Data Scouting in CMS

Abstract

Data scouting in collider experiments refers to the use of physics objects reconstructed online during data taking to perform searches and measurements. The technique, pioneered by the CMS experiment, allows events to be recorded for analyis at a rate of several additional kHz with negligible impact on total data volume. Dijet resonance searches have used data scouting to probe resonance masses far lower than those explorable with a standard offline physics analysis, and new developments for LHC Run II enable a wider range of analyses to take advantage of this new trigger paradigm. We describe the scouting technique, give an overview of its past use in CMS, and provide details on the implementation of the scouting streams being used in Run II. We also show results from the first scouting-based physics analysis with 13 TeV data.

Computing and Data Handling

“…The CMS collaboration started using the strategy, Data Scouting, for jet events with high energy calorimeter deposits during Run I. For Run II, they expanded the strategy to include events with the particle flow topology, and have produced several promising physics results [28].…”

Naturalness confronts nature: searches for supersymmetry with the CMS detector in pp collisions at √s = 8 and $13$ TeV

“…An extension of the alignment/calibration data-taking strategy, referred to as data scouting [155], is based on reducing the event size from the default of ∼ 1 Megabyte (MB) in order to increase the recorded event rate and thus increase physics signal acceptance. This approach, first implemented at the LHC by the CMS experiment in 2011 [156], allows us to increase the physics signal acceptance of CMS even in the presence of backgrounds with large cross sections.…”

“…B, where this strategy allows the search to be extended into a low-dijet-mass region previously only accessible at lower-energy colliders [157,158]. the corresponding event content [155]. Calo scouting, which selects events based only on Calo jets and records only calorimetric information, has a very small event size of ∼ 1.5 kilobyte (kB), allowing the rate to go as a high as 3.8 kHz.…”

“…T , reconstructed vertices, PFreconstructed electrons, muons, photons, and the median energy density in an event ρ, which amounts to ∼ 10 kB. The event content for Calo scouting (right), consists of anti-k T R = 0.4 Calo jets, Calo E miss T , vertices (if another trigger reconstructed them for this event), and the median energy density in an event ρ, which amounts to ∼ 1.5 kB [155].…”

“…First, a low-mass search, for resonances with mass between 0.6 and 1.6 TeV, is performed using dijets that are reconstructed in the high-level trigger in a process called data scouting [155]. Data scouting was previously used for a low-mass search by CMS at √ s = 8 TeV [157], and a similar trigger-level search was recently reported by ATLAS at √ s = 13 TeV [266].…”