Λ hypernuclear spectroscopic experiment via (e,e’K + ) at JLab Graduate school of science, Tohoku Univ. Toshiyuki Gogami JLab Hall-C in May 2009

Contents (e,e’K + ) experiment Introduction of JLab E Development for high multiplicity data

(e,e’K + ) reaction experiment

Spectroscopic experiment via (e,e’K + ) reaction p n γ*γ* Λ K+K+ e-e- e + p ➝ e’ + K + + Λ ee M 2 HY = (E e + M T - E K+ - E e’ ) 2 - ( p e - p K+ - p e’ ) 2 measure target nucleus Feynman diagram u u d u s s u d – p K+K+ Λ γ*γ* Missing mass : Binding energy Cross section

(e,e’K + ) reaction u u d u s s u d ee – p K+K+ Λ γ*γ* u d d d u u s s d u ––π+π+ Λ n u s d d u u d s d u – K-K- Λ n – π-π- e + p ➝ e + K + + Λπ + + n ➝ K + + Λ K+K+ K - + n ➝ π - + Λ (π +, K + )(K -, π - )(e,e’K + ) Momentum transfer (Typical ) ~300 [MeV/c] ~90 [MeV/c] Λ’s Spin At forward angle Λ’s from proton neutron flip ≈ non-flip non-flip Beam primary secondary Target Thin (~100 mg/cm 2 ) (Isotopically enriched) Thick(> a few [g/cm 2 ] ) Reaction Λ can be bounded in deeper orbit Spin dependent structure Mirror lambda hypernuclei High quality, high intensity Fine structure Energy resolution (FWHM) ≤ 500 [keV]1 – 3 [MeV]

JLab CEBAF ( Continuance Electron Beam Accelerator Facility ) (e,e’K + ) experiment 1.Coincidence experiment (K + and e - ) 2.Small cross section ( ~100 [nb/sr] ) 1/ Energy resolution sub MeV (FWHM) 22 nd Indian-summer school (SNP2010) 100 [m] Requirement for accelerator 1.high duty factor 2.high intensity 3.small emittance small ΔE/E CEBAF can satisfy these requirements Thomas Jefferson National Accelerator Facility

(e,e’K + ) experiment in JLab Hall-C Strangeness 2010 at KEK 2000 年 1 st generation exp. JLab E ENGE(e’) + SOS(K + ) 12 Λ B ~ 900 [keV] (FWHM) 2005 年 2 nd generation exp. JLab E ENGE(e’) + HKS(K + ) + Tilt method 7 Λ He, 12 Λ B, 28 Λ Al ~ 500 [keV] (FWHM) 2009 年 3 rd generation exp. JLab E HES(e’) + HKS(K + ) + Tilt method 7 Λ He, 9 Λ Li, 10 Λ Be, 12 Λ B, 52 Λ V ≤ 500 [keV] (FWHM) Luminosity ×137 e’ rate 1/200 S/N ×2.7 Proof of feasibility Establish exp. method Medium heavy

JLab E experiment

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

JLab E experimental setup 2× [msr] 3 – 12 [deg] 2× [msr] 2 – 12 [deg] e + p → e’ + Λ + K + 7 Li, 9 Be, 10 B, 12 C, 52 Cr

JLab E experimental setup 2× [msr] 3 – 12 [deg] 2× [msr] 2 – 12 [deg] e + p → e’ + Λ + K + 7 Li, 9 Be, 10 B, 12 C, 52 Cr

HKS detectors K + p, π + Drift chambers -KDC1,KDC2- TOF walls -2X,1Y,1X- (Plastic scintillators) Cherenkov detectors -AC,WC- Aerogel (n=1.05) Water (n=1.33) 1 [m] June 2009 in JLab Hall-C HKS trigger CP = 1X ×1Y × 2X K = WC × AC  CP × K ~18 [kHz] (8 [μA] on 52 Cr) − π+π+ K+K+ p σ ≈ 200 [μm] TOF σ ≈ 170 [ps]

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

Data Summary JLab E (2009/June – 2009/Nov)

Analysis process tracking x, x’, y, y’ at Reference plane x’, y’, p at Target Missing Mass tracking x, x’, y, y’ at Reference plane x’, y’, p at Target F2T function particle ID (select K + ) HKS HES tune This talk

Λ and Σ 0 Because of high multiplicity of HKS (analysis code cannot handle with high multiplicity) ~40 hours (5 shifts) p(γ*,K + )Λ,Σ 0

Analysis for high multiplicity data KDC1 KDC2 HKS event display

Background event of HKS HKS dipole magnet NMR port z [cm] y [cm] x [cm] KDC1 KDC2 KDC1 KDC2 9 Be, 38.4 [μA] Overhead view Background events Events on HKS optics Β ≈ 1 e -, e + SIMULATION

Singles rate summary Up to ~30 [MHz] Up to ~15 [MHz] HES HKS HKS trigger ~ 10[kHz] HES trigger ~ a few[MHz]

Multiplicity of typical layer of chamber HES HKS ~1.13 ~1.28 ~2.24 ~4.94 Multiplicity is high for HKS

HKS drift chamber wire configuration

Hit wires in KDC1 Overhead view KDC1 Black : hit wires Blue : selected wires Red : track Black : hit wires Blue : selected wires Red : track CH 2 52 Cr Misidentification chance in hit wires selection increase ! REAL DATA lowhighlowhigh Overhead view

New tracking scheme Good TDC Pattern recognition Track fit Solve left right Select good combination Combination selection with TOF counters Reduce hit wire combinations (h_tof_pre.f) High multiplicity Reduce hit wires to analyze NEW

DC hit info. selection with TOF Selective region Maximum gradient Minimum gradient Particle direction Gravity CUT ~8% ~17% Procedure in “h_dc_tofcut.f” 1.Get KTOF1X & 2X hit counter information 2.Make combination of 1X and 2X hit counter if those two are in same group (grouping) 3.Determine cut conditions on KDC1 & KDC2 4.Select Hit wires in KDC and Reorder them CUT

Hit wires event display (1) GREEN region Selective region RED markers Selected hit wires BLACK markers Rejected hit wires Seems to work well Particle direction Gravity

Apply to u,v-layer Applied to uu’ and vv’ layers, too. Selective region determined by 1X and 2X Convert v v’-layer x x’-layer

Hit wires event display (2) GREEN region Selective region RED markers & lines Selected hit wires BLACK markers & lines Rejected hit wires v v’ u u’u u’ x x’ v v’ u u’u u’ x x’ KDC1 KDC2 particle

Results of Introduction new code Λ c.s. (CH 2 /H 2 O) issue is solved Increased ! CH 2 52 Cr

Summary and Outlook 3 rd generation exp. E at JLab Hall-C in Λ He, 9 Λ Li, 10 Λ Be, 12 Λ B, 52 Λ V Analysis for high multiplicity data – Developed new tracking code Analysis efficiency is improved ! (number of event) Λ cross section of H 2 O and CH 2 are consistent To get better energy resolution – Fine parameter optimization – Matrix tuning

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