Np Final-state Interaction Research Articles

The reactionH2(p,pp)nin three kinematical configurations atEp=16MeV

We measured the cross sections of the $^2$H(p,pp)n breakup reaction at E$_p$=16 MeV in three kinematical configurations: the np final-state interaction (FSI), the co-planar star (CST), and an intermediate-star (IST) geometry. The cross sections are compared with theoretical predictions based on the CD Bonn potential alone and combined with the updated 2$\pi$-exchange Tucson-Melbourne three-nucleon force (TM99'), calculated without inclusion of the Coulomb interaction. The resulting excellent agreement between data and pure CD Bonn predictions in the FSI testifies to the smallness of three-nucleon force (3NF) effects as well as the insignificance of the Coulomb force for this particular configuration and energy. The CST also agrees well whereas the IST results show small deviations between measurements and theory seen before in the pd breakup space-star geometries which point to possible Coulomb effects. An additional comparison with EFT predictions (without 3NF) up to order N$^3$LO shows excellent agreement in the FSI case and a rather similar agreement as for CD Bonn in the CST and IST situations.

Neutron - proton fsi in <sup>2</sup>H(d,pd) reaction at Energy 13,6 mev

The pd coincidence spectra of the d + d reaction are measured at deuteron beam energy E 0 = 13. 6 MeV. Particle emission ʋ angles ʋ p/ ʋ d = 39.3/39.3, 39.3/31.0, Ψ p- Ψ d =180 degrees have been taken to accent the neutron - proton (np) final state interaction (FSI) and in some degree to diminish influence of other mechanisms. The experimental results are compared to theoretical calculations using the Watson - Migdal approximation for FSI of np 3 S 1 and 1 S 0 (isospin forbidden) states. At symmetric angles the optimum fitting is obtained with contribution of a singlet state equal (8 ± 2)%, in nonsymmetrical geometry no influence of the singlet np FSI has been found.

Analyzing power of the [formula omitted] breakup reaction at 67 MeV in selected kinematical configurations

The angular distribution of the analyzing power A y for the 2 H( n, np)n breakup reaction at 67 MeV was measured in two kinematical regions: np quasi-free scattering and np final-state interaction. The results are compared with rigorous three-nucleon calculations using the Paris potential and allowing for charge dependence in the 1S 0 state. According to the actual experimental conditions energy averaging was simulated in the theoretical calculations. In both configurations agreement between experimental and calculated values is found.

Study of the kinematically complete breakup reaction 2H(p̄, pp)n at Ep = 3 Mev with polarized protons

The breakup reaction 2H(p̄, pp)n at E p = 13.0 MeV has been measured in a kinematically complete experiment with polarized protons in four special kinematical situations: np final-state interaction, pp quasi-free scattering, collinearity and symmetric space star. These configurations are identical to those of a corresponding 2H(n, nn) 1H experiment. The cross sections d 3σ/ dΩ 3 dΩ 4 dS and the vector analyzing powers A 1 are presented as a function of the arclenght of the relevant kinematical loci. They are compared to the rigorous Faddeev calculations using realistic meson-exchange NN potentials, i.e. the Paris and Bonn potential. Comparison with the cross section data of the analog neutron experiment is made. In the quasi-free scattering and the space-star cross sections marked discrepancies with the theoretical predictions, in the latter case also with the neutron results are found. In the collinear and final-state interaction situations the agreement is rather good as well as for all analyzing powers and is even improved by taking the finite angular spread into account.

Differential cross section of the 2H(n, nnp)-reaction at En = 13 MeV

The differential cross section of the nD break-up reaction was investigated at E n = 13 MeV using the Erlangen multidetector neutron facility. Twenty-two different configurations including np final-state interaction, collinearity, coplanar- and space star were measured in a kinematically complete experiment. The results are compared with rigorous Faddeev calculations based on the Paris potential. The discrepancies between data and calculations indicate imperfections in the potential and may be caused by three-particle effects such as wrong off-shell behavior of the potential or an additional three-body force.

Neutron-proton final-state interaction in pi d breakup: Differential cross section.

Threefold differential cross sections \ensuremath{\sigma}(${\ensuremath{\theta}}_{\ensuremath{\pi}}$,${\ensuremath{\theta}}_{\mathrm{p}}$,${P}_{\mathrm{p}}$) have been measured in a kinematically complete experiment. The experiment has been designed to extend earlier measurements into the kinematic region of the np final-state interaction. The data are compared with the predictions from the new relativistic Faddeev theory of Garcilazo.

Neutron-proton final-state interaction in pi d breakup: Vector analyzing power.

The vector analyzing power iT/sub 11/ has been measured for the ..pi..d breakup reaction in a kinematically complete experiment. The dependence of iT/sub 11/ on the momentum of the proton has been obtained for 36 pion-proton angle pairs at T/sub ..pi../ = 134 and 228 MeV. The data are compared with predictions from the new relativistic Faddeev theory of Garcilazo. The sensitivity of the observable iT/sub 11/, in particular in the np final-state interaction region, to details of the theory is investigated.

Measurements of cross sections and analyzing powers for the inclusive pp-->pn pi

Single arm spectrometer measurements of the differential cross sections and analyzing powers of the pp pn reaction have been performed at 400 and 450 MeV incident proton energy. The measurements covering an angular range from 46 to 90 (lab) spanned pion energies corresponding to production of the np system with relative energies between 0 and 30 MeV, a region where the influence of the np final state interaction is particularly important. The trend of the measured analyzing power is very similar to that of the pp d reaction, and is well explained by calculations that use this latter data as input. Dominance of the triplet pn final state is implied by these results.

Kinematically complete measurement of cross sections and vector and tensor analyzing powers of 4He( [formula omitted], pα)n at [formula omitted

Differential cross sections and vector and tensor analyzing powers have been measured in the breakup reaction 4He( d , pα)n at E d = 10 MeV , for θ α = 46°, θ p = 46° complete coincidence experiment. The kinematics allow for np final-state interaction (FSI) ( E np = 0). A comparison with theoretical predictions based on Faddeev equations is presented. Phenomenologically it appears that there are large interference effects between the different FSI and the importance of Coulomb interaction emerges clearly.

The deuteron break-up in the reaction dd → dpn at 52 MeV

The three-particle reaction dd → dpn has been investigated systematically at an energy of 52 MeV. Proton-deuteron and neutron-deuteron coincidences have been measured in kinematically complete experiments in order to study the angular dependence of the np final state interaction and of pd and nd quasifree scattering. The experimental results show that the angular distribution for the production of np pairs with zero relative energy can be predicted absolutely from elastic dd scattering. No indication of violation of isospin conservation is found in the experiment. The measured angular distributions for nd and pd quasifree scattering are identical within the experimental errors over a wide range of angles. Their shape is similar to the distribution of elastic nucleon-deuteron scattering. Significant deviations between the pd and nd coincidence spectra (measured under identical kinematical conditions) have been observed only at forward angles, indicating the influence of the Coulomb force on the break-up mechanism. In order to analyze the spectra and angular distributions, different model calculations have been carried out.