1. Hypernuclei Production Experiment E05115 at Jefferson Laboratory by the (e,e’K + ) Reaction Chunhua Chen March 31, 2012  Introduction  Experimental Setup and Kinematics  System Calibration  Preliminary Results  Summary Outline

2. Introduction Physical Goals: To understand YN and YY interactions To explore and understand nuclear structure using  as a probe Model the baryonic many body system Study the role of  in the nuclear medium E05115 ： The 3 rd generation spectroscopic investigation of Lambda hypernuclei by the Reaction (e,e’K + ) at Jlab Hall C Shield Model with  -N Effective Potential (p N s  ) ssss V  N = V 0 (r)+V  (r) s N  s  +V  (r) L N   s  +V N (r) L N   s N +V T (r)S 12 Additional Contribution:  -  coupling 

3. Introduction-Cont. Experimental Goals:  Spectroscopy of Medium - heavy hypernucleus 52 Cr(e,e’K+) 52  V  Spectroscopy of Light  hypernuclei- p shell hypernuclei 12 C(e,e'K+) 12 Λ B, 7 Li(e,e'K+) 7 Λ He, 10 B(e,e'K+) 10 Λ Be, and 9 Be(e'K+) 9 Λ Li Calibration by the elementary process p(e,e’K + )  or  : H 2 O and CH 2 Merits of (e,e’K + ) experiment:  Large momentum transfer → Excitation of deeply-bound state  p to  conversion → Mirror or Neutron-rich hypernuclei  Production of both spin-flip/non-flip states;  High resolution because of the quality of the CEBAF beam Merits of (e,e’K + ) experiment:  Large momentum transfer → Excitation of deeply-bound state  p to  conversion → Mirror or Neutron-rich hypernuclei  Production of both spin-flip/non-flip states;  High resolution because of the quality of the CEBAF beam Results are important in determining , S N and V 0 terms from  s states and S  term from states with  at higher orbits

4. Experimental Setup Splitter Magnet HKS HES Bremsstralung flux Virtual photon flux factor  K+K+ e’ e

5. Kinematics of the E05-115 Experiment  p →  K + Momentum: 2.344GeV/c Momentum: 0.844GeV/c ±17% Angular acceptance: 3° 〜 9° Momentum: 1.2GeV/c ±12.5% Angular acceptance : 1° 〜 13 ° 1.5GeV γ* Scattered electron K+K+ Electron beam Target nucleus p Coincidence measurement 

6. Spectrometer System Calibration Spectrometer system calibration: key to reach 400 keV energy resolution Common splitter : Separated single arm kinematics calibration is not possible Technique: 2-arm coupled calibration for both kinematics and optics Using known masses of ,   from CH2 target and identified known hypernuclear bound states 12  Bgs for spectrometer calibration HES spectrometer system Beam Target Splitter HKS HES Sieve Slit To beam dump   12  B (gs) Kaon Momentum (MeV/c) Kinematics coverage Sieve Slit

7.  Field Map Correction Real Optics （ Yuncheng Han T10 ） Agreement between Simulation data and Real SS data Independence of invariant mass to reconstructed kinematical parameters. (Λ&Σ; P,xt’,yt’) Initial Matrices  Mathematical optimization by Nonlinear Least Chi 2 fitting a.Central kinematics scan (m Λ,m Σ,Δm ΛΣ ) b.Angular matrices (m Λ,m Σ,σ) c.Momentum matrices ( 12 Λ Bgs) d.Iteration

8. Preliminary Status Preliminary Status #1 #2 Peak#Mean(MeV)σ (MeV) 1-11.390.411 2-0.40~1.8 FWHM ~1.675MeV FWHM ~1.775MeV FWHM ~1.7MeV FWHM ~2.0MeV P(e,e’K+)Λ&Σ 0 (CH 2 ) P(e,e’K+)Λ&Σ 0 (H 2 O)

9. Preliminary Result 7 Λ He Preliminary Result 7 Λ He E01011 data E. Hiyama, et al., PRC53 2078 (1996)  n n 6 He core 3/2 + &5/2 + E05115 data

10. Preliminary Results 9 Λ Li B  = -8.53  0.18 (emulsion, average over only 8 events) ss ss ss Sotona and Millener Saclay-Lyon model for elementary process ss Ex: 0.0 ~0.84 ~1.90 ~ 2.75 ~3.77 ~4.38 Hall C HKS E05-115 B  = -10.1  0.3

11. Preliminary Result 10 Λ Be Preliminary Result 10 Λ Be 3-3- 2-2- 4-4- 3-3- ΛsΛs ΛsΛs ΛsΛs E05115 0.00 0.11 2.48 2.59 6.43 4-4- 3-3- ΛsΛs 3/2 - 0.00 5.59 3/2 - 7/2 - 6.38 5/2 - 7.94 2.43 5/2 - 1/2 - 2.78 1/2 + 1.68 5/2 + 3.04 3/2 + 4.70 9/2 + 6.76 Low Lying 9 Be Level Structure 1-1- 2-2- (< 0.1) 10  Be Theory 7/2 - 11.28 10.93 11.53 6.51

12. Summary and to do By current calibration method, we are able to get clear mass spectroscopy, which is not included in the calibration data set; Current resolution is still factor of 2 away from expected resolution, the iteration will continue to improve the optical matrices as well as the kinematics; Other issue: High multiplicity tracking problem for heavy target data. 12

13. Backup

15. ΔE beam0 optimization Kinematical Calibration Optical Calibration Momentum Matrix Angle Matrix ΔP K,ΔPe optimization Beam Energy Scan iterate gs : 12 Λ B gs

16. Forward Optics Tuning Purple: Real HKS SS data Blue: Geant4 Simulation Splitter field contour on xoz plane The leakage of splitter fringe field causes the cross talk between the splitter and quadrupoles Purple: Geant4 simulation green: Real HES SS data Target BeamKaon Q1 Q2

17. Forward Optics Tuning The asymmetry functions are introduced and tuned for HKS&HES quadruple field Bx and By, independently.

18. Introduction Physical Goals: To understand YN and YY interactions To explore and understand nuclear structure using  as a probe Model the baryonic many body system Study the role of  in the nuclear medium