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

Abstract

We report a preliminary measurement of $\cos2β$ in $B^0\to D^{(*)0}h^0$ decays with a time-dependent Dalitz plot analysis of $D^0\to K_Sπ^+π^-$, where $h^0$ is a light neutral meson such as $π^0$, $η$, $η'$ or $ω$. The strong phase variation on the Dalitz plot allows the access to the angle $β$ with only a two-fold ambiguity ($β+π$). Using $311\times 10^{6}$ $B\bar{B}$ pairs collected at the Babar detector, we obtain $\cos2β= 0.54 \pm 0.54 \pm 0.08 \pm 0.18$, $\sin2β= 0.45 \pm 0.36 \pm 0.05 \pm 0.07$, and $|λ| = 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 $β= 22^\circ$ over $68^\circ$ at an 87% confidence level.