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 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

18th Indian-Summer School

D.Kawama

Hypernuclaer Spectroscopy via (e,e’K+)

ee’

p

γ* 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

(52ΛV, 51

ΛTi, 89ΛSr)

• 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

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D.Kawama

1.2GeV/c K+

0.3 GeV/c e’

HKS-Enge Setup (2nd Exp.)

keep in mind this picture…

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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.

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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

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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

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D.Kawama

Expected performance of HES

Target

Λ 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 90 300 360

28Si - 4 40 130 320

51V - - 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)

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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

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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) 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)

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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. 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. 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

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Backup

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D.Kawama

Experimental Condition

Cross section for 12C(γ,K+)Virtual Photon Energyshould 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

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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

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Some Results from Geant4 Simulation

HES Acceptance HES Angular Acceptance

e’ momentum [GeV/c]

HES Solid Angle [msr]

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D.Kawama

3D view of HES-HKS system

HKS

HES

Splitter

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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)

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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”

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D.Kawama

51Ti and 51

V spectra

KEK SKS dataSimulation

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Virtual Photon distribution and acceptance

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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

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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