| Compact Muon Solenoid Experiment



Compact Muon Solenoid Experiment


The major achievement of particle physics in the second half of the 20th century is the development of the Standard Model. It describes three of the four known fundamental forces, the weak, the electromagnetic and the strong force, within the electroweak theory and the quantum chromodynamics. However, it does not include the fourth force, the gravity, and leaves a number of questions open, among them:

• Do the four fundamental forces unify at large energies?
• What is dark matter made of?

Supersymmetry (SUSY) is one of the most attractive theories providing a framework for the unification of all four forces. In addition, some SUSY models propose a light stable supersymmetric particle (LSP), being neutral, weakly interacting and therefore invisible for our detectors so far. These LSPs are promising candidates for dark matter.

Within SUSY, one partner particle is assigned to each known elementary particle. These superpartners are expected to have masses above the reach of current colliders. Accelerators like the Large Hadron Collider (LHC), which will start this year, or the future International Linear Collider (ILC) will reach energies which offer the possibility to measure new particles with masses up of 1 TeV and above, (about 2 000 000 times the electron mass), called the Terascale.

The main focus of the group is the search for SUSY particles at the LHC, using one of the two multi-purpose detectors called CMS (Central Muon Solenoid). The search for supersymmetric signatures is a challenging task, as they are hidden in the experimental data under a huge background.
The main signature of SUSY particles in the CMS detector is given by the following scenario:
Heavy SUSY particles, initially produced in the proton-proton interaction, induce high energetic bundles of particles during their subsequent decay into the lightest SUSY particle. These leave the detector without trace, leading to missing energy in the energy balance. This signature can be mimicked by known processes described by the Standard Model as well as by electronic noise or malfunction in detector components.

So far, the DESY CMS SUSY group has been working on searches for supersymmetric partner of the gluon, the top quark and the tau lepton.

For a review of 8 TeV LHC results on the search for Supersymmetry please have a look here:
Lessons for SUSY from the LHC after the first run