Simulation Studies of Charged Particle Detectors for Collider Experiments
Authors: Mohamed Taif , Renganathan Neeraja 
Published: July 2019

The Compact Muon Solenoid (CMS) experiment in the Large Hadron Collider (LHC) at CERN has been the tool to performing ground-breaking research in high energy physics. The CMS detector has been built over the last two decades by an international collaboration of scientists from all over the world. Two years after its operation, the two experiments ATLAS and CMS have announced in 2012 the discovery of the Higgs boson, a long awaited particle responsible to give elementary particles their respective masses.

After the first 3 years of operation at moderate luminosity, the LHC is entering a new phase of high luminosity and energy regimes, which will put stringent requirements on the detectors.

The CMS experiment has planned a rigorous plan of upgrade of its different components to cope with the harsh conditions imposed by the new regime. One of the subsystem of CMS detector that will require upgrade is the muon system. This latter detects muon particles, which are the signature of most of the interesting physics channels we are looking for at the LHC.

The Qatar team, together with an international team of scientists, has proposed the Gas Electron Multiplier (GEM) as the future detecting element of the upgrade of the muon system.

We have conducted an extensive simulation program to assess the GEM detector and optimize it for the future upgrade.

During this project, various simulations have been conducted to predict the efficiency and time resolution of the GEM. The simulations, which have been conducted using ANSYS, computational fluid dynamics software, focus on producing the electric field maps inside the detector. In addition, the resulting electron avalanche was simulated based on the solution of the Boltzmann equation. A signal was then generated to study the gain, resolution, and other parameters. During this work, several conditions were simulated in order to reach the optimum conditions under which the GEM would be most effective. These simulations had to be conducted using a supercomputing facility since their range surpasses the regular computing powers of personal computers. Using Raad, the cluster at Texas A&M University at Qatar, helped widen the scope of the simulations to approach a realistic situation that would occur within the CMS.

Furthermore, as part of its next upgrade, a novel detector, the Fast Timing Micropattern (FTM) detector is being considered as a possible beneficial addition to the CMS. Initial investigations of the FTM detector have shown a considerable improvement in the time resolution that is proportional to the number of layers. In addition, the use of resistive WELL techniques solves the problem of spark occurrences and discharges that such detectors experience with high electric fields. It also differs from the GEM in the sense that the gain is extracted at every multiplication stage rather than at the very last level of the detector where the readout plane exists. The FTM detector could be cost-efficient in its assembly process. Simulations are being further extended in order to evaluate the FTM's performance and optimize its gain and other resulting parameters.