The Upgrade of the CMS RPC System during the First LHC Long Shutdown

TL;DR

The paper discusses the upgrade of the CMS Resistive Plate Chamber system during the first LHC long shutdown, including new detector installation, simulation studies, and quality control to maintain high trigger efficiency at increased luminosities.

Contribution

It introduces the addition of a 4th RPC layer in the CMS endcap regions, with detailed plans for production, assembly, and testing during the shutdown.

Findings

Trigger simulation studies show improved performance with the new RPC layers.

Successful production and quality control procedures for the new chambers.

Enhanced muon detection efficiency at high particle rates.

Abstract

The CMS muon system includes in both the barrel and endcap region Resistive Plate Chambers (RPC). They mainly serve as trigger detectors and also improve the reconstruction of muon parameters. Over the years, the instantaneous luminosity of the Large Hadron Collider gradually increases. During the LHC Phase 1 (~first 10 years of operation) an ultimate luminosity is expected above its design value of 10^34/cm^2/s at 14 TeV. To prepare the machine and also the experiments for this, two long shutdown periods are scheduled for 2013-2014 and 2018-2019. The CMS Collaboration is planning several detector upgrades during these long shutdowns. In particular, the muon detection system should be able to maintain a low-pT threshold for an efficient Level-1 Muon Trigger at high particle rates. One of the measures to ensure this, is to extend the present RPC system with the addition of a 4th layer in both endcap regions. During the first long shutdown, these two new stations will be equipped in the region |eta|<1.6 with 144 High Pressure Laminate (HPL) double-gap RPCs operating in avalanche mode, with a similar design as the existing CMS endcap chambers. Here, we present the upgrade plans for the CMS RPC system for the fist long shutdown, including trigger simulation studies for the extended system, and details on the new HPL production, the chamber assembly and the quality control procedures.