Performance of the CMS Muon Detectors in early 2016 collision runs

Minor updates to text 12.08.2016

This twiki page contains the plots in CMS DP-2016/046, which summarizes the performance of the CMS Muon subdetectors (CSC, DT, and RPC) in the early LHC running of 2016 and supersedes CMS-DP-2016-023 (June 2016). All data are from pp collisions at √s = 13 TeV and with full magnetic field, B = 3.8 T. Clicking on a small image will open a full-size PNG. If a PDF version of a plot is available, click the pdf version link at the top of the image to display or download it (web-browser dependent.)

Abstract

The performance of the three CMS muon subdetectors: DT, RPC and CSC, was evaluated with the first collision data in 2016 and compared to 2015. Unless otherwise noted, these measurements were performed using a sample enriched in Z → μμ events.

Contacts

CMS DPG conveners of the Muon subdetectors

subdetector	email
Muon DPG Office	cms-muon-DPGO@cernNOSPAMPLEASE.ch
RPC	cms-dpg-conveners-rpc@cernNOSPAMPLEASE.ch
DT	cms-dpg-conveners-dt@cernNOSPAMPLEASE.ch
CSC	cms-dpg-conveners-csc@cernNOSPAMPLEASE.ch

References

This is the link to CMS DP-2016/046

• http://cds.cern.ch/record/2202964
  
• http://cds.cern.ch/record/2202964/files/DP2016_046.pdf

This is the link to the earlier Detector Performance Note CMS-DP-2016-023

• http://cds.cern.ch/record/2160350
  
• http://cds.cern.ch/record/2160350/files/DP2016_023.pdf

The following published CMS papers are useful for understanding the terminology of the Muon system, the techniques used in obtaining these performance results, and the concepts of muon reconstruction:

• http://cds.cern.ch/record/1558674 - The performance of the CMS muon detector in proton-proton collisions at √s = 7 TeV at the LHC - CMS MUO-11-001
• http://cds.cern.ch/record/1456510 - Performance of CMS muon reconstruction in pp collision events at √s = 7 TeV - CMS MUO-10-004

Figure	Caption
pdf version	One quadrant of the CMS detector This figure depicts one quadrant of the CMS detector in its Run II configuration (from 2015), with the Muon detectors in colour.

Local reconstruction efficiency

CSC Segment Efficiency

A segment in a CSC is a straight-line track segment reconstructed from the hits on the 6 layers of the CSC. Segments are used as seeds for the full CMS muon track reconstruction algorithm, in combination with tracks reconstructed in the Silicon Tracker, in both the CMS High-Level Trigger (HLT) and CMS offline muon reconstruction. These efficiencies were obtained using a Tag & Probe technique in which Z→μμ candidates are selected from events collected with a 'single muon' trigger, according to the invariant mass of the combination of a reconstructed muon (tag) with a reconstructed track (probe). The tag is a silicon tracker track matched to at least two segments in the muon detectors, the probe is a high quality silicon tracker track, and the invariant mass of the pair, considered as muons, should be near that of the Z. The probe track is projected into the CSC system and a matching segment is searched for in each CSC the track traverses. To reduce backgrounds and ensure the probe actually enters the CSC under consideration, compatible hits are also required in a downstream CSC. In rings ME2/1, 3/1, and 4/1 each chamber covers 20° in φ all other chambers cover 10° in φ.

