# ALPS2017 -- an Alpine LHC Physics Summit

Apr 17 – 22, 2017
UZ Obergurgl
Europe/Zurich timezone

## Model-independent measurement of the CKM phase $\varphi_1$ in $b\to c\overline{u}d$ transitions

Apr 21, 2017, 6:20 PM
15m
UZ Obergurgl

#### UZ Obergurgl

University Center Obergurgl Gaisbergweg 5 6456 Obergurgl Austria
Afternoon Session Flavor Physics of Quarks and Leptons

### Speaker

Vitaly Vorobyev (Novosibirsk State University)

### Description

A time-dependent analysis of the $B$ meson decays governed by $b\to c\overline{u}d$
quark transition allows to measure the CKM angle $\varphi_1$ with a negligible effects
of strong interactions. The binned Dalitz plot technique is a promising approach for a
model-independent measurement of the angle $\varphi_1$ in the $B^0\to \overline{D}{}^0\pi^0$
and $B^0\to \overline{D}{}^0\pi^+\pi^-$ decays followed by $\overline{D}{}^0$ decays into
$K_S^0\pi^+\pi^-$ and CP-eigenstates. We apply this technique to a full data sample of
the Belle experiment and perform a time-dependent analysis of $B^0 \to \overline{D}{}^{(*)0}h^0$,
$\overline{D}{}^0\to K_S^0\pi^+\pi^-$ decays, where $h^0\in\{\pi^0, \eta^{(\prime)}, \omega\}$.
The obtained value $\cos{2\varphi_1} = 1.06\pm0.33{}^{+0.21}_{-0.15}$ is the most precise
single measurement of the $\cos{2\varphi_1}$ to date and resolves the twofold ambiguity at
the confidence level exceeding five standard deviations. The binned Dalitz plot technique can
be employed to measure the angle $\varphi_1$ in the $b\to c\overline{u}d$ transitions at
the precision level of one degree with expected statistics of the LHCb and Belle II experiments.
Such precise results together with measurements of the $b\to c\overline{c}s$ transition
would provide a valuable check of the KM mechanism.

### Primary author

Vitaly Vorobyev (Novosibirsk State University)