Calculate the scattering phase sift

[sanjibghosh]

Homework Statement

calculate the scattering phase sift for given potential
v(r)=-a/r +b/r²( consider only s-wave scattering)
a=+ve constant
b=+ve constant

Homework Equations

phase sift=f(-k,0)/f(k,0)
k²=2mE/$$\hbar$$²
r*f(k,r)=solution of Schrödinger equation

The Attempt at a Solution

I have solved the Schrödinger equation and i have found that 'phase sift' =1
but physically i did not understand the ans..

 

[malawi_glenn]

what does a positive phase shift tells you?

 

[sanjibghosh]

i have found that
exp(2i$$\delta$$)=1
=>$$\delta$$=n*pi ,n=+ve or -ve integer
therefore s-wave contribution to the differential scattering cross section=lim(k²-->0)1/(k² +k²cot²$$\delta$$)=0
i do not understand this.potential is nonzero but there is no scattering contribution!