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The Next Generation of Hypernucleus and Hyperatom Experiments GSI, 18.10.2000 Josef Pochodzalla Univ. Mainz
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J. Pochodzalla Quark Structure of Hyperons u u d u d d ProtonNeutron s u d s d d s d s s s s 00 ... Nucleons Hyperons
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J. Pochodzalla Present Status of s=-1 Nuclei Until few years ago hypernuclear studies focused on ( +,K + ) or (K -, - reaction New tools e + e - 1020 KK tagging (FINUDA @ DA NE) -spectroscopy with Ge (BNL, KEK, GSI) (e,e’K + )YX(TJNAF, MAMI-c) Topics YN interaction non-mesonic weak decay p pn n nn unique chance to study baryon-baryon weak interaction ! W su du sd dd Weak decays...
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J. Pochodzalla Hypernuclei and Deconfinement Manifestation of the Pauli priciple on the quark ? Quark configuration u d s Baryon configuration p n s p s p 5 He 4 He Question...
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J. Pochodzalla Status of Multi - Hypernuclei Multi-Hypernuclei are a terra incognita......but they exist ! 6 candidates for -hypernuclei are observed 1963: Danysz et al. 10 Be 1966: Prowse 6 He 1991: KEK-E176 10 Be or 13 Be 1991: KEK-E176 3 non-mesonic decays (K -,K + ) HypernucleusB [MeV] B [MeV] He10.9 0.64.7 0.6 Be17.7 0.44.3 0.4 B27.6 0.74.8 0.7 HypernucleusB [MeV] B [MeV] He10.9 0.64.7 0.6 Be17.7 0.44.3 0.4 B27.6 0.74.8 0.7 6 10 13
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J. Pochodzalla -Nuclei as a Laboratory Hyperon-hyperon interaction H -particle R.L. Jaffe (1977) Sakai et al (nucl-th/9912063)... „The situation in a finite nucleus will be that the low-lying states have the character of bound states, but that some of excited states may have strong admixture of the H-nuclear states.“
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J. Pochodzalla hypernuclei by production Electric quadrupole moment of the by hyperfine splitting in -atoms* ) tensor forces between quarks expectation Q = (0 - 3.1) 10 -2 fm 2 E(ℓ=10 ℓ=9) ~ 515 keV E Q ~ few keV for Pb The s=-3 Challange * ) C.J. Batty (1995)... “…The precision measurements of X-rays from Pb atoms will certainly require a future generation of accelerators and probably also of physicists.“ - spin-orbit E ℓs ~ ( Z) 4 ℓm W quadrupole E Q ~ ( Z) 4 Q 33 m 3 spin-orbit E ℓs ~ ( Z) 4 ℓm W quadrupole E Q ~ ( Z) 4 Q 33 m 3 Q = +0.02 fm 2 Q = - 0.02 fm 2
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J. Pochodzalla Production of s=-2 Hypernuclei relativistic HI collisions coalescence of hyperons Bodmer (1971), Rufa et al. (1989), Schaffner et al. (1991)... - capture: - p + 28 MeV (K -,K + ) KEK-PS E373, BNL-E906... pp annihilation at rest K. Kilian (1987), DIANA coll. threshold - - pp K*K* p(K*) = 285 MeV/c K*N K p d {KK } + - pp K*K* p(K*) = 285 MeV/c K*N K p d {KK } + - _ _ _ -- 3 GeV/c 2K 1000 1 _ p _
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J. Pochodzalla - capture -atoms: x-rays conversion - (dss) p(uud) (uds) (uds) Q = 28 MeV Conversion probability......approximatly 5-10%
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J. Pochodzalla + -+ - + -+ - _ 2.6 GeV/c Hyperon Production For example... with L =2·10 32 cm -2 s -1 700 s -1 for a C target
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J. Pochodzalla - Properties - mean life 0.164 ns Consequence... minimize distance production – capture initial momentum 100-500 MeV/c range ~ few g/cm 2
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J. PochodzallaSetup beam: 3 GeV/c, 1mm; no halo (roman pots?) internal gas target e.g. Ne, width 1mm Tracking detector for - 2-3 cm thick diamond strip Si strip capillary fiber p - - readout gas jet
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J. Pochodzalla Capillary Detector Glascapillaries filled with szintillator 20 m - interaction (CHORUS) Problem... fast readout possible solution :Hybrid Phototube + ALICE pixel chip Needs R&D !
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J. Pochodzalla Gamma Spectroscopy Ge box based on VEGA type detectors segmented Clover 7 cm , 14 cm long 4 seg. clover, PH = 0.13 @ 1.33 MeV resolution ~ 0.5 % fast electronics under development beam p - crucial point...
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J. Pochodzalla Count Rate - luminosity 2·10 32 cm -2 s -1 cross section 2 b for pp 700 Hz p(100-500 MeV/c) p 500 0.0005 reconstruction probability 0.5 stopping and capture probability p CAP 0.20 total stopped 3000 / day to conversion probability p 0.05 total hyper nucleus production 4000 / month gamma emission/event, p 0.5 -ray peak efficiency p GE 0.1 total single line rate ~ 5/day „golden events“ ( trigger) ~ 500/day with KK trigger
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J. Pochodzalla 20000 stopped - K - beam, diamond target neutron detector arrays ( --, 12 C) 12 B + n BNL-AGS E885 few tens 2 decays of 4 H K - beam lineCylindrical Detector System 2 decays BNL-AGS E906 Observed captured - per day beam/ targetdevicereactionfacility several hundreds stopped - (K -,K + )emulsion (K -,K + ) KEK-PS E373 vertex detector + spectrometer vertex detector spectrometer, =30 msr device 3000 „golden events“ ~ 300000 KK trigger L =2·10 32, thin target, production vertex decay vertex p p GSI-HESR 200010 6 stopped p per sec p p K * K * K * N K cold anti-protons <70008·10 6 /sec 5 cm 12 C (K -,K + ) JHF statusbeam/ targetreactionexperiment Competition ¯ ¯ ¯ ¯ ¯ ¯
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J. PochodzallaConclusion The anti-proton storage ring HESR @ GSI can provide a unique facility to study strange hyperatoms and hypernuclei. Key points highest luminosity possible moderate beam quality micro tracking device high rate Germanium array Detailed spectroscopic studies of multi-strange systems will be possible. “hyperon laboratory”
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