Abstract

The CMS High-Level Trigger (HLT) is designed to reduce the Level-1 accept trigger rate of 100 kHz to a final output rate of 100 Hz, at which selected events are written to permanent storage. In order to satisfy the very high performance requirements of CMS, the HLT will consist of a farm of commercial processors performing the online event filtering. The flexibility provided by a fully programmable environment implies that algorithmic changes can be easily introduced to improve the selection of various physics channels, as well as to deal with unforeseen experimental conditions. The filter farm software includes all major features of the offline reconstruction code. In this report, the selection algorithms and physic performance of the CMS HLT are presented.

Highlights

  • The Compact Muon Solenoid (CMS) [1] is a general purpose detector that will operate at LHC [2], a proton-proton c¢o¡¤l£¦l¥ ̈id§e©r witha centre-of-mass energy of 14 TeV and a bunch crossing rate of 40 MHz

  • The CMS trigger consists of two physical levels: a Level-1 trigger [3] and a High-Level Trigger (HLT) [4]

  • The main physics guidelines that direct the HLT code development are the following: 0 the HLT has to fulfil the CMS physics program with high efficiency; 0 the event selection must be inclusive in order to select unexpected new phenomena; 0 selection conditions must be independent of the detailed knowledge of calibration constants and other run conditions; 0 trigger and reconstruction efficiencies must be measurable from data alone; 0 events selected should be tagged in order to indicate the reasons for their selection; 0 the code should be as close as possible to the offline reconstruction code

Read more

Summary

Introduction

The Compact Muon Solenoid (CMS) [1] is a general purpose detector that will operate at LHC [2], a proton-proton c¢o¡¤l£¦l¥ ̈id§e©r witha centre-of-mass energy of 14 TeV and a bunch crossing rate of 40 MHz. At the design luminosity of , each crossing results in an average of about 20 inelastic pp events producing approximately 1 MB o!f ze¡¤r¢o" -suppressed data. The!sefi¡#g¢u" res are many orders of magnitude larger than the archival storage capability of. For this reason, CMS needs of an excellent trigger system in order to reduce the event rate to the storage rate, while maintaining a high selection efficiency for the physics phenomena that the experiment intends to study

CMS Trigger System
Physics requirements for HLT
HLT Reconstruction and Selection
Electrons and photons
Jets and Missing Energy
HLT Performance
Findings
Summary
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call