Dear all,

On behalf of Jesse, I would like to invite you to his master thesis presentation tomorrow at 1pm in room *H220*. Please see below for details and abstract!

Cheers, Wouter

Dear all,

I am very happy to announce that I will be doing my master thesis presentation this friday the 28th at 13:00 in room H220 at Nikhef. The abstract is down below and I hope to see you all there!

Cheers Jesse

If the weak phase in $B_{s}^{0}-\overline{B_{s}^{0} }$ mixing (2$\beta_{s}$) is found to be significantly different from the Standard Model prediction it would be a clear sign of new physics. One possible method of determining this angle is through the $B_{s}^{0} \to \overline{D^{0}}K^{0}_{S}$ decay. This specific decay channel is chosen due to its similarity to the $B_{s}^{0} \to J/\psi\phi$ decay which is normally used for determining $\beta_{s}$. To investigate this possibility the $B_{s}^{0} \to \overline{D^{0}}K^{0}$ branching fraction is determined relative to the known $B^{0} \to \overline{D^{0}}K^{0}$ branching fraction. The $B^{0}_{s} \to \overline{D^{0}}K^{0}_{S}$ decay is searched for in data samples of 1.0 and 2.0 fb$^{-1}$ collected with the LHCb detector during 2011 and 2012 respectively. A significant signal is observed and the branching fraction ratio is determined to be $\frac{BF(B^{0}_{s} \to \overline{D^{0}}K^{0}_{S}, \overline{D^{0}} \to K\pi, K^{0}_{S} \to \pi^{+}\pi^{-})}{BF(B^{0} \to \overline{D^{0}}K^{0}_{S}, \overline{D^{0}} \to K\pi, K^{0}_{S} \to \pi^{+}\pi^{-})}=4.95 \pm 0.81$ (stat) $ \pm$ $0.38$ (syst). This corresponds to a branching fraction of $BF(B^{0}_{s} \to \overline{D^{0}}K^{0})=(2.6 \pm 0.6$ (stat) $\pm$ $0.2$ (syst) $)\cdot10^{-4}$. This is the first observation of this decay channel. The $B^{0}_{s} \to \overline{D^{0}}K^{0}_{S}$ decay channel is probably not a suitable channel for $\beta_{s}$ determination and time dependent CP asymmetry measurements because insufficient signal is found in this paper and due to the lower proper time resolution of the decay channel in comparison to $B_{s}^{0} \to J/\psi\phi$.