Navigation auf

Science Pavilion UZH

The largest particle accelerator in the world

Time machine to the origins of the universe: The CMS detector at CERN

CERN is located near Geneva, Switzerland. The diagram shows the 27 km circular tunnel of the Large Hadron Collider (LHC).

Why are there so many fundamental particles when ordinary matter is only made of a few of them? Why is there more matter than antimatter in the universe? What is dark matter made of? Why is gravity so weak? Are there other elementary particles waiting to be discovered? Even after the last predicted elementary particle, the Higgs boson, was recently observed, there are still many questions left unanswered. One of the primary facilities seeking answers is CERN.

On the border of Switzerland, but in the middle of space

CERN (Conseil Européen pour la Recherche Nucléaire) is a research organization that operates the Large Hadron Collider (LHC), the highest energy particle collider in the world. CERN is located near Geneva, Switzerland. The LHC is situated underground and crosses the Franco-Swiss border, It accelerates two high-energy particle beams travelling, at close to the speed of light, before colliding them in four different crossing points, which correspond to the positions of four experiments. University of Zurich research groups are involved in two of these experiments: CMS (Compact Muon Solenoid) and LHCb (Large Hadron Collider beauty).

Masse des LHC-Ringtunnels: Länge 27 Kilometer, Querschnitt Tunnelröhre: 2.8 Meter, Tiefe unter der Erdoberfläche 50-175 Meter
Parts of the LHC accelerator above and below ground at CERN: the diagram shows the circular tunnel of the LHC: the experiments ATLAS, ALICE, CMS, and LHCb; and the 7 km Super Proton Synchrotron (SPS) particle accelerator.

What happened so far: CERN and the CMS experiment in numbers


CERN established


First particle accelerator at CERN commences operation


Detection of the W and Z bosons
The 1984 Nobel Prize in Physics is awarded for contributions that led to the discovery of the two bosons.


Large Electron-Positron Collider (LEP) commences operation


The Large Hadron Collider (LHC) project is launched
1994 UZH joins the CMS experiment
2000 Construction of the LHC begins
2008 LHC begins colliding protons
The ATLAS, ALICE, CMS, and LHCb experiments of the LHC begin collecting data to address fundamental physics questions.
2012 Detection of the Higgs boson by the ATLAS and CMS collaborations
The 2013 Nobel Prize in Physics is awarded for the theoretical prediction of the Higgs boson.
2017 Replacement of the inner tracking detector of the CMS experiment
The 66-megapixel tracker was replaced with a faster, lighter, 124-megapixel tracker that was partly developed at the UZH by Professors Florencia Canelli and Ben Kilminster.
2018 - 2025 Development of the next inner tracking detector of the CMS experiment
The next inner tracker detector will have about 2 gigapixels, and features a large forward extension being developed and built by UZH and PSI. It will record data in the CMS detector from 2027 to 2040.


One of the largest international scientific collaborations in history: 3000 scientists and PhD students, 50 countries and 200 institutions
This linear accelerator is the first stage of the LHC accelerator complex. It uses radio frequency cavities to accelerate negative hydrogen ions up to 160 MeV of energy. After which, the electrons are stripped off, and the resulting protons are injected into the next stage of acceleration. © CERN | Melissa Marie Jacquemod | 2017

Good to know

A heavyweight in every respect: The CMS detector: 21 meters length, 15 meters height and 14,000 tons weight and the 124-megapixel tracker produces 40 million images per second

Using the Large Hadron Collider, physicists accelerate particles using radio-frequency cavities and bend these particles into circular orbits using superconducting magnets, steering them to collide with each other at specific points. Like the Big Bang at the beginning of the universe, the collisions momentarily produce unstable particles, which then decay into lighter particles via strong, electroweak and potentially unknown forces. These particles can leave signals in the CMS detector, enabling the energy and the paths of the particles to be measured. CMS researchers analyze these signals and thus can identify the particles that were originally produced in the collisions.

