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NN & NY interactions at small energies

NN & NY interactions at small energies. Hartmut Machner, FZ Jülich and Univ. Duisburg-Essen Frank Hinterberger , Univ. Bonn Regina Siudak , PAN Krakow for the HIRES & GEM collaborations. Why is this important ? NN interactions  Nuclear potential , nuclear structure

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NN & NY interactions at small energies

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  1. NN & NY interactions at small energies Hartmut Machner, FZ Jülich and Univ. Duisburg-Essen Frank Hinterberger, Univ. Bonn Regina Siudak, PAN Krakow for the HIRES & GEM collaborations • Whyisthisimportant? • NN interactions Nuclearpotential, nuclearstructure • NY interactions  Hypernuclearpotential, hypernuclearstructure 1

  2. All possible interactions

  3. focussingspectrometer (W = 10 msr) • high resolutionDp/p < 510-5 • combinedwithdetectorsclose to target: • multi-layer Germanium detector GEM Germanium detector Detectors: Big Karl + Ge-Wall

  4. Particleidentification NIM A 596 (08)311

  5. Often the target or the beam is not available or even impossible. Way out: three body final states with fsi (Watson+Migdal theory): factorisation: with Problem leads to

  6. A lot of studies made use of a Gauss potential. However the Bargman potential is the potential which has the effective range expansion as exact solution: a, r a, b. a defines the pole position (positive ↔ bound, negative ↔ unbound). FSI approaches

  7. Elastic pp scattering, Coulomb force seems to be well under controle: app=-7.83 fm However: an IUCF group Claimed „…the data requireapp=-1.5 fm.“ Theyquestioned the validity of the factorization. Experiment at GEM, differential and total cross sections. The pp-case PRC 65(02)0641001

  8. Modell FSI withGamowfactor, toaccount for Coulomb repulsion PRC 65(02)0641001

  9. Projection of Dalitzplot

  10. FIT Ss, Pp (Ps frompolarisationexperiments) blue: no D resonance red: withDresonance, usualfsi black: withDbutfsiwith half the usual pp scattering length No need for a change of the scattering length! pp®ppp0

  11. Fäldt & Wilkin derived a formula ( for small k) From this follows, that from a the cross section of a known pole (bound or quasi bound) the continuum cross section is given [N(d)®N(pn)t®xN(pn)s]. The fsi is large for excitation energies Q of only a few MeV. Connection bound-continuum best: an experiment avoiding the con’s. ® high resolution single arm

  12. d+p®p+(pn) singlet Td=1600 MeV triplet Old analysis

  13. Uppsala PLB 446(99)179 Recent data Celsius

  14. p=1642.5 MeV/c GEM data PLB 610(05)31

  15. Singlet FSI absolute

  16. Triplet FSI absolute

  17. Why is there no singlet state? The isospin related reaction to the singlet state is pp®ppp0 Full spectrum • first high resolution measurement allowing to study the threshold region of the d break up • fixed cross section for the unbound triplet state • the upper limit for the singlet break up contribution was reduced by a factor of 3 • the ratio for unbound to bound state is < (1.9±0.5) ´10-3

  18. Data vs FäldtWilkin Why? Tensor force? PRC 79(09)061001(R)

  19. 3 bodycalculationwithtensorforce Relativisticphasespace Reid soft core Also necessity to normalize

  20. It‘s not the tensorforce! Whatisitthen? Long ranging force!

  21. pp®K+Lp: why the forward Kaons underzerodegree? Kaons beingbackwardemitted in the cm system Kaons beingforwardemitted in the cm system FSI asdeducedfrom the presentexperiment

  22. Hyperon production Pbeam=2735 MeV/c and 2081.2 MeV/c PLB 687(10)31

  23. Threeinputs 2 1 K-d2p-Lp: (Tai Ho Tan, PRL 23(69)695 at =−2.0 ±0.5 fm and rt = 3.0±1.0 fm 3

  24. Resultsfrom 6 parameter fit

  25. Total cross sections Almost isotropic Kaon angular distribution *4p

  26. Comparisonwith exclusive data Data: COSY TOF No fit: input: total cross sectiongiven plus FSI

  27. Data at higher beam momentum

  28. cusp in pL due to tensor force?

  29. Summary • Wehavemeasured pp®p0pp (full Dalitzplot) • Data and total cross sectionscan be discribedwithstandardparameters of pp FSI • Wehavemeasured pp®p+npwithvery high missingmassresolution (DMM/MM=5*10-5) • FW theoremdiscribes the shape of the continuumbutfails to give the absolute height • The tensorforceis not the origin for that, butlongrangedforces • Wehavemeasured pp®K0Lp at two beam momenta. • FSI parameterscould be deducedas well as total cross sections. • Wesee an enhancement at and below the SN thresholds.

  30. Summary cont. • Whatthisstructure? • - twostepprocesswithkinematicmatching? No, too large width • - acusp? (Nijmegen group: in3S1channel, Haidenbauer) • - aresonance in Lp®Lp, shoulderfromS+n®Lp (Dalitz: fourthsheet pole) ? • - boundstateisexcluded (no second sheet pole) np and Lpseem to haveoppositebehavior in FSI: np almost only spintriplet, boundstateexists Lp almost only spinsinglet, noboundstateexists

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