-- RoumyanaHadjiiska - 2017-06-29

RPC Performance Results for 2016, approved for EPS Conference in Venice

RPC Geometry

Barrel

RPC Barrel Geometry: The Barrel RPC system consists of 5 wheels, and a wheel consists of 4 muon stations (RB1, RB2, RB3 and RB4) at increasing radius (R) and is divided in 12 sectors in φ A station consists of 2 layers in the inner two stations: RB1in, RB1out, RB2in and RB2out and a single layer in RB3 and RB4; RPCs in RB3 and RB4 are divided in + and – along φ for mechanical reasons in all sectors apart from sectors S04, S09, S11 in RB4; RB4/S09 and RB4/S11 are in the feet of the barrel wheel and consists of a single chamber; RB4/S04 is divided in 4 chambers: ++, +, -, –; . Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Barrel Eta Partitions (Rolls): All RPC barrel chambers are divided along the beam axis in 2 η partitions: forward and backward. Except for RB2in in Wheels -1, 0, 1 and RB2out in Wheel -2, +2 that is divided in 3 η partitions: forward, middle and backward. Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Barrel Chambers: In total there are 480 RPC barrel chambers, each consisting of two or three η partitions, resulting in 1020 detector units (η-partitions). Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

Endcap

RPC Endcap Geometry: The picture on the left side shows a quarter of the CMS layout. The RPCs are indicated in blue and cover abs (η) < 1.9; The RPC system has two endcaps: negative and positive, according to the z-coordinate of CMS; Each endcap consists of 4 stations (RE±1-4, the so-called disks) instaled on the iron endcap yokes (YE); RE±1,2 are installed on the front resp. the back of the first iron endcap yoke (YE±1); RE±3,4 are installed on the front resp. the back of the first iron endcap yoke (YE±3); During Run-1 there were just 3 stations (RE±1-3) installed, during LS-1 RE±4 was installed. Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Endcap Chambers: Each stations in the Endcap consists of 3 rings. RPCs are installed on the second and third ring (REX_R2 and REX_R3). Each of them consists of 36 chambers, divided in 6 sectors of 60 degree; The chamber at φ=0 degree (measured w.r.t. x-axis) is chamber no 1 for all stations. The figure of the left shows the grouping of chambers into sectors for RE±2; For readout the chambers are named with their segment numbering, ranging from 1 to 36. For example RE+2_R3_CH36. Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Background Studies

RPC Barrel Chambers: Background in the cavern has been studied in terms of RPC currents and rates as function of the instantaneous luminosity. Their values have been measured during the proton-proton collision data taking and have been averaged per run. The instantaneous luminosity is also averaged per run. During the 2015-2016 YETS the vertical slits in the HF have been filled with steel plate and covered from the top with multilayer plates at both Endcaps (plot on left). In addition, the vertical slit in the rotating shielding at the +Z Endcap has been filled with steel and borated polyethylene bars (plot on right). Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

Azimuthal Asymmetry

RPC Hit Rate RE-4: The plot represents the RPC hit rate measured in a proton-proton collision run with instantaneous luminosity 1.2 x 10^34 cm-2 s-1 for the the negative (this plot) and positive (please, see the plot below) fourth endcap stations. The RPC hit rate is measured directly from the link boards and was normalized to the active area of the fired strips. The Y axes corresponds to the detector segmentation in pseudorapididy (η), where the lowest layers (R2_C) are closer to the beam pipe and the outermost ones (R3_A) are farthest from it. As might be seen from the plots a clear φ asymmetry has been observed in both the stations. The lower value in the positive one is caused by reduced background after the installation of additional layer in the rotating shielding only in the positive part. The “hottest” points have been spotted to be in the top vertical sectors. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Hit Rate RE+4: The plot represents the RPC hit rate measured in a proton-proton collision run with instantaneous luminosity 1.2 x 10^34 cm-2 s-1 for the the negative (please, see the plot above) and positive (this plot) fourth endcap stations. The RPC hit rate is measured directly from the link boards and was normalized to the active area of the fired strips. The Y axes corresponds to the detector segmentation in pseudorapididy (η), where the lowest layers (R2_C) are closer to the beam pipe and the outermost ones (R3_A) are farthest from it. As might be seen from the plots a clear φ asymmetry has been observed in both the stations. The lower value in the positive one is caused by reduced background after the installation of additional layer in the rotating shielding only in the positive part. The “hottest” points have been spotted to be in the top vertical sectors. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

