Level 1 trigger system for the Belle II experiment

Yoshihito Iwasaki, Byung Gu Cheon, Eunil Won, Xin Gao, Luca Macchiarulo, Kurtis Nishimura, Gary Varner

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)


The super-KEKB B factory, currently under construction at the KEK High Energy Accelerator Research Organization in Japan, has a goal of producing 50 ab -1 of integrated luminosity, thus allowing the Belle II experiment to study rare decays of B mesons, D mesons, and τ leptons. Such large statistics on these decays provide an experimental probe of physics beyond the Standard Model. An online trigger system is indispensable to Belle II to reduce the number of beam background events associated with high electron and positron beam currents, as well as to enhance physics-oriented events. For this purpose, we have designed the Belle II online trigger system with two kinds of primary Level 1 trigger components: a track trigger and an energy trigger. The track trigger is composed of 2-dimensional and 3-dimensional tracking algorithms, and the energy trigger implements algorithms based on total energy, isolated clusters, and identification of Bhabha events. In addition, precise event trigger timing and muon tagging information are provided by the time-of-propagation detector and iron flux return muon detector, respectively.

Original languageEnglish
Article number5740389
Pages (from-to)1807-1815
Number of pages9
JournalIEEE Transactions on Nuclear Science
Issue number4 PART 1
Publication statusPublished - 2011 Aug

Bibliographical note

Funding Information:
Manuscript received June 30, 2010; revised December 02, 2010, February 10, 2011; accepted February 17, 2011. Date of publication March 28, 2011; date of current version August 17, 2011. This work was supported by the National Research Foundation of Korea under Grant No. 2009-0076449.


  • Belle II experiment
  • Level I hardware trigger
  • super-KEKB factory

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering
  • Electrical and Electronic Engineering


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