Observation of the mass difference between neutral charm-meson eigenstates

Abstract

A measurement of mixing and $CP$ violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4${\text{fb}}^{-1}$. A total of $30.6$ million $D^0\to K_{\mathrm{S}}^0{\pi }^{+}{\pi }^{-}$ decays are analyzed using a method optimized for the measurement of the mass difference between neutral charm-meson eigenstates. Allowing for $CP$ violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be $x_{CP}=\left[3.97\pm 0.46\text{(stat)}\pm 0.29\text{(syst)}\right]\times 10^{-3}$ and $y_{CP}=\left[4.59\pm 1.20\text{(stat)}\pm 0.85\text{(syst)}\right]\times 10^{-3}$, respectively. The $CP$-violating parameters are measured as $\Delta x=\left[-0.27\pm 0.18\text{(stat)}\pm 0.01\text{(syst)}\right]\times 10^{-3}$ and $\Delta y=\left[0.20\pm 0.36\text{(stat)}\pm 0.13\text{(syst)}\right]\times 10^{-3}$. This is the first observation of a nonzero mass difference in the $D^0$ meson system, with a significance exceeding seven standard deviations. The data are consistent with $CP$ symmetry, and improve existing constraints on the associated parameters.

arXiv commentAll figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2021-009.html (LHCb public pages). Updated to correct sign of reported value of phi

References in corpus (23)

• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2016
• LHCb Detector Performance
• sPlot: a statistical tool to unfold data distributions
• Model-independent constraints on Delta F=2 operators and the scale of New Physics
• Decay Chain Fitting with a Kalman Filter
• Flavor Physics Constraints for Physics Beyond the Standard Model
• Evidence for D0-anti-D0 Mixing
• Implications of D^0-\bar D^0 Mixing for New Physics
• The $D^0-{\bar{D}}^0$ mass difference from a dispersion relation
• D^0 - D^0-bar Oscillations as a Probe of Quark-Hadron Duality
• Model-independent determination of the strong-phase difference between D^0 and D^0-bar-> K^0_S,L h^+ h^- (h=pi,K) and its impact on the measurement of the CKM angle gamma/phi_3
• Measurement of D0-antiD0 mixing parameters using D0 -> K0S pi+ pi- and D0 -> KS0 K+ K- decays
• Lessons from CLEO and FOCUS Measurements of D0-anti-D0 Mixing Parameters
• How large can the SM contribution to CP violation in $D^0-{\bar{D}}^0$ mixing be?
• Search for D^0 - barD^0 Mixing in the Dalitz Plot Analysis of D^0 --> K_S^0 pi^+ pi^-
• Measurement of the mass difference between neutral charm-meson eigenstates
• Measurement of the CKM angle gamma from a combination of B->Dh analyses
• Model-independent determination of the relative strong-phase difference between $D^0$ and ${\bar{D}}^0\to K_{S,L}^0{\pi }^{+}{\pi }^{-}$ and its impact on the measurement of the CKM angle $\gamma /{\varphi }_3$
• Measurement of $D^0$-$\overline{D}{}^0$ Mixing and Search for Indirect $CP$ Violation Using $D^0\to K_S^0{\pi }^{+}{\pi }^{-}$ Decays
• Dispersive and Absorptive CP Violation in $D^0-\overline{D^0}$ Mixing
• Novel method for measuring charm-mixing parameters using multibody decays
• Model-independent measurement of mixing parameters in $D^0\to K_S{\pi }^{+}{\pi }^{-}$ decays
• First evidence for $\cos 2\beta >0$ and resolution of the CKM Unitarity Triangle ambiguity by a time-dependent Dalitz plot analysis of $B^0\to D^{(\ast )}{h}^0$ with $D\to K_S^0{\pi }^{+}{\pi }^{-}$ decays

Cited by in corpus (23)

• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of 2021
• 50 Years of Quantum Chromodynamics
• Observation of charge-parity symmetry breaking in baryon decays
• Measurement of the time-integrated $CP$ asymmetry in $D^0\to K^{-}{K}^{+}$ decays
• Heavy Flavour Physics and CP Violation at LHCb: a Ten-Year Review
• Search for time-dependent $CP$ violation in $D^0\to K^{+}{K}^{-}$ and $D^0\to {\pi }^{+}{\pi }^{-}$ decays
• Two is better than one: The U-spin-CP anomaly in charm
• Search for rare decays of $D^0$ mesons into two muons
• Measurement of the charm mixing parameter $y_{CP}-y_{CP}^{K\pi }$ using two-body $D^0$ meson decays
• Measurement of $CP$ asymmetries in ${\Lambda }_b^0\to p{h}^{-}$ decays
• Search for time-dependent $CP$ violation in $D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays
• Model-independent measurement of charm mixing parameters in $\bar{B}\to D^0(\to K_S^0{\pi }^{+}{\pi }^{-}){\mu }^{-}{\bar{\nu }}_{\mu }X$ decays
• Recent advances in charm mixing and $CP$ violation at LHCb
• Measurement of $D^0-{\overline{D}}^0$ mixing and search for $CP$ violation with $D^0\to K^{+}{\pi }^{-}$ decays
• Revealing inherent quantum interference and entanglement of a Dirac particle
• Exploring Strange Origin of Dirac Neutrino Masses at Hadron Colliders
• A Review of $CP$ Violation Measurements in Charm at LHCb
• First observation of the charmless baryonic decay $B^{+}\to \bar{\Lambda }p\bar{p}p$
• Theory Motivation: What measurements are needed?
• Model-independent measurement of $D^0$-$\overline{D}{}^0$ mixing parameters in $D^0\to K_S^0{\pi }^{+}{\pi }^{-}$ decays at Belle and Belle II
• A novel measurement of the strong-phase difference between $D^0\to K^{-}{\pi }^{+}$ and ${\bar{D}}^0\to K^{-}{\pi }^{+}$ decays using $C$-even and $C$-odd quantum-correlated $D\bar{D}$ pairs
• First observation of quantum correlations in $e^{+}{e}^{-}\to XD\bar{D}$ and $C$-even constrained $D\bar{D}$ pairs
• Measuring Electroweak Quantum Numbers of Color Sextet Resonances at the LHC