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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
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18th Indian-Summer School
for the next generation (e,e’K+) hypernuclear experiment, JLab E05-115
Department of Physics, Tohoku Univ. JapanD. Kawama
for the JLab E05-115 Collaboration
The design of a High resolutionElectron Spectrometer (HES)
18th Indian-Summer School
D.Kawama
Outline
1. Hypernuclear Spectroscopy via (e,e’K+) and its history2. Backgrounds in scattered electron side 3. The setup for E05-115 experiment4. Design of Splitter Magnet5. Expected performance of HES6. Summary & Future
18th Indian-Summer School
D.Kawama
Hypernuclaer Spectroscopy via (e,e’K+)
ee’
pγ* 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
18th Indian-Summer School
D.Kawama
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
ΛV, 51ΛTi, 89
ΛSr) • High resolution ( < 400keV in FWHM )• High statistics (~10/hour/(100nb/sr)) for 51V target
Need New Spectrometer (=HES)
18th Indian-Summer School
D.Kawama
The history of hypernulear spectroscopy via (e,e’K+) @ JLab-HallC
2000 1st experiment, target : 12C• using existing spectrometer in HallC
2005 2nd experiment, target : 12C, 28Si• newly-constructed HKS and Tilted ENGE-Spectrometer
~2008 3rd experiment, target : 51V, 89Y• Accepted as E05-115 in PAC28• HKS and new HES HES under construction
Our (e,e’K+) experiment and Spectromters
• Limited energy resolution• A lot of backgrounds in e’ side
1.8GeV electron
K+
e’
HKS
ENGE
SplitterThe 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
18th Indian-Summer School
D.Kawama
1.2GeV/c K+
0.3 GeV/c e’
HKS-Enge Setup (2nd Exp.)
keep in mind this picture…
18th Indian-Summer School
D.Kawama
HES-HKS Setup (3rd Exp.)
1000
2.0-2.5GeV e- Beam
1.2GeV K+
0.5-1.0GeV e’
HKSHKSHESHES
SplitterSplitter
under construction in Japan
• new Splitter (very big)• new HES• HKS is same as 2nd Exp.
18th Indian-Summer School
D.Kawama
About Tilt MethodSpectrometer(Enge or HES)
Background
Signal
One of the difficult points in (e,e’K+)→ many e- background bremsstrahlung, moller scatteringhow to avoid? → Tilt Enge (2nd Exp.) or HES (3rd Exp.)→ Reduced Background Ratio→ Good Signal/Noise Ratio
S/N was improved!
2nd experimentCH2 target
S/N~4
Tilt Method worked excellently
1st experimentCH2 target
S/N~1
18th Indian-Summer School
D.Kawama
Experimental Condition
1st Exp. 2nd Exp. 3rd Exp. HallA exp
Beam Energy (GeV) 1.8 1.8 2.0-2.5 4.0
Beam Current (μA) 0.66 30 30-100 50
e’ Momentum, Acceptance (GeV/c)
0.3±30%
0.3±30%
0.5-1.0±10%
2.0±9%
e’ Solid Angle (msr) 1.6 2 10 4.5
γ* Energy (GeV) 1.5 1.5 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) 4 16 8 4.5
18th Indian-Summer School
D.Kawama
Expected performance of HES
TargetΛ yield
(1st Exp.)data
Λ yield(2nd Exp.)
data
Λ yield /hour(3rd Exp., 30uA)
simulation
Λ yield /hour(3rd Exp.,100uA)
simulation
Mass resolution
(keV FWHM)simulation
12C 0.9 8 90 300 36028Si - 4 40 130 32051V - - 20 60 310
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
MC simulation : Geant4
~10 time larger Λ yield
Λ yield means the count rate/(100nb/sr)
18th Indian-Summer School
D.Kawama
History of our 12ΛB Spectrum improvement
1st Experiment (E89-009)
2nd Experiment (E01-001)
3rd Experiment (E05-115)292hr
90hr
simulation24hr
Excitation Energy(MeV)
count
18th Indian-Summer School
D.Kawama
Summary & Future
• The 3rd 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) desi
gn is being considered.• HES is now under construction to be shipped to JLab i
n 2007.
