# ICHEP2012

Jul 4 – 11, 2012
Melbourne Convention and Exhibition Centre
Australia/Melbourne timezone
ICHEP2012 - 36th International Conference for High Energy Physics

## Direct CP violation in charm at Belle

Jul 5, 2012, 5:00 PM
15m
Room 220 (Melbourne Convention and Exhibition Centre)

### Room 220

#### Melbourne Convention and Exhibition Centre

Melbourne Australia
Parallel Sessions Track 7. CP Violation, CKM, Rare Decays, Meson Spectroscopy

### Speaker

Mr Byeong Rok Ko (Korea University (KR))

### Description

We measure the time-integrated rate $R_{WS}$ of the wrong-sign decay $D^0 \to K^+ \pi^- \pi^+ \pi^-$ relative to the Cabibbo-favored right-sign process. The data was recorded with the Belle detector and corresponds to an integrated luminosity of 800 fb${}^{-1}$ at the $\Upsilon(4S)$ resonance. We also report a measurement of the $CP$ asymmetry factor $A_{CP}$ by fitting the $D^0$ and $\bar D^0$ samples separately. We observe evidence for $CP$ violation in the decay $D^+ \to K^0_S \pi^+$ using a data set corresponding to an integrated luminosity of 977 fb${}^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The $CP$ asymmetry in the decay is measured to be $(-0.363 \pm 0.094 \pm 0.067)\%$, which is 3.2 standard deviations away from zero. This is consistent with the expected $CP$ violation due to neutral kaons in the final state. Using data from the Belle experiment at KEKB asymmetric-energy $e^+ e^-$ collider, we present a measurement of the weak-decay asymmetry parameter $\alpha_{\Lambda_c}$ in the decay $\Lambda_c^+ \to \Lambda \pi^+$. By comparing the results for particle and antiparticle decays, we also present a measurement of the $CP$ violating asymmetry parameter $A_{CP} = (\alpha_{\Lambda_c} \alpha_{\Lambda} - \alpha_{\bar \Lambda_c} \alpha_{\bar \Lambda}) /(\alpha_{\Lambda_c} \alpha_{\Lambda} + \alpha_{\bar \Lambda_c} \alpha_{\bar \Lambda})$. We report preliminary results on the time-integrated $CP$ asymmetry $A_{CP}$ in the decay $D^0 \to \pi^+\pi^-\pi^0$ using a 673 fb$^{-1}$ data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We set an upper limit on the rate of the Dalitz-distribution-dependent asymmetry between two flavor samples: $D^0$ and $\overline{D^0}$.

### Primary author

Mr Byeong Rok Ko (Korea University (KR))

 Slides