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Measurement of Spin-Dependent Inelastic Nucleon-Antinucleon Cross Section: A Proposal

This proposal aims to measure the spin-dependent part of the inelastic nucleon-antinucleon cross section using polarized antiproton beams. The study includes complete mapping of nucleon spin structure, measurement of nucleon electromagnetic form factors, investigation of hard antiproton scattering, and hadron spectroscopy. The calculation of cross sections is based on the Paris nucleon-antinucleon optical potential, with the main theoretical uncertainty being the absence of spin-dependent measurements for annihilation cross sections.

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Measurement of Spin-Dependent Inelastic Nucleon-Antinucleon Cross Section: A Proposal

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  1. Measurement of the Spin-dependent part of inelastic nucleon-antinucleon cross section (first proposal) A.Bondar, V.Dmitriev, I.Koop, A.Milstein, V.Strakhovenko, D.Toporkov Novosibirsk

  2. Polarized antiproton beams (PAX Collaboration arXiv:hep-ex/0505054) 1. Complete mapping of the nucleon spin structure 2. Measurement of moduli and phases of the nucleon electromagnetic form-factors GE and GM 3. Investigation of the hard antiprotons scattering 4. Hadron spectroscopy Spin-filtering method is the most promising way to get polarized antiprotons beams Novosibirsk

  3. To estimate the beam life-time and degree of polarization the cross section which describes a loss of antiprotons is necessary Where - total cross section of annihilation - total charge-exchange cross section - elastic scattering cross section - vector of the nucleon momentum - vectors of the polarization Novosibirsk

  4. The calculation of the cross sections based on Paris nucleon-antinucleon optical potential The main theoretical uncertainty in the calculation is due to absence of spin-dependent measurements for annihilation cross sections They can be obtained using reaction with longitudinally polarized electrons as a source of highly polarized antinucleons Though direct measurement of the spin-dependent part of inelastic cross section for slow antiprotons is practically impossible, both isospin amplitudes can be obtained from polarized antineutrons interaction with different polarized targets (H,D) Novosibirsk

  5. nbar p annihilation cross section calculation based on Paris optical potential Paris 2008 Paris 1999 Novosibirsk

  6. Novosibirsk

  7. Spin asymmetry for nbar p annihilation cross section Novosibirsk

  8. Polarization scheme with 3 snakes (arc=1200+2 damping wigglers in the arc’s middle ) IP snake2 snake3 damping wiggler2 damping wiggler1 snake1 Novosibirsk

  9. 5 snakes 3 snakes 1 snake Polarization degree overview Novosibirsk

  10. The value of the spin dependent asymmetry for nbar p annihilation measurement and necessary statistics Aexp= A0zbeamztargetD = 0.15*0.8*0.8*0.34=3.2% D = 3/(3+AN2/3)=0.34 dN/dt = snn*L*h*e*(cosqmax-cosqmin)/(l*sinq)=0.1sec-1 snn=1nb L = 5.1033 cm-2sec-1 l = 35cm (T=20MeV) h=8cm e=0.3 cosqmax=0.9 cosqmin=0.7 10 days statistic will be enough for s(Aexp) = 0.1% Novosibirsk

  11. Polarization filling pattern IP snake Novosibirsk

  12. Summary • Super ct factory is unique source of polarized nucleons • It can be used for measurement of spin-dependent part of inelastic nucleon-antinucleon annihilation • These data may constrain the parameters of the phenomenological potential of the NNbar interaction Novosibirsk

  13. Polarization degree of the antineutrons in the e+e- -> n nbar Novosibirsk

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