CORDIS - EU research results

The charm of asymmetries or the asymmetries in charm (entangled edition)

Project description

Looking for a lucky charm – and revelations of the Big Bang

Matter and antimatter particles have the same mass, but other properties, such as their electric charge, are opposite. They are always produced as a pair and annihilate one another if they come in contact, so the observed predominance of matter over antimatter (matter–antimatter asymmetry known as the CP violation) suggests a missing link. Theories that predict the amount of CP violation in the Universe and observed CP violation in experiments cannot account for the difference. In 2019, CP violation in particles containing charm quarks was observed for the first time. The EU-funded CharmAsymmetries project is building on this historical revelation with new analyses of the data, searching for CP violation processes in other charm meson decays that have not yet been observed.


The study of difference between matter and antimatter (CP violation) is one of the most exciting fields at the frontier of fundamental physics research. It is driven by the question of what happened to the antimatter after the Big Bang. The mesons, particles that contain both matter and antimatter quarks are ideal laboratories for the discovery of CP violation. This proposal aims at looking for CP violation in decays of mesons containing one charm (or anti-)quark, the only type of mesons where CP violation has not yet been observed.

One of the objectives is to carry out a measurement of the matter-antimatter mixing and CP violation parameters in the most sensitive charm decay mode (D0->Kspipi) using the unprecedented charm data sample collected by the LHCb experiment at CERN. To achieve maximal precision of both measurements, external input from the unique Chinese flavour factory, BESIII, is crucial. Key attributes of the decays of the D meson, the strong phases and their variation across the phase space, require the use of quantum-entangled states that are accessible at BESIII. Usually, these quantities are measured in regions of the phase space, the definition of which is inspired by a model. Wrong definition of these regions would lead to dilution of the sensitivity of these measurements. We propose to measure these quantities at every point of the phase space to maximise the precision.

The second objective is to look for CP violation in the charm D0->(anti-)K*0KS decays with LHCb data ignoring time-dependent effects arising from matter-antimatter mixing. The three-body final state after an instant decay of the exited K*0 meson, K pi KS, will be studied using novel model-dependent and model independent methods, the former has been pioneered by the Manchester LHCb group, and the latter has not yet been tested. Currently, these decays have been highlighted by theorists as the most likely discovery channel for time-integrated CP violation in the charm system.


Net EU contribution
€ 212 933,76
M13 9PL Manchester
United Kingdom

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North West (England) Greater Manchester Manchester
Activity type
Higher or Secondary Education Establishments
Total cost
€ 212 933,76