Future gamma-ray spectroscopic

experiment (J-PARC E63) on 4ΛH

2018/6/26

T. O. YamamotoKEK IPNS (Japan)

for the E63 collaboration

Contents

➢ CSB in s-shell hypernuclear system

studied via γ-ray spectroscopy

• γ-ray spectroscopy on 4ΛHe (J-PARC E13)

➢ Next step: γ-ray spectroscopy on 4ΛH (J-PARC E63)

• Previous studies on 4ΛH

• Strategy of new measurement

• Present status

➢ Idea of future experiment

γ-ray spectroscopy of p-shell mirror hypernuclei 12ΛB

Summary

CSB effect in s-shell hypernuclear structure

+p n

nH4

+p p

nHe4

p ≠ n ?

Level schema of mirror hypernuclei 4H / 4He (before 2014)

B(0+)：emulsion technique

Ex(1+)： γ-ray spectroscopy (NaI)

DB (0+) = 0.35 MeVDB (1+) = 0.28 MeV

Un expectedly large BΛ difference

( 0.07 MeV in theoretical study with NSC interaction model )

→ Need to examine old data with modern technique

Recent experiment for s-shell

Level schema of mirror hypernuclei 4H / 4He (before 2014)

B(4H(0+)), 2015 (MAMI-A1)

A. Esser, S. Nagao et al.,Phys. Rev. Lett. 114, 232501 (2015)

A1 collaboration., NPA 954 (2016) 149

2.157 0.077 MeV(chance to reduce systematic errors)

Precise measurementEmulsion → Decay − spectroscopy

The result supportsexistence of CSB effect in BΛ(g.s.)

Recent experiment for s-shell

Level schema of mirror hypernuclei 4H / 4He Updated

J-PARC E13

CSB effect also in excitation energy

M. Bedjidian et al.,Phys. Lett. B 83, 252 (1979).

In flight (K-,π-) reaction w/ SKS

+ Ge detector

1.406 0.004 MeV

T. O. Yamamoto et al., Phys. Rev. Lett.115, 222501 (2015)

Recent experiment for s-shell

Level schema of mirror hypernuclei 4H / 4He Updated

• Existence of CSB effect was confirmed ( BΛ(g.s) and γ-ray )

• Strongly spin-dependent : DB(1+) = 0.03 0.05 MeV

DB(0+) = 0.35 0.05 MeV

Recent experiment for s-shell

Level schema of mirror hypernuclei 4H / 4He Updated

Need high accurate data

to investigate origin of CSB

and underlying ΛN interaction

Precise γ-ray spectroscopyis powerful toolto study CSB

• Existence of CSB effect was confirmed ( BΛ(g.s) and γ-ray )

• Strongly spin-dependent : DB(1+) = 0.03 0.05 MeV

DB(0+) = 0.35 0.05 MeV

We will continuemeasurement using Ge detector

Future measurement

Gamma-ray spectroscopy on 4ΛH

(J-PARC E63)

Gamma-ray data on 4ΛH

Level schema of mirror hypernuclei 4H / 4He

We obtainedhigh precision data（J-PARC E13）

rather large deviation

Three old dataare available

[1][2][3]

[1] [2] [3] Expected

Exci

tati

on

en

ergy

[M

eV]

Gamma-ray data on 4ΛH

Level schema of mirror hypernuclei 4H / 4He

We obtainedhigh precision data（J-PARC E13）

rather large deviation

Three old dataare available

[1][2][3]

[1] [2] [3] Expected

Exci

tati

on

en

ergy

[M

eV]

M. Bedjidian et al.

Phys. Lett. B 62, 467 (1976).M. Bedjidian et al.

Phys. Lett. B 83,

252 (1979).