Figure	Caption
pdf version	Measured efficiency (%, with statistical uncertainty) of each CSC in the CMS endcap muon detector to provide a reconstructed muon track segment The efficiency (in %, with statistical uncertainty only) of each Cathode Strip Chamber in the CMS endcap muon detector to provide a reconstructed muon track segment. There are a few (out of the total 540) chambers with known inefficiency usually due to one or more failed electronics boards which cannot be repaired without major intervention and dismantling of the system. There are also occasional temporary failures of electronics boards, lasting from periods of hours to days, which can be recovered without major intervention. Both contribute to lowered segment efficiency.
pdf version	Measured efficiency (%, with statistical uncertainty) of each CSC in the CMS endcap muon detector to provide a reconstructed muon track segment The efficiency (in %) of each Cathode Strip Chamber in the CMS endcap muon detector to provide a reconstructed muon track segment. As the previous plot, but without uncertainty in each cell.
pdf version	Measured efficiency (%, with statistical uncertainty) of each CSC in the CMS endcap muon detector to provide a reconstructed muon track segment The efficiency (in %) of each Cathode Strip Chamber in the CMS endcap muon detector to provide a reconstructed muon track segment. As the previous plot, but without any text in each cell.
pdf version	Measured efficiency (with statistical uncertainty) of each ring of CSCs in the ME1 station to provide a reconstructed muon track segment, as a function of pT The efficiency of each ring of CSCs in the first station (closest to the IP), ME1, to provide a reconstructed muon track segment, as a function of the pT of the muon. These values average over all the CSCs in the ME1 station.
pdf version	Measured efficiency (with statistical uncertainty) of each ring of CSCs in the ME1 station to provide a reconstructed muon track segment, as a function of φ The efficiency of each ring of CSCs in the first station (closest to the IP), ME1, to provide a reconstructed muon track segment, as a function of the φ of the muon. These values average over all the CSCs in the ME1 station.
pdf version	Measured efficiency (with statistical uncertainty) of each station of CSCs to provide a reconstructed muon track segment, as a function of pT The efficiency of each station of CSCs (ME1, ME2, ME3, ME4) to provide a reconstructed muon track segment, as a function of the pT of the muon. These values average over all the CSCs in each station separately.
pdf version	Measured efficiency (with statistical uncertainty) of each station of CSCs to provide a reconstructed muon track segment, as a function of η The efficiency of each station of CSCs (ME1, ME2, ME3, ME4) to provide a reconstructed muon track segment, as a function of the η of the muon. These values average over all the CSCs in each station separately.
pdf version	Measured efficiency (with statistical uncertainty) of each station of CSCs to provide a reconstructed muon track segment, as a function of φ The efficiency of each station of CSCs (ME1, ME2, ME3, ME4) to provide a reconstructed muon track segment, as a function of the φ of the muon. These values average over all the CSCs in each station separately.
pdf version	CSC reconstructed segment efficiency - 1D summary Measured efficiency (%) of each CSC in the CMS Endcap Muon detector to provide a reconstructed muon track segment. There is one entry per CSC. Note that there are 540 CSCs in the system, but that the ME1/1 chambers are divided into two strip regions, labelled ME1/1A and ME1/1B giving effectively 612 separate detector regions, thus accounting for the total number of entries of 612 in each plot.

DT Hit Efficiency

The Drift Tube (DT) efficiency to detect a single hit was defined and measured as the ratio between the number of detected and expected hits. The position of expected hits was determined using sets of well reconstructed track segments: at least 7 or at least 3 hits were required to be associated to a segment, in the φ and θ view respectively. Moreover the segment itself was required to cross the chamber with an inclination lower than 45 degrees. The intersection of such a high quality track segment with a DT layer determined the position of the expected hit. The cell is considered efficient if a hit is found within the tube where it is expected to be. Such efficiency can be computed choosing different detector granularities. We present results for Phi (φ) layer, Theta (θ) layer, Phi (φ) super-layer, and chamber efficiency. The plots show the efficiency distributions of the considered detector components.

Figure	Caption
	DT single hit efficiency (2016) - φ layers This figure shows the measured efficiencies for φ layers.
	DT single hit efficiency (2016) - θ layers This figure shows the measured efficiencies for θ layers.
	DT single hit efficiency (2016) - φ superlayers This figure shows the measured efficiencies for φ superlayers.

pdf version

DT single hit efficiency (2016) - chambers This figure shows the measured efficiencies for chambers.

