Strangeness in Nucleus

Transcription

1 Strangeness in Nucleus L. Fabbietti! Technische Universitaet Muenchen Excellence Cluster Origin and Structure of the Universe Utrecht University WS O. Arnold, Jia-Chii Berger-Chen, T. Gaitanos, K. Lapidus, J. Weil! K s in p+a reactions: detailed studies of the production and interaction Λ-p femtoscopy in p+a collisions: a new method to test the Hyperon-Nucleon interactions

2 Strange Effective Hadron-Hadron Interaction Confinement Small Q (~1 GeV) Large Distances (1 fm) Effective Field Theory of interacting Hadrons Test-bed of the strong interaction in few body systems Strange quarks are intermediate between light and heavy -> Interplay between spontaneous and explicit chiral symmetry breaking in low energy QCD. Testing ground: K-N and K-N interactions

3 Hyperon Star Neutron J. Haidenbauer, S. Petschauer et al., Nucl. Phys. A 915 (213) 24 Λ attraction LO phase shift Possible Processes: n + n! n + p + e! + e n + n! p + n + e! + e hypernuclei NLO neutron star matter phenomenological potential repulsion Λ-p distance It all depends upon the Λ-N and Λ-ΝΝ interaction and whether or not it has a repulsive core This repulsive core could stiffen again the EOS allowing for heavy neutron stars

4 Reactions in the GeV Energy Range Fixed Target experiments, E kin ~ AGeV proton-proton π-proton proton-nucleus π-nucleus Heavy-ion Collisions ρ B <2-3 ρ HADES High Acceptance Di-Electron Spectrometer Fixed Target Experiment SIS18, Ekin=1-3 GeV/nucl Full azimuthal coverage, 18 o -85 o in polar angle δp/p ~ 1-3 % Vienna University of Technology Vacuum ρ B ~ρ T~ 8-1 MeV

5 Kaons in the Nucleus p+nb, GeV K K K + K π * K K Kaon interactions in nuclear medium: Elastic scattering Charge Exchange Inelastic reactions π-induced secondary reactions

6 K S Detection in p-induced reactions Associate K production in p+p collisions at GeV: the role of the Δ(1232)++, G. Agakishiev et al. (HADES Coll.) Phys. Rev C9 (214) 1522 Medium effects in proton-induced K production G. Agakishiev et al. (HADES Coll.) Phys. Rev. C9 (214) 5496 J.-C. Chen, K. Lapidus K π + π vacuum ρ B = p+p at GeV in-medium ρ B ρ p+nb at GeV Data are interpreted with the GiBUU transport model O. Buss et al., Phys. Rept. 512, 1 (212)

7 K in p+p: reference measurement Tsushima Tsushima improved G. Agakishiev et al. (HADES Coll.) Phys. Rev C9 (214) 1522 J.-C. Chen, K. Lapidus p+p 4-body states produced via Δ-resonances Final states with two pions (5-body) added to the model via NN Δ ++ Y* K, Y* is Σ(1385) or Λ(145). Good description of the elementary reference.

8 ! In-medium kaon potential ChPT potential, ~35 MeV (ρ=ρ, k=) m K = V µ = E = s m 2 K 3 8f 2 j µ KN = 25 KN f 2 q k 2 + m 2 K + V k = k s + V µ V µ V 45 MeV f = 93 MeV, f 2 =.6f 2 T. Gaitanos, K. Lapidus For nuclear matter at rest <V 1,2,3 > = k* = k U = p k 2 + m 2 + V p k2 + m 2 vac., m <m

9 Effect of the potential in p+nb: pt-y GiBUU w/o pot. GiBUU w. pot. G. Agakishiev et al. (HADES Coll.) Phys. Rev. C9 (214) 5496 K. Lapidus p+nb Systematical modification of p t -spectra owe to the repulsive potential. Uncertainties in the model parameters (np cross sections, ).

10 G. Agakishiev et al. (HADES Coll.) Phys. Rev. C9 (214) 5496 χ 2 Analysis Set K. Lapidus Meaning χ 2 /NDF pot OFF 1 standard 2 ΔN +25% 3 ΔN -25% 4 πn +25% Parameter set pot ON 5 πn -25% 6 np3 +25% 7 np3-25% 8 KN +25% 9 KN -25% 1 np3 +3% & 5b -3%

11 G. Agakishiev et al. (HADES Coll.) Phys. Rev. C9 (214) 5496 χ 2 Analysis Set K. Lapidus Meaning χ 2 /NDF Parameter set U = 25 MeV U = 35 MeV U = 45 MeV 1 standard 2 ΔN +25% 3 ΔN -25% 4 πn +25% 5 πn -25% 6 np3 +25% 7 np3-25% Potential strength is adjusted by changing: 3 V µ = 8f U = p 2 j µ p k 2 + m 2 + V k2 + m 2 vac., m <m 8 KN +25% 9 KN -25% 1 np3 +3% & 5b -3%

