Angular distribution of the background

This figure shows the fitted λ_θ and λ_φ parameters for the background in each of the 12 ranges of invariant mass indicated on the previous plot.

The numbers near the small ellipses for the background parameters indicate to which mass range they correspond. We can make the following observations:

• The angular distribution of the di-muon background evolves rapidly with invariant mass. For this reason we are concerned that the sidebands will not provide a good description of the angular distribution under the ϒ(nS) signal peaks.
• The angular distribution parameters for the background are at all times very different from those for the ϒ(nS) decay angular distributions.
• The angular distribution for ϒ(nS) decays is much more isotropic than is the angular distribution of the background.
• The parameters for the angular distributions of background under the ϒ(nS) signals are similar to the angular distributions in the sidebands and are themselves very different from the fitted parameters from the ϒ(nS) signal component.