RPC Hit Efficiency

The RPC efficiency is calculated as the ratio between the number of detected and the number of expected hits. Expected hits are defined using a segment extrapolation method. Standalone muon tracks are reconstructed without taking into account RPC hits in order to avoid biases. Segments (DT in the Barrel and CSC in the Endcap) that belong to a standalone muon track are selected and extrapolated to the plane of a given RPC. The detector unit is considered efficient if an RPC reconstructed hit is found within ± 2 strips from the position extrapolated from the DT/CSC segment. More details about the segment extrapolation method can be found in the following references:
[1] Camilo Andrés Carrillo Montoya et al., Search for Heavy Stable Charged Particles in the CMS Experiment using the RPC Detectors, CMS-TS-2011-018, CERN-THESIS-2011-032, http://inspirehep.net/record/1088194
[2] CMS Collaboration, Performance study of the CMS barrel resistive plate chambers with cosmic rays, JINST 5 (2010) T03017, http://iopscience.iop.org/article/10.1088/1748-0221/5/03/T03017

Figure	Caption
pdf version	RPC hit efficiency (2016) - Barrel This figure shows the overall efficiency for each RPC barrel roll. The underflow entries are from rolls with efficiency lower than 70%, caused by the known hardware problems – chambers with gas leak problems in the barrel and low voltage problems in the endcap. These rolls are 1.8% of all barrel rolls.
pdf version	RPC hit efficiency (2016) - Endcap This figure shows the overall efficiency for each RPC endcap roll. The underflow entries are from rolls with efficiency lower than 70%, caused by the known hardware problems – chambers with gas leak problems in the barrel and low voltage problems in the endcap. These rolls are 1.2% of all endcap rolls.

Local Trigger Efficiency

CSC trigger primitive efficiency

A Trigger Primitive in a CSC is a pattern of hits consistent with arising from a muon track crossing the chamber. The CSC trigger primitive efficiency is defined as the ratio between number of observed trigger primitives and the expected number of trigger primitives. These efficiencies were obtained using a Tag & Probe technique in which Z→μμ candidates are selected from events collected with a 'single muon' trigger, according to the invariant mass of the combination of a reconstructed muon (tag) with a reconstructed track (probe). The tag is a silicon tracker track matched to at least two segments in the muon detectors, the probe is a high quality silicon tracker track, and the invariant mass of the pair, considered as muons, should be near that of the Z. The probe track is projected into the CSC system and a nearby trigger primitive is searched for in each CSC the track traverses. A matching trigger primitive must be found within 5 cm or 5σ (where σ is the uncertainty in the position measurement).To reduce backgrounds and ensure the probe actually enters the CSC under consideration, compatible hits in a CSC downstream are also required. In rings ME2/1, 3/1, and 4/1 each chamber covers 20° in φ; all other chambers cover 10° in φ.

