Excitation of the Δ(1232) isobar in deuteron charge exchange on hydrogen at 1.6, 1.8, and 2.3 GeV (original) (raw)
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Excitation of the isobar in deuteron charge exchange on hydrogen at 1.6, 1.8, and 2.3 GeV
Physics Letters B, 2013
The charge-exchange break-up of polarised deuterons dp → {pp}sn, where the final {pp}s diproton system has a very low excitation energy and hence is mainly in the 1 S0 state, is a powerful tool to probe the spin-flip terms in the proton-neutron charge-exchange scattering. Recent measurements with the ANKE spectrometer at the COSY storage ring at 1.6, 1.8, and 2.27 GeV have extended these studies into the pion-production regime in order to investigate the mechanism for the excitation of the ∆(1232) isobar in the dp → {pp}sX reaction. Values of the differential cross section and two deuteron tensor analysing powers, Axx and Ayy, have been extracted in terms of the momentum transfer to the diproton or the invariant mass MX of the unobserved system X. The unpolarised cross section in the high MX region is well described in a model that includes only direct excitation of the ∆ isobar through undistorted one pion exchange. However, the cross section is grossly underestimated for low MX , even when ∆ excitation in the projectile deuteron is included in the calculation. Furthermore, direct ∆ production through one pion exchange only reproduces the angular dependence of the difference between the two tensor analysing powers.
The neutron-proton charge-exchange amplitudes measured in the dp → ppn reaction
The European Physical Journal A, 2013
The unpolarised differential cross section and the two deuteron tensor analysing powers Axx and Ayy of the dp → {pp}sn charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were obtained for small momentum transfers to a {pp}s system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27 GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteronproton spin-correlation parameters Cx,x and Cy,y that were carried out in the d p → {pp}sn reaction at 1.2 and 2.27 GeV. The values obtained for the proton analysing power A p y also suggest the need for a radical reevaluation of the neutron-proton elastic scattering amplitudes at the higher energy. It is therefore clear that such measurements can provide a valuable addition to the neutron-proton database in the charge-exchange region. PACS. 13.75.-n Hadron-induced low-and intermediate-energy reactions and scattering (energy ≤ 10 GeV)-25.45.De Deuteron breakup-25.45.Kk Charge-exchange reactions
2006
Vector and tensor analysing powers of the ~ dp → (pp)n (charge–exchange) and ~ dp → (pn)p (non–charge–exchange) breakup reactions have been measured with the ANKE spectrometer at the COSY ring at a deuteron beam energy of 1170MeV for small momentum transfers to the low excitation energy (pp) or (pn) systems. A quantitative understanding of the values of Axx and Ayy for the charge–exchange reaction is provided by impulse approximation calculations. The data suggest that spin–flip isospin–flip transitions, which dominate the charge–exchange breakup of the deuteron, are also important in the non–charge–exchange reaction. 1 Corresponding author: d.chiladze@fz-juelich.de Preprint submitted to Elsevier Preprint 15 March 2006
Spin-Dependent Electron-Proton Scattering in the Δ-Excitation Region
Physical Review Letters, 2002
We report on measurements of the cross section and provide first data on spin correlation parameters A TT 0 and A TL 0 in inclusive scattering of longitudinally polarized electrons from nuclear-polarized hydrogen. Polarized electrons were injected into an electron storage ring operated at a beam energy of 720 MeV. Polarized hydrogen was produced by an atomic beam source and injected into an open-ended cylindrical cell, located in the electron storage ring. The four-momentum transfer squared ranged from Q 2 0.2 GeV 2 ͞c 2 at the elastic scattering peak to Q 2 0.11 GeV 2 ͞c 2 at the D͑1232͒ resonance. The data provide a stringent test of pion electroproduction models.
High-Energy Deuteron Cross Sections: Charge-Exchange Effects
Physical Review, 1967
The effects of charge exchange in collisions of high-energy particles of isotopic spin! with deuterons are investigated. The diffraction approximation is used to express the deuteron charge exchange cross section in terms of the elastic scattering amplitudes of the neutron and proton and the deuteron ground state wave function. Examinations are also made of the influence of the
Spin observables for pion photoproduction on the deuteron in the Δ(1232)-resonance region
Journal of Physics G: Nuclear and Particle Physics, 2005
Spin observables for the three charge states of the pion for the pion photoproduction reaction on the deuteron, γd → πN N , with polarized photon beam and/or oriented deuteron target are predicted. For the beam-target double-spin asymmetries, it is found that only the longitudinal asymmetries T ℓ 20 and T ℓ 2±2 do not vanish, whereas all the circular and the other longitudinal asymmetries do vanish. The sensitivity of spin observables to the model deuteron wave function is investigated. It has been found that only T 21 and T 22 are sensitive to the model deuteron wave function, in particular in the case of π 0-production above the ∆-region, and that other asymmetries are not.
The dp → ppn reaction as a method to study neutron-proton charge-exchange amplitudes
The European Physical Journal A, 2009
The differential cross section and deuteron analysing powers of the d p → {pp}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using a deuteron beam of energy 1170 MeV, data were obtained for small momentum transfers to a {pp} system with low excitation energy. A good quantitative understanding of all the measured observables is provided by the impulse approximation using known neutron-proton amplitudes. The proof of principle achieved here for the method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable.
Vector and tensor analysing powers in deuteron–proton breakup reactions at intermediate energies
Physics Letters B, 2006
Vector and tensor analysing powers of the dp → (pp)n (charge-exchange) and dp → (pn)p (non-charge-exchange) breakup reactions have been measured with the ANKE spectrometer at the COSY ring at a deuteron beam energy of 1170 MeV for small momentum transfers to the low excitation energy (pp) or (pn) systems. A quantitative understanding of the values of A xx and A yy for the charge-exchange reaction is provided by impulse approximation calculations. The data suggest that spin-flip isospin-flip transitions, which dominate the charge-exchange breakup of the deuteron, are also important in the non-charge-exchange reaction.
Pion-Exchange Effects in Elastic Backward Proton-Deuteron Scattering
Few-Body Systems, 1999
The elastic backward proton-deuteron scattering is analyzed within a covariant approach based on the Bethe-Salpeter equation with realistic meson-exchange interaction. Contributions of the one-nucleon and one-pion exchange mechanisms to the cross section and polarization observables are investigated in explicit form. Results of numerical calculations for the cross section, tensor analyzing power and spin transfers are presented. The onepion exchange contribution is essential for describing the spin averaged cross section, while in polarization observables it is found to be less important.
Physics Letters B
The vector and tensor analysing powers, AyA_yAy and AyyA_{yy}Ayy, of the vecpdtonpps\vec{p}d \to n\{pp\}_{s}vecpdtonpps charge-exchange reaction have been measured at a beam energy of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3 MeV on the diproton excitation energy ensured that the two protons were dominantly in the 1S0^{1}S_{0}1S0 state, here denoted by pps\{pp\}_{s}pps. The polarisation of the deuterium gas was established through measurements in parallel of proton-deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers qgeq160q\geq 160qgeq160 MeV/$c$. These data provide a good continuation of the earlier results at qleq140q\leq 140qleq140 MeV/$c$ obtained with a polarised deuteron beam. ...