Performance of a Soft Muon, Hard Jet and Moderate Missing Energy Trigger in 2018 Data (CMS DP-2020/004)

This note presents the performance of a dedicated High-Level Trigger (HLT) algorithm that requires a low p_T muon, a jet with transverse momentum p_T greater than 100 GeV and missing transverse momentum p_T^miss greater than 80 GeV. The trigger algorithm targets events with ISR signatures with moderate p_T^miss and soft muons, that are typical in SUSY models with very compressed mass spectra. The rate of the trigger is approximately 12 Hz for an instantaneous luminosity of 1.8 x 10³⁴ cm^-2 s^-1 and an average pileup of 50. The efficiency measurements are performed using 59.7 fb^-1 of data recorded by the CMS detector in 2018, in orthogonal control samples collected using triggers based on pure p_T^miss and single-muon requirements. The trigger efficiencies are parametrised in terms of the offline quantities of the three legs of the trigger: muon p_T, jet p_T and p_T^miss.

Muon Leg The efficiency of the muon leg of a High-Level Trigger (HLT) algorithm that requires a muon with transverse momentum pT greater than 3 GeV, within pseudorapidity |η| < 1.5, a missing transverse momentum pTmiss greater than 80 GeV, a missing transverse hadronic energy HTmiss greater than 80 GeV and a jet with transverse momentum pT greater than 100 GeV, within an |η| < 2.5. The Level-1 (L1) trigger seed condition has the same requirements on the muon and jet legs, while requiring 40 GeV of pTmiss. The rate of the HLT algorithm is approximately 12 Hz for an instantaneous luminosity of 1.8 x 1034 cm-2 s-1 and an average pileup of 50, defined as the number of secondary proton-proton collisions occurring in an LHC bunch crossing. pTmiss is defined as the amplitude of the negative vector sum of the transverse momentum pT of all particle candidates. HTmiss is defined as the amplitude of the negative vector sum of the transverse momentum pT of all jets with pT > 20 GeV and |η| < 5 that pass tight identification criteria based on their charged or neutral, hadronic or electromagnetic energy fractions. The calculation of both pTmiss and HTmiss includes the contribution from all muons in the event. At the L1 trigger, jets and pTmiss are reconstructed based on the calorimeter information only and do not include muons. The efficiency measurement is performed using 59.7 fb-1 of data recorded by the CMS detector in 2018, in orthogonal control samples collected using reference triggers based on pure pTmiss, requiring pTmiss > 120 GeV and HTmiss > 120 GeV, in order to minimise any potential biases in the measurement. Additional requirements on the offline leading jet pT > 150 GeV and pTmiss > 250 GeV are applied to ensure that the measurement is done in a parameter space in which the other two legs are on the plateau of the efficiency turn-on curves. The efficiency is shown as a function of the offline muon pT and is represented by black points that are associated to the y-axis on the left. The numerator (filled histogram) and denominator (dashed line) entering the efficiency calculation are also shown and are associated to the y-axis on the right, indicating the number of events. Events beyond the range of the histograms are summed into the final overflow bin. [Get pdf version] Contact: Mateusz Zarucki

