CP violation in the D0 -> pi+ pi- decay at CDF

TL;DR

This paper reports a highly precise measurement of CP violation in D0 -> pi+ pi- decays using CDF data, finding no evidence of CP violation and setting a new world-best limit.

Contribution

First measurement of CP asymmetry in D0 -> pi+ pi- decays with unprecedented precision using CDF data and novel systematic uncertainty suppression methods.

Findings

Measured CP asymmetry: 0.22% ± 0.24% (stat) ± 0.11% (syst)

Result consistent with no CP violation

Most precise measurement to date

Abstract

We report a measurement of the \CP\ violating asymmetry in $D^0\to\pi^+\pi^-$ decays using approximately 215,000 decays reconstructed in about $5.94$ fb$^{-1}$ of CDF data. We use the strong $D^{\star +}\to D^0\pi^+$ decay ("$D^{\star}$ tag") to identify the flavor of the charmed meson at production time and exploit \CP-conserving strong $c\bar{c}$ pair-production in $p\bar{p}$ collisions. Higher statistic samples of Cabibbo-favored $D^0\to K^-\pi^+$ decays with and without $D^{\star}$ tag are used to highly suppress systematic uncertainties due to detector effects. The result, $\Acp(D^0 \to \pi^{+}\pi^{-}) = \bigl[0.22\pm0.24\stat\pm0.11\syst\bigr]%$, is the world's most precise measurement to date and it is fully consistent with no \CP\ violation.