Measurement of CP violation observables and parameters for the decays $B^{\pm}\to D K^{*\pm}$

TL;DR

This paper measures CP violation observables in B meson decays to determine the CKM angle gamma, using a large data sample and multiple analysis methods, providing new constraints on the parameters of the Standard Model.

Contribution

It presents the first comprehensive measurement of CP violation observables in B to DK* decays, combining GLW and ADS methods to constrain the CKM angle gamma.

Findings

Measured CP asymmetries and ratios with statistical and systematic uncertainties.

Determined the ratio of suppressed to favored amplitudes, r_B, as 0.31.

Excluded certain gamma intervals at 1-2 sigma confidence levels.

Abstract

We study the decay $B^-\to DK^{*-}$ using a sample of 379$\times 10^6$ $\Upsilon(4S)\to B\bar{B}$ events collected with the BABAR detector at the PEP-II $B$-factory. We perform a "GLW" analysis where the $D$ meson decays into either a CP-even ($CP+$) eigenstate ($K^+K^-$, $\pi^+\pi^-$), CP-odd ($CP-$) eigenstate ($K^0_S\pi^0$, $K^0_S\phi$, $K^0_S\omega$) or a non-CP state ($K^-\pi^+$). We also analyze $D$ meson decays into $K^+\pi^-$ from a Cabibbo-favored $\bar{D}^0$ decay or doubly suppressed $D^0$ decay ("ADS" analysis). We measure observables that are sensitive to the CKM angle $\gamma$: the partial-rate charge asymmetries ${\cal A}_{CP\pm}$, the ratios ${\cal R}_{CP\pm}$ of the B-decay branching fractions in $CP\pm$ and non-CP decay, the ratio ${\cal R}_{ADS}$ of the charge-averaged branching fractions, and the charge asymmetry ${\cal A}_{ADS}$ of the ADS decays: ${\cal A}_{CP+}= 0.09\pm0.13 \pm 0.06$, ${\cal A}_{CP-}=-0.23\pm 0.21\pm 0.07$, ${\cal R}_{CP+} =2.17 \pm 0.35 \pm 0.09$,${\cal R}_{CP-} =1.03\pm 0.27\pm 0.13$, ${\cal R}_{ADS}=0.066\pm0.031\pm0.010$, and ${\cal A}_{ADS}=-0.34\pm0.43\pm 0.16$, where the first uncertainty is statistical and the second is systematic. Combining all the measurements and using a frequentist approach yields the magnitude of the ratio between the Cabibbo-suppressed and favored amplitudes, $r_B$ = 0.31 with a one (two) sigma confidence level interval of [0.24, 0.38] ([0.17, 0.43]). The value $r_B=0$ is excluded at the 3.3 sigma level. A similar analysis excludes values of $\gamma$ in the intervals $[0, 7]^{\circ}, [55, 111]^{\circ}$, and $[175, 180]^{\circ}$ ([85, 99]$^{\circ}$) at the one (two) sigma confidence level.