The first LHC operation in December 2009 has now resulted in a first particle physics publication of the CMS experiment. This is after a remarkably short time, given the complexity and the size of this gigantic experiment constructed and operated by more than 3000 physicists and engineers from close to 40 countries.
The new ring accelerator at CERN, the Large Hadron Collider (LHC) resumed operation end of November 2009 after the major incident, which caused a delay of more than a year. However, now it is working so well that millions of collisions between protons from the two different beams have been induced.
Each head-on collision between a pair of protons creates new elementary particles, which fly away from each other like flinders of an explosion. The pixel detector developed by the Paul Scherrer Institute is located just a few centimetres away from the collision site, and registers the particles’ flight direction from this ring-side seat.
Detector within a detector
Scientists during the installation of the BPIX detector in the centre of the vast CMS detector (Credit: H.R. Bramaz/PSI)
The development of this pixel detector alone has involved 15 years of work by dozens of scientists – from other institutions as well as PSI.
For example, the lightweight carbon fibre mechanics was supplied by the University of Zurich. ETH Zurich made vital contributions to the design of the overall electronic system. Key components, such as the connection technology, sensor and readout chip, were developed at PSI where the detector was also assembled.
The pixel detector developed by PSI’s scientists is placed in the centre of the 22-metre long CMS (Compact Muon Solenoid) detector at CERN. It weighs 12,500 tonnes and is one of the largest measuring instruments ever built. CMS is one of four experiments at the enormous LHC accelerator at CERN, which physicists hope to use to discover more about among others, the legendary Higgs boson in the mysteries of matter.
In just a few hours, researchers from the participating institutes were able to collect enough data to take an initial particle-physics recording. It confirmed predictions made in advance by computer simulation, and led to the first scientific article based on this experiment, which was accepted for publication in record time.