Time-dependent Dalitz Plot Analysis of B0 --> Ks pi+ pi-

TL;DR

This paper presents a time-dependent Dalitz plot analysis of B0 decays to measure CP violation parameters and asymmetries, using data from the BaBar experiment, providing insights into CP violation in specific decay channels.

Contribution

It introduces a novel time-dependent Dalitz plot analysis method to extract CP violation parameters in B0 decays to K0_S pi+ pi- channels, with results from a large data sample.

Findings

Measured 2β_eff for f0(980)K0_S and ρ(770)K0_S decays.

Found a 4.3σ significance for non-zero 2β_eff in f0(980)K0_S.

Determined direct CP asymmetry and phase differences in B0 decay amplitudes.

Abstract

We perform a time-dependent Dalitz plot analysis of $B^0 \to K^0_{\scriptscriptstyle S}\pi^+\pi^-$ in order to extract the ${CP}$ violation parameters of $f_0(980) K^0_{\scriptscriptstyle S}$ and $\rho^0(770) K^0_{\scriptscriptstyle S}$ and direct ${CP}$-asymmetries of $K^{*+}(892) \pi^-$. The results are obtained from a data sample of $(383\pm3)\times10^{6}$ $B \bar{B}$ decays, collected with the BaBar detector at the PEP2 asymmetric--energy $B$ factory at SLAC. The measured values of $2\beta_{\rm eff}$ in $B^0$ decays to $f_0(980)K^0_{\scriptscriptstyle S}$ and $\rho^0(770) K^0_{\scriptscriptstyle S}$ are $(89^{+22}_{-20} \pm 5 \pm 8)^\circ$ and $(37 ^{+19}_{-17} \pm 5 \pm 6)^\circ$, respectively, where the first quoted uncertainty is statistical, the second is systematic and the third is Dalitz plot signal model uncertainty. We measure the significance of $2\beta_{\rm eff}(f_0(980)K^0_{\scriptscriptstyle S})\neq 0$ to be $4.3 \sigma$. In decays to $K^*(892) \pi$ we find $A_{{CP}} = -0.18 \pm 0.10 \pm 0.03 \pm 0.03$. The measured phase difference between the decay amplitudes of $B^0 \to K^{*+}(892) \pi^-$ and $\bar{B}^0 \to K^{*-}(892) \pi^+$ is $(-164 \pm 24 \pm 12 \pm 15)^\circ$. All results are preliminary.