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Electrophoto-production of strangeness and L Hypernuclei

Electrophoto-production of strangeness and L Hypernuclei. Osamu Hashimoto Department of Physics, Tohoku University. October 21-22, 2004 Jeju University. p ( g , K + ) L Total cross section. 2.0. 1.0. σ total ( m b). Phys. Lett. B 445, 20 (1998) M. Q. Tran et al. 1.2. 1.4. 1.6.

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Electrophoto-production of strangeness and L Hypernuclei

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  1. Electrophoto-production of strangeness and L Hypernuclei Osamu Hashimoto Department of Physics, Tohoku University October 21-22, 2004 Jeju University

  2. p(g,K+)L Total cross section 2.0 1.0 σtotal(mb) Phys. Lett. B 445, 20 (1998) M. Q. Tran et al. 1.2 1.4 1.6 1.8 2 1 Eγ(GeV) Strangeness production by pions and photons

  3. Basic characteristics of the (e,e’K+) spectroscopy • Proton converted to L Neutron rich L hypernuclei • Large angular momentum transfer Similarly to (p+,K+) reaction • Spin-flip amplitude  Unnatural parity hypernuclear states • High quality primary beam  Sub MeV resolution

  4. The (e,e’K+) reactions --- elementary and hypernuclear --- Elementary process Hypernuclear production

  5. gngK0Lreaction data near the threshold play an important role Elementary processes of photo-strangeness production Six possible isospin channels: (1) p(g,K+)L (2) p(g,K+)S0 (3) p(g,K0)S+ (4) n(g,K+)S- (5) n(g,K0)L (6) n(g,K0)S0 Isobar model • No contribution from the t-channel Born term • Less contribution of resonances terms Coupling constants Resonances to be included New high-quality data being available for K+ However, • g(K0S0n) = -g(K+S0p)

  6. n(g,K)L Model calculation Angular distribution Energy dependence γ + p → K+ + Λ Eγ = 1.05 GeV Kaon-MAID: T.Mart, C.Bennhold, Phys. Rev. C61 (2000) 012201(R) http://kph.uni-mainz.de/MAID/ kaon/kaonmaid.html SLA: T.Mizutani et al., Phys. Rev. C58 (1998) 75. γ + n → K0 + Λ Eγ = 1.05 GeV calculated by Sotona’s code

  7. Laboratory for Nuclear Science, Tohoku University at Sendai • 200 MeV LINAC • 1.2 GeV • Booster/stretcher ring • エネルギー標識化光子ビーム • up to 1.1 GeV/c • Good duty factor Neutral Kaon Spectrometer ( NKS )

  8. Invariant Mass (p+p-) (GeV/c2) First observation of neutral kaons in the threshold region K0 ~ 450 counts/20MeV 12C target Background K0s: ct~2.68cm Ks0 p+ + p- (64 %)

  9. Comparison with recent modelsg + 12C  K0 + X( Quasi-free K0 production) preliminary preliminary solid: Kaon-MAID n(g,K0)L only dashed: Kaon-MAID include p(g,K0)S+ + n(g,K0)S0 solid: SLA n(g,K0)L Neff = 4.2 kF0=0.22GeV/c

  10. Neutral kaons from the liquid deuterium target K0S : ct～ 2.68 cm sx～1.6mm

  11. Comparison of D2 target data with theoretical models preliminary

  12. Upgrade plan at LNS, Tohoku STB ring radiator 1.2 GeV e- NKS2 g Pole diameter : 160 cm BMAX: 0.5 T High momentum & mass resolution Efficiency more than 2X for K0 Efficiency more than 10 x for L Ready in 2005

  13. Hypernuclear production by the (e,e’K+) reaction K+ detection At very forward angle (~ 0 degrees) Maximum hypernuclear production cross section Target nucleus K+ pK=1.2 GeV/c Eg=1.5 GeV e- Beam pe=0.3GeV/c Ee=1.8 GeV e’ e’ detection At extremely forward angles Advantage : Large virtual photon flux Disadvantage : Huge backgrounds from Bremsstrahlung

  14. ds/dW (nb/sr) angle (deg) Angular distribution of electrons and kaons electrons kaons (degrees) Calculated by Sotona’s code Ee = 1.864 GeV Ee’ = 0.38 GeV Ee = 1.864 GeV Ee’=0.4 GeV

  15. Jlab Accelerator Beam characteristics Emax 6 GeV Max. Current 200 mA Duty factor 100% Emittance 2.0 mm·mrad DEbeam 2.510-5 (FWHM) Hall A Hall B Hall C E89-009 E01-011 E97-107

  16. E89-009 experimental setup To beam dump

  17. e’ e+ e- p(e,e’K+)L p(e,e’K+)S0 e 12C(e,e’K+) quasi-free Accidental E89-009 calibration A(e,e’;(e+,e-))A CHx target 815 keV (FWHM)

  18. (1-,2-) (2+,3+) 90 80 (1-,0-) 70 (2-,1-) 60 50 40 -15 -10 -5 0 5 10 15 12LB spectrum of E89-009 Ground state doublet Binding energy BL = 11.52±0.35 MeV 1 month data Emulsion data BL = 11.37 MeV ds/dW nb/sr/0.3 MeV Cross section 140±17(stat) ±18(sys) nb/sr Motoba’s calculation Jp cross section 1- 23.4 nb/sr 2- 114.5 nb/sr 138 nb/sr -BL(MeV) 750 keV(FWHM)

