There are many different ways of looking at quantum mechanics, so here is one way of answering your confusion. Probably the standard way of looking at quantum

There are many different ways of looking at quantum mechanics, so here is one way of answering your confusion. Probably the standard way of looking at quantum mechanics right now is quantum field theory. In quantum field theory, you give up the notion of "particles" and instead view them as vibrations in fields. Once you do that, it makes more sense that these "particles" can turn into other particles, be absorbed or emitted by other particles, or split. Here's a video of Sean Carroll talking about it, roughly 28:00-33:00. https://youtu.be/gEKSpZPByD0?t=1680 https://youtu.be/gEKSpZPByD0?t=1680