Measurement of cos(2beta) in B0 -> D(*)0 h0 decays with a time-dependent Dalitz plot analysis of D0 -> Ks pi+ pi-

TL;DR

This paper presents a measurement of the cosine of 2β in B0 decays using a time-dependent Dalitz plot analysis of D0 decays, providing insights into the CP-violating phase with reduced ambiguity.

Contribution

It introduces a novel method to measure cos(2β) in B0 decays through a time-dependent Dalitz plot analysis of D0 decays, reducing the ambiguity in determining β.

Findings

Measured cos(2β) = 0.54 ± 0.54 ± 0.08 ± 0.18

Favors β=22° over 68° at 87% CL

Uses 311 million B Bbar pairs from BaBar

Abstract

We report a preliminary measurement of $\cos2\beta$ in $B^0\to D^{(*)0}h^0$ decays with a time-dependent Dalitz plot analysis of $D^0\to K_S\pi^+\pi^-$, where $h^0$ is a light neutral meson such as $\pi^0$, $\eta$, $\eta'$ or $\omega$. The strong phase variation on the Dalitz plot allows the access to the angle $\beta$ with only a two-fold ambiguity ($\beta+\pi$). Using $311\times 10^{6}$ $B\bar{B}$ pairs collected at the Babar detector, we obtain $\cos2\beta = 0.54 \pm 0.54 \pm 0.08 \pm 0.18$, $\sin2\beta = 0.45 \pm 0.36 \pm 0.05 \pm 0.07$, and $|\lambda| = 0.975^{+0.093}_{-0.085} \pm 0.012 \pm 0.002 $, where the first errors are statistical, the second are experimental systematic uncertainties, and the third are the signal Dalitz model uncertainties. This measurement favors the solution of $\beta= 22^\circ$ over $68^\circ$ at an 87% confidence level.