CP violation in Bs meson decay

Measurements of the weak φs phase

The observed difference between properties of matter and antimatter is governed by violation of the Charge-Parity (CP) symmetry. The Standard Model (SM) of particle physics predicts such violation, however the predicted size is to small to explain our observations. Therefore it is expected that some new phenomena are responsible for the excessive CP violation.

Measurement of the difference between properties of matter and antimatter for the strange beauty Bs mesons is one of promising ways to verify such assumption. The size of this difference is controlled by the parameter φs, which is predicted to be small in the Standard Model. However, effects of new particles not predicted by the Standard Model can make the measured value much larger. The measurement of φs is one of the most important goals of LHCb experiment.

The decay of the strange-beauty particle B0s, composed of a beauty antiquark (b) bound with a strange quark (s), into a J/ψ meson and a φ meson is used for this measurement. The J/ψ meson decays in turn into a μ+μ– or e+e– pair, and the φ decays to K+K– pair. In order to make this difficult measurement one has to analyze the Bs decay particles in 3 dimensions as well as to measure precisely the fast oscillations of strange beauty. In the world of quantum mechanics the strange-beauty meson Bs matter antimatter system is alternatively described as a heavy and light mass Bs meson system. The mass difference Δms between the heavy and light states leads to matter antimatter oscillations namely B0s changing back and forth into anti-B0s.

Our group is involved in measurements of the weak phase φs with the reaction B0s→J/ψ(e+e–)φ(K+K–) where J/ψ→e+e– and φ→K+K–.

The conference presentations presented by Warsaw LHCb group:

  • Measurement of the phase φs at the LHCb, XXIII Cracow Epiphany Conference, 9-12.01.2017, Cracow, Poland, Epiphany2017_Batozskaya
  • Measurement of the CP-violating phase φs at LHCb, 6th International Conference on New Frontiers in Physics (ICNFP2017), 17-29.08.2017, Crete, Greece, ICNFP2017_Batozskaya_v2

  • Overview of CPV parameter φs determination, The 3rd International Conference on Particle Physics and Astrophysics (ICPPA2017), 2-5.10.2017, Moscow, Russia, ICPPA2017_Batozskaya

  • Determination of the phase φs at LHCb, The XXI International Scientific Conference of Young Scientists and Specialists (AYSS2017), 2-6.10.2017, Dubna, Russia, AYSS2017_Batozskaya

  • Future contributions to φs measurements, XXIV Cracow Epiphany Conference, 9-12.01.2018, Cracow, Poland, Epiphany2018_Batozskaya

The conference proceedings prepared by Warsaw LHCb group:

  • Measurement of the phase φs at the LHCb, APhysPolB.48.913
  • Measurement of the CP-violating phase φs at LHCb, submitted to EPJ Web Conf.
  • Overview of CPV parameter φs determination, Ken.v3i1.1773
  • Determination of the phase φs at LHCb, EPJ Web Conf., 177 (2018) 04003
  • Future contributions to φs measurements, submitted to APhysPolB