1. Atsushi Tokiyasu ELPH ELPH workshop C015 @ Sendai Dec. 2nd, 2016.
Hypernuclei spectroscopy by the photo-induced reaction 光生成反応によるハイパー核分光実験
東北大の時安です。
今日はこのようなタイトルでお話ししたいと思います。
Atsushi Tokiyasu
ELPH
ELPH workshop Sendai
Dec. 2nd, 2016.

2. Abstract
In the FOREST Upgrade project, a forward spectrometer will be installed.
By adding K+ ID counters and improving the momentum resolution,
　we can study hypernuclei via the A(γ,K+)X reaction.
Physics motivation and the feasibility of the experiment will be discussed for the following reaction:
12C(γ, K+)12ΛB
4He (γ, K+)4ΛH
今日のトークの概要を話します。
現在、ELPHで行われているFORESTではUpgrade
Outline
1. Hypernuclei photo-production
2. FOREST Upgrade project
3. 12C(γ, K+)12ΛB
4. 4He (γ, K+)4ΛH
ELPH Workshop C15, Dec. 2th, 2016.

3. Hypernclei photo-production
ELPH Workshop C15, Dec. 2th, 2016.

4. Hypernuclei
Λ-N interaction
Unified Baryon-Baryon Interaction
Experiment  K+ trigger, Signal as peak structure, low physics BG
Theory  Shell model, DWIA …
Recent Progress
neutron rich Hypernuclei : Unstable Hypernuclei Dr. Gogami’s talk
Light Hipernuclei : CSB, precise information on 3-body int  Dr. Nagao’s talk
S=-2 Hypernuclei : Ξ-n int., Dibaryon?  Koshikawa-san’s talk
Excited Hypernuclei : Λ(1405)-Nuclei, KaonicNuclei?　  Dr. Ma’s talk
Reaction : (K-, π-) , (π+, K+), (e,e’K+) , Heavy Ion… + (γ, K+) n p p
-impurity effect: Shrink　
-glue like role
extraordinaly neutron rich 7ΛH etc Λ n n p
g-factor in medium
:chiral symmetry restoration?
(g=eh/2mc)
ハイパー核ですが、Λが原子核に束縛された系のことを言います。
ELPH Workshop C15, Dec. 2th, 2016.

5. Hypernuclei production by (γ,K+)
☆property of the (γ,K+) reaction.
1.Λ is produced via EM int.
2. convert proton to Λ
3.Large momentum transfer
4. Spin-flip amplitude (J γ = 1)
それではγ, K+ がどんな特徴を持つのかというのを一覧にしてみました。
ELPH Workshop C15, Dec. 2th, 2016.

6. Hypernuclei production by (γ,K+)
☆property of the (γ,K+) reaction.
1.Λ is produced via EM int.
Free from ISI, FSI
2. convert proton to Λ
3.Large momentum transfer
4. Spin-flip amplitude (J γ = 1) π- K- Λ γ K+ Λ
ELPH Workshop C15, Dec. 2th, 2016.

7. Hypernuclei production by (γ,K+)
☆property of the (γ,K+) reaction.
1.Λ is produced via EM int.
Free from ISI, FSI
2. convert proton to Λ
neutron rich hypernuclei
3.Large momentum transfer
4. Spin-flip amplitude (J γ = 1)
7ΛLi
(π+, K+) Λ
p: 3
n: 3
Λ: 1
7Li p n
7ΛHe
(γ, K+)
p: 2
n: 4
Λ: 1 Λ
cf. (π-, K+) 2step reaction
ELPH Workshop C15, Dec. 2th, 2016.

8. Hypernuclei production by (γ,K+)
☆property of the (γ,K+) reaction.
1.Λ is produced via EM int.
Free from ISI, FSI
2. convert proton to Λ
neutron rich hypernuclei
3.Large momentum transfer
excite high-spin states
4. Spin-flip amplitude (J γ = 1)
qΛ　～400 MeV/c
Comparable to (π+,K+)
ELPH Workshop C15, Dec. 2th, 2016.