Figure	Caption
pdf version	Measured efficiency (%, with statistical uncertainty) of each CSC in the CMS endcap muon detector to provide a trigger primitive for the CMS Level-1 trigger The efficiency (in %, with statistical uncertainty only) of each Cathode Strip Chamber in the CMS endcap muon detector to provide a trigger primitive for input to the CMS Level-1 trigger. There are a few (out of the total 540) chambers with known inefficiency usually due to one or more failed electronics boards which cannot be repaired without major intervention and dismantling of the system. There are also occasional temporary failures of electronics boards, lasting from periods of hours to days, which can be recovered without major intervention. Both contribute to lowered trigger primitive efficiency.
pdf version	Measured efficiency (%, with statistical uncertainty) of each CSC in the CMS endcap muon detector to provide a trigger primitive for the CMS Level-1 trigger The efficiency (in %) of each Cathode Strip Chamber in the CMS endcap muon detector to provide a trigger primitive for the CMS Level-1 trigger. As the previous plot, but without uncertainty in each cell.
pdf version	Measured efficiency (%, with statistical uncertainty) of each CSC in the CMS endcap muon detector to provide a trigger primitive for the CMS Level-1 trigger The efficiency (in %) of each Cathode Strip Chamber in the CMS endcap muon detector to provide a trigger primitive for the CMS Level-1 trigger. As the previous plot, but without any text in each cell.
pdf version	Measured efficiency (with statistical uncertainty) of each ring of CSCs in the ME1 station to provide a trigger primitive for the CMS Level-1 trigger, as a function of pT The efficiency of each ring of CSCs in the first station (closest to the IP), ME1, to provide a trigger primitive for the CMS Level-1 trigger, as a function of the pT of the muon. These values average over all the CSCs in the ME1 station.
pdf version	Measured efficiency (with statistical uncertainty) of each ring of CSCs in the ME1 station to provide a trigger primitive for the CMS Level-1 trigger, as a function of φ The efficiency of each ring of CSCs in the first station (closest to the IP), ME1, to provide a trigger primitive for the CMS Level-1 trigger, as a function of the φ of the muon. These values average over all the CSCs in the ME1 station.
pdf version	Measured efficiency (with statistical uncertainty) of each station of CSCs to provide a trigger primitive for the CMS Level-1 trigger, as a function of pT The efficiency of each station of CSCs (ME1, ME2, ME3, ME4) to provide a trigger primitive for the CMS Level-1 trigger, as a function of the pT of the muon. These values average over all the CSCs in each station separately.
pdf version	Measured efficiency (with statistical uncertainty) of each station of CSCs to provide a trigger primitive for the CMS Level-1 trigger, as a function of η The efficiency of each station of CSCs (ME1, ME2, ME3, ME4) to provide a trigger primitive for the CMS Level-1 trigger, as a function of the η of the muon. These values average over all the CSCs in each station separately.
pdf version	Measured efficiency (with statistical uncertainty) of each station of CSCs to provide a rtrigger primitive for the CMS Level-1 trigger, as a function of φ The efficiency of each station of CSCs (ME1, ME2, ME3, ME4) to provide a trigger primitive for the CMS Level-1 trigger, as a function of the φ of the muon. These values average over all the CSCs in each station separately.
pdf version	CSC trigger primitive efficiency - 1D summary Measured efficiency of each CSC in the CMS Endcap Muon detector to provide a trigger primitive for the CMS Level-1 trigger. There is one entry per CSC. Note that there are 540 CSCs in the system, but that the ME1/1 chambers are divided into two strip regions, labelled ME1/1A and ME1/1B giving effectively 612 separate detector regions, thus accounting for the total number of entries of 612 in each plot.

DT local trigger efficiency

The performance of the DT Local Trigger (DTLT) was checked using 2016 data and compared to last year. The DT Local Trigger (DTLT) efficiency was defined and measured as the ratio between the number of observed and expected triggers. The expected triggers were defined requiring the presence in a chamber of a track segment, reconstructed in both θ and φ views, belonging to a "Global Muon", and having at least 4 associated hits in the φ layers (minimum number of hits required to build a trigger primitive). At least two other stations were required to deliver trigger primitives in the event, in order to avoid the bias of self-triggering stations. The DTLT was then considered efficient if a trigger primitive was delivered at the correct bunch crossing in the same chamber. Note that no efficiency can be computed if no reconstructed segments are available. In the following plots the computed efficiency is shown chamber by chamber and as a function of the "Global Muon" direction and transverse momentum.

