A novel in situ trigger combination method

Abstract

Searches for rare physics processes using particle detectors in high-luminosity colliding hadronic beam environments require the use of multi-level trigger systems to reject colossal background rates in real time. In analyses like the search for the Higgs boson, there is a need to maximize the signal acceptance by combining multiple different trigger chains when forming the offline data sample. In such statistically limited searches, datasets are often amassed over periods of several years, during which the trigger characteristics evolve and system performance can vary significantly. Reliable production cross-section measurements and upper limits must take into account a detailed understanding of the effective trigger inefficiency for every selected candidate event. We present as an example the complex situation of three trigger chains, based on missing energy and jet energy, that were combined in the context of the search for the Higgs (H) boson produced in association with a W boson at the Collider Detector at Fermilab (CDF). We briefly review the existing techniques for combining triggers, namely the inclusion, division, and exclusion methods. We introduce and describe a novel fourth in situ method whereby, for each candidate event, only the trigger chain with the highest a priori probability of selecting the event is considered. We compare the inclusion and novel in situ methods for signal event yields in the CDF W H search. This new combination method, by virtue of its scalability to large numbers of differing trigger chains and insensitivity to correlations between triggers, will benefit future long-running collider experiments, including those currently operating on the Large Hadron Collider.

Search for the standard model Higgs boson produced in association with aW±boson with7.5 fb−1Aaltonen1, González2, Amerio3 et al. 2012Phys. Rev. D100110View full textAdd to dashboardCite

“…The efficiency of the different triggers is measured using the lepton triggered data and is parametrized using sigmoid turn-on curves as a function of / E T , without correcting for the muon momenta. The novel method exploited to combine and parametrize all the three trigger paths is described in [30], which can be generalized to any combination of different trigger paths, allowing optimal performance.…”

“…The lepton trigger efficiency is measured using a clean W → lν data sample, obtained from other triggers after applying more stringent offline cuts. The / E T trigger efficiency is obtained using a trigger combination method [30]. The primary vertex efficiency is obtained using the vertex distribution from the minimum bias data.…”

Measurement of the Single Top Quark Cross Section in the Lepton Plus Jets Final State in Proton-Antiproton Collisions at a Center of Mass Energy of 1.96 TeV Using the CDF II Detector

“…A sophisticated method [124] is developed for combining these triggers. For an event in which more than one trigger fired, the probability of passing a specific trigger is computed (called the "trigger weight") for each trigger fired.…”

The performance of the jet trigger for the ATLAS detector during 2011 data taking

“…Multi-jet triggers have been used in signal selection and multi-jet background estimation in searches for the Higgs boson, supersymmetry, and other, beyond-the-SM, processes [39][40][41]. During 2011, multi-jet triggers requiring between three and six jets were available, with E T thresholds at the EF ranging from 30 to 100 GeV.…”