12 All the results System (energy) Experiment Kaon potential at ρ p= π+a (2 GeV) FOPI 2 ± 5 p+a (2.3 GeV) ANKE U = 25 MeV 2 ± 5 U = 35 MeV Ar+KCl (1.76 GeV) HADES 1) U = 45 MeV 39 p+nb ( GeV) HADES 2) 4 ± 5 FOPI: M. Benabderrahmane et al., Phys. Rev. Lett. 12 (29) HADES: 1) G. Agakishiev et al., Phys. Rev. C 82 (21) 4497; 2) Phys. Rev. C9 (214) 5496.

13 Hyp-N: Experimental Evidence I Λ- or Σ- Hypernuclei Λ-Nucleon Potential Σ-Nucleon Potential? U~ -3 MeV (attractive) from Hypernuclei No idea yet about the momentum and density dependence No Idea at all

14 Hyp-N: Experimental Evidence II Λ p Λ-p Σ-p scattering Λ and Σ beams from K-+p collisions seen by Bubble chambers Cross-section -> scattering length -> Interacting Potential J. Haidenbauer, S. Petschauer et al., Nucl. Phys. A 915 (213) 24 Λp -> Λp Σ + p -> Σ + p 3 25 Sechi-Zorn et al. Kadyk et al. Alexander et al. 2 Eisele et al. 2 σ (mb) σ (mb) p lab (MeV/c) p lab (MeV/c) Scarce Data and all above 15 MeV/c

15 The Femtoscopy Method Distinguishable and Undistinguishable pairs of particles emitted from a common source Correlation function is a measure of the source size and also of the particle interaction Theoretical Function Experimental Observable p-p-, π-π Correlations in Ar+KCl at 1.75 AGeV Hades, EPJA 47, 63 (211) Λ-p Correlations in Ar+KCl at 1.75 AGeV Hades, [PRC 82, 2191 (21)].

16 Femtoscopy in p+a reactions (GeV) p+nb, GeV Interaction kinematic freeze-our surface Can be determined for p-p and Λp pairs via Transport Calculation (UrQMD) -> The Source is hence known and the measured correlation provides the interaction strength.

17 Calibration on the p-p Correlation pp Pairs: Coulomb Interaction Strong Interaction Quantum Statistics for Fermions O. Arnold Koonin Fit Function -> Extraction of the Source Radius R G S. E. Koonin, Phys. Le. B 7 (1977) 43 S. Pra et al., Nucl. Phys. A 566 (1994) 13c C(k) = Z dr 3 r 2 2 rel(r, k)exp 4R 2 G φ rel from S.G. with Coulomb and Strong interaction Preliminary p-p Strong Pot.

18 Source Determination via UrQMD Proton-Proton pairs: Lambda-Proton pairs: p-p Pairs Λ-p Pairs Pair Separation in the Pair-CM system Λ-p source: 1.24 times smaller than p-p source (from UrQMD)

19 Experimental Distribution Λp Scattering Length Fit Function O. Arnold Preliminary First Fit of the correlation delivers parameters in perfect agreement with scattering data!!!! Further Improvements: Source-Radius Determination, Improved S/B Ratio, Fit for S= and S=1 components.

20 Test-Bed for Lattice Calculations Comparison with the measured correlations After-Burner which includes the relevant Interactions Simulation of the particle Production and FreezeOut coordinates Constrain the Hyperon - Nucleon Interactions from Lattice QCD potential mπ = 47 MeV same as NN same as NN V VV u,d,s=.1384 u,d,s=.1384 u,d,s= VVC C 5 5 VC -5-5 u,d,s=.1384 u,d,s= !#$*"!#$" V!#$*" V V VVCC VVV CT T VT =.1384 u,d,s =.1384 u,d,s u,d,s= !#$"!#a" VV!#$" V =.1384 u,d,s =.1384 u,d,s u,d,s=.1384 u,d,s= ! Mainly a matter of statistics VVCC VV VTCT VT T. Inoue et al. (HAL QCD) 1: attractive instead of repulsive 1: attractive PTP 124 (21) 591instead core! attraction only.of repulsive core! attraction only. Nucl. Phys. 3 3 A881!#a" (212) 1 28 VC Hyperon-Nucleon Correlation Hyperon-Nucleon-Nucleon Correlation?? :1 repulsive attractive core. instead of repulsive repulsion only. same core. as NNrepulsion only. 18s: strong 8s: strong repulsive repulsive core.only repulsion only. [1strong [8 ] +core same as NN ΛN(3 S1 ) = 8s: a!] attraction C -2-2 u,d,s=.1384 VCV!"# VV!"# mps =.47 GeV V(r) V(r) -1-1!#s"!"#!#s" V!r" V!r" V(r) u,d,s= VC V C V!r" V!r" V!r" VC VT V!r" V!r" VVV u,d,s= !#s"!#$"!#$" V!r"V!r" V!r" V!r" V!r" V!r" VC 5 T. Inoue et al. Nucl. Phys. A881 (212) mππ MeV [27] + [8s ] ΛN(MeV S ) = m fm, fm, LL mπ 47 MeV, =.1384 u,d,s V!#a" V VV TC VT u,d,s= =.1384 u,d,s [fm] r r[fm] same core. as NNweak attraction.1: strong8a: repulsive core. weak attraction. 1: strong repulsive weak repulsive core. note: strong short-distance same as NN 1: strongrepulsive repulsive core. interaction weak attraction. strong attraction. 8a: weak repulsive core. 8a: weak repulsive core. strong attraction