Figure	Caption
pdf version	DT Local Trigger Efficiency: map DT local trigger efficiency map chamber by chamber. Each map represents one station where the wheel number is indicated in the y axis and the sector number in the x axis. The lower DTLT efficiency observed in two chambers was due to trigger electronics issues which were later fixed.

pdf version

	DT Local Trigger Efficiency vs muon η DT local trigger efficiency, station by station, versus the global muon η, compared to the measurement from 2015 data. The different ranges where the stations have full efficiency are related to the geometrical acceptance of the barrel muon detector: see next figure for clarification.
pdf version	DT Acceptance vs muon η This figure highlights the different geometrical acceptance of the MB1 and MB4 stations.

pdf version

	DT Local Trigger Efficiency vs muon pT DT local trigger efficiency, station by station, versus the global muon transverse momentum, pT, compared to the measurement from 2015 data.
pdf version	DT local trigger efficiency: η vs φ DT Local Trigger efficiency, station by station, plotted as function of the global muon η and φ coordinates.

pdf version

DT Local Trigger Efficiency: 1D Summary The measured local trigger efficiency for each DT chamber is one entry in this 1D summary histogram. There are 250 DT chambers, but sectors 4 and 10 of all 5 wheels are served by two MB4s which are treated as a single logical chamber in the trigger chain, thus leading to 240 entries.

Spatial Resolution

DT single hit resolution

The resolution was computed from the width of the distribution of the observed distance ("residual") between any reconstructed hit and the fitted segment it belongs to. Ideally, any hit for which the residual is being computed should be excluded from the segment fit, but this procedure is extremely demanding in terms of CPU time. For this reason, segments were fitted only once, keeping all compatible hits. Analytically-computed correction factors were then applied to the widths of residual distributions, in order to correct the bias and derive final results for hit resolution. Relying on the azimuthal symmetry of the detector, hits reconstructed within the same station of the same wheel were added together. However φ superlayers (measuring position on the R φ plane) and θ superlayers (measuring position on the R z plane) were kept separated in order to take their geometrical differences into account. The present results show no differences with respect to last year, that are available in https://twiki.cern.ch/twiki/bin/view/CMSPublic/DTDPGResults201120152 and in CMS DP-2015/061:
The resolution in the φ SLs (i.e. in the bending plane) is better than 250 μm in MB1, MB2 and MB3, and better than 300 μm in MB4.
In the θ SL's the resolution is always better than ~500 μm except in the external wheels of MB1 (because of the track inclination and the effect of the transverse component of the magnetic field).
The resolution observed in 2016 is compatible with that in 2015 and slightly better than that obtained with 2012 data.

Figure	Caption
pdf version	DT Single Hit Resolution Examples Examples of residual distributions, in YB0 and YB2 for MB1 φ layers (A and B), for MB4 φ layers (C and D), and for MB1 θ layers (E and F).
pdf version	DT Single Hit Resolution Summary Plot depicting the DT single hit resolution as a function of station MB1, MB2, MB3, MB4 and wheel. Within every station, both θ and φ SLs show a symmetric behaviour w.r.t. to the z=0 plane, as expected from the detector symmetry. In Wheel 0, where tracks from the interaction region are mostly normal to all layers, the resolution is the same for θ and φ SL's. Going from Wheel 0 towards the forward regions, tracks from the interaction region have increasing values of η: this affects φ and θ SL’s in opposite ways. The θ angle lies on the measurement plane of θ layers, while it is orthogonal to it for φ layers. The result is that in θ SL's the increasing inclination angle, by spoiling the cell linearity, also worsens the resolution. In contrast, in φ SL's the inclination angle increases the track path within the tube (along the wire direction), thus increasing the ionization charge and improving the resolution. The poorer resolution of the φ SL's in MB4, compared to MB1-MB3, is because in MB4 no θ measurement is available, thus no corrections are applied to the hit position in the z coordinate in order to take into account the muon time-of-flight and the signal propagation time along the wire.

RPC spatial resolution

The segment extrapolation method described earlier (method for measuring RPC efficiency) also allows the RPC spatial resolution to be estimated. Residuals are calculated as the distance in local x coordinates (transverse view at the RPC detection plane) between the extrapolated point and the matched RPC rechit (center of the cluster of the rechit). Along the strip length, the RPC reco hit is reconstructed in the middle of the strip.
Another important quantity defining the RPC spatial resolution is the cluster size, defined as the number of adjacent fired strips in a given time window.

