LHCb

LHCb Collaboration in front of the LHCb detector
(Credit: CERN)

LHCb is one of the four main experiments at the Large Hadron Collider at CERN LHCb was built in a cavern 100m below ground near Ferney-Voltaire in France.

It is investigating the subtle differences between matter and antimatter. One of the most fundamental questions is why is our Universe made of matter? It is widely thought that initially equal amounts of matter and antimatter were created, and currently there is no evidence opposing this. Experimental measurements and theoretical calculations hint that almost all matter and antimatter would have annihilated each other leaving behind a residual amount of matter to form our Universe. The mechanism that would have favoured matter against antimatter is called CP violation.

Although absent from the Universe today, particles known as ‘beauty (b) quarks’ were common in the aftermath of the Big Bang, and are generated in their billions by the LHC, along with their antimatter counterparts, anti-beauty quarks.

LHCb studies the decay of particles containing b and anti-b quarks, collectively known as ‘B mesons’. Physicists believe that by comparing these decays, they may be able to gain useful clues as to why nature prefers matter over antimatter.

Quick facts

About the LHCb detector
Size 21 m long, 10 m high, 13m wide
Weight 5600 tonnes
Design Forward spectrometer with planar detectors
About the LHCb people
Collaboration 920 physicists, engineers, technicians, students and support staff
Number of countries 17
Number of institutes 65
Number of UK institutes 11

LHCb introduction
(Credit: CERN)

LHCb Schematic
(Credit: CERN)

Rather than flying out in all directions, B mesons formed by the colliding proton beams (and the particles they decay into) stay close to the line of the beam pipe, and this is reflected in the design of the LHCb detector.

Unlike ALICE, ATLAS and CMS which each surround the entire collision point with layers of sub-detectors, like an onion, the LHCb detector stretches for 20 metres along the beam pipe, with its sub-detectors stacked behind each other like books on a shelf.

Each one of LHCb’s sub-detectors specializes in measuring a different characteristic of the particles produced by colliding protons. Collectively, the detector’s components gather information about the identity, trajectory, momentum and energy of each particle generated, and can single out individual particles from the billions that spray out from the collision point.

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