Measurement of the Mass Difference Between Neutral Charm-Meson Eigenstates

Area of Science:

• Particle Physics
• High-Energy Physics
• Quantum Mechanics

Background:

• Neutral charm mesons (D0) are particles composed of a charm quark and an up antiquark.
• Understanding the properties of D0 mesons is crucial for testing the Standard Model of particle physics.
• CP violation in the charm sector is a key area of investigation.

Purpose of the Study:

• To precisely measure the mass difference between neutral charm-meson eigenstates.
• To investigate CP violation in the mixing and decay of D0 mesons.
• To provide new data for the study of fundamental symmetries in particle physics.

Main Methods:

• Analysis of 2.3×10^6 D0→KS0π+π- decays from LHCb experiment data (2011-2012).
• A novel approach was employed to enhance sensitivity to the mass difference parameter.
• Inclusion of CP violation in mixing and interference between mixing and decay was considered.

Main Results:

• CP-averaged normalized mass difference x_CP = [2.7±1.6(stat)±0.4(syst)]×10^-3.
• CP-violating parameter Δx = [-0.53±0.70(stat)±0.22(syst)]×10^-3.
• Measurements are consistent with CP symmetry and represent the most precise from a single experiment.

Conclusions:

• The precise measurements of D0 meson properties offer the first experimental evidence for a mass difference between neutral charm-meson eigenstates.
• Combined with world averages, these results refine our understanding of CP symmetry in the charm sector.
• This study contributes significantly to precision tests of the Standard Model.