9. Hypernuclei production by (γ,K+)
Ref) Prof.Motoba’s slide (HYP2015)
☆property of the (γ,K+) reaction.
1.Λ is produced via EM int.
Free from ISI, FSI
2. convert proton to Λ
neutron rich hypernuclei
3.Large momentum transfer
excite high-spin states
4. Spin-flip amplitude (J γ = 1)
Unnatural parity state 2- 3+
最後にこれが一番重要なのですが、γはスピン１を持ちます。
したがって、閾値付近で、スピンがフリップする
こちらの素ペクトラムは 2- 3+
ELPH Workshop C15, Dec. 2th, 2016.

10. Hypernuclei production by (γ,K+)
☆property of the (γ,K+) reaction.
1.Λ is produced via EM int.
Free from ISI, FSI
2. convert proton to Λ
neutron rich hypernuclei
3.Large momentum transfer
excite high-spin states
4. Spin-flip amplitude (J γ = 1)
Unnatural parity state
Complementary to Hadron-induced reaction!
-Theoretical calculation :1980s ~
But.
- small cross section.
- No facility for high intensity beam.
- (e,e’K+) reaction
これらの特徴からγ,K+は
π、K+のハイパー核を e e’ γ*
ELPH Workshop C15, Dec. 2th, 2016.

11. virtual photon vs real photon
γ　 p  K Λ /
x x x = 12
x x x = 8
spin
Virtual
Real
Merit:
- simple elementary process.
- High transparency of γ  long target, low background
- coincidence measurement. (Production and decay)
Demerit (compared to e- beam):
- poor mass resolution
- low intensity beam
FOREST Upgrade
ELPH Workshop C15, Dec. 2th, 2016.

12. FOREST Upgrade
ELPH Workshop C15, Dec. 2th, 2016.

13. Hypernuclei spectroscopy at FOREST
bremsstrahlung γ-ray from 1.3 GeV e-
107 cps tagged-γ (0.8 GeV < Eγ < 1.2 GeV)
4π EM calorimeter FOREST
☆FOREST Upgrade Project
1. FOREST : Installation of Fwd spectrometer (K+ detection)
2. Tagger : Improve Eγ resolution
 (γ, K+) by Missing Mass Method
FOREST実験はここELPHにおいて遂行されている実験です。
アぷグレードする計画が進められております。
改良する事項はおもに二つあｒます。
ひとつは、
ELPH Workshop C15, Dec. 2th, 2016.

14. FOREST Upgrade Detection of the charged particle at 0 degrees
Acceptance (vert ±0.6°, hori ±1.2°)
BL = 1.37 T・m
Resolution ~ Δp/p ~ 10-3
under study
ELPH Workshop C15, Dec. 2th, 2016.

15. Tagger Upgrade + Current Setup New Setup ΔE/ch 0.5 – 2.5 MeV (σ)
MPPC + Scintillator
York
iron shield +
MWDC
Scintillating
fiber
PMT
Current Setup
New Setup
ΔE/ch
0.5 – 2.5 MeV (σ)
~1 MeV(σ) ΔT
0.4 – 0.6 ns (σ)
0.2 n (σ)
ELPH Workshop C15, Dec. 2th, 2016.

16. Physics Program of FOREST Upgrade
　　　☆By detecting charged particle at forward angle,
　 　　　　many physics channel is accessible!
d (γ, p )η n  Dr.Nakamura’s talk
Scattering Length measurement
d (γ, K+)Λ n
Λ-n interaction measurement
d(γ, d)π0π0
D* search  Inoue-san’s talk
C(γ, p) ηB
η mesic nuclei search
ELPH Workshop C15, Dec. 2th, 2016.

17. 12C(γ, K+)12ΛB
ELPH Workshop C15, Dec. 2th, 2016.

18. ES132 @ INS-TAGX - 0 ° < θlab < 40°
Ref) PRC52, R1157
- 0 ° < θlab < 40°
-0.8 GeV < Eγ < 1.1 GeV
 Comparable
-Photon flux = 4.5 * 105 /s
 ~10 ELPH
-Δp/p ~ 0.06 (RMS),ΔEγ ~5MeV
 improved
ELPH Workshop C15, Dec. 2th, 2016.

