Abstract
The VBF \(H^0\rightarrow b\bar{b}\) search channel has not been studied previously in the ATLAS collaboration. Some truth level studies were conducted for this channel for a generic analysis [61], but the work was very preliminary, and did not include any detector specific information. It did, however, list a few features of signal that could be exploited in the event selection: the presence of two “high-p T ” b-jets, showing an invariant mass peak, and a pair of jets in the forward and backward rapidity regions.
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Notes
- 1.
Note that the method used to determine the optimized selection criteria used “training” samples (of both MC signal and background samples), however, the resulting significance is calculated using “testing” samples, which is completely different MC samples of both signal and background. This was done to avoid sample bias in the selection criteria.
- 2.
If a certain trigger has thresholds that are too low, it may record events at a rate above the software and hardware set limits of the trigger system (as detailed in Sect. 4.3.1). Therefore, it often becomes “prescaled”, meaning only a fraction of triggered events are actually recorded. When a trigger is “unprescaled”, every event that satisfies the trigger requirement is recorded.
- 3.
Note that trigger signatures used at ATLAS are represented by a character string that always begins with the level of trigger considered (L1, L2 or EF), followed by strings that describe the cuts applied. For example EF_njX, where n represents the number of jets, and X describes the p T threshold. If no n is printed, a single jet trigger is implied.
- 4.
Trigger efficiencies are the ratio of the number of events that satisfy a trigger and the total number of events.
- 5.
The L1 jet trigger thresholds (eg. J10) does not directly represent the p T of the reconstructed jet, but rather a very rudimentary approximation of it. In reality, the J10 requirement at L1 translates to an offline jet with \(p_T>30\;\text{GeV}\) typically.
- 6.
The trigger EF_2b10_medium_4L1J10 required L1_4J10 to be used as a seed (4L1J10), and two b-jets (2b10) with “medium” selection criteria (medium).
- 7.
The trigger EF_2b10_medium_4j30_a4tc_EFFS satisfies the same requirements as EF_2b10_medium_4L1J10, and the requirement of four jets with \(p_T\gtrsim30\;\text{GeV}\) (4j30), reconstructed using the anti-k T algorithm with C = 0.4 (see Eq. 4.3) and topoclusters as objects (a4tc), with a full scan at EF (EFFS).
- 8.
The c-jets have the same scale factors as b-jets due to low statistics in the scale factor measurements.
- 9.
Efficiencies for MC samples are determined by using the flavour of jets taken from truth level information. Efficiencies for data are determined by extracting highly purified samples of b-jets, using various methods.
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Ouellette, E. (2015). Analysis and Trigger Strategy. In: Search for the Higgs Boson in the Vector Boson Fusion Channel at the ATLAS Detector. Springer, Cham. https://doi.org/10.1007/978-3-319-13599-1_5
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DOI: https://doi.org/10.1007/978-3-319-13599-1_5
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