  19. 7Li(e,e’K+)7LHe 7Li(e,e’K+)7LHe Background subtracted 200 80 180 60 40 ds/dW nb/sr/0.3 MeV 160 20 140 0 120 -20 -10 0 10 20 -10 0 10 20 7LHe Spectrum of E89-009 6LHe + n 6He + L 0.04 3/2- 1/2+ 0.03 3/2- 7/2- 0.02 5/2- 5/2- 5/2+ 3/2+ 0.01 -10 -5 0 5 10 15 20 -BL ( MeV) -BL ( MeV) Shell model calc. by Sotona • No peaks observed in the bound region • A suggestive bump at around 7-8 MeV Sotona

  20. Beam energy spread and spectrometer resolutions as planned Projected Data 12C (e,e’K)12BL From Prof. Garibaldi HALL A Very Preliminary Data “Standard” PID DE=1.3 MeV (FWHM) with Multiple Uncorrected Beam Energies DE~800 keV Full statistics with fitted peaks. Resolution still not fully optimized Subsets of data appear to have better resolution Limited statistics + cut on Beamx position at 1C12 + ± 50 keV on relative beam energy DE~400 keV Guarantees beam within specs

  21. Hypernuclear spectroscopy experiments at Jlab MAINZ to join

  22. The tilt method for higher luminosity Side view

  23. Future spectrometer system for the (e,e’K+) reaction HES High resolution Electron Spectrometer (2.2~2.5GeV)

  24. Yield comparison of E01-011 and E89-009

  25. Expected 28LAl hypernuclear spectra 28Si(p+,K+)28LSi SKS E140a

  26. Summary • Photo strangeness production in the 1 GeV region • Neutral kaon measurement plays a unique role • NKS at LNS, Tohoku measured neutral kaons • NKS2 for further experimental study of neutral kaon production is under construction • Hypernuclear production by the (e,e’K+) reaction • The first 2 experiments were successfully carried out at Jlab Hall C and Hall A • 2nd generation hypernuclear spectroscopy by the (e,e’K+) reaction is to be carried out in 2005 • High resolution electron spectrometer is under construction for the 3rd generation (e,e’K+) spectroscopy

  27. Acceptable energy windows of HKS systemwith ENGE or HES revised 04/10/10 ENGE HES Acceptable Central Energy (GeV) 0.3 0.4 0.6 0.8 1 0.65 0.55 Ee’ (GeV) 1.8 1.9 2.0 2.2 2.4 2.5 Ee at Hall (GeV) 2.15 2.05 Etop2pass (GeV) 4.4 4.55 5.0 6.0 Etop1pass (GeV) 9.45 10.3 10.8 12.0

  28. Invariant mass spectrum k0 candidates K0 mass region 0.46 – 0.54 GeV/c2 preliminary Invariant mass [GeV/c2] accidental events miss ID events

  29. Momentum distribution preliminary preliminary Error : statistical only

  30. Experimental condition Phys. Lett. B 445, 20 (1998) M. Q. Tran et al. σtotal(mb) Virtual photon energy Eg ~ 1.5 GeV Beam energy Ee= 1.721, 1.864 GeV p(g, K+)L 2.0 Total cross section 1.0 Beam current < 2 mA < 0.6 mA for 12C target Target thickness < 100 mg/cm2 natC 22 mg/cm2 CH2 8.8 mg/cm2 1.2 1.4 1.6 1.8 2 1 Eγ(GeV) Reaction Threshold(MeV) gp  KL 911 KS 1046 KL(1405) 1452 K*(892)L 1679 Limited by bremsstrahlung electrons at 0 deg. in scattered electron spectrometer

  31. Cross section Triple-differential cross section Cross sections were extracted with experimental yields NT: target density NX : L or 12LB g.s yield Ng : Number of virtual photon integrated over Ee’ and W e’ etotal : total correction factor

  32. 12LB spectrum fitting results • Fitted by 3 Gaussians and a constant • Energy resolution was fixed 0.9 MeV(FWHM) Constant = 5±1 nb/sr/400keV

  33. Energy level of 12LB spectrum ds/dW(nb/sr) Ex(MeV) Ex(MeV) 5.44 5.0 30±15±4 0.20 3/2 - 2.51 2.1 59±14±7 0.26 1/2 - 3/2 - 1.72 122 ±12 ±15 11B x s L12LB S factor 12C(e,e’p)11B Emulsion data BL=11.37±0.06 MeV BL(g.s)=12.20±0.06±0.25 MeV :

  34. 12LB spectrum v.s 12LC spectrum 12LC KEK E369 PL SL PL SL • Structure is similar • SL and PL states are observed

  35. Theoretical prediction of 12LB spectrum DWIA calculation with phenomenological potential by Motoba Eg=1.3GeV, qK=3deg., 900 keV(FWHM), NSC97f

  36. Theoretical calculation of 28LAl spectrum high spin and unnatural parity states ls splitting ??? 300 keV (FWHM) Calculated by Sotona et al.

  37. Angular distribution Angular distribution of 12LB states Expected yield ratio between g.s. (p3/2)-1(p3/2)L3+ (s1/2)-1(p1/2)L 2- (p3/2)-1(s1/2)L 2- (s1/2)-1(s1/2)L 1+ DWIA calculation by a code of M.Sotona

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