Preliminary results on the performance of the Track-Based Muon Alignment in 2018

The performance of Track-Based muon alignemnt algorithm was studied with a subset of 2018 data.
The DT and CSC geometries have been derived with early 2018 data. Also, Alignment Position Error have been estimated.
Link to the DP: http://cds.cern.ch/record/2290516?ln=en

See also: CMS DP-2017/046

Introduction

These plots quantify the reconstruction improvement due to the Track Based muon alignment performed with 2018 early data in comparison with 2017 data and geometries.

We reconstruct muons using 3 different scenarios:
→ Reconstructed 2017 data based on geometry obtained using 2017 data
→ Reconstructed 2018 data based on geometry obtained using 2017 data
→ Reconstructed 2018 data based on geometry obtained using 2018 data

We analyzed 23.35% of the 2018A dataset, produced in Fall of 2018 (Lint=~2.2 fb-1), looking for μ and Z→μμ decays.
→ Basic set of requirements on pT(μ)>30 GeV, χ2, num. of hits…
→ One μ is reconstructed using only tracker information and the other using both the
tracker and the muon system information (randomly).
→ The mass resolution is shown as a function of Φ/η of the STA muon
→ Why 23.35%? A data deletion accident deleted much of the v1 dataset shortly before alignment was run. Still, enough data was present to produce quality results.

The performance are expected to be similar al low η, since the position of the Drift Tubes is similar between 2017 and 2018, while at high η a substantial improvement is expected, as a consequence that the CMS detector has been opened and closed.

Dimuon width

The invariant mass of dimuon pairs is computed by reconstructing one muon using only muon detector information (standalone) and the other using both the tracker and the muon system information (global). The width of the dimuon invariant mass distribution is shown in bins of the standalone muon η.

The black distribution refers to muons reconstructed using the muon system geometry computed in 2017 with 2018 data, the red distribution refers to muons reconstructed using the geometry computed with early 2018 data, and the blue distribution refers to muons reconstructed using the muon system geometry computed in 2017 with 2017 data. In other words, the blue and red distributions compare 2017 and 2018 performance, while black shows 2018 startup performance.

The performances are similar at low η, since the position of the Drift Tubes is similar in 2017 and 2018. However, at high η a substantial improvement is observed, as the CMS detector has been opened and closed.

Dimuon mean

The invariant mass of dimuon pairs is computed by reconstructing one muon using only muon detector information (standalone) and the other using both the tracker and the muon system information (global). The mean of the dimuon invariant mass distribution is shown in bins of the standalone muon η.

The black distribution refers to muons reconstructed using the muon system geometry computed in 2017 with 2018 data, the red distribution refers to muons reconstructed using the geometry computed with early 2018 data, and the blue distribution refers to muons reconstructed using the muon system geometry computed in 2017 with 2017 data. In other words, the blue and red distributions compare 2017 and 2018 performance, while black shows 2018 startup performance.

The performances are similar at low η, since the position of the Drift Tubes is similar in 2017 and 2018. However, at high η a substantial improvement is observed, as the CMS detector has been opened and closed.

-- RyanDalrympleMueller - 2018-08-14