def projection_y(th2d):
    """
    create the projection on the y axis of a th2d
    :param th2d:
    :return: TH1D of the projected data on the y axis
    """
    yproj = th2d.ProjectionY('Projection on y axis')
    yproj.SetXTitle("Slices")
    yproj.SetYTitle("Nb of Counts")
    return yproj