Quantum decoherence signatures in charmless non-leptonic $B$ decays

TL;DR

This work investigates quantum decoherence in non-leptonic neutral B decays by introducing a decoherence parameter $\lambda$ in the time evolution of the $B_d^0$–$\bar B_d^0$ system. It studies the CKM phase $\beta$ and penguin contributions using $B_d^0\to J/\psi K_S$ and its $U$-spin partner $B_d^0\to J/\psi\pi^0$, along with $B_d^0\to \pi^+\pi^-$, employing a toy Monte Carlo framework and $SU(3)$ flavor relations to control hadronic uncertainties. Decoherence enters the time-dependent CP asymmetries through an exponential damping $e^{-\lambda t}$, enabling profile-likelihood bounds on $\lambda$ from simulated data. The analysis yields no evidence for decoherence, placing 95% CL upper limits on $\lambda$ of 0.3195, 0.1093, and 0.1982 ps$^{-1}$ for the three channels, respectively, and demonstrates a robust framework to quantify potential quantum-physics effects as data statistics improve. The results underscore the persistence of quantum coherence in $B$-meson oscillations while providing a pathway to tighter constraints on new-physics scenarios in flavor with future high-luminosity experiments.

Abstract

Quantum coherence plays a crucial role in the dynamics of neutral meson systems, aiding in the extraction of various Standard Model parameters. However, real physical systems always interact with their surroundings, which causes decoherence. In case of time dependent analysis of non-leptonic neutral $B$ meson decays, this decoherence can be modeled using a single parameter, $λ$. Since decoherence can affect the observed dynamics of flavor oscillations and CP violation, it becomes essential to revisit the key SM parameters such as the CKM angles $(α, β, γ)$ and the mass differences of neutral $B$ mesons ($Δm_{d,s}$). In this work, we study the CKM phase $β$ as well as the penguin contributions in the $B_d^0 \to J/ψK_S$ decay mode in the presence of decoherence. We employ the pseudo-experiment (Toy Monte-Carlo) technique and perform an $SU(3)_F$ analysis using the $B_d^0 \to J/ψπ^0$ process. Furthermore, we investigate the $B_d^0 \to π^+ π^-$ decay mode to understand how the decoherence influences the CP violating observables. Our findings reveal that the presence of decoherence can affect crucially the measured values of the observables.

Figures (9)

• Figure 1: Distributions of fitted CP-violation parameters obtained from toy Monte Carlo samples of $B_d^0 \to J/\psi K_S$ decays (upper: without decoherence and Lower: with decoherence.)
• Figure 2: Distributions of fitted CP-violation parameters obtained from toy Monte Carlo samples of $B_d^0 \to J/\psi \pi^0$ decays (upper: without decoherence and Lower: with decoherence.)
• Figure 3: Distributions of fitted CP-violation parameters obtained from toy Monte Carlo samples of $B_d^0 \to \pi^+ \pi^-$ decays (upper: without decoherence and Lower: with decoherence.)
• Figure 4: Pull distributions (upper: without decoherence, lower: with decoherence) of the fitted parameters for $B_d^0 \to J/\psi K_S$ mode obtained from toy Monte Carlo studies.
• Figure 5: Pull distributions (upper: without decoherence, lower: with decoherence) of the fitted parameters for $B_d^0 \to J/\psi \pi^0$ decays obtained from toy Monte Carlo studies.