CMS Detector in 2024: Advancements in Data Collection and Detector Performance

Andrea Massironi (Universita & INFN, Milano-Bicocca), Gianni Masseti (Universita e INFN, Bologna ), Giulia Negro (Purdue University) 16th Sep 2024

On April 5th, 2024, stable beams returned to the LHC, marking the official start of the 2024 physics data-taking season. The photo captures CMS' Run Coordination team in the newly upgraded CMS control center, ready to oversee the exciting season ahead.

The CMS detector is effectively collecting data in 2024, marking a full year of proton-proton (pp) production. A notable development early in the year was the relocation of the shift crew to a newly commissioned control room. This control room will continue to be used for the remainder of Run 3 data collection and into the HL-LHC era.

Preparation of the New CMS control room.

During the winter shutdown, a new forward shielding system was installed to protect the experimental cavern from beam halo muons and the LHC tunnel from collision products. This was a critical step in preparation for the HL-LHC phase [1,2].

Photo of the new CMS Forward Shielding.

The CMS experiment has made considerable progress in data collection and detector performance since the first proton-proton (pp) collisions. After the initial weeks dedicated to setting up the experiment [3], the early data from pp collisions were primarily used for detector commissioning [4]. Once this phase was completed, efficient data collection from pp collisions began at full capacity [5].

In 2024, the CMS detector's data-taking capabilities have reached their operational limits. The experiment is running during extended periods of high pileup with luminosity levelled to the maximum sustainable value for CMS, a period much longer than previously achieved in the Large Hadron Collider (LHC) in recent years. Additionally, data parking is being fully utilized, especially during the luminosity decay part of the fills [6]. Each LHC fill has resulted in an impressive collection rate, averaging approximately 0.8 fb⁻¹ of data per fill.

A significant improvement in 2024 came from enhanced LHC operations, which provided both CMS and ATLAS experiments with the flexibility to control the pileup target during luminosity levelling. This is achieved through beam separation adjustments, enabling the experiments to fine-tune their data collection strategies. This flexibility has allowed further testing and optimization within CMS, aimed at maximizing both data quality and quantity for Physics Run 3 analyses.

The performance of the CMS detectors is continuously monitored to ensure optimal operation. Key components such as the Tracker [7-9], the Electromagnetic Calorimeter (ECAL) trigger [10], and the Muon detectors [11-14] undergo regular performance evaluations and improvements. These efforts are crucial to maintaining stability and ensuring the data collected is of the highest quality for physics research.

Pixel cluster charge distribution for different barrel layers as a function of Run 3 integrated luminosity [9].

Recent CMS results highlight the success of these operational improvements. The experiment has recorded high-quality data for several important physics analyses, including studies of Higgs boson properties, precision measurements of Standard Model processes, and searches for new physics beyond the Standard Model.

Drift Tubes segment reconstruction for muons measured in different years of Run 3 [11].

With these advancements, CMS continues to play a central role in exploring fundamental physics, delivering groundbreaking results, and providing insights into the nature of matter and forces at the smallest scales. As we approach the conclusion of Run 3 and the beginning of Run 4, the performance and quality of the CMS data remain a top priority, ensuring the experiment continues to push the boundaries of high-energy physics research.

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CMS Detector in 2024: Advancements in Data Collection and Detector Performance

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