1. 18th Indian-Summer School 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 The design of a High resolution Electron Spectrometer (HES)

2. D.Kawama 18th Indian-Summer School Outline 1.Hypernuclear Spectroscopy via (e,e’K + ) and its history 2.Backgrounds in scattered electron side 3.The setup for E05-115 experiment 4.Design of Splitter Magnet 5.Expected performance of HES 6.Summary & Future

3. D.Kawama 18th Indian-Summer School Hypernuclaer Spectroscopy via (e,e’K + ) e e’ p γ* K+K+ Λ (e,e’K + ) reaction 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 of sub-MeV

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

5. D.Kawama 18th Indian-Summer School The history of hypernulear spectroscopy via (e,e’K + ) @ JLab-HallC 2000 1 st experiment, target : 12 C using existing spectrometer in HallC 2005 2 nd experiment, target : 12 C, 28 Si newly-constructed HKS and Tilted ENGE-Spectrometer ~2008 3 rd experiment, target : 51 V, 89Y Accepted as E05-115 in PAC28 HES HKS and new HES under construction Our (e,e’K + ) experiment and Spectromters Limited energy resolution A lot of backgrounds in e’ side 1.8GeV electron K+K+ e’ HKS ENGE Splitter The picture of E01-011 Setup Main theme of this presentation 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) 2004 E94-107 at JLab-HallA

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

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

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

9. D.Kawama 18th Indian-Summer School Experimental Condition 1 st Exp.2 nd Exp.3 rd Exp.HallA exp Beam Energy (GeV)1.8 2.0-2.54.0 Beam Current (μA)0.663030-10050 e’ Momentum, Acceptance (GeV/c) 0.3 ±30% 0.3 ±30% 0.5-1.0 ±10% 2.0 ±9% e’ Solid Angle (msr)1.62104.5 γ* Energy (GeV)1.5 2.0 K + Momentum, Acceptance (GeV/c) 1.2 ±20% 1.2 ±12.5% 1.2 ±12.5% 1.8 ±9% K + Solid Angle (msr)41684.5

10. D.Kawama 18th Indian-Summer School Expected performance of HES Target Λ yield (1 st Exp.) data Λ yield (2 nd Exp.) data Λ yield /hour (3 rd Exp., 30uA) simulation Λ yield /hour (3 rd Exp.,100uA) simulation Mass resolution (keV FWHM) simulation 12 C0.9890300360 28 Si-440130320 51 V--2060310 condition : E in =2.5GeV, target density=100mg/cm 2 w/ assumption of HKS ⊿ p/p=2.0e-4 and solid angle=8msr considering K + decay, HES 7.9deg tilt MC simulation : Geant4 ~10 time larger Λ yield Λ yield means the count rate/(100nb/sr)

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

12. D.Kawama 18th Indian-Summer School Summary & Future The 3 rd 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)

13. D.Kawama 18th Indian-Summer School JLab E05–115 collaborators in proposal 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 87 people from 19 institutes

14. D.Kawama 18th Indian-Summer School Backup

15. D.Kawama 18th Indian-Summer School Experimental Condition Cross section for 12 C(γ,K + ) Virtual Photon Energy should be ~1.5GeV (Q 2 <10MeV) (γ,K + ) cross section become maximum K + momentum = 1.2GeV Momentum transfer = 0.3-0.4GeV Scattered Electron Energy → 0.55~1.0GeV Incident Beam Energy → 2.05~2.5GeV γ energy vs recoil momentum

16. D.Kawama 18th Indian-Summer School Splitter Design Splitter : Split e’ from K + Field calculation : using TOSCA (3D finite element method) Requirement : Bending angle, Convergence property Kaon side e’ side beam Target Full Gap190mm Magnetic Field1.65T Current density2.65A/mm 2 weight27ton Coil Cross Section 290*254mm TOSCA の絵

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

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

19. D.Kawama 18th Indian-Summer School accept E in =2.5GeV (HES case)E in =1.8GeV (Enge case) y’ vs x’ @ Target accept Backgrounds in e’ arm Main background→bremsstrahlung, Moller scattering vp associated 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)

20. D.Kawama 18th Indian-Summer School 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”

21. D.Kawama 18th Indian-Summer School 51  Ti and 51  V spectra KEK SKS data Simulation

22. D.Kawama 18th Indian-Summer School 50 22 Ti and 51 23 V

23. D.Kawama 18th Indian-Summer School Virtual Photon distribution and acceptance

24. D.Kawama 18th Indian-Summer School 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

25. D.Kawama 18th Indian-Summer School Cross section for 12 C(γ,K + ) Motivation to construct HES 1.Higher statistics The case of E01-011 Enge Spectrometer → Central momentum ~ 0.3GeV The energy of virtual photon should be ~1.5GeV → E in ~ 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 →E in 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