COLLISIONS OF ANTIPROTONS WITH HYDROGEN ATOMS

Abstract

The !east-squares variational method (LSVM) has been employed for treating the elastic scattering of antiprotons by hydrogen atoms at a relatively wide scale of incident energies below the first excitatfon threshold of the target atom. Particularly the variation of - tan(r;o )/k'P

(where 1]

is the s-wave phaseshift and k p is the wave number of the

antiproton) with k p , when k p---+ 0 has been investigated. The resultant

scattering length was positive, a matter which supports the possible formation of an j5 H bound-state. The existence of this bound state has been reconfirmed by calculating the ground-state and binding energy of a quantum mechanical system composed of an electron moving in the field of an electric dipole produced by a pair of stationary proton and antiproton where we found that the antiproton-hydrogen system exists as a bound state with ground state energy for the electron in the field of electric dipole is Eb = -0.175848 Ry. Comparison between present s­ wave elastic cross sections of j5 -H scattering and of previously calculated e--H scattering has shown that the first system assumes different behaviour below the first excitation threshold of the target atom. In the present work, a least-squares variational technique has been also developed for the teatmenl of arbilrmy two-channel problems. Particularly, the inelastic scattering of antiprotons by hydrogen atoms

6

has been investigated using this new formalism. In this case, both the elast ic and excitation channels are open and the s-wave cross sections are calculated at large number of incident energies lying between the first and second excitation thresholds of t he target atom. On the other hand the variation of K11 with the nonlinear parameters and the number of components of the trial wavefunctions (up to 120 components) have emphasized in all cases the commonfeatures of the variational method considered. Finally, the elastic cross sections for antiproton-hydrogen calculated by two different methods give the same result at the threshold value of E P = 0.75 Ry.