Background composition
------------------------

Geometry and shower energy
****************************

.. plot:: cascadel3_ic79/background_composition/plots/espec.py
	:scale: 40
	
	Energy spectrum of cosmic-ray primaries at various cut levels. The primaries are
	grouped by nuclear charge using the scheme of Hoerandel_.

.. plot:: cascadel3_ic79/background_composition/plots/zenii.py
	:scale: 40
	
	Zenith angle of cosmic-ray showers.

.. plot:: cascadel3_ic79/background_composition/plots/impact.py
	:scale: 40
	
	Distance of closest approach of the shower axis to the detector center. Heavy-primary
	showers pass the L3 cuts in large numbers only near the edges of the detector.

.. _Hoerandel: http://dx.doi.org/10.1016/S0927-6505(02)00198-6

Reconstructing the muons
*************************

.. plot:: cascadel3_ic79/background_composition/plots/vertex_res.py
	:scale: 40
	
	Difference between the reconstructed cascade vertex and the
	brightest stochastic energy loss in the detector for contained events at L3.
	



Stochastic energy losses
*************************

The background at L3 is dominated by isolated stochastic energy losses from atmospheric muons. These can be much brighter than the parent track, mimic a true neutrino-induced cascade; one way to characterize this mimicry is to bin the energy losses along the track and calculate the ratio of the energy losses in the brightest track segment to the total energy loss in the detector volume:

.. math::

	k \equiv \frac{E_{max}}{\sum_i E_i}
	
.. seealso::

	A `study of cascade-like muon events <https://events.icecube.wisc.edu/indico/contributionDisplay.py?contribId=89&sessionId=17&confId=43>`_ by Marcel Usner

.. plot:: cascadel3_ic79/background_composition/plots/stochastics.py
	:scale: 40
	
	Ratio of the brightest stochastic to total energy losses for atmospheric muons that pass
	the L3 containment criterion.