Rate and Currents vs Instantaneous Luminosity 2016

RPC Hit Rate vs Inst. Luminosity - Barrel: RPC hit rates vs instantaneous luminosity dependence for all barrel wheels corresponding to 2016. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Currents vs Inst. Luminosity - Barrel: RPC currents vs instantaneous luminosity dependence for all barrel wheels corresponding to 2016. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

Extrapolated Rates after HL-LHC

*RPC extrapolated Hit Rate - Barrel *: The linear dependence of the RPC hit rates on the instantaneous luminosity for every RPC chamber have been extrapolated to the instantaneous luminosity of 5x1034 cm-2 s-1. The plot shows the expected mean and maximum rate for all RPC barrel stations. Maximum expected rate is about 120 Hz/cm2. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

*RPC extrapolated Hit Rate - Barrel *: The linear dependence of the RPC hit rates on the instantaneous luminosity for every RPC chamber have been extrapolated to the instantaneous luminosity of 5x1034 cm-2 s-1. The plot on the left top shows the expected mean and maximum rate for all RPC endcap stations. Maximum expected rate is about 185 Hz/cm2. By applying a safety factor 3, dedicated longevity studies at GIF++ aim to certify RPC detector performance up to 600 Hz/cm2. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

*RPC extrapolated Hit Rate - Barrel *: The linear dependence of the RPC hit rates on the instantaneous luminosity for every RPC chamber have been extrapolated to the instantaneous luminosity of 5x1034 cm-2 s-1. The plot on the left top shows the expected mean and maximum rate for the entire RPC system. Maximum expected rate is about 185 Hz/cm2. By applying a safety factor 3, dedicated longevity studies at GIF++ aim to certify RPC detector performance up to 600 Hz/cm2. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Integrated Charge

Methodology

The RPC currents read by the Detector Control System (DCS) have been integrated in time. For every single RPC HV channel the current in [µA], being constant for a given period, have been multiplied by the length of that period. The area Qj is the integrated charge for the period j. The accumulated integrated charge is obtained by summing over all periods when all RPC HV channels have been at working point (α = 1 when RPC ON, otherwise α = 0). The integrated charge in [C] has been normalized to the RPC gap area in order to obtain the density of the integrated charge in [C/cm^2]. This procedure has been applied to all p-p and HI-p collision runs, as well as cosmics and commissioning periods. Since the RPC detector was OFF during the first long shutdown (LS1) the integrated charge was not calculated.

As of June 2017, the HV channel offsets and the ohmic contribution of each RPC chamber are not yet subtracted in the present analysis. In the next phase of tool development it is foreseen to introduce also HV board offset subtraction.

Since the integrated charge and its density are proportional by the inverse of the areas, in these plots when we speak about the Integrated charge we will mean the Density of the integrated charge in [mC/cm^2].

RPC Integrated Charge Approved plots

Below you can find the list of plots already approved at the CMS RC plot approval session on June 26th, 2017.

#	RPC Integrated Charge	Source	Caption
1		view	The plot represents the integrated charge for CMS RPC Barrel detector. The integrated charge per year is shown in blue. The red curve shows the evolution of the accumulated integrated charge in time. The LS1 period does not contribute to accumulating charge since RPC detector was OFF. The total integrated charge for the entire operation period (Oct.2009 - Dec.2016) is estimated to be about 1.1 mC/cm^2 for the Barrel. pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

2

view

The plot represents the integrated charge for CMS RPC Endcap detector. The integrated charge per year is shown in blue. The red curve shows the evolution of the accumulated integrated charge in time. The LS1 period does not contribute to accumulating charge since RPC detector was OFF. The total integrated charge for the entire operation period (Oct.2009 - Dec.2016) is estimated to be about 2.7 mC/cm^2 for the Endcap. pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

