Plots approved for Muon APE Performance

Impact of the muon Alignment Position Errors (APE) on the 2016 Startup HLT efficiency of the Mu20 trigger path :

The two CMS endcaps were opened during the 2015 EOY shutdown, hence all the endcap muon chambers were misaligned in the 2016 startup phase (typical transverse shift of about 2mm).Instead the barrel muon detectors were not moved during the 2015 EOY. The non-zero muon APE, covering the expected misalignments, were introduced for the first time in the 2016 Run.

The HLT efficiencies have been measured from Z → 𝜇+𝜇- events, using the Tag-and-Probe method, where the offline reconstructed tag and probe muons are required to satisfy a tight selection (tight identification and isolation cuts). The tag muon is matched to the isolated trigger muon object that has been used to collect the events, and is required to have an offline transverse momentum pT > 22 GeV. The probe muon is required to be matched to the L1 trigger object used as seed for the HLT muon reconstruction. The two muons are required to have opposite charge, a geometrical separation of ΔR > 0.6 and an invariant mass within [86, 96] GeV. The efficiency measurements in the plots are shown as a function of the offline muon 𝜂 and pT. The HLT muon efficiency is defined as the number of probe muons passing the HLT and offline quality criteria over the number of probe muons passing the offline quality criteria and L1 matching requirements described above. The non-zero muon startup APE has increased the HLT efficiency by ~ 7% for 2.1 < 𝜂 < 2.4, ~ 3.5% for -2.4 < 𝜂 < -2.1 and ~ 1% over the remaining endcap regions. No change in the barrel region has been observed as expected. A consistent increase of ~ 2% in HLT efficiency has been observed over the whole pT range, for 1.2 < 𝜂 < 2.4. The stronger impact of APE has been observed is the highest positive eta bin (2.1 < 𝜂 < 2.4), larger compared to the respective negative side, resulting from an overall rotation of the whole positive endcap detector after the 2015 EOY shutdown. This was cured by the standard muon alignment, which introduced the updated conditions in the trigger during Summer 2016, after the startup phase.

Caption Figure Figure
HLT efficiency versus muon eta and muon pt. The error bars include only the statistical uncertainty. Two bins at pT < 20 GeV have efficiencies below 10%, falling outside the top panel. The corresponding ratios are visible in the bottom panel with large error bars. Startup indicates the initial alignment in 2016. [Get pdf version left],[Get pdf version right]
Contacts: Giovanni Abbiendi, Simranjit Singh Chhibra

-- ElisabettaGallo - 2016-11-02

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Topic revision: r1 - 2016-11-02 - ElisabettaGallo
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