Latest results concerning short range correlations obtained in the dp elastic and dp breakup processes at Nuclotron, JINR

Deuteron spin structure program is aimed on extraction of two and three nucleon forces information, including their spin dependent parts, from dp elastic and dp breakup processes investigated at intermediate energies. The dp elastic data were obtained at Internal Target Station of Nuclotron (JINR) in the energy range 400-1800 MeV using polarized deuteron beam. Strong sensitivity to the short range spin structure of the isoscalar nucleon-nucleon correlations is observed in deuteron analyzing powers. Preliminary results of the the cross section for the dp breakup reaction have been obtained at 400 MeV of deuteron energy.

VME–based DAQ system for the Deuteron Spin Structure setup at the Nuclotron internal target station

The new powerful VME–based data acquisition (DAQ) system has been designed for the Deuteron Spin Structure setup [1] placed at the Nuclotron Internal Target Station [2]. The DAQ system is built using the netgraph–based data acquisition and processing framework ngdp [3, 4]. The software dealing with VME hardware is a set of netgraph nodes in the form of the loadable kernel modules. The specific for current implementation nodes are described, while specific software utilities for the user context are the following. The b2r (binary–to–ROOT) server converts raw data into per trigger and per accelerator spill representations, which are based on C++ classes derived from the ROOT framework [5] ones. This approach allows us to generalize the code for histograms filling and polarization calculations. The b2r optionally stores ROOT events as ROOT TTree in file(s) on HDD, and supports the design of some express offine. The histGUI software module provides an interactive online access for human operator to histograms filled by the r2h (ROOT–to–histograms) server, which obtains the ROOT event representations from b2r. The r2h supports the calculation and histograming of runtime configurable variables as well as raw data variables, and optionally stores ROOT histograms in file(s) on HDD. Since the spin studies at the Nuclotron require fast and precise determination of the deuteron and proton beam polarization, the polarization calculator software module is introduced. This calculator based on runtime configurable r2h code allows us to compute polarization values online and integrate them into the Web–based scheme of representation and control of the polarimeters [6, 7].

Various types of theoretical uncertainties by example of the elastic nucleon-deuteron scattering spin correlation coefficient Cz,x

The elastic nucleon-deuteron scattering process can be used to study three-nucleon dynamics, but in order to draw reliable conclusions based on the comparison of theoretical predictions and data, an estimation of theoretical uncertainties is necessary. We consider the statistical errors arising from a propagation of uncertainties of the two-nucleon interaction parameters to the three-nucleon system, truncation errors, regulator dependencies, and uncertainties arising from using the formalism of partial waves. We give an example of the nucleon-deuteron spin correlation coefficient Cz,x, obtained within the Faddeev approach, to discuss magnitudes of the above mentioned theoretical uncertainties. We find that using various models of the nuclear forces results in the dominant theoretical uncertainty for the nucleon-deuteron elastic scattering observables.

Helicity-dependent reaction γd → π0d near the η-threshold and its contribution to the E-asymmetry and the GDH sum rule for the deuteron

The helicity-dependent coherent π0-photoproduction in the reaction γd → π0d near the η-threshold is investigated. The calculations are performed within an approach which includes the reaction amplitudes of the impulse approximation (IA), two-step process with intermediate πN- and ηN-rescattering, and the higher order terms in the multiple scattering series for the intermediate ηNN interaction. The contribution of γd → π0d to the deuteron spin asymmetry is calculated and its contribution to the Gerasimov–Drell–Hearn (GDH) integral is explicitly evaluated by integration up to a photon energy of 900 MeV. In addition, the helicity E-asymmetry is calculated. The results revealed that the doubly polarized differential cross-sections and the helicity E-asymmetry are sensitive to the interference of rescattering effects, specially at photon energies 600–800 MeV and extreme backward pion angles. The sensitivity of the obtained results for the GDH integral to the choice of NN potential model governing the deuteron wave function is discussed. We find that the deviation among results obtained for the deuteron GDH integral using different deuteron wave functions is quite large.