Figure	Caption
pdf version	RPC Barrel residuals for each layer The plots show the residuals for all RPC barrel layers. The order of layers is that layer 1 is the closest to the beam pipe, and layer 6 is furthest from it. The residual distributions have been fitted to Gaussian distributions and the resulting mean and σ are given on each plot. The obtained σs are in agreement with the expectations and less than one strip pitch of the strip for a given layer.
pdf version	RPC Endcap residuals for rings 2 and 3 The plots show the residuals for the RPC endcap stations. The order of roll names is that Rolls C from the Rings 2 are closest to the beam pipe and Rolls A from Rings 3 are furthest from it. The distributions have been fitted to Gaussian distributions and the resulting mean and σ are given on each plot. The obtained σs are in agreement with the expectations and less than one strip pitch of the strip for a given layer.
pdf version	RPC cluster size for each roll of endcap disk RE-4 The plot shows the RPC cluster size for each roll of endcap disk RE-4.
pdf version	RPC cluster size - Barrel This 1D summary shows one entry per RPC roll in the Barrel. The mean value of the cluster size is < 2 strips.
pdf version	RPC cluster size - Endcap This 1D summary shows one entry per RPC roll in the Endcap. The mean value of the cluster size is < 2 strips.

CSC spatial resolution

A CMS Cathode Strip Chamber (CSC) contains 6 layers of gas, each with cathode and anode planes. The cathode planes are divided into radial strips and allow a precise measurement of the azimuthal position of a hit from a muon traversing the layer. This is the direction of bending of a muon in the solenoidal field. A muon typically leaves a hit in each layer, with charge deposited on a few neighboring strips, and a muon track segment is a straight line fit to these hits. To estimate the spatial resolution one hit is removed from a segment and the segment refit from the remaining hits. The residuals between segment and hit are quite Gaussian so a simple fit to a Gaussian is used to measure a ‘resolution’ per layer. There are 10 types of CSC in the CMS Endcap Muon system, labelled MEi/j where i labels the station and j the ring. There are two independent regions of strips in the ME1/1 CSCs, with the split at |η| = 2.1.The inner region, closest to the beam line, is called ME1/1A and the outer ME1/1B. In non-ME1/1 CSCs, alternate layers are offset by half a strip width between each other. Better resolution is obtained if a hit is near the edge of a strip, rather than near the center, because then more charge is shared between strips. Therefore resolutions are measured separately for center and edge regions.The layer measurements are combined to give an overall resolution per CSC (‘station’) by 1/σ²_station = 6/σ²_L (ME1/1) and 1/σ²_station = 3/σ²_C + 3/σ²_E (non-ME1/1 chambers.) The following plots show residual distributions obtained from a data sample enriched in Z → μμ events, in strip-width units. The strip widths are the same for each chamber type, and range from 2.2 to 4.7 mrad according to chamber type. A Gaussian fit to the central region is also shown, together with the parameters of the fit.

