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JLab における (e,e'K + ) 反応を用いた 精密ラムダハイパー核分光実験

JLab における (e,e'K + ) 反応を用いた 精密ラムダハイパー核分光実験. 東北大学理学研究科 後 神　利志 Toshiyuki Gogami. June2009 @ JLab Hall-C. Contents. Introduction ( e,e’K + ) JLab , CEBAF JLab E05-115 experiment Motivation Setup Analysis Summary. Spectroscopic experiment via (e,e’K + ) reaction.

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JLab における (e,e'K + ) 反応を用いた 精密ラムダハイパー核分光実験

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  1. JLabにおける(e,e'K+)反応を用いた精密ラムダハイパー核分光実験JLabにおける(e,e'K+)反応を用いた精密ラムダハイパー核分光実験 東北大学理学研究科 後神　利志 Toshiyuki Gogami June2009 @ JLab Hall-C Strangeness 2010 at KEK

  2. Contents • Introduction • (e,e’K+) • JLab, CEBAF • JLab E05-115 experiment • Motivation • Setup • Analysis • Summary Strangeness 2010 at KEK

  3. Spectroscopic experiment via (e,e’K+) reaction e + p➝ e’ + K+ + Λ Feynman diagram e- e e u u γ* K+ – γ* u s p d s p K+ u Λ Λ d n target nucleus measure Missing mass : M2HY = (Ee + MT - EK+ - Ee’)2 - ( pe - pK+- pe’)2 • Binding energy • Cross section

  4. (e,e’K+) reaction (e,e’K+) (π+ , K+) (K- , π-) e + p➝ e + K+ + Λ π+ + n➝ K+ + Λ K- + n➝ π- + Λ e e – – u u u u Reaction K+ π+ – – K- π- s s d u d u γ* K+ – u s p d s d s d s n d d n d d u Λ Λ Λ u u u u d Momentum transfer (Typical ) ~300 [MeV/c] ~300 [MeV/c] ~90 [MeV/c] Λ can be bounded in deeper orbit Λ’s Spin At forward angle flip ≈ non-flip non-flip non-flip Spin dependent structure proton neutron neutron Λ’s from Mirror lambda hypernuclei primary secondary secondary Beam High quality , high intensity Target Thin (~100 mg/cm2) (Isotopically enriched) Thick(> a few [g/cm2] ) Thick(> a few [g/cm2] ) Energy resolution (FWHM) ≤ 500 [keV] 1 – 3 [MeV] 1 – 3 [MeV] Fine structure

  5. JLab CEBAF ( Continuance Electron Beam Accelerator Facility ) • Requirement for accelerator • high duty factor • high intensity • smallemittance • small ΔE/E • (e,e’K+) experiment • Coincidence experiment (K+ and e-) • Small cross section ( ~100 [nb/sr] ) 1/1000 • Energy resolution sub MeV (FWHM) CEBAF can satisfy these requirements Thomas Jefferson National Accelerator Facility 22nd Indian-summer school (SNP2010) 100 [m]

  6. (e,e’K+) experiment in JLab Hall-C 2000年 1st generation exp.JLab E89-009 ENGE(e’) + SOS(K+) 12ΛB ~ 900 [keV] (FWHM) Proof of feasibility 2005年 2nd generation exp.JLab E01-011 ENGE(e’) + HKS(K+) + Tilt method 7ΛHe,12ΛB,28ΛAl ~ 500 [keV] (FWHM) Establish exp. method Luminosity ×137 e’ rate 1/200 S/N ×2.7 2009年 3rd generation exp.JLab E05-115 HES(e’) + HKS(K+) + Tilt method 7ΛHe,9ΛLi,10ΛBe,12ΛB,52ΛV ≤ 500 [keV] (FWHM) Medium heavy Strangeness 2010 at KEK

