CERN

The European Laboratory for Particle Physics (CERN) is located just outside Geneva, Switzerland and overlaps the border between France and Switzerland. It has a 27 kilometer circumference circular tunnel which houses the Large Electron-Positron Collider (LEP). Entering service in 2008 in the same tunnel used for the LEP was the Large Hadron Collider which should produce proton-proton collisions in the energy range 10-14 TeV. This was the major tool used in the search for the Higgs boson.

The Super Proton Synchrotron (SPS) at CERN is one of the worlds largest protron synchrotrons, reaching energies of 450 GeV.

Another major facility at CERN is the Intersecting Storage Rings (ISR), the first proton-proton collider to be put into operation (1971). It had a maximum proton energy of 31 GeV per beam.

LEP

The world's largest electron synchrotron was the Large Electron-Positron Collider (LEP) at CERN. It operated from 1989 to 2000 in the same tunnel used to build the Large Hadron Collider. It has a radius of about 4 km. For the electron synchrotrons, the maximum energy is limited by the losses to synchrotron radiation which increases with the fourth power of the particle energy. Since those losses are inversely proportional to the square of the orbit radius, these accelerators are made as large as possible.

A part of CERN, the Large Electron-Positron Collider (LEP) occupied a 27 kilometer circumference circular tunnel near Geneva which overlaps the Swiss-French border. It was designed to study electron-positron collisions at a center of mass energy equal to the Z⁰ mass energy, about 100 GeV. It was capable of very precise measurements, but didn't reach a high enough energy to find the Higgs boson.

Large Hadron Collider

The Large Hadron Collider is latest member of CERN's collection of extraordinary high-energy facilities and is the world's largest and highest-energy accelerator. It occupies a 27 kilometer circumference circular tunnel near Geneva which overlaps the Swiss-French border, the same tunnel that contained the LEP. It is designed to produce proton-proton collisions. Successful particle beams were produced in the LHC in 2008 and in 2010 the two beams reached 3.5 TeV, half the target maximum for the accelerator. The Atlas bulletin of 2018 reported on data taken at 13 TeV.

Currently the work at the LHC is divided into six experiments denoted by the names ATLAS, CMS, ALICE, LHCb, TOTEM and LHCf.

A major objective for the LHC was the search for the Higgs boson. The Atlas and CMS detectors were major parts of that discovery and subsequent study.

Currently some excitement is being generated by results at the LHCb or "Beauty" detector, a portion of which is shown at left. A 0.8% imbalance between the decay rates of the D-meson and its antiparticle has been discovered. 目前，LHCb或“Beauty”探测器的某些结果正在引起关注，其中一部分如左图所示。已发现D介子与其反粒子的衰变率之间存在0.8%的不平衡。

Though a small difference, it is a newly discovered difference between matter and antimatter and could contribute to the solution of the "antimatter problem" in cosmology.

References:

CERN Home

CERN Document Server

Wiki Large Hadron Collider