Calorimeter Level 1 Trigger

Triggering is one of the extraordinary challenges facing detector designers at the high luminosity LHC collider. For the nominal LHC design luminosity of , an average of 25 events occur at the beam crossing frequency of 40 MHz. This input rate of interactions every second must be reduced by a factor of at least to 100 Hz, the maximum rate that can be archived by the on-line computer farm.

The US groups presently working on the Level 1 Calorimeter trigger are Fermilab and the University of Wisconsin. Other groups with potential interest in either calorimeter, muon or luminosity level 1 triggers include University of Michigan and Ohio State University. The Wisconsin group designed, built, and sucessfully operated the Zeus Calorimeter first level trigger, a fully pipelined deadtimeless 83 MHz system accepting data every 96 nsec. For SDC, the Wisconsin and Fermilab groups in this proposal collaborated on the trigger system. There was a considerable body of work produced on triggering including simulation studies, performance requirements, engineering and conceptual designs, hardware modules and Integrated Circuits. We had also produced detailed cost estimates based on this hardware and design work. Much of this research and experience is directly applicable to CMS.

As a first step in this effort we have reworked our SDC fast simulation program to describe the CMS detector geometry and materials. We have studied the expected CMS trigger rates and efficiencies for various algorithms and the efficiencies for several high physics processes. Our next steps are to investigate the numbers of bits, granularity and dynamic range of information needed for the ECAL and HCAL energy sums used in the cluster calculations and isolation schemes. We will study the jet, missing and total energy trigger rates and efficiencies. In particular the dynamic range needed for data transmission needs to be explored. We will perform a similar analysis for LHC triggers as we did for SDC triggers, where we determined the trigger efficiency for each process defined as a physics goal.

We have started to analyze the CMS baseline trigger system, along with the stated physics goals and are developing a proposal for requirements for the global level 1 trigger system, calorimeter level 1 trigger system and interface of the trigger system to the calorimeter front end electronics. We are studying thresholds and other requirements for single electrons, di-electrons, jets, single hadrons, , and missing . We propose to continue these studies. We will study the transmission of trigger data via fiber optics and work on the development of specification and performance requirements for the front end electronics and trigger interfaces to the fiber optics system. We will study the use of our GaAs Adder ASIC developed for SDC in the energy summation networks. We will continue our design studies of electron trigger algorithms and will work to develop the design for an ASIC to implement the electron trigger algorithm after a determination is made on the best algorithm. We also plan to investigate trigger system engineering, with particular attention paid to interfaces to front ends and control systems through use of our hardware trigger emulation modules developed for SDC.

List of Interested Groups:

• FNAL (Butler, Patrick), Michigan (Chapman), Ohio State (Ling), Wisconsin (Smith).