Avoiding doble loops to gain efficience

Hi.

I have solved a problem by using a doble loop but it is taking too long and I am pretty sure there are more efficient ways to solve it, but I am quite a begginer with the program. I would be glad if you could help me with this.

Basically, I have two arrays of different size and I want to multiply each element of the first array for all the elements of the second one. The second vector also changes size in every iteration and that's why I have ended with a doble loop. I am doing something like this.

for j=1:length(s)
    t=T-s(j):0.00025:T-0.00025;

    for i=1:length(x)
        aux1=exp(-x(i)^2/2./(T-t))./((t.*(T-t)).^(3/2));
        aux2=sum(aux1)*0.00025;
        omega(i)=exp(-mu^2/2*T+mu.*x(i)).*x(i)/2/pi.*aux2;
    end
      aux3=sum(omega)*0.00025;
      Psnj(j)=aux3*exp(-lambda*s(j));
  end

How could I do this more efficiently?

Thank you in advance Javier