reference : Miyoshi et. al. Phys. Rev. Lett. 90, 232502 (2003)
18th Indian-Summer School
D.Kawama
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. MiyagiDept. 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. YuanDept. of Phys. Florida International Univ.A. Acha, W. Boeglin, L. Kramer, P. Markowitz, N. Perez, B. Raue, J. Reinhold, R. RiveraDept. of Phys. Yamagata Univ.S. KatoInstitute of Particle and Nuclear Physics High Energy Accel. Res. Org. (KEK)H. Noumi, Y. Sato, T. TakahashiLaboratory of Phys. Osaka Electro-Comm. Univ.T. MotobaDept. of Phys. Univ. of HoustonEd. V. Hungerford, K.J. Lan, Y. Li, N. Elhayari, S. Randeniya, N. KlantrainsThomas Jefferson National Accel. FacilityP. Bosted, R. Carlini, V. Dharmawardane, R. Ent, H. Fenker, D. Gaskell, M. Jones, D. Mack, J. Roche, G. Smith, W. Vulcan, S. Wood, C. YanYerevan Physics InstituteR. Asaturyan, H. Mkrtchyan, A. Margaryan, S. Stepanyan, V. TadevosyanNuclear Physics InstituteLanzhou Univ. X. Chen, B. Hu, S. Hu, Y. Song, W. Luo, B. WangDept. of Physics / Applied Phys. Univ. of ZagrebD. Androic, M. Furic, T. Petkovic, M. Planinic, T. SevaDept. of Phys. North Carolina A&T State Univ.A. Ahmidouch, S. Danagoulian, A. GasparianDept. of Phys. Louisiana Tech Univ. N. Simicevic, S. Wells
Dept. of Phys. James Madison Univ.G. Niculescu, M.-I. NiculescuDept. of Phys. Univ. of North Carolina at WilmingtonL. GanDept. of Phys. Duke Univ.M.W. AhmedDept. of Phys. Univ. of MarylandF. Benmokhtar, T. HornDept. of Phys. Southern Univ. at New OrleansM. ElaasarPhys. and Astro. Dept. California State Univ. Ed F. Gibson
87 people from 19 institutes
18th Indian-Summer School
D.Kawama
Backup
18th Indian-Summer School
D.Kawama
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 = 1.2GeVMomentum transfer = 0.3-0.4GeV
Scattered Electron Energy → 0.55~1.0GeV
Incident Beam Energy → 2.05~2.5GeV
γ energy vs recoil momentum
18th Indian-Summer School
D.Kawama
Splitter Design
Splitter : Split e’ from K+
Field calculation : using TOSCA (3D finite element method)Requirement : Bending angle, Convergence property
Kaon sidee’ side
beamTarget
Full Gap 190mm
Magnetic Field 1.65T
Current density 2.65A/mm2
weight 27ton
Coil Cross Section 290*254mm
TOSCAの絵
18th Indian-Summer School
D.Kawama
Some Results from Geant4 Simulation
HES Acceptance HES Angular Acceptance
e’ momentum [GeV/c]
HES Solid Angle [msr]
18th Indian-Summer School
D.Kawama
3D view of HES-HKS system
HKS
HES
Splitter
18th Indian-Summer School
D.Kawama
accept
Ein=2.5GeV (HES case)Ein=1.8GeV (Enge case)
y’ vs x’ @ Target
accept
Backgrounds in e’ arm
Main background→bremsstrahlung, Moller scattering
vp associatedbremsstrahlungMoller 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)
18th Indian-Summer School
D.Kawama
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
D.Kawama
51Ti and 51
V spectra
KEK SKS dataSimulation
18th Indian-Summer School
D.Kawama
Virtual Photon distribution and acceptance
18th Indian-Summer School
D.Kawama
The design of DetectorsDetectors 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
D.Kawama
Cross section for 12C(γ,K+)
Motivation to construct HES
1. Higher statisticsThe 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