12 Triggering and High-Level Data Selection
541
Fig. 12.4 ATLAS calorimeter electron/photon trigger algorithm
of each of four pairs of strips of 5 cells to the total tower level E T of all 25 crystals
(this “Fine Grain” veto uses a strip due to electron bending in the magnetic field),
and the longitudinal shower profile defined by the ratio of E T deposits in the HCAL
and ECAL portions of the calorimeter (H/E veto). The isolated electron/photon
has two additional requirements: the ECAL E T deposited in one of the five trigger
towers surrounding the central tower is below a programmable E T threshold and the
eight trigger towers surrounding the central tower in the 3 × 3 region have passed
the Fine Grain and H/E vetoes. For Run-2, the CMS Calorimeter Trigger hardware
was upgraded so that more complex algorithms could be deployed [21]. The e/γ and
τ candidates started with a local maximum around which the trigger towers were
dynamically clustered.
The LHCb Level-0 calorimeter trigger system combines the E T measurement in
clusters of 2 × 2 cells in the electromagnetic (ECAL) and hadronic calorimeters
(HCAL), as well as information from the Scintillator Pad Detector (SPD) and a
Preshower (Prs) to indicate the charged and electromagnetic nature of the clusters.
The calorimeter trigger system sends the highest E T hadron, electron, photon and
π 0 candidates and the total HCAL E T and SPD multiplicity to the Level 0 Decision
Unit (L0DU).
541
Fig. 12.4 ATLAS calorimeter electron/photon trigger algorithm
of each of four pairs of strips of 5 cells to the total tower level E T of all 25 crystals
(this “Fine Grain” veto uses a strip due to electron bending in the magnetic field),
and the longitudinal shower profile defined by the ratio of E T deposits in the HCAL
and ECAL portions of the calorimeter (H/E veto). The isolated electron/photon
has two additional requirements: the ECAL E T deposited in one of the five trigger
towers surrounding the central tower is below a programmable E T threshold and the
eight trigger towers surrounding the central tower in the 3 × 3 region have passed
the Fine Grain and H/E vetoes. For Run-2, the CMS Calorimeter Trigger hardware
was upgraded so that more complex algorithms could be deployed [21]. The e/γ and
τ candidates started with a local maximum around which the trigger towers were
dynamically clustered.
The LHCb Level-0 calorimeter trigger system combines the E T measurement in
clusters of 2 × 2 cells in the electromagnetic (ECAL) and hadronic calorimeters
(HCAL), as well as information from the Scintillator Pad Detector (SPD) and a
Preshower (Prs) to indicate the charged and electromagnetic nature of the clusters.
The calorimeter trigger system sends the highest E T hadron, electron, photon and
π 0 candidates and the total HCAL E T and SPD multiplicity to the Level 0 Decision
Unit (L0DU).