Quantum100 ⊗ AI Workshop

Compared to the $\Upsilon(4S)$, the $\Upsilon(5S)$ can decay into excited $B^{0*}$, giving rise to $B^0/\bar{B}^0$ pairs in different quantum states. Directly after the $\Upsilon(5S)$ decay, the produced $B^{0(*)}\bar{B}^{0(*)}$ pairs are expected to be in a $J^{PC} = 1^{--}$ state. Following the radiative transition $B^{0*} \to B^0 \gamma$, the system evolves into states with $J^{PC} = 1^{-+}$. Depending on the C-parity, the $B^0/\bar{B}^0$ can be in a symmetric (triplet) or antisymmetric (singlet) wave function, leading to different time evolutions of the entangled states. By mixing the two C-parity states $C = -1$ and $C = +1$, one can create a mixed state that is physically indistinguishable from a disentangled system.

We currently study these effects using $\Upsilon(5S)$ Monte Carlo data simulated from the Belle experiment. The analysis includes the reconstruction of the signal $B^{0(*)}$ meson pairs through the decay chain $B^0 \rightarrow D^-(\rightarrow K^+ \pi^-\pi^-)\pi^+$, as well as obtaining the vertex and flavor information of the other B-meson inclusively. In addition, the $B^0/\bar{B}^0$ quantum states are separated using the variables $M_{bc}$ and $\Delta E$.