4.7 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Compact Muon Solenoid | 5/5 | https://en.wikipedia.org/wiki/Compact_Muon_Solenoid | reference | science, encyclopedia | 2026-05-05T13:03:00.987311+00:00 | kb-cron |
=== Trigger system === To have a good chance of producing a rare particle, such as a Higgs boson, a very large number of collisions is required. Most collision events in the detector are "soft" and do not produce interesting effects. The amount of raw data from each crossing is approximately 1 megabyte, which at the 40 MHz crossing rate would result in 40 terabytes of data a second, an amount that the experiment cannot hope to store, let alone process properly. The full trigger system reduces the rate of interesting events down to a manageable 1,000 per second. To accomplish this, a series of "trigger" stages are employed. All the data from each crossing is held in buffers within the detector while a small amount of key information is used to perform a fast, approximate calculation to identify features of interest such as high energy jets, muons or missing energy. This "Level 1" calculation is completed in around 1 μs, and event rate is reduced by a factor of about 1,000 down to 50 kHz. All these calculations are done on fast, custom hardware using reprogrammable field-programmable gate arrays (FPGA). If an event is passed by the Level 1 trigger all the data still buffered in the detector is sent over fibre-optic links to the "High Level" trigger, which is software (mainly written in C++) running on ordinary computer servers. The lower event rate in the High Level trigger allows time for much more detailed analysis of the event to be done than in the Level 1 trigger. The High Level trigger reduces the event rate by a further factor of 100 down to 1,000 events per second. These are then stored on tape for future analysis.
=== Data analysis === Data that has passed the triggering stages and been stored on tape is duplicated using the Grid to additional sites around the world for easier access and redundancy. Physicists are then able to use the Grid to access and run their analyses on the data. There are a huge range of analyses performed at CMS, including:
Performing precision measurements of Standard Model particles, which allows both for furthering the knowledge of these particles and also for the collaboration to calibrate the detector and measure the performance of various components. Searching for events with large amounts of missing transverse energy, which implies the presence of particles that have passed through the detector without leaving a signature. In the Standard Model only neutrinos would traverse the detector without being detected but a wide range of Beyond the Standard Model theories contain new particles that would also result in missing transverse energy. Studying the kinematics of pairs of particles produced by the decay of a parent, such as the Z boson decaying to a pair of electrons or the Higgs boson decaying to a pair of tau leptons or photons, to determine various properties and mass of the parent. Looking at jets of particles to study the way the partons (quarks and gluons) in the collided protons have interacted, or to search for evidence of new physics that manifests in hadronic final states. Searching for high particle multiplicity final states (predicted by many new physics theories) is an important strategy because common Standard Model particle decays very rarely contain a large number of particles, and those processes that do are well understood.
== Milestones ==
== Etymology == The term Compact Muon Solenoid comes from the relatively compact size of the detector, the fact that it detects muons, and the use of solenoids in the detector. "CMS" is also a reference to the center-of-mass system, an important concept in particle physics.
== See also == List of Large Hadron Collider experiments
== Notes ==
== References == Bayatian, G L; Korablev, A; Soha, A; Sharif, O; et al. (The CMS Collaboration) (2006). "CMS Physics : Technical Design Report Volume 1: Detector Performance and Software". CERN. Retrieved 2026-02-21. (mirror: inspire)
== External links ==
CMS home page CMS experiment record in INSPIRE-HEP CMS Public Results CMS Outreach CMS Times Archived 2008-05-22 at the Wayback Machine CMS section from US/LHC Website The assembly of the CMS detector, step by step, through a 3D animation The CMS Collaboration, S Chatrchyan; et al. (2008-08-14). "The CMS experiment at the CERN LHC". Journal of Instrumentation. 3 (8) S08004. Bibcode:2008JInst...3S8004C. doi:10.1088/1748-0221/3/08/S08004. hdl:10067/730480151162165141. (Full design documentation) Copeland, Ed. "Inside the CMS Experiment". Sixty Symbols. Brady Haran for the University of Nottingham.