def dslab(Ni, Ns, n, dOmega, cor_factor=1):
    """
    function to find dσ/dΩ[mb/str] in the lab system

    Arguments
    ---------
    Ni : number of incident particle
    Ns : number of scattering particle
    n : particle number / area [/mb]
    dOmega : solid angle [str]

    Return
    ------
    dσ/dΩ[mb/str] in the lab system
    """
    return Ns / (Ni * n * dOmega) * cor_factor