CMS Bulletin

TRIGGER

Level-1 Trigger

Data-taking continues at cruising speed, with high availability of all components of the Level-1 trigger. We have operated the trigger up to a luminosity of 7.6E33, where we approached 100 kHz using the 7E33 prescale column.  Recently, the pause without triggers in case of an automatic "RESYNC" signal (the "settle" and "recover" time) was reduced in order to minimise the overall dead-time. This may become very important when the LHC comes back with higher energy and luminosity after LS1. We are also preparing for data-taking in the proton-lead run in early 2013. The CASTOR detector will make its comeback into CMS and triggering capabilities are being prepared for this. Steps to be taken include improved cooperation with the TOTEM trigger system and using the LHC clock during the injection and ramp phases of LHC.

Studies are being finalised that will have a bearing on the Trigger Technical Design Report (TDR), which is to be ready early next year. For muons, the question of how and in which system muon isolation may be best achieved is important: this might be the Global Trigger, the Global Muon Trigger, or the Calorimeter Trigger. Another important question is how improved calorimeter trigger information will be made available right after LS1. By early next year the hardware platforms will have to be chosen so that in 2014 systems can be installed first in the CMS Electronics Integration Facility in B904 and then at P5, to be ready for parallel operation in 2015. The project recently passed an important milestone with the completion of Part 1 of a Conceptual Design Review of the L1 upgrade.

Trigger Studies Group

Since the last CMS Week the Trigger Studies Group (TSG) has successfully developed and deployed trigger menus targeting luminosities of 7E33 and 8E33 (the latter was never used in real running).  Dedicated menus were also prepared for data-taking during the high-pileup and b*=90m fills. Other highlights include the successful development and integration of triggers for heavy-ion physics in preparation of the 2013 proton-lead run.

The HLT continues to perform well and numerous improvements have been made to control rates at the highest luminosities/pile-up. The average “core” and “parking“ rates are ~350 Hz and ~600 Hz, and the cross-section is almost constant up to the highest pile-up. The CPU performance of the HLT is being monitored on a regular basis; the CPU time per event scales linearly with luminosity/pile-up and fits within the total budget of the extended HLT farm.

The TSG organised a two-day workshop in November to focus on plans and actions for the 2014/2015 run.  New members who wish to contribute to this effort are very welcome. The TSG also welcomes Simone Gennai who will take over from Tulika Bose as the new Deputy Trigger Coordinator.