Jet Leg The efficiency of the jet leg of a High-Level Trigger (HLT) algorithm that requires a muon with transverse momentum pT greater than 3 GeV, within pseudorapidity |η| < 1.5, a missing transverse momentum pTmiss greater than 80 GeV, a missing transverse hadronic energy HTmiss greater than 80 GeV and a jet with transverse momentum pT greater than 100 GeV, within an |η| < 2.5. The Level-1 (L1) trigger seed condition has the same requirements on the muon and jet legs, while requiring 40 GeV of pTmiss. The rate of the HLT algorithm is approximately 12 Hz for an instantaneous luminosity of 1.8 x 1034 cm-2 s-1 and an average pileup of 50, defined as the number of secondary proton-proton collisions occurring in an LHC bunch crossing. pTmiss is defined as the amplitude of the negative vector sum of the transverse momentum pT of all particle candidates. HTmiss is defined as the amplitude of the negative vector sum of the transverse momentum pT of all jets with pT > 20 GeV and |η| < 5 that pass tight identification criteria based on their charged or neutral, hadronic or electromagnetic energy fractions. The calculation of both pTmiss and HTmiss includes the contribution from all muons in the event. At the L1 trigger, jets and pTmiss are reconstructed based on the calorimeter information only and do not include muons. The efficiency measurement is performed using 59.7 fb-1 of data recorded by the CMS detector in 2018, in orthogonal control samples collected using reference triggers based on a single-muon condition, requiring an isolated high pT muon with pT > 24 GeV, as well as triggers based on pure pTmiss, requiring pTmiss > 120 GeV and HTmiss > 120 GeV, in order to minimise any potential biases in the measurement. Additional requirements on the offline muon pT > 30 GeV and pTmiss > 100 GeV are applied to ensure that the measurement is done in a parameter space on the plateau of the efficiency turn on curves of both the other two legs and the reference trigger. The efficiency is shown as a function of the leading offline jet pT and is represented by black points that are associated to the y-axis on the left. The numerator (filled histogram) and denominator (dashed line) entering the efficiency calculation are also shown and are associated to the y-axis on the right, indicating the number of events. Events beyond the range of the histograms are summed into the final overflow bin. [Get pdf version] Contact: Mateusz Zarucki

Missing Transverse Energy Leg The efficiency of the missing transverse momentum pTmiss leg of a High-Level Trigger (HLT) algorithm that requires a muon with transverse momentum pT greater than 3 GeV, within pseudorapidity |η| < 1.5, a missing transverse momentum pTmiss greater than 80 GeV, a missing transverse hadronic energy HTmiss greater than 80 GeV and a jet with transverse momentum pT greater than 100 GeV, within an |η| < 2.5. The Level-1 (L1) trigger seed condition has the same requirements on the muon and jet legs, while requiring 40 GeV of pTmiss. The rate of the HLT algorithm is approximately 12 Hz for an instantaneous luminosity of 1.8 x 1034 cm-2 s-1 and an average pileup of 50, defined as the number of secondary proton-proton collisions occurring in an LHC bunch crossing. pTmiss is defined as the amplitude of the negative vector sum of the transverse momentum pT of all particle candidates. HTmiss is defined as the amplitude of the negative vector sum of the transverse momentum pT of all jets with pT > 20 GeV and |η| that pass tight identification criteria based on their charged or neutral, hadronic or electromagnetic energy fractions. The calculation of both pTmiss and HTmiss includes the contribution from all muons in the event. At the L1 trigger, jets and pTmiss are reconstructed based on the calorimeter information only and do not include muons. The efficiency measurement is performed using 59.7 fb-1 of data recorded by the CMS detector in 2018, in orthogonal control samples collected using reference triggers based on a single-muon condition, requiring an isolated high pT muon with pT > 24 GeV, in order to minimise any potential biases in the measurement. Additional requirements on the offline leading jet pT > 150 GeV and muon pT > 30 GeV are applied to ensure that the measurement is done in a parameter space in which the other two legs are on the plateau of the efficiency turn-on curves. In order to obtain a cleaner sample, offline jets that are within ΔR < 0.4 (where ΔR = √(Δφ2+Δη2)) with respect to leptons are not considered. In order to make the measurement less susceptible to the differences between the pTmiss definitions at L1 and HLT, an upper cut of 40 GeV is applied on the muon pT. The efficiency is shown as a function of the offline pTmiss and is represented by black points that are associated to the y-axis on the left. The numerator (filled histogram) and denominator (dashed line) entering the efficiency calculation are also shown and are associated to the y-axis on the right, indicating the number of events. Events beyond the range of the histograms are summed into the final overflow bin. [Get pdf version] Contact: Mateusz Zarucki

-- ElisabettaGallo - 2020-02-05