what's the result of KDL::Jacobian*JntArray? is it a Twist?

What I mean is:

When I put my Twist t into ChainIkSolverVel_pinv::CartToJnt i get an JntArray qdot as output.
So I have the calculation qdot = PseudoInverse*t
Now, I've written a function which calculates twist = Jacobian*qdot, but when I put the result of CartToJnt qdot into this function it doesn't return my twist. the translational parts of both twists are the same, but not the rotational parts.

this is my function:

KDL::Twist ChainIkSolverVel_pinv::JacMultJoints(const std::vector &cur_Pos, const std::vector &q_Dot)
{
KDL::JntArray q(cur_Pos.size());

for (unsigned int i=0;i q(i) = cur_Pos[i];

jnt2jac.JntToJac(q,jac2);

double add;
unsigned int i;
unsigned int j;

for (i=0;i add = 0.0;
for (j=0;j add+= jac2(j,i)*q_Dot[j]; //xdot = J*qdot

twist(i) = add;
}

return twist;
}