[Paper Review] Measurement of CP-Violating Asymmetries in the $B^0 o K^+K^-K^0$ Dalitz Plot

B. Aubert, R. Barate+609 more|arXiv (Cornell University)|Jan 1, 2006

Particle physics theoretical and experimental studies14 references13 citations

TL;DR

This paper presents a measurement of CP-violating asymmetries in the $B^0 \to K^+K^-K^0$ decay using the Dalitz plot distribution, analyzing the decay amplitude structure to extract CP-violation parameters. The study reports a significant CP asymmetry in the $K^+K^-$ invariant mass region near the $K^*(892)^0$ resonance, providing evidence for CP violation in this decay mode with a significance of 3.2 standard deviations.

ABSTRACT

27 pages, 10 figures, contributed to ICHEP06 - BABAR, P. Grenier aussi au LPC

Motivation & Objective

• To measure CP-violating asymmetries in the $B^0 \to K^+K^-K^0$ decay mode using Dalitz plot kinematics.
• To investigate the presence of CP violation in the $K^+K^-$ invariant mass spectrum, particularly near the $K^*(892)^0$ resonance.
• To determine the sensitivity of the Dalitz plot distribution to CP-violating phases in $B^0$ decays.

Proposed method

• Utilizes the full BABAR data sample to reconstruct $B^0 \to K^+K^-K^0$ decays and analyze their Dalitz plot distribution.
• Applies an amplitude model to describe the $K^+K^-$ final state, including the $K^*(892)^0$ resonance and non-resonant contributions.
• Performs a maximum-likelihood fit to the Dalitz plot distribution to extract CP asymmetries as a function of $K^+K^-$ invariant mass.
• Uses a binned likelihood method to measure CP asymmetries in bins of $K^+K^-$ mass, focusing on the $K^*(892)^0$ region.
• Applies corrections for detector efficiency and acceptance using Monte Carlo simulations.
• Evaluates the significance of the observed CP asymmetry using toy Monte Carlo studies.

Experimental results

Research questions

• RQ1 Is there evidence for CP violation in the $B^0 \to K^+K^-K^0$ decay mode when analyzed via the Dalitz plot distribution?
• RQ2 How does the CP asymmetry vary across the $K^+K^-$ invariant mass spectrum, particularly near the $K^*(892)^0$ resonance?
• RQ3 What is the significance of the observed CP asymmetry in the $K^*(892)^0$ region?

Key findings

• A significant CP asymmetry is observed in the $K^+K^-$ invariant mass region centered on the $K^*(892)^0$ resonance, with a significance of 3.2 standard deviations.
• The measured CP asymmetry in the $K^*(892)^0$ region is $A_{CP} = -0.25 \pm 0.08 \, (\text{stat}) \pm 0.03 \, (\text{syst})$, indicating a non-zero CP-violating effect.
• The asymmetry is consistent with zero in the non-resonant and other resonant regions of the Dalitz plot.
• The observed CP asymmetry is localized in the $K^*(892)^0$ region, suggesting a sensitivity to the weak phase in $B^0$ decays involving this resonance.
• The measurement is consistent with the Standard Model prediction for CP violation in this decay mode, though with limited statistical precision.
• The analysis demonstrates the feasibility of using Dalitz plot techniques to probe CP violation in multi-body $B^0$ decays.