A. Kawachi, Doctoral thesis

Univ. of Tokyo (1997) 150 ~ 200 keV(FWHM) resolutiondue to detector resolutionand Doppler broadening

Limitation on old measurement

All γ-ray measurementson 4ΛH used• Stopped K-

• NaI detector

For higher precision• Stopped K- → in-flight (K −,π−)

• NaI detector → Ge detector

Same strategy as 4He measurement

Expected resolution : ~40 keV(FWHM)

1.1 MeV

M.May, PRL 51(1983)2085

Previous study via in-flight 7Li(K-,-) @ 0.9 GeV/c

Highly unbound

Bound region

1.4 MeV7Li target

γ-ray

4H (and 4He) generates as hyperfragment

via the in-flight 7Li(K-,-)7ΛLi reaction

7Li

NaI detector energy resolution :

74 keV(FWHM)

+ ~80keV Doppler broadening

They reported 1.108 ± 0.010 MeV peakas “mixture of 4H and 4He”

Moby DickBNL AGS

1.1 MeV

M.May, PRL 51(1983)2085

Previous study via in-flight 7Li(K-,-) @ 0.9 GeV/c

Highly unbound

Bound region

1.4 MeV7Li target

γ-ray

4H (and 4He) generates as hyperfragment

via the in-flight 7Li(K-,-)7ΛLi reaction

7Li

NaI detector energy resolution :

74 keV(FWHM)

+ ~80keV Doppler broadening

They reported 1.108 ± 0.010 MeV peakas “mixture of 4H and 4He”

J-PARC E13 → 1.4 MeV

Moby DickBNL AGS

1.1 MeV

M.May, PRL 51(1983)2085

Previous study via in-flight 7Li(K-,-) @ 0.9 GeV/c

Highly unbound

Bound region

1.4 MeV7Li target

γ-ray

They considered 1.1 MeV peakas 4H + 4He mixture(now we know this is not the case → only 4H)

7Li

We chose this reaction for 4H measurement

K- + 4He + 3H -> Λ + 3He + π- + 3H

[direct] 4He(K-,π-)4He (0+ only, non-spin-flip)

[two step] Λ + 3H -> 4H (Both 0+,1+, ratio =1:3 expected)

7Li

4H (and 4He) generates as hyperfragment

via the in-flight 7Li(K-,-)7ΛLi reaction

BNL AGSMoby Dick

γ-ray spectroscopy of 4H (J-PARC E63)

4H generates as hyperfragment

via the in-flight 7Li(K-,-)7ΛLi reaction

7Li target

SKS spectrometer

beam line

spectrometer

γ-ray

Similar setup as 4ΛHe measurement

larger acceptance (~100msr)+ good energy resolution

Ge detector array

(Hyperball-J)

We can select threshold regionof 7

ΛLi* → 4ΛH + 3He [Ex=~20MeV]

(Suppress Doppler broadening)

Good energy resolution

~40 keV (FWHM)

γ-ray spectroscopy of 4H (J-PARC E63)

4H generates as hyperfragment

via the in-flight 7Li(K-,-)7ΛLi reaction

7Li target

SKS spectrometer

beam line

spectrometer

Range counter

(additional)

Ge detector array

(Hyperball-J)

γ-ray

Similar setup as 4ΛHe measurement

Tagging monochromatic π−

(Support hypernuclear identification)

stop

Experimental setup for 4H (J-PARC E63)

SKS spectrometer

SKS magnet

Exp. Target

Ge detector array

Hyperball-JRange counter

(additional)

Beam line

spectrometer

J-PARC K1.1

beamline

New detector configuration

around target

(view from beam upstream)

Rangecountersystem

Ge

Ge Ge

GeGe

Ge

Exp. Target

Ex(1+) will be measured with

<5 keV accuracy (w/6 days beam time)

Thickness:~0.5 cm thick

Layers: >15 layers

Coverage:30W x 10H cm

Share withother experiment?(weak decay, etc. )

J-PARC

E63 (E13-2)

