Speaker
Alex Tapper
(Imperial College Sci., Tech. & Med. (GB))
Description
The Compact Muon Solenoid (CMS) experiment has implemented a
sophisticated two-level online selection system that achieves
a rejection factor of nearly 10e5. During Run II, the LHC will
increase its centre-of-mass energy up to 13 TeV and progressively
reach an instantaneous luminosity of 2e34cm-2s-1. In order to
guarantee a successful and ambitious physics programme under
this intense environment, the CMS Trigger and Data acquisition
(DAQ) system has been upgraded. The upgraded CMS L1 trigger is
designed to improve the performance at high luminosity and large
number of simultaneous inelastic collisions per crossing (pile-up).
During the technical stop at the beginning of 2016, all the
electronic boards of the CMS L1 trigger have been replaced,
tested, and commissioned with data. The L1 calorimeter trigger
hardware and architecture have been redesigned to maintain the
current thresholds for electrons and photons in these more challenging
conditions. This design benefits from recent microTCA technology,
allowing sophisticated algorithms to be deployed, better exploiting
the calorimeter granularity and opening the possibility of making
correlations between different parts of the detector. The new
Level-1 Calorimeter Trigger uses a novel Time Multiplexed Trigger
which allows the L1 trigger a global view of the entire event with
higher granularity. Smarter, more complex, and innovative algorithms
are now the core of the first decision layer of CMS: the upgraded
trigger system implements pattern recognition and MVA (Boosted
Decision Tree) regression techniques in the trigger boards for
$\text{p}_{\text{T}}$ assignment, pile up subtraction, and
isolation requirements for muons, electrons, and taus. In addition,
the new global trigger is capable of evaluating complex selection
algorithms such as those involving the invariant mass of trigger
primitives. All the above is drastically reducing the trigger rate
and improving the trigger efficiency for a wide variety of physics
signals. In this presentation the upgraded CMS L1 trigger design
and its performance are described. The impact of the improved
selection criteria on benchmark physics channels such as Higgs
and Supersymmetry will be presented as well in this talk.
