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Double- polarised np-scattering experiments at ANKE

Double- polarised np-scattering experiments at ANKE. David Mchedlishvili for the ANKE collaboration. HEPI, Tbilisi State University IKP, Forschungszentrum Jülich. July 8 , 2014. Outline:. Introduction Experimental facility Impulse approximation Experiments Results

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Double- polarised np-scattering experiments at ANKE

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  1. Double-polarisednp-scattering experiments at ANKE David Mchedlishvilifor the ANKE collaboration HEPI, Tbilisi State University IKP, ForschungszentrumJülich July 8, 2014

  2. Outline: • Introduction • Experimental facility • Impulse approximation • Experiments • Results • Summary and Outlook NN pp np dp pd Unpolarised Single polarised Double polarised

  3. d/d Ayy Existing np scattering data • Current experimental status of np data np charge-exchange ANKE np charge-exchange np forward ANKE ANKE is able to provide the experimental data for ppandnpsystemsat up to 2.8 GeVand improve our understanding of NN interaction np forward

  4. Experimental facility: COSY storage ring COSY (COoler SYnchrotron) at Jülich (Germany) • Energy range: • 0.045 – 2.8 GeV (p) • 0.023 – 2.3 GeV (d) • Max. momentum ~ 3.7 GeV/c • Energy variation (ramping mode) • Electron and Stochastic cooling • Internal and external beams • High polarisation (p,d) • Spin manipulation

  5. Apparatus: ANKE spectrometer • Main features: • Excellent Kaon identification (Positive and Negative) • Low energy proton (spectator) detection (STT) • Di-proton ({pp}s) selection (by FD) • Polarized (unpolarized) dense targets STT S. Barsov et al., NIM A 462, 364 (1997)

  6. Polarised internal gas target at ANKE • Atomic Beam Source (ABS) • Lamb-shift Polarimetry • Cell: 20 x 15 x 370 mm3 COSY beam Benefit from cell: • Increased target density by factor of ≈100 (up to1013 cm-2) Drawback: • Dedicated beam development • Background handling • Vertex reconstruction in analyses

  7. np Scattering at ANKE Large cm scattering angles(np charge-exchange) Small cm scattering angles(np forward) “Diproton”{pp} p p p n p p p p n n n p n p n n p p p p p p n p

  8. Impulse approximation dp→{pp}1S0n ƒnp→pn(SAID) Transition F.F. ~ 1S0 F.F. is evaluated with PARIS wave function np charge-exchange amplitudes in cm: with basis vectors in terms of initial and final cm momenta p and p':

  9. dp→{pp}1S0n: Spin observables Unpolarised intensity depends only upon spin-flip amplitudes: Define a ratio of form factors by Terms can be separated by measuring with polarized beams/targets: d and p vector analysing powers Unpolarised cross section d tensor analysing powers d-p vector spin correlations d-p tensor spin correlation D.V.Bugg & C.W., Nucl.Phys.A467 (1987) 575

  10. dp → {pp}X reaction channels dp→{pp}X: • Td=1.2GeV • Td=2.27GeV dp→{pp}sn dp→{pp}s∆0 Valuable information on the modelling of the np→p∆0 amplitudes Data sensitive tothe np→pn elastic amplitudes (large cm angles)

  11. → dp → {pp}s n: Ayp, Cy,y, Cx,x → Epp< 3 MeV D.Mchedlishvili et al. EPJA, 49, 49 (2013) Td = 1.2 GeV Td = 1.2 GeV Td = 2.27 GeV reduced by 25% Problem with Td = 2.27 GeV

  12. → dp→ {pp}s n: dσ/dq, Axx, Ayy Epp< 3 MeV D.Mchedlishvili et al. EPJA, 49, 49 (2013) Td = 1.6 GeV (800 MeV/A) Td = 1.8 GeV (900 MeV/A) Td = 2.27 GeV (1135 MeV/A) reduced by 25%

  13. pd experiments: Extension of np program in inverse kinematics Maximum COSY energy: Td = 2.3 GeV (1.15 GeV/nucleon)vsTp = 2.8 GeV • Polarised deuteron target commissioning • Unpolarised proton beam at Tp = 600 MeV • Polarised deuteron cell target, with vector and tensor polarisations. • 10 days of data taking. • Solid state spectator detectors are involved to extend the ANKE capabilities.

  14. Deuteron breakup in inverse kinematics → pd→ {pp}n at Tp = 600 MeV Two different region: pp in same side of STT small Epp, large q pp in oposite side of STT large Epp, small q

  15. → pd→ {pp}sn:Ayd, Ayy • Tp = 600 MeV • Epp< 3 MeV • STT data: • <cos2φ> = 0.9 no Axx signal! Ayd≈ 0 as predicted in impulse approximation for small Epp FD STT → → dp → {pp}sn pd→ {pp}sn Will be submitted to Phys. Lett. B

  16. Future studies Upcomingpdexperiment at ANKE: • Polarised proton beam at 0.6, 1.135, 1.3and 1.8 GeV • Polarised deuterium target from the ABS → → Primary aims: • Tensor analysing powers (Axx, Ayy) and spin correlation parameters (Cx,x, Cy,y) in the pd→ {pp}sXreaction (X=n, X=∆0). • Opportunity to study the ∆ polarisation by detecting the decay products in ANKE • Spin correlation parameters (Ax,x, Ay,y) for quasi-free pn elastic. Due to the Fermi motion, several energy intervals will be produced at given beam energy in the angular range 5° < θcm < 40°.

  17. Summary D.Mchedlishvili et al. EPJA, 49, 49 (2013) • dp→{pp}sn observables: • dσ/dq, Axx, AyyatTd = 1.2, 1.6, 1.8, 2.27 GeV • Ayp, Cx,x, Cy,yatTd = 1.2, 2.27 GeV • dp→{pp}s∆0 observables: • dσ/dm, Axx, AyyatTd = 1.6, 1.8, 2.27 GeV D.Mchedlishvili et al. PLB 726, 145 (2013) • np→dπ0 observables: • Ax,x,Ay,y at Tn = 600 MeV. D.Mchedlishvili et al. PLB 726, 634 (2013) • pd→{pp}sn observables: • Ayd,Ayy at Tp = 600 MeV (Td = 1.2 GeV equivalent). Will be submitted to PLB • pd→{pp}sX (X=n, X=∆0) observables: • Ayp,Ayd,Axx, Ayy, Cx,x, Cy,yatTp = 1.3, 1.8 GeV • AypatTp= 0.8, 1.6, 1.8, 2.0, 2.2, 2.4 GeV

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