1 Hypernuclear physics is a good tool to match nuclear and particle physics. The study of this field may help in understanding some crucial questions: four baryon weak interaction vertex; YN and YY strong interactions; change of hyperon and meson properties in the nuclear medium; existence of di-baryon particles; Origin of spin-orbit interaction the role played by the quark degrees of freedom, flavor symmetry and chiral models in nuclear and hypernuclear field. Hypernuclear Hypernuclear & & Strangeness nuclear physics Strangeness nuclear physics The experimental approach The experimental approach
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Hypernuclear physics is a good tool to match nuclear and particle
physics. The study of this field may help in understanding some
crucial questions:
four baryon weak interaction vertex;
YN and YY strong interactions;
change of hyperon and meson properties in the nuclear medium;
existence of di-baryon particles;
Origin of spin-orbit interaction
the role played by the quark degrees of freedom,
flavor symmetry and chiral models in nuclear and hypernuclear field.
HypernuclearHypernuclear Physics:Physics: the experimental approachthe experimental approach
1. Spectroscopy (different types of production hyperfine splittings)
2. Decays3. Γn/Γp puzzle4. The FINUDA experiment5. Σ hypernuclei studies6. Deeply bound kaonic nuclei7. Other topics of interest
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The 3rd roundNew reactions with New Detectors1985 (π+,K+) started at AGS1990 S=-2 searches at AGS and KEK (Emulsion-counter hybrid technique)1993 S=-1 Λ Spectroscopy, Weak decay, SKS spectrometer1998 γ ray spectroscopy (Hyperball)
ΛΛΛΛN potential definition ΓΓΓΓn/ ΓΓΓΓp puzzle in the non-mesonic decays
The 3rd roundNew reactions with New Detectors1985 (π+,K+) started at AGS1990 S=-2 searches at AGS and KEK (Emulsion-counter hybrid technique)1993 S=-1 Λ Spectroscopy, Weak decay, SKS spectrometer1998 γ ray spectroscopy (Hyperball)
ΛΛΛΛN potential definition ΓΓΓΓn/ ΓΓΓΓp puzzle in the non-mesonic decays
The 2nd roundFirst Counter Experiments CERN & BNL1973 Stopped (K−,π−) at CERN1974 in-flight (K−,π−) at CERN PS and BNL AGS
very small spin-orbit splitting
The 2nd roundFirst Counter Experiments CERN & BNL1973 Stopped (K−,π−) at CERN1974 in-flight (K−,π−) at CERN PS and BNL AGS
very small spin-orbit splitting
The 1st round 1953 Discovery of Λ hypernucleiEmulsion detectors --- CERN PS, BNL AGS K− beam
ΛΛΛΛ potential depth about 1/2
The 1st round 1953 Discovery of Λ hypernucleiEmulsion detectors --- CERN PS, BNL AGS K− beam
ΛΛΛΛ potential depth about 1/2
50 years of 50 years of HypernuclearHypernuclear PhysicsPhysics
real and virtual photoproductionσ ≈ 0.1 µb; Ibeam=1012 s-1
Jlab-HSSN(E89-009)Jlab-HSSN(E89-009)
A novel technique, an experimental challenge• very low cross sections• more particles to be measured in the final state• very high beam intensities• very high beam quality ∆p/p≈10-5
• possible achievable resolution 350 keV FWHM• generates non-natural parity and charge symmetric
hypernuclei• difficult mesurement of hypernuclear decay
A novel technique, an experimental challenge• very low cross sections• more particles to be measured in the final state• very high beam intensities• very high beam quality ∆p/p≈10-5
• possible achievable resolution 350 keV FWHM• generates non-natural parity and charge symmetric
hypernuclei• difficult mesurement of hypernuclear decay
900 keV resolutiondemonstrated
900 keV resolutiondemonstrated
present best resolution with othertechniques: 1.5 - 2.0 MeV
present best resolution with othertechniques: 1.5 - 2.0 MeV
3. The (γ,K + ) Reaction
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Hypernuclear Spectroscopy
Most of the info about the YN potential (and medium effects, etc…) comes from the knowledge of hypernuclei structure.
Momentum (energy) resolution is the crucial parameter in order to see (distinguish) different hypn. states.
• For details, seeH. Tamura et al., PRL84(2000)5963K. Tanida et al., PRL86(2001)1982
Li7Λ
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KEK-PS E419(3) -- discussion
• Eγ(M1) = 692 keV gives strength of ΛN spin-spin force- 6Li(1+) state has pure 3S1 (α+d) structure ∆ = 0.48 ~ 0.50 MeV
(D. J. Millener, NPA691(2001)93c,H. Tamura et al., PRL84(2000)5963)
• B(E2) is related to hypernuclear size or cluster distance between αααα and d as B(E2) ∴ <r2>2
(T. Motoba et al., PTP70(1983)189)• Without shrinkage effect, B(E2) is expected to be
8.6±0.7 e2fm4 from B(E2) data of 6Li.• Present result (3.6±0.7 e2fm4) is significantly smaller strong evidence for gluestrong evidence for glue--like rolelike role
• (3.6/8.6)1/4 = 0.81±0.04 shrinkage of 19±±±±4%(K. Tanida et al., PRL86(2001)1982)
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BNL-AGS E930(1)
• Experiment performed at BNL (New York, USA) • Measured γ ray from created by 9Be(K−,π−) reactionBe9
• Two peaks separated!• |∆E| = 31±3 keV - very small indeed surprisingly small spinsurprisingly small spin--orbit forceorbit force (~ 1/100 of NN case)