The Spin Response of the $$\vec{\boldsymbol{\gamma}}\vec{\boldsymbol{d}}\to\pi^{0}\boldsymbol{d}$$ Reaction Near Thresho
- PDF / 1,438,666 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 86 Downloads / 158 Views
HYSICS OF NUCLEI AND ELEMENTARY PARTICLES
The Spin Response of the γd → π 0d Reaction Near Threshold and Its Implication to the GDH Sum Rule and the Double Polarization E -Asymmetry E. M. Darwish1, 2* , H. M. Abou-Elsebaa1, 2 , Kh. S. Alsadi1 , and M. Saleh Yousef1, 3 1
Physics Department, Faculty of Science, Taibah University, Medina, 41411 Saudi Arabia 2 Physics Department, Faculty of Science, Sohag University, Sohag, 82524 Egypt 3 Physics Department, Faculty of Science, Cairo University, Giza, 12613 Egypt Received April 17, 2020; revised April 24, 2020; accepted April 29, 2020
Abstract—The spin response of the γ d → π 0 d reaction near threshold is investigated. Our formalism based on the impulse approximation, uses the realistic Bonn N N potential (full model) for the deuteron wave function and the unitary isobar MAID-2007 model for the elementary γN → πN amplitude. We present the first results for the double polarized differential and total cross sections for parallel and antiparallel helicity states, the deuteron spin asymmetry, the helicity E-asymmetry, the deuteron GDH integral, and the double spin asymmetries of the total cross section in the near-threshold region. Sensitivity of the estimated results to the D-wave effect of the deuteron wave function for a realistic N N potential is studied. We find an insignificant sensitivity of most of the estimated observables to the D-wave component. A noticeable role is obtained only in the double polarized differential cross section with antiparallel spins of photon and deuteron dσ A /dΩπ close to the threshold energy at forward and backward pion angles as well as in the double spin asymmetry of the total cross section σ T˜20 at relatively large photon energies. Thus, we compare results for these two observables using various N N potential models with different D-state probabilities, and a noticeable influence is found. Keywords: meson production, photoproduction reactions, polarization phenomena in reactions, polarized beams, polarized targets. DOI: 10.3103/S002713492003008X
1. INTRODUCTION During the last two decades, various theoretical and experimental programs have been pursued in view of the investigation of coherent and incoherent pion photoproduction on the deuteron including polarization observables (see, for example, [1– 20]). Since the deuteron is the simplest nuclear system consisting of two bound nucleons, electroand photo-nuclear reactions on the deuteron provide us with a wealth of important information about the role of the nuclear environment on the elementary amplitudes. In addition, because of its simple and well-known structure, the deuteron can be used as an effective neutron target. Thus, it allows one to obtain information about the mechanisms of the elementary pion photoproduction on the free neutron which otherwise is not possible due to the absence of any free *
E-mail: [email protected]
neutron targets. Furthermore, the deuteron represents also an ideal object for the study of nucleonnucleon (N N ) interactions. The coherent pho
Data Loading...
