The process of beta plus ($\beta^+$) decay can be represented by $$\begin{align*} & n \\ & \quad \downarrow \\ & p + X + Y + \beta^+ \end{align*}$$ Which row identifies particles X and Y? - AQA - A-Level Physics - Question 8 - 2019 - Paper 1

In beta plus ($\beta^+$) decay, a proton is formed from a neutron by emitting a positron ($\beta^+$) and a neutrino. Thus, particle X is the $W^+$ boson, which mediates the weak interaction and is responsible for the decay process, and particle Y is the neutrino ($\nu_e$). Therefore, the correct identification is (A): X = $W^+$ and Y = $\nu_e$.