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

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.

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+)

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 keV @ 1MeV ■ PWO counters - Fast background suppression ■ LSO pulsers – Ge monitoring of in-beam condition

Data Sample for 𝚲 𝟏𝟗 𝐅 2. Experiment Data Target (Thickness [g/cm2]) ■ 05.2015~06.2015 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

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

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

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.]

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: 1.1894±0.0001 GeV/c2 - B Λ of Λ 12 C g.s.: -11.1±0.2 MeV

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.

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 keV @1.0 MeV (the sum of all germaniums) γ rays were measured under ~0.5 keV accuracy level at E < 1.0 keV.

- 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.

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

The 315 keV 𝜸 ray 4. Results signal 𝚲 𝟏𝟗 𝐅 sideband ± 𝚲 𝟏𝟗 𝐅 g.s. Energy: 315.8 ± 0.4(stat.) keV  Signal Yield: 134 ± 22(stat.) events

The 579 keV 𝜸 ray 4. Results signal sideband 𝚲 𝟏𝟗 𝐅 𝚲 𝟏𝟗 𝐅 g.s. Energy: 579.0 ± 0.6(stat.) keV  Signal Yield: 36 ± 12(stat.) events

The 895 keV 𝜸 ray 4. Results signal sideband 𝚲 𝟏𝟗 𝐅 𝟓𝟔 𝐌𝐧 𝟏𝟖 𝐅 𝚲 𝟏𝟗 𝐅 g.s. Energy: 895.3 ± 0.3(stat.) keV  Signal Yield: 95 ± 13(stat.) events

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 315.8 ± 0.4 keV, 579.0 ± 0.6 keV, and 895.3 ± 0.3 keV energy. ■ Final analysis results for Λ 19 F and secondary hypernuclei ( Λ 18 O ) will soon be reported.