3

view

The stacked plot shows data driven extrapolations of the integrated charge after HL-LHC data taking period for the RPC Barrel HV channels distributed per Barrel station. Considering the total delivered luminosity from p-p collisions of 75 fb-1 for the entire period, we expect for Integrated Luminosity of 3000 fb-1 a maximum integrated charge of about 0.165 C/cm^2 (no safety factor is applied). pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

4

view

The stacked plot shows data driven extrapolations of the integrated charge after HL-LHC data taking period for the RPC Endcap HV channels distributed per Endcap station. Considering the total delivered luminosity from p-p collisions of 45 fb-1 since the beginning of Run-II data taking period, we expect for Integrated Luminosity of 3000 fb-1 a maximum integrated charge of about 0.277 C/cm2 (no safety factor is applied). Due to the HV cable reshuffling performed in the RPC Endcap HV system at the end of LS1, only Run-II data is used for the extrapolation value since mapping changed after the reshuffling. For the same reason RE1, RE2, RE3 stations are grouped and plotted together since after the above mentioned hardware intervention cases where one HV channel started to supply power to two chambers in neighbouring endcap stations occurred. pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

5

view

The plot represents a R/φ Distribution of the integrated charge in barrel wheel W+2 for the entire Run-I and Run-II data taking period. The x-axes correspond to the 12 barrel sectors in φ, each of them covering 30 degrees in azimuthal direction. The y-axes correspond to the four RPC barrel stations where RB1 is the closest to the beam pipe. Integrated charge is highest in the innermost and top outermost stations. The red spot in W+2/S12 is due to the HV board offsets which should be subtracted in the next development phase of the automated tool. pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

6

view

The plot represents a R/φ Distribution of the integrated charge in barrel wheel W+1 for the entire Run-I and Run-II data taking period. The x-axes correspond to the 12 barrel sectors in φ, each of them covering 30 degrees in azimuthal direction. The y-axes correspond to the four RPC barrel stations where RB1 is the closest to the beam pipe. Integrated charge is highest in top outermost stations, though generally is much lower than the one of the external wheels (W+/-2). The few green spots in the inner RB2 and RB3 stations are due to the HV board offsets which should be subtracted in the next development phase of the automated tool. pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

7

view

The plot represents a R/φ Distribution of the integrated charge in barrel wheel W0 for the entire Run-I and Run-II data taking period. The x-axes correspond to the 12 barrel sectors in φ, each of them covering 30 degrees in azimuthal direction. The y-axes correspond to the four RPC barrel stations where RB1 is the closest to the beam pipe. Integrated charge is highest in top outermost stations, though generally is much lower than the one of the external wheels (W+/-2). The few green spots in the inner RB2 and RB3 stations are due to the HV board offsets which should be subtracted in the next development phase of the automated tool. pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

8

view

The plot represents a R/φ Distribution of the integrated charge in barrel wheel W-1 for the entire Run-I and Run-II data taking period. The x-axes correspond to the 12 barrel sectors in φ, each of them covering 30 degrees in azimuthal direction. The y-axes correspond to the four RPC barrel stations where RB1 is the closest to the beam pipe. Integrated charge is highest in top outermost stations, though generally is much lower than the one of the external wheels (W+/-2). The few green spots in the inner RB2 and RB3 stations are due to the HV board offsets which should be subtracted in the next development phase of the automated tool. pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

9

view

The plot represents a R/φ Distribution of the integrated charge in barrel wheel W-2 for the entire Run-I and Run-II data taking period. The x-axes correspond to the 12 barrel sectors in φ, each of them covering 30 degrees in azimuthal direction. The y-axes correspond to the four RPC barrel stations where RB1 is the closest to the beam pipe. Integrated charge is highest in the innermost and top outermost stations. pdf file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC HV Scans 2016

RPC HV Scans Definition

Definition: The RPC HV scan is a special sequence of runs usually taken during the calibration runs with first collisions at the very beginning of each operational year. The HV scan is taken at effective, equidistant voltages in the working range of [8600, 9800] V. The collected data is being analyzed in order to calculate the best HV working points of RPC chambers and further apply them on the detector.

