[1] LHCb specializes in the measurements of the parameters of CP violation in the interactions of b- and c-hadrons (heavy particles containing a bottom and charm quarks).
The detector is also able to perform measurements of production cross sections, exotic hadron spectroscopy, and electroweak physics in the forward region.
The LHCb collaborators, who built, operate and analyse data from the experiment, are composed of approximately 1650 people from 98 scientific institutes, representing 22 countries.
[4] The experiment is located at point 8 on the LHC tunnel close to Ferney-Voltaire, France just over the border from Geneva.
These are described in a roadmap document[5] that formed the core physics programme for the first high energy LHC running in 2010–2012.
They include: The fact that the two b-hadrons are predominantly produced in the same forward cone is exploited in the layout of the LHCb detector.
The Vertex Locator (VELO) is built around the proton interaction region.
[6][7] It is used to measure the particle trajectories close to the interaction point in order to precisely separate primary and secondary vertices.
The detector operates in vacuum and is cooled to approximately −25 °C (−13 °F) using a biphase CO2 system.
The data of the VELO detector are amplified and read out by the Beetle ASIC.
However, the most important change is the switch to the fully software trigger of the experiment, which means that every recorded collision will be analysed by sophisticated software programmes without an intermediate hardware filtering step (which was found to be a bottleneck in the past).
[9] During the 2011 proton-proton run, LHCb recorded an integrated luminosity of 1 fb−1 at a collision energy of 7 TeV.
In addition, small samples were collected in proton-lead, lead-lead, and xenon-xenon collisions.
The LHCb design also allowed the study of collisions of particle beams with a gas (helium or neon) injected inside the VELO volume, making it similar to a fixed-target experiment; this setup is usually referred to as "SMOG".
[11] These datasets allow the collaboration to carry out the physics programme of precision Standard Model tests with many additional measurements.
In addition to precision studies of the known particles such as mysterious X(3872), a number of new hadrons have been discovered by the experiment.
As of 2021, all four LHC experiments have discovered about 60 new hadrons in total, vast majority of which by LHCb.
[13] In 2015, analysis of the decay of bottom lambda baryons (Λ0b) in the LHCb experiment revealed the apparent existence of pentaquarks,[14][15] in what was described as an "accidental" discovery.
Studies of charge-parity (CP) violation in B-meson decays is the primary design goal of the LHCb experiment.
As of 2021, LHCb measurements confirm with a remarkable precision the picture described by the CKM unitarity triangle.
[20] In 2019, LHCb announced discovery of CP violation in decays of charm mesons.
The rate of the observed CP asymmetry is at the upper edge of existing theoretical predictions, which triggered some interest among particle theorists regarding possible impact of physics beyond the Standard Model.
[22] In 2020, LHCb announced discovery of time-dependent CP violation in decays of Bs mesons.
[23] The oscillation frequency of Bs mesons to its antiparticle and vice versa was measured to a great precision in 2021.
In 2014, LHCb and CMS experiments published a joint paper in Nature announcing the discovery of the very rare decay
[24] This measurement has harshly limited the possible parameter space of supersymmetry theories, which have predicted a large enhancement in rate.
Since then, LHCb has published several papers with more precise measurements in this decay mode.
As a consequence, in decays of b hadrons, electrons and muons should be produced at similar rates, and the small difference due to the lepton masses is precisely calculable.
[27][28] However, as the decays in question are very rare, a larger dataset needs to be analysed in order to make definitive conclusions.
In March 2021, LHCb announced that the anomaly in lepton universality crossed the "3 sigma" statistical significance threshold, which translates to a p-value of 0.1%.