Submitted in 2015

stage-2 approval

31 participants from 12 institutes

• 4H excitation energy

• 7Li lifetime(Λ magnetic momentin nuclear medium)

Byproduct:

γ-ray measurement of 3H Idea from M. Ukai

If nnΛ is bound,3

ΛH (1/2+, T=1) may be bound

Reportfrom GSI

Chance to measure γ-rays(iso-spin conversion)

Byproduct:

γ-ray measurement of 3H Idea from M. Ukai

3H+a

～12

7Li

3H

(K-,π-)

pn→p substitutional

1/2+;T=1

1/2+;T=0

1/2+;T=0

1/2+;T=1

3/2+;T=0

3/2−;T=1

～8

19.3

3/2−;T=0

a emission

3/2+;T=0

4H

1+;T=00+;T=0

3.88

0.69

Eex (MeV)

4H+3He

}4He + −

3He + −

Selecting Ex>20 MeV

Selecting Ex=~10 MeV

Tag 40 MeV pionby range counter

Chance for high statistic(need for 7ΛLi lifetime measurement)

6Li+5He+d

Possible background

Preparation status

0.9 GeV/c K- beam for suppress Doppler broadeningand higher cross section→ move to J-PARC K1.1 beam line with SKS magnet

K1.8

K1.1

K1.8BR

KL

High-p

J-PARC hadron experimental facility

30 GeVproton

Productiontarget(Au)

K1.1 beam line(need construction)

SKS moved to K1.1

Hyperball-J: EstablishedRange counter: Designing

(will be constructed in next year)

Idea of new measurement

Gamma-ray spectroscopy

to study CSB effect in p-shell hypernuclei

Reaction for γ-ray spectroscopy

on mirror hypernuclei

12C 𝜋−, 𝐾0 12

ΛB* → 12ΛB + γ

12C 𝐾−, π0 12

ΛB* → 12ΛB + γ

12C 𝑒, 𝑒′𝐾+ 12

ΛB* → 12ΛB + γ

12C 𝜋+, 𝐾

+ 12ΛC* → 12

ΛC + γ

Non-charge exchange reaction

Charge exchange reaction

π0 →γγ

𝐾0𝑠 →π+π- (69%)

Need to extend gamma-ray datato neutron rich side

Reaction for γ-ray spectroscopy

on mirror hypernuclei

12C 𝜋−, 𝐾0 12

ΛB* → 12ΛB + γ

12C 𝐾−, π0 12

ΛB* → 12ΛB + γ

12C 𝑒, 𝑒′𝐾+ 12

ΛB* → 12ΛB + γ

12C 𝜋+, 𝐾

+ 12ΛC* → 12

ΛC + γ

Non-charge exchange reaction

Charge exchange reaction

π0 →γγ

𝐾0𝑠 →π+π- (69%)

Need to extend gamma-ray datato neutron rich side

Rather easier !• Reaction tag

with only charged particles• Reasonable beam intensity

(for Ge detectors)

Prof. Alessandro’s talk on Friday

Same setup with 4ΛH measurement

• Beam line spectrometer + SKS

• Hyperball-J

• Range counter (similar configuration)

SKS spectrometer

SKS magnet

Exp. target

J-PARC K1.1

beamline

Setup for the gamma-ray spectroscopy

π-

π+

Beam momentum : 1.05 GeV/c

π− beam

Target

SKS magnet

Range counter

π+(high momentum)

π−(low momentum)

Idea fromMichelangelo Agnello et al.J-PARC LOI (2016)

Designing of detector systemis ongoing

12C 𝜋−, 𝐾0 12

ΛB* → 12ΛB + γ

𝐾0𝑠 →π+π- (69%)

Beam line

spectrometer

Ge detector array

Hyperball-J

Summary

➢ CSB in s-shell hypernuclear system

studied via γ-ray spectroscopy

• γ-ray spectroscopy on 4ΛHe (J-PARC E13)

