Louisiana Tech Univ. N. Simicevic, S. Wells Dept. of Phys. James Madison Univ. G. Niculescu, M.-I. Niculescu Dept. of Phys. Univ. of North Carolina at Wilmington L. Gan Dept. of Phys. Duke Univ. M.W. Ahmed Dept. of Phys. Univ. of Maryland F. Benmokhtar, T. Horn Dept. of Phys. Southern Univ. at New Orleans M. Elaasar Phys. and Astro. Dept. California State Univ. Ed F. Gibson 18th Indian-Summer School

  14. Backup 18th Indian-Summer School

  15. Experimental Condition Cross section for 12C(γ,K+) Virtual Photon Energy should be ~1.5GeV (Q2<10MeV) (γ,K+) cross section become maximum K+ momentum = 1.2GeV Momentum transfer = 0.3-0.4GeV Scattered Electron Energy → 0.55~1.0GeV γ energy vs recoil momentum Incident Beam Energy →2.05~2.5GeV 18th Indian-Summer School

  16. Splitter Design Kaon side e’ side Target beam Splitter :Split e’ from K+ Field calculation : using TOSCA (3D finite element method) Requirement : Bending angle, Convergence property TOSCAの絵 18th Indian-Summer School

  17. Some Results from Geant4 Simulation HES Acceptance HES Angular Acceptance HES Solid Angle [msr] e’ momentum [GeV/c] 18th Indian-Summer School

  18. 3D view of HES-HKS system HES HKS Splitter 18th Indian-Summer School

  19. Backgrounds in e’ arm Ein=1.8GeV (Enge case) Ein=2.5GeV (HES case) accept accept y’ vs x’ @ Target Main background→bremsstrahlung, Moller scattering how to avoid ? → Apply ‘Tilt Method’ !! The acceptance of Moller scattering is limited by momentum (Moller Ring) → Avoiding Moller by tilting HES (or Enge), large portion of B.G. can be avoided (but still there is brems. B.G., we can never avoid all of them) vp associated bremsstrahlung Moller scattering 18th Indian-Summer School

  20. How to Analyze? (e,e’K+) experiment → very high rate around the target (~GHz) Detectors can never work → how to get the angle ? Answer : Use the “Transfer Matrix” 18th Indian-Summer School

  21. 51LTi and 51LV spectra KEK SKS data Simulation 18th Indian-Summer School

  22. Virtual Photon distribution and acceptance 18th Indian-Summer School

  23. The design of Detectors Detectors we need : New Drift Chamber, New Hodoscope @ FP • New DC • Size : 30cm×150cm (slightly larger than Enge-DC) • Requested position resolution : ~300um • Plane type or Honeycomb type or Straw type ? • more detail is now under consideration • New Hodoscope • 2 plane will be needed, which is same as Enge Hodoscope • More detail such as the number of counters is now • under consideration 18th Indian-Summer School

  24. Motivation to construct HES Cross section for 12C(γ,K+) • Higher statistics • The case of E01-011 • Enge Spectrometer → Central momentum ~ 0.3GeV • The energy of virtual photon should be ~1.5GeV • → Ein ~ 1.8GeV but… The higher energy beam can concentrate B.G on front → Bigger acceptance is available (refer the last page) The case of E05-115, Central momentum of HES is 0.5-1.0GeV →Ein is 2.0-2.5GeV, single arm yield is 10 times larger than Enge • 2. Optical property • Tilted Enge → As Enge was not assumed to be tilted, its optical property is • not easy to understand • HES → Simple structure and optimized to tilt method, optical property is • easy to understand 18th Indian-Summer School

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