Cms Calorimeter Trigger Implementation and Performance

For most of the CMS ECAL, a 6 crystal by 6 crystal array of physical calorimeter towers is mapped into trigger towers. There is a 1:1 correspondence between the HCAL and ECAL trigger towers. The trigger tower size is equivalent to the HCAL physical towers, .087 x .087 in η x φ. The φ size remains constant in ∆φ and the η size remains constant in ∆η out to an η of 2.1, beyond which the η size doubles. There are 3888 total ECAL and 3888 total HCAL trigger towers from η = -2.6 to η = 2.6 (54 x 72 η−φ divisions).