• Determination of the 2016 Working Points.
• Stability of the RPC HV Scan Parameters in time.

For the second study 4 HV scans taken since 2011 were considered. To the standard 2011, 2012 and 2016 HV scans, usually taken during the first calibration runs with collisions at the beginning of each operational year, an additional HV scan was taken at the end of the 2012 proton collision data taking period. These two 2012 HV scans are denoted in all the analysis as 2012a and 2012b, respectively. Due to the Long Shutdown 1 (LS1) maintenance period the RPC detector was OFF, therefore no HV scans were performed in 2013 and 2014. The 2015 scan was omitted in order to avoid introducing unknown bias to the study due to the missing magnetic field. For historical reasons, the HV scan WP definition differed from year to year, so it was mandatory to rerun all 4 HV scans with the latest WP definition in order to be able to compare the results.

RPC HV Scans - Sigmoid Fit: The efficiency data points, taken at effective voltage (corrected for pressure variations), are fitted by a sigmoid function. For each calibration run the efficiency is calculated for every single RPC eta partition, the smallest RPC granularity object, also known as roll. Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

The three parameters of the fit are:

• maximum fit efficiency (emax)
• voltage at which the fit efficiency is 50% (HV50)
• slope of the sigmoid rise at 50% of fit efficiency (Slope50).

The WP is defined as the knee voltage plus 100 Volts for Barrel and 120 Volts for Endcap. In 2016 HV scan we slightly changed the old data fitting procedure by binding one of the fit parameters, namely the maximum efficiency (emax <= 100%), to achieve better fits with physical meaning of this parameter. In the HV scan analysis the regions are divided in three: Barrel (1020 rolls), Endcap, including the existing 1296 rolls before the long shutdown 1 period (LS1), and the installed during LS1 fourth muon station RE4 (432 rolls). All sigmoid fits which have failed to fit the data are excluded from the clean sample. The clean sample, containing approx. 90% of the rolls, is quite representative. What causes fits to fail may vary between missing extrapolations from other muon detectors and hardware problems like chambers OFF or rolls with higher number of inactive (masked) electronic channels (strips). The clean sample contains 959 Barrel rolls, 1157 rolls of the old Endcap RE1, RE2 and RE3 stations and 281 rolls in the lately installed fourth muon station RE4.

Stability

RPC HV Scans per Years - Barrel: The plots represent the working point, the efficiency at the working point evolution and the Voltage at 50% Efficiency evolution in the Barrel. The efficiency at WP distributions have been presented with a light blue color. With a blue, full circle is presented the mean efficiency at WP for each of the HV scans. By red, full squares is represented the mean of the working point distribution for each HV scan with their Standard deviations. In magenta, full triangles represent the mean of the voltage at 50% Efficiency distribution for each HV scan with their standard deviations. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC HV Scans per Years - Endcap: The plots represent the working point, the efficiency at the working point evolution and the Voltage at 50% Efficiency evolution in the Endcap. The efficiency at WP distributions have been presented with a light blue color. With a blue, full circle is presented the mean efficiency at WP for each of the HV scans. By red, full squares is represented the mean of the working point distribution for each HV scan with their Standard deviations. In magenta, full triangles represent the mean of the voltage at 50% Efficiency distribution for each HV scan with their standard deviations. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Efficiency and Cluster Size History 2016

RPC Efficiency History 2016 - Barrel: RPC efficiency history for the barrel in 2016 is shown on the plot. After deploying the new HV working points in September 2016, the efficiency increases with more than a percent. A small increase of the mean cluster size is also observed. Nevertheless the average cluster size remains stably below 2 strips as specified in the CMS requirements for trigger unambiguity. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch

RPC Cluster Size History 2016 - Barrel: RPC cluster size history for the barrel in 2016 is shown on the plot. After deploying the new HV working points in September 2016, the efficiency increases with more than a percent. A small increase of the mean cluster size is also observed. Nevertheless the average cluster size remains stably below 2 strips as specified in the CMS requirements for trigger unambiguity. pdf file, C file Contact: cms-dpg-conveners-rpc@cernSPAMNOTNOSPAMPLEASE.ch