Effects of nuclear structure in the spin-dependent scattering of weakly interacting massive particles

Abstract

We present calculations of the nuclear from factors for spin-dependent elastic scattering of dark matter WIMPs from¹²³Te and¹³¹Xe isotopes, proposed to be used for dark matter detection. A method based on the theory of finite Fermi systems was used to describe the reduction of the single-particle spin-dependent matrix elements in the nuclear medium. Nucleon single-particle states were calculated in a realistic shell model potential; pairing effects were treated within the BCS model. The coupling of the lowest single-particle levels in¹²³Te to collective 2⁺ excitations of the core was taken into account phenomenologically. The calculated nuclear form factors are considerably less then the single-particle ones for low momentum transfer. At high momentum transfer some dynamical amplification takes place due to the pion exchange term in the effective nuclear interaction. But as the momentum transfer increases, the difference disappears, the momentum transfer increases and the quenching effect disappears. The shape of the nuclear form factor for the¹³¹Xe isotope differs from the one obtained using an oscillator basis.