Learn more about the CMS detector:

How to control a beam of particles:

The next generation of CMS detector:

Higgs boson and beyond: The CMS experiment

In 2012, the CMS and ATLAS collaborations discovered the Higgs boson, the last particle predicted by the Standard Model. Its existence confirms the theory developed in the 1960s that explains how particles acquire mass. Despite the amazing predictive power of the Standard Model, it has notable shortcomings. For instance, it does not explain dark matter, the imbalance of matter over anti-matter, the relative strengths of the forces, and the existence of superfluous copies of matter particles, only one of which, the top quark, interacts strongly with the Higgs boson. CMS is designed to detect new particles and interactions that can shed light on these unknowns and to test the theory of the Standard Model with an unprecedented precision.

Searching for traces: Reconstructing particles with the CMS detector

The following images show various events recorded by the CMS detector. They are candidates for events in which Higgs bosons, top quarks, or hypothetical new particles are produced. These particles have an extremely short lifespan and can only be detected through the products of their decay.

Figure 1: This graphical display is a candidate for an event with a Higgs boson decaying into two tau leptons. One tau lepton decays into a more stable muon, displayed ass a red line linked to a signal in the muon chambers, while the other tau lepton decays into a narrow jet of particles, visualized as an orange cone.
Figure 2: This graphical display is a candidate for an event in which two top quarks are produced with two bottom quarks. The top quarks decay into lighter quarks. These quarks cannot be observed directly, and instead form bundles of particles known as jets that are shown in the image as orange cone-shaped objects.
Figure 3: A graphical display of a candidate for an event in which a Higgs boson is produced in association with a pair of top quarks. The Higgs boson decays into muons, displayed are red lines, along with neutrinos that are undetected, and the top quarks decay into lighter quarks, which are detected as jets, conical sprays of particles hitting the detector, and displayed as orange cones. The big structures in the display represent the muon chambers.
Figure 4: This graphical display is a candidate for an event in which a hypothetical particle is produced. The new particle could result from the existence of extra dimensions or new forces. The new particle is unstable and decays into four jets of observable particles, visualized as cones.

What does the UZH have to do with this?

Research groups from the University of Zurich are involved in various experiments at CERN: Florencia Canelli, Lea Caminada, and Ben Kilminster are conducting research on the CMS experiment, and Nico Serra and Olaf Steinkamp at the LHCb experiment. In parallel, they are also proposing new experiments beyond the timescale of the LHC.


The Higgs boson was detected by the CMS collaboration in 2012. Higgs bosons produced in the accelerator exist for just 0,00000000000000000000016 seconds,
which we write as 1.6 x 10-22 seconds.

And on it goes…

The LHC has been designed with a plan for long-term exploration. CMS will operate for at least another two decades while undergoing a steady evolution over time. New sub-detectors are being designed and manufactured. Groups at the University of Zurich are developing a central component of the next silicon tracking detector that will allow CMS to measure and search for particles that are produced closer to LHC beams. This will then be installed in the next phase of the CMS experiment, which will record data from 2027 to 2040.

Studies are currently underway at CERN for a new particle collider, with a tunnel three times longer than the LHC. This new collider would provide precision measurements of the Higgs boson and test for the effects of physics beyond the Standard Model.

Who is doing research on the CMS? And what for?

UZH physicists Florencia Canelli and Ben Kilminster develop and build key components of the inner tracking detector for the CMS experiment. Their research focuses on detecting new particles and interactions that could answer some of the open questions of fundamental physics.

Prof. Florencia Canelli
Experimental particle physicist

Originally from Argentina,
working at the UZH since 2012

Video portrait of Prof. Florencia Canelli:

Prof. Ben Kilminster
Experimental particle physicist

originally from the USA and UK,
working at the UZH since 2012

Video portrait of Prof. Ben Kilminster:

Do you want to test your knowledge?

Select the quiz at the desired difficulty level:

easy, medium, advanced

Weiterführende Informationen