19. Yield Estimation Yield (2-) = dσ/dΩ * Ω * RK * Ntarget * Nbeam
Ref) PTPS
Notice date 1994
Yield (2-) = dσ/dΩ * Ω * RK * Ntarget * Nbeam
= 100 nb/sr *1.0E-4 * * 1.0E * E+13
inside FOREST C(10 mm) cps, eff=50%
~ 1 event /day
adjustable　(w/o FOREST, active target) x
ELPH Workshop C15, Dec. 2th, 2016.

20. Expected Spectrum Toy MC simulation. - Eγ = 1.1 GeV fix
- 100 day statistics
- Energy straggling in Target ΔE/E << 10-3 %, w.o. energy loss correction
- Multiple Scattering angle is not considered.
- scattering angle was assumed to be 0 degree.
ΔpK/pK = 0.1 %
ΔEγ/Eγ = 1 MeV
ΔpK/pK = 0.6 %
ΔEγ/Eγ = 2 MeV
2-, 1-
3+, 2+
3+, 2+
Q.F.
Q.F.
2-, 1-
ELPH Workshop C15, Dec. 2th, 2016.

21. Coincidence Measurement
Measurement of Decay product of hypernuclei with FOREST
Free:
Λ  Nπ
Hyper nuclei :
Λ  Nπ Mesonic Weak decay
Λ N  NN
ΛNN  NNN
Exp : KEK-E462/E508
Γp/Γn ~ 0.5 (solve the NMWD puzzle)
Measurement of ΛNN  NNN is awaited.
PID (n/p/π), Large acceptance (non-back-to-back event)
Detection with FOREST
( > 10 times statistic)
Non-Mesonic Weak decay
しかしパズルが解決された枠ではなくて、
ELPH Workshop C15, Dec. 2th, 2016.

22. 4He(γ, K+)4ΛH
ELPH Workshop C15, Dec. 2th, 2016.

23. Charge Symmetry breaking
Λ4He
Mean
3H + Λ
3He + Λ
1.09 ± 0.03 MeV
1.04 ± 0.04 MeV
1.114 ± MeV
1.03± 0.02 MeV 1+
0.98± 0.03 MeV 1+
1.09 ± 0.02 MeV
To be measured again.
1.406±0.002
± MeV
Measured by J-PARC
Ref) PRL 114,232501 0+ 0+
2.12 ± 0.01
± 0.04 MeV
Measured by MAINZ
Ref) PRL 114,232501
軽い核では
2.39 ± 0.03 MeV
-He(π0, Ks) 4ΛH
-He(K-, π0)4ΛH
-Hyper fragment
He(γ, K+) 4ΛH
Severe BG
ELPH Workshop C15, Dec. 2th, 2016.

24. 4He (γ, K+) Λ4H reaction He(γ,K+)Λ4He He(γ,K+)Λ4H
1+ state will be enhanced
in the (γ、K+) reaction
10 FOREST Upgrade
K+ tag and γ-ray measurement. ( Ge array? )
 Measurement of NMWD mode (BR ~0.1)
days beam time (dep. BG)
1+ ~270 nb/sr
0+ ~3 nb/sr
おもしろい結果がみえるおのではと考えております。
Ref) Prof. Motoba’s slide (HYP2015)
ELPH Workshop C15, Dec. 2th, 2016.

25. Summary FOREST Upgrade experiment 4π EM calorimeter
+ Forward spectrometer
+ New Tagger System
Hypernuclei spectroscopy via the (γ, K+) reaction.
12C(γ, K+)12ΛB  coincidence measurement (NMWD)
4He (γ, K+)4ΛH  CSB test by measuring γ-ray
ELPH Workshop C15, Dec. 2th, 2016.

26. BackUp
ELPH Workshop C15, Dec. 2th, 2016.

27. Elementary cross section
SAPHIR
CBELSA/TAPS
GRAAL
CLAS
LEPS
N* contribution
dσ/dcosθ ~ 3μb
Ref) PRC73,
ELPH Workshop C15, Dec. 2th, 2016.