Figure	Caption
pdf version	Spatial Resolution of CSC ME1/1A The figure shows the residuals for CSCs in ME1/1A. The overall value obtained for one chamber (6 layers) is shown as the 'station' value, converted from strip widths to μm.
pdf version	Spatial Resolution of CSC ME1/1B The figure shows the residuals for CSCs in ME1/1B. The overall value obtained for one chamber (6 layers) is shown as the 'station' value, converted from strip widths to μm.
pdf version	Spatial Resolution of CSC ME1/2 for hits near the centre of a strip The figure shows the residuals for CSCs in ME1/2 for hits near the centre of a strip.
pdf version	Spatial Resolution of CSC ME1/2 for hits near the edge of a strip The figure shows the residuals for CSCs in ME1/2 for hits near the edge of a strip.
pdf version	Spatial Resolution of CSC ME1/3 for hits near the centre of a strip The figure shows the residuals for CSCs in ME1/3 for hits near the centre of a strip.
pdf version	Spatial Resolution of CSC ME1/3 for hits near the edge of a strip The figure shows the residuals for CSCs in ME1/3 for hits near the edge of a strip.
pdf version	Spatial Resolution of CSC ME2/1for hits near the centre of a strip The figure shows the residuals for CSCs in ME2/1 for hits near the centre of a strip.
pdf version	Spatial Resolution of CSC ME2/1 for hits near the edge of a strip The figure shows the residuals for CSCs in ME2/1 for hits near the edge of a strip.
pdf version	Spatial Resolution of CSC ME2/2 for hits near the centre of a strip The figure shows the residuals for CSCs in ME2/2 for hits near the centre of a strip.
pdf version	Spatial Resolution of CSC ME2/2 for hits near the edge of a strip The figure shows the residuals for CSCs in ME2/2 for hits near the edge of a strip.
pdf version	Spatial Resolution of CSC ME3/1 for hits near the centre of a strip The figure shows the residuals for CSCs in ME3/1 for hits near the centre of a strip.
pdf version	Spatial Resolution of CSC ME3/1 for hits near the edge of a strip The figure shows the residuals for CSCs in ME3/1 for hits near the edge of a strip.
pdf version	Spatial Resolution of CSC ME3/2 for hits near the centre of a strip The figure shows the residuals for CSCs in ME3/2 for hits near the centre of a strip.
pdf version	Spatial Resolution of CSC ME3/2 for hits near the edge of a strip The figure shows the residuals for CSCs in ME3/2 for hits near the edge of a strip.
pdf version	Spatial Resolution of CSC ME4/1 for hits near the centre of a strip The figure shows the residuals for CSCs in ME4/1 for hits near the centre of a strip.
pdf version	Spatial Resolution of CSC ME4/1 for hits near the edge of a strip The figure shows the residuals for CSCs in ME4/1 for hits near the edge of a strip.
pdf version	Spatial Resolution of CSC ME4/2 for hits near the centre of a strip The figure shows the residuals for CSCs in ME4/2 for hits near the centre of a strip.
pdf version	Spatial Resolution of CSC ME342 for hits near the edge of a strip The figure shows the residuals for CSCs in ME4/2 for hits near the edge of a strip.
pdf version	Spatial resolutions of CSCs in 2012, 2015 and 2016 (μm per station) The table summarizes the resolutions per station measured for all chamber types in the CMS CSC system in 2016 data, and values measured in 2015 and 2012 for comparison. Statistical uncertainties from the fits are negligible, and systematic uncertainties dominate. These arise primarily from variation of the resolution with atmospheric pressure (the gas gain has been measured to increase by 7-8% as atmospheric pressure decreases by 1%, and this improves the spatial resolution), with angle of incidence of the muon, and with muon momentum. The apparent improvement in resolution in 2016 is likely due to the difference in average atmospheric pressure in the data collection periods. All values are well within the design specifications of the CSC system.

Time Resolution

CSC time resolution

The offline reconstruction of the muon time is calibrated so that prompt muons have a distribution that is centered near 0. The CSC reconstructed hit time is determined by combining the times measured from matching cathode and anode hits. The cathode time is determined from a template fit to the digitized cathode pulse followed by a series of calibrations.The applied calibrations were determined from studies of chamber response prior to and during LHC Run I, together with a heuristic correction determined using collision data collected during 2015 running (the start of LHC Run II).

