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  • Future gamma-ray spectroscopic

    experiment (J-PARC E63) on 4ΛH

    2018/6/26

    T. O. Yamamoto KEK 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

    n H4

    +p p

    n He4

    p ≠ n ?

    Level schema of mirror hypernuclei 4 H /

    4 He (before 2014)

    B(0 +):emulsion technique

    Ex(1 +): γ-ray spectroscopy (NaI)

    DB (0 +) = 0.35 MeV

    DB (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 4 H /

    4 He (before 2014)

    B( 4 H(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 measurement Emulsion → Decay − spectroscopy

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

  • Recent experiment for s-shell

    Level schema of mirror hypernuclei 4 H /

    4 He 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 4 H /

    4 He 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 4 H /

    4 He Updated

    Need high accurate data

    to investigate origin of CSB

    and underlying ΛN interaction

    Precise γ-ray spectroscopy is powerful tool to 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 continue measurement using Ge detector

  • Future measurement

    Gamma-ray spectroscopy on 4ΛH

    (J-PARC E63)

  • Gamma-ray data on 4ΛH

    Level schema of mirror hypernuclei 4H / 4 He

    We obtained high precision data (J-PARC E13)

    rather large deviation

    Three old data are available

    [1] [2] [3]

    [1] [2] [3] Expected

    Ex ci

    ta ti

    o n

    e n

    er gy

    [ M

    eV ]

  • Gamma-ray data on 4ΛH

    Level schema of mirror hypernuclei 4H / 4 He

    We obtained high precision data (J-PARC E13)

    rather large deviation

    Three old data are available

    [1] [2] [3]

    [1] [2] [3] Expected

    Ex ci

    ta ti

    o n

    e n

    er gy

    [ 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) resolution due to detector resolution and Doppler broadening

    Limitation on old measurement

    All γ-ray measurements on 4ΛH used • Stopped K-

    • NaI detector

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

    Same strategy as 4He 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 MeV 7Li target

    γ-ray

    4 H (and

    4 He) generates as hyperfragment

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

    7 LiNaI detector energy resolution :

    74 keV(FWHM)

    + ~80keV Doppler broadening

    They reported 1.108 ± 0.010 MeV peak as “mixture of 4H and

    4 He”

    Moby Dick BNL 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 MeV 7Li target

    γ-ray

    4 H (and

    4 He) generates as hyperfragment

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

    7 LiNaI detector energy resolution :

    74 keV(FWHM)

    + ~80keV Doppler broadening

    They reported 1.108 ± 0.010 MeV peak as “mixture of 4H and

    4 He”

    J-PARC E13 → 1.4 MeV

    Moby Dick BNL 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 MeV 7Li target

    γ-ray

    They considered 1.1 MeV peak as 4H +

    4 He mixture

    (now we know this is not the case → only 4H)

    7 Li

    We chose this reaction for 4H measurement

    K- + 4He + 3H -> Λ + 3He + π- + 3H

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

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

    7Li

    4 H (and

    4 He) generates as hyperfragment

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

    BNL AGS Moby Dick

  • γ-ray spectroscopy of 4H (J-PARC E63)

    4 H 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 region of 7ΛLi* →

    4 ΛH +

    3He [Ex=~20MeV] (Suppress Doppler broadening)

    Good energy resolution

    ~40 keV (FWHM)

  • γ-ray spectroscopy of 4H (J-PARC E63)

    4 H 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 4H (J-PARC E63)

    SKS spectrometer

    SKS magnet

    Exp. Target

    Ge detector array

    Hyperball-J Range counter

    (additional)

    Beam line

    spectrometer

    J-PARC K1.1

    beamline

    New detector configuration

    around target

    (view from beam upstream)

    Range counter system

    Ge

    Ge Ge

    GeGe

    Ge

    Exp. Target

    Ex(1 +) will be measured with

    15 layers

    Coverage: 30W x 10H cm

    Share with other experiment? (weak decay, etc. )

  • J-PARC

    E63 (E13-2)

    Submitted in 2015

    stage-2 approval

    31 participants from 12 institutes

    • 4H excitation energy • 7Li lifetime

    (Λ magnetic moment in nuclear medium)

  • Byproduct:

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

    If nnΛ is bound, 3

    ΛH (1/2 +, T=1) may be bound

    Report from GSI

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

  • Byproduct:

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

    3 H+a

    ~12

    7 Li

    3 H

    (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

    4 H

    1+;T=0 0+;T=0

    3.88

    0.69

    Eex (MeV)

    4 H+

    3He

    } 4He + −

    3He + −

    Selecting Ex>20 MeV

    Selecting Ex=~10 MeV

    Tag 40 MeV pion by range counter

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

    6Li+ 5 He+d

    Possible background

  • Preparation status

    0.9 GeV/c K- beam for suppress Doppler broadening and 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 GeV proton

    Production target (Au)

    K1.1 beam line (need construction)

    SKS moved to K1.1

    Hyperball-J: Established Range counter: Designing

    (will be constructed in next year)

  • Idea of new measurement

    Gamma-ray spectroscopy

    to study CSB eff