1. The First 𝜸-ray Spectroscopic Study of sd-shell Hypernucleus, 𝚲 𝟏𝟗 𝐅
YANG Seongbae
for the J-PARC E13 collaboration
Department of Physics and Astronomy
Seoul National University

2. Previous Hyperball Experiments and the J-PARC E13 1st Part
1. Introduction
Previous Hyperball Experiments and the J-PARC E13 1st Part
■ Previous experiments at KEK and BNL (Hyperball Project)
■ From 1998, γ rays from several p-shell hypernuclei ( Λ 7 Li , Λ 9 Be , Λ 11 B , Λ 12 C , Λ 15 N and Λ 16 O ) were successfully measured.
■ J-PARC E13 1st Part
■ High precision gamma-ray spectroscopy (new Ge array, Hyperball-J) of 𝚲 𝟒 𝐇𝐞 and 𝚲 𝟏𝟗 𝐅 hypernuclei at J-PARC. We successfully took the data in this year.

3. What we can learn from 𝚲 𝟏𝟗 𝐅 study?
1. Introduction
What we can learn from 𝚲 𝟏𝟗 𝐅 study?
■ Ground state doublet (1/2+, 3/2+)
■ First measurement of ΛN spin-spin interaction in the sd-shell hypernuclei
■ Information on radial dependence of the ΛN spin-spin interaction in comparison to p-shell hypernuclei.
Spin-flip state
■ Spin-flip B(M1) measurement
■ Nuclear shrinkage
■ E2(5/2+1/2+)

4. Experimental Setup for E13 1st Phase
■ K1.8 Beamline : High intensity and high purity K beam
■ Reaction: 𝐴 𝑍 (𝐾 − , 𝜋 − ) Λ 𝐴 𝑍 ∗  Λ 𝐴 𝑍 + γ
■ SksMinus & Beamline Spectrometers
■ High resolution of missing mass
■ Large acceptance for (𝐾 − , 𝜋 − ) and good beam decay suppressor (SP0, SMF)
■ Hyperball-J
■ 28 HPGe detectors - ∆E ~3 1MeV
■ PWO counters - Fast background suppression
■ LSO pulsers – Ge monitoring of in-beam condition

5. Data Sample for 𝚲 𝟏𝟗 𝐅 2. Experiment Data Target (Thickness [g/cm2])
■ ~ at the J-PARC K1.8 Beamline
Data
Target
(Thickness [g/cm2])
Momentum [GeV/c]
Number of K
Beam through .
1.2, 1.37, 1.5,
and 1.8
𝚺 + and 𝚲 𝟏𝟐 𝐂
CH2 (6.6)
1.8
0.6 G
𝚲 𝟏𝟗 𝐅
CF2 (6.6)
2.3 G
Physics Run
Liquid. CF4 (20)
63 G

6. Kaon beam Selection using Beam TOF
3. Analysis
Kaon beam Selection using Beam TOF
■ Beam TOF at 1.8 GeV/c
Κ −
π −
*Kaon beam during physics run
Intensity: 350 k/spill
K-/π-: ~2.5

7. Vertex Point (z-direction) and Reaction Angle
3. Analysis
Vertex Point (z-direction) and Reaction Angle
■ CF4 target during physics run
vtz cut ± 70 mm
BH2
π −
Reaction angle cut
*CF4 target real length: 125 mm

8. Scattered 𝛑 − Selection using M2
3. Analysis
Scattered 𝛑 − Selection using M2
■ M2 verse reaction angle
𝐊 −
Mass Square [(GeV/c2)2]
𝛑 −
Reaction Angle [deg.]

9. 𝚺 + and 𝚲 𝟏𝟐 𝐂 Production with CH2 target (6.6 g/cm2)
3. Analysis
𝚺 + and 𝚲 𝟏𝟐 𝐂 Production with CH2 target (6.6 g/cm2)
■ 𝚺 + production
■ 𝚲 𝟏𝟐 𝐂 production
𝚺 +
𝚲 𝟏𝟐 𝐂 g.s.
Σ + Mass: ± GeV/c2
- B Λ of Λ 12 C g.s.: -11.1±0.2 MeV

10. 𝚲 𝟏𝟗 𝐅 Production with CF2 target (6.6 g/cm2)
3. Analysis
𝚲 𝟏𝟗 𝐅 Production with CF2 target (6.6 g/cm2)
Estimated background from 𝚲 𝟏𝟐 𝐂
Data
𝚲 𝟏𝟗 𝐅 pΛ
𝚲 𝟏𝟐 𝐂 g.s.
𝚲 𝟏𝟗 𝐅 g.s.
*Background from 𝚲 𝟏𝟐 𝐂 estimated using CH2 target study.

11. γ-ray Energy Resolution and Residuals
3. Analysis
γ-ray Energy Resolution and Residuals
■ Residuals with reference
■ Energy Resolution
used for calibration
used for calibration
 Energy Resolution: ~5 MeV (the sum of all germaniums)
γ rays were measured under ~0.5 keV accuracy level at E < 1.0 keV.

12. - B 𝚲 Distribution of 𝚲 𝟏𝟗 𝐅 with CF4 target (20 g/cm2)
4. Results
- B 𝚲 Distribution of 𝚲 𝟏𝟗 𝐅 with CF4 target (20 g/cm2)
𝚲 𝟏𝟗 𝐅 pΛ
𝚲 𝟏𝟗 𝐅 g.s.
Unbound
Selected
𝚲 𝟏𝟐 𝐂 g.s.

13. 𝜸-ray Spectrum with - B 𝚲 cut
4. Results
𝜸-ray Spectrum with - B 𝚲 cut
* without Doppler shift correction
𝟏𝟗 𝐅
selected
unbound
𝐞 + 𝐞 − annhilation
𝚲 𝟏𝟗 𝐅
𝚲 𝟏𝟗 𝐅
𝚲 𝟏𝟗 𝐅
𝟏𝟎 𝐁

14. The 315 keV 𝜸 ray 4. Results signal 𝚲 𝟏𝟗 𝐅 sideband ± 𝚲 𝟏𝟗 𝐅 g.s.
Energy: ± 0.4(stat.) keV
 Signal Yield: 134 ± 22(stat.) events

15. The 579 keV 𝜸 ray 4. Results signal sideband 𝚲 𝟏𝟗 𝐅 𝚲 𝟏𝟗 𝐅 g.s.
Energy: ± 0.6(stat.) keV
 Signal Yield: 36 ± 12(stat.) events

16. The 895 keV 𝜸 ray 4. Results signal sideband 𝚲 𝟏𝟗 𝐅 𝟓𝟔 𝐌𝐧 𝟏𝟖 𝐅
𝚲 𝟏𝟗 𝐅 g.s.
Energy: ± 0.3(stat.) keV
 Signal Yield: 95 ± 13(stat.) events

17. 5. Summary
Summary
■ A new 𝛾-ray spectroscopy experiment of Λ 19 F via the ( 𝛫 − , 𝜋 − ) reaction was performed at the J-PARC K1.8 beam line.
■ Preliminary, we observed 3 𝛾 rays from Λ 19 F . They have ± 0.4 keV, ± 0.6 keV, and ± 0.3 keV energy.
■ Final analysis results for Λ 19 F and secondary hypernuclei ( Λ 18 O ) will soon be reported.