Figure	Caption
pdf version	Measured times of CSC reconstructed hits from cathodes The figure shows the distribution of times measured by the CSC cathodes from reconstructed muons in a sample of 2016 data enriched in Z → μμ events. The mean of 0.5 ns and RMS of 7.4 ns in 2016 are close to those measured in 2015, -0.1 ns and 7.5 ns respectively.
pdf version	Measured times of CSC reconstructed segments The figure shows the distribution of times of CSC reconstructed segments associated with reconstructed muons in a sample of 2016 data enriched in Z → μμ events. The mean of 0.2 ns and RMS of 3.2 ns in 2016 are close to those measured in 2015, 0.6 ns and 3.1 ns respectively.
pdf version	Measured times of CSC reconstructed hits from cathodes, ring by ring The figure shows the distribution of times measured by the CSC cathodes from reconstructed muons in a sample of 2016 data enriched in Z → μμ events. The mean and RMS of the distribution in each ring are shown.
pdf version	Measured times of CSC reconstructed segments, ring by ring The figure shows the distribution of times of CSC reconstructed segments associated with reconstructed muons in a sample of 2016 data enriched in Z → μμ events. The mean and RMS of the distribution in each ring are shown.
pdf version	CSC muon time resolution The figure shows the distribution of times at the primary vertex for reconstructed muons in a sample of 2016 data enriched in Z → μμ events, where the time is measured from the CSC reconstructed segments associated with each muon.

RPC time resolution

Figure	Caption
pdf version	RPC bunch crossing distribution - Barrel The figure shows the distribution of the bunch crossing of RPC reconstructed hits associated with global muons in the barrel.
pdf version	RPC bunch crossing distribution - Endcap -z The figure shows the distribution of the bunch crossing of RPC reconstructed hits associated with global muons in the -z endcap.
pdf version	RPC bunch crossing distribution - Endcap +z The figure shows the distribution of the bunch crossing of RPC reconstructed hits associated with global muons in the +z endcap.

DT time resolution

DT time information is obtained from a 3-parameter fit of segments, where position, direction and time of a crossing track are determined simultaneously. This method was shown to allow high reconstruction and identification efficiency for Out-Of-Time tracks and to improve the resolution for In-Time-Tracks. See the public results https://twiki.cern.ch/twiki/bin/view/CMSPublic/DTDPGResults10072015. The slight asymmetry that is observed in the central peak of the DT time distribution is due to residual contamination by delta rays and e.m. showers from muons. Any ionization charge reaching a DT wire before that produced by a muon of interest causes an early hit and the resulting intrinsic electronic dead time of 150 ns then hides later hits, including that of the muon. Therefore these spurious hits at early times contribute only to the negative side of the central peak. Track segments were selected to have hits in both projections (at least 5 in the Φ view) and to be less inclined than 45 degrees. To compute a time for complete muon tracks, based on the measurements in up to 4 DT stations, a new iterative pruning mechanism was implemented this year, which discards "outlier" hits. In fact, as the calculation makes use of all hits associated to a muon track, the hits from delta rays and showers can be rejected within an individual chamber using the other chambers as reference. As usual these measurements were performed on a sample of 2016 data enriched in Z → μμ events.

Figure	Caption
	DT time resolution - muon track segments The figure shows the time distribution from single track segments with at least 5 hits in the φ view and inclination less than 45 degrees, from all DT chambers.
	DT time resolution - standalone muons The figure shows the time-at-vertex distribution for standalone muons in the barrel, using the times measured from DT chambers.

RPC Occupancy Displays

Figure	Caption
pdf version	RPC endcap occupancy plots (x-y) The plots represent the cross-sectional view of all RPC stations in the forward region of CMS (Endcaps). The points show the position of the reconstructed hits in the middle of the signal electrodes (strips).
pdf version	RPC barrel occupancy plots (x-y) The plots represent the cross-sectional view of all RPC stations in the central region of CMS (Barrel). The points correspond to the position of reconstructed hits.
pdf version	RPC barrel occupancy plots (z-φ) The plots represent the z-φ view of rechits from all RPC layers in the central region of the CMS (Barrel). In the Barrel, the RPC strips are parallel to the global z direction, and the RPC rechit is assigned to the middle of the strip in z. Following the CMS geometry the chambers can have different size in z. Thus the global z coordinate of the RPC rechits from chambers in the same wheel may differ. The feature does not affect muon reconstruction.

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