21 Example for p-p correlations Simulation of the particle Production and Freeze- Out coordinates After-Burner which includes the relevant Interactions Comparison with the measured correlations p+nb reaction simulated in UrQMD + CRAB afterburner Coulomb + Excellent Agreement

22 Summary and Outlook KS-nucleons attractive potential verified with p+nb reactions at GeV χ2/ndf 2 15 U = 25 MeV U = 35 MeV U = 45 MeV Parameter set Test the Hyperon-Nucleon Interaction with Femtoscopy at intermediate and high energies ( compare to QCD Lattice potential or other calculations) Hyperon - Nucleon Interactions from Lattice mπ = 47 MeV me as NN 3. me as NN u,d,s=.1384 u,d,s=.1384 u,d,s= VVC C 5 5 VC u,d,s=.1384 u,d,s=.1384 u,d,s= !#$*"!#$"!#$*" V VV V!r" V!r" V!r" =.1384 u,d,s =.1384 u,d,s u,d,s= VV V =.1384 u,d,s =.1384 u,d,s u,d,s=.1384 u,d,s= T. Inoue et al. (HAL QCD) instead 1: attractive of repulsive 1: attractive instead PTP 124 (21) 591 core! attraction only.of repulsive corephys.! attraction only. Nucl. 3 3 A881!#a" (212) 1 28 VC u,d,s= VVCC VV VTCT VT C !#$"!#a"!#$" VVCC VVV CT T VT VCV!"# VV!"# mps =.47 GeV 1:1 repulsive attractive core. instead of repulsive repulsion only. same core. as NNrepulsion only. 18s: strong 8s: strong repulsive repulsive core.only repulsion only. [1strong [8 ] +core same as NN ΛN(3 S1 ) = 8s: a!] attraction. u,d,s= VC VT V!r" V!r" !#s"!"#!#s" V VV V!r"V!r" V!r" 35 3 VC V C V(r) V(r) V!r" V!r" V!r" T. Inoue et al. Nucl. Phys. A881 (212) !#s"!#$"!#$" VVV V!r" V!r" V(r) VC u,d,s= mππ MeV [27] + [8s ] ΛN(MeV S ) = m fm, fm, LL mπ 47 MeV V!#a" V VV TC VT u,d,s= =.1384 u,d,s [fm] r r[fm] same core. as NNweak attraction.1: strong8a: repulsive core. weak attraction. 1: strong repulsive weak repulsive core. note: strong short-distance same as NN 1: strongrepulsive repulsive core. interaction weak attraction. strong attraction. 23 8a: weak repulsive core. 8a: weak repulsive core. strong attraction. strong attraction

23 The people in Munich Thanks

24 Experiments with π Beams π p" π p" p" π-absorption mostly on the nucleus surface less model dependent Study of Hadron-nucleon interaction Not so easy to measure, since π -beams are secondary beams with large emittance CERBEROS: 3-heads dog at the HADES entrance

25 Experiments with π Beams π p" π p" p" π-absorption mostly on the nucleus surface less model dependent Study of Hadron-nucleon interaction First Measurement of K absorption in normal nuclear matter

26 Hyperon Star Neutron J. Schaffner-Bielich, NPA 84 (28) Λ Possible Processes: p + e n + n! n +! + e n + n! p + ρ 2ρ 3ρ 4ρ.. n + e! + e Strangeness violation possible due to large time scale of NS Appearance of Hyperon already starting at 2ρ This scenario might also be problematic for large masses (~ 2M. ) since the hyperon appearance implies new degree of freedom and hence a softening of the EOS