LHCb

Matter and antimatter

Nikhef’s LHCb research programme brings together the Dutch contribution to the LHCb experiment at CERN. Researchers analyse the detector’s measurement data and work on technical innovations. LHCb studies the differences between matter and antimatter.

What is LHCb?

The LHCb research group at Nikhef is involved, from the Netherlands, in the construction, operation and data analysis of the LHCb particle detector at CERN. The LHCb experiment is one of the large particle detectors at the LHC accelerator at CERN in Geneva. Around 1,700 scientists from 22 countries, including the Netherlands, are working on the experiment.

The underground detector is 21 metres long and measures 13 by 10 metres, and studies the colliding protons in the accelerator. Unlike many particle detectors, LHCb is asymmetrical and looks in one direction of the accelerator tube, where large magnets deflect the released charged particles. This reveals any differences between matter and antimatter.

The signals from the sensors in LHCb are transmitted to computers for data storage and processing. LHCb groups around the world analyse the enormous amounts of data and attempt to interpret them theoretically.

What does LHCb investigate?

LHCb searches for differences between particles and their antiparticles. These might explain why both matter and antimatter must have been created in the Big Bang, yet only matter remained in the first nanosecond.

LHCb is designed for the precise identification of decay products of unstable particles and for the accurate measurement of their tracks. A magnet is used to separate particles and antiparticles and analyse their properties.

LHCb studies the minute differences between matter and antimatter by observing processes involving so-called bottom quarks and anti-bottom quarks (the letter b in the name LHCb). Particles containing b-quarks are extremely unstable and can only be produced in proton collisions within a powerful particle accelerator such as the LHC.

So far, LHCb has found subtle indications that b-particles and anti-b-particles differ in certain respects, but further measurements are needed to prove any discrepancies.

A recent groundbreaking result, published in Nature, was the discovery of a decay of a b-particle into two muons, which was ‘forbidden’ by theory.
Nikhef and LHCb

The Nikhef LHCb group comprises around 35 researchers affiliated with VU University Amsterdam, the University of Groningen and Maastricht University who are helping to build LHCb and analyse and interpret the measurement data. Nikhef was and remains closely involved in the construction and ongoing upgrades of the LHCb detector.

Researchers, technicians and engineers helped develop and build the Vertex Locator (VELO) and the Outer Tracker (SciFi). These components measure the starting point (the vertex) of the tracks left by emitted particles. In addition, Nikhef developed software that reconstructs the tracks left by charged particles in the detector.

Nikhef pioneered the use of graphics processing units (GPUs) in the detector and data acquisition, enabling vast amounts of measurement data to be rapidly collected and analysed.

During the LS3 maintenance shutdown (2026–2029), further modifications will be carried out to prepare LHCb for the much more intense proton beams of the High Luminosity LHC at CERN.
More information

Through Nikhef, researchers from VU University Amsterdam, the University of Groningen and Maastricht University contribute to the research at the LHCb research programme.

Read more about LHCb at CERN: http://lhcb-outreach.web.cern.ch and http://lhcb.web.cern.ch/