  7. E05-115 experimental motivation (1) • 2009 Aug – Nov @ JLab Hall-C • (e,e’K+) reaction • Target : 7Li , 9Be , 10B , 12C , 52Cr First try It is difficult experimentally. “ b.g. electron due to brems. ∝ ~Z2 “ • p-shell(7He , 9Li , 10Be , 12B) • Charge symmetry breaking • Λ-Σ coupling Λ Λ Λ Λ BΛ[MeV] • Medium heavy (52V) • s-,p-,d-,f-orbit binding energy • & cross section • Mass dependence of Λ single particle energy • l・s splitting　∝ 2l+1 Λ A = 52

  8. E05-115 experimental motivation(2) 1f7/2 FULL(8) f 7+ 6+ or 1d3/2 FULL(4) FULL(4) 6- 5- d • ls splitting • Core excited or ・ ・ ・ ・ ・ ・ 5+ 4+ p ls splitting ∝ 2l+1 or n = 28 p = 24 4- 3- s or 52Cr Λ 52ΛV d p f s Photo- and electro production of medium mass Λ-hypernuclei ,P.Bydzovsky et al. (2008) 22nd Indian-summer school (SNP2010)

  9. JLab E05-115 experimental setup e + p → e’ + Λ + K+ 7Li , 9Be , 10B , 12C , 52Cr 2×10-4 7 [msr] 3 – 12 [deg] 2×10-4 11 [msr] 2 – 12 [deg] Strangeness 2010 at KEK

  10. HKS detectors June 2009 in JLab Hall-C 1 [m] • HKS trigger • CP = 1X ×1Y × 2X • K = WC ×AC •  CP × K − π+ K+ p ~18 [kHz] (8 [μA] on 52Cr) K+ p, π+ Drift chambers -KDC1,KDC2- • Cherenkov detectors -AC,WC- • Aerogel (n=1.05) • Water (n=1.33) TOF walls -2X,1Y,1X- (Plastic scintillators) σ ≈ 250 [μm] TOF σ ≈ 170 [ps] Strangeness 2010 at KEK

  11. HES Detectors HES D magnet Drift chambers - EDC1 , EDC2 - TOF walls - EH1 , EH2 - (Plastic scintillators) σ ~ 300 [ps] Time Of Flight HES trigger EH1 ×EH2 ~2 [MHz] (8 [μA] on 52Cr) e Strangeness 2010 at KEK

  12. E05-115 ( 2009 Aug – Nov ) Data summary Physics Data Λ Λ Λ Λ (@36μA) Λ Calibration Data 22nd Indian-summer school (SNP2010)

  13. Analysis process HES HKS tracking tracking x , x’ , y , y’ at Reference plane x , x’ , y , y’ at Reference plane 450.8 [mg/cm2] 2.0 [μA] 38 [hours] p(e,e’K+)Λ p(e,e’K+)Σ0 σ = 2 [MeV/c2] (NOT TUNED) F2T function F2T function x’ , y’ , p at target x’ , y’ , p at target particle ID (select K+) Missing Mass tune tune p : Λ , Σ0 ,12ΛB Angle : Sieve slit

  14. Tracking for high multiplicity 52Cr target CH2 target particle KDC1 tracking particle Blue : selected wires Black: hit wires mean ~ 2 hit mean ~ 6 hit CH2 target 52Cr target Multiplicity of typical layer Traditional JLab Hall-C tracking code cannot handle with high multiplicity data. Tracking eff. CH2 52Cr Developing new code Multiplicity Strangeness 2010 at KEK

  15. Summary • 3rd generation exp. E05-115 experiment • 2009 Aug – Nov @JLab Hall C • 7He,9Li,10Be,12B,52V • Spectrometers and Detectors work well • Now analyzing • Tracking for high multiplicity first try to measure Λ-hypernuclei up to A=52 via (e,e’K+) Λ Λ Λ Λ Λ

  16. ENDありがとうございました Strangeness 2010 at KEK

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