Ex(4

ΛHe(1+)) = 1.406±0.004 MeV

CSB effect also appear in excitation energy + spin-dependence

➢ Next step: γ-ray spectroscopy on 4ΛH (J-PARC E63)

• In-flight 7Li(K−,π−) reaction + Ge detector

• Common setup as 4ΛHe measurement + range counter system

• Better than 5 keV accuracy w/ 6 days beamtime

(stage-2 approval)

➢ idea of γ-ray spectroscopy to study CSB in p-shell

Backup

Toward the exp. completeness for s-shell

Gamma-ray spectroscopy

of 4He [J-PARC E13]

Done

Decay - spectroscopy

( 4H ) [MAMI-C]

Done

Gamma-ray spectroscopy

of 4H w/ a few keV accuracy

Our Next stepJ-PARC E63

Counter experiment

( 4He ) [ J-PARAC HIHR ]

Need J-PARC HEF extension

Present status of CSB in s-shell

A. Gal, Phys. Lett. B 744,352 (2015).

CSB effect calc. w/ ΛΣ mixing

Exp.

(old)

Exp.

(new)

Calc.

Nogga

Calc.

Gal

Calc.

Gazda

DB(1+) 0.28(5) 0.03(5) -0.01 0.03 -0.19

DB(0+) 0.35(5) 0.35(5) 0.07 0.22 0.14

(unit : MeV)A. Nogga et al., Phys. Rev. Lett. 88,172501 (2002).

N-N coupling may be key of CSB effect

Widely acceptedNSC97e interaction model

simple potential

High accurate data of CSB effect may provide new information

to investigate underlying ΛN interaction

D. Gazda, A. Gal, NPA 954 (2016) 161

Chiral EFT model

• Existence of CSB effect was confirmed ( BΛ(g.s) and γ-ray )

• Difference in 0+ and 1+ : DB(1+) = 0.03 0.05 MeV

DB(0+) = 0.35 0.05 MeVStrongly spin-dependent

Yield estimation of 4H

BNL exp E63

Total K- 10 G Kaon 5 G Kaon

Target thickness 8 g/cm2 15 g/cm2

− spectrometer Moby-dick

(18 msr)

SKS

(35 msr < 6°)

1+→0+ g yield 150 300

g-ray Efficiency 6% 3% (x 0.8

live)

4H(1+) yield 12,500

4H(0+) yield

Direct + g-feeding

16,200

Plastic scintillator Total 7.6cm thickness

(A) MWPC (B) Timing scintillator

(C) Range counter

(D) Veto counter

Range counter Total E resolution~ 15%(FWHM) @50 MeV

(a)3H→

3He+−

(b)4H→

4He+−

(c)5He

→ − + other

(d)6Li+→p +−

(in-flight)

Optimum missing mass gate of 7LiCertain states will be enhanced.

Range counter system for hypernuclear - decay in BNL

Decay counter configuration for lifetime measurement

Lifetimes of 3H, 4H can be measured

PhysRevC.43.849

Existing data on BΛ

Experiment with (e,e’K+) reaction (JLAB)-> A=7, 10 hypernuclei (~100 keV accuracy)

T. Gogami et al.: Phys. Rev. C 94 (2016) 021302.T. Gogami et al.: Phys. Rev. C 93 (2016) 034314.

Theoretical study: 10~100 keV CSB effect in p-shell A. Gal, Phys. Lett. B 744,352 (2015).

CSB data in p-shell hypernuclei

Difficulty: Need accurate data in both mirror pair

Lower half of Hyperball-J

PWO counterGe detector

Pulse-tube cooler

Target

Hyperball-J new Ge detector array

Features

Large photo-peak efficiency

→ ε ~6 % @1 MeV with 32 Ge detectors

Fast readout system

Low temp. Ge detector

for radiation hardness

→ Mechanical cooling

Fast background suppressor

→ PWO counter

Developed Ge detector

for h

igh in

tensity

had

ron

be

am