The Strange Baryon-Baryon Interaction J urgen Schaffner-Bielich - PowerPoint PPT Presentation

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter The Strange Baryon-Baryon Interaction J¨ urgen Schaffner-Bielich Institut f¨ ur Theoretische Physik Chiral Group Meeting Frankfurt, June 6, 2016 HGS-HIRe Helmholtz Graduate School for Hadron and Ion Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Content Hyperon-Nucleon Interaction: Hypernuclei 1 Baryon-Baryon Interactions: Dibaryons 2 Finding Strange Matter 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Content Hyperon-Nucleon Interaction: Hypernuclei 1 Baryon-Baryon Interactions: Dibaryons 2 Finding Strange Matter 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Baryon octet and decuplet eightfold way: baryons have three quarks lowest multiplets: octet (spin 1/2) and decuplet (spin 3/2) baryon mass increases with number of strange quarks (strangeness) nucleon (no s-quark): m N = 940 MeV → nuclear chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Baryon masses hyperons with one s-quark: m Λ = 1116 MeV, m Σ + = 1189 MeV, m Σ 0 = 1193 MeV, m Σ − = 1197 MeV hyperons with two s-quarks: m Ξ 0 = 1314 MeV, m Ξ − = 1321 MeV hyperon with three s-quarks: m Ω − = 1672 MeV (spin 3/2, Pauli principle!) bound system with nucleons and hyperons: hypernuclei! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter First hypernuclear event first hypernuclear measurement: 1953 by Danysz and Pniewski from cosmic ray emulsion event unique double-star feature on emulsion plate: one from hypernuclear production, one from hypernuclear decay! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Danysz and Pniewski Polish postcard commemorating Danysz and Pniewski (check out the stamp!) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Hypernuclear production mechanism hypernuclei produced by incoming K − beam nucleon transformed to a hyperon: K − + n → Λ + π − measurement by outgoing π − prominent feature: recoilless production, Λ is produced at rest inside nucleus! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Light hypernuclei Light�Hypernuclei�(Restricted�fit) Binding�Energy�(MeV) -4 Exp. -6 RMF -8 -10 -12 -14 6 8 10 12 14 16 Atomic�Mass�A emulsion data up to mass number A = 15 good measurement of Λ binding energies increases linearly with mass number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Hypernuclear spectra and levels peak structure in pion spectra related to single-particle levels of hypernucleus! first surprise: tiny spin-orbit splitting for 16 Λ O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Nuclear and hypernuclear levels in 17 Λ O hyperon potential (dotted) is shallower than nucleon potential (solid line) Coulomb potential: dot-dashed line spin-orbit splitting for hyperons is much smaller than for nucleons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Heavy hypernucleus 89 Λ Y (Hotchi et al., PRC 61 (2001) 044302) modern spectroscopy of hypernuclei via reaction: π + + n → Λ + K + several hypernuclei measured up to 208 Λ Pb, measured shells: s, p, d, f, g and h! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Λ Single–Particle Energies 30 Λ Single Particle States (pi,K) 208 (e,e’K) 139 Emulsion Binding Energy (MeV) 89 (K,pi) 51 4032 20 28 s Λ 16 131211 10 10 d Λ 8 7 f Λ p Λ g Λ 0 0 0.05 0.1 0.15 0.2 0.25 A − 2 / 3 (Gal, Hungerford, Millener 2016) measured with pion, kaon or electron beams or in emulsion spin–orbit splitting smaller than experimental resolution fit to single particle energies: U Λ = − 27 MeV for A → ∞ note: only for the Λ (besides nuclei) do we know its in-medium . . . . . . . . . . . . . . . . . . . . properties! . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Hypernuclear chart (Bando 1990) many light hypernuclei observed in emulsion experiments (up to A=15) heavier systems measured spectroscopically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter HypHI program at GSI (Take Saito et al.) exploration of the whole hypernuclear chart for light systems! determination of the hypernuclear drip-line note: hyperons stabilize nuclei, 8 Be is unbound, but 9 Λ Be is bound! evidence for 6 Λ H by the FINUDA collaboration (2012)! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Hyperon decays Hyperons decay mainly by weak interactions: conserves baryon number and charge but changes strangeness by one unit n + π 0 ( 36 %) Λ → p + π − ( 64 %) , Σ + → p + π 0 ( 52 %) , n + π + ( 48 %) Σ 0 → Λ + γ (electromagnetic) Σ − → n + π − Ξ 0 → Λ + π 0 Ξ − → Λ + π − typical lifetime: τ ≈ 10 − 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Hypernuclear decays (Park et al., PRC61 (2000) 054004) Hyperons in the medium can also decay non-mesonically: Λ + N → N + N , Σ + N → N + N Ξ + N → Σ + N or Λ + N , Λ + Λ → Σ + N or Λ + N . . . nonmesonic decay dominates already for moderate mass number! . . . . . . . . . . . . . . . . . . . . hypernuclear lifetime saturates around 200 ps . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Sigma-atomic states Σ − bound mainly by Coulomb forces to a nucleus slight shift of energy levels due to strong interactions Σ -potential is attractive at low densities but repulsive inside the nucleus → no bound Σ -hypernuclear states (Mares, Friedmann, Gal, Jennings 1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Sigma hypernuclei (Bart et al., PRL 83 (1999) 5238) older data: peaks in Σ -hypernuclear spectra, bound states? recent data: no peaks, strongly repulsive Σ -potential needed to explain spectrum! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hyperon-Nucleon Interaction: Hypernuclei Baryon-Baryon Interactions: Dibaryons Finding Strange Matter Sigma hypernuclear potential indirect measurement of Σ -nucleon potential by ( π − , K + ) reaction on 28 Si: U Σ ≈ + 30 MeV depends also on imaginary part of the potential (absorption) combining with Σ -atomic data: need density dependent potential (attractive at low densities, repulsive in the nuclear core) (Harada and Hirabayashi 2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .