Speaker
Description
During the second run of operation, the LHC delivers proton-proton collisions at a
centre-of-mass energy of 13 TeV with a peak instantaneous luminosity of $1.5 \cdot
10^{34} cm^{-2}s^{-1}$ in 2016, almost double the peak luminosity reached during
Run-1 and far larger than the design value. To maintain acceptance for proton and
heavy ion collision events of interest without exceeding the 100 kHz limit, the CMS
Level-1 (L1) trigger has been being upgraded. The upgraded system makes use of
new Xilinx Virtex-7 based AMC cards form the microTCA technology. The L1
calorimeter trigger, which finds electrons, photons, tau leptons, jet candidates and
computes energy sums has been upgraded implementing isolation requirement,
multivariate regression, and pile-up mitigation techniques in order to reach
acceptable performance. The CMS muon detector was designed for preserving the
complementarity and redundancy of three separate muon detection systems,
Cathode Strip Chambers (CSC), Drift Tubes (DT) and Resistive Plate Chambers
(RPC), until they were combined at the input to the Global Trigger. The upgrade of
the muon trigger aimed at exploiting the redundancy of the three muon detection
systems earlier in the trigger processing chain in order to obtain a high-performance
trigger with higher efficiency and better rate reduction, implementing pattern
recognition and MVA (Boosted Decision Tree) regression techniques directly in the
trigger boards. In addition, the new global trigger is capable of evaluating complex
selection algorithms such as those involving the invariant mass of trigger objects.
The talk will cover the technological aspects of the Run II calorimeter trigger system.
Results of its performance during the 2016 collisions of the LHC will be presented
along with 2017 optimization for more intense conditions foreseen.
