Sorry this is so late, but you can measure the probability that the particle exists. Null hypothesis tests basically try to calculate the probability of a data

Sorry this is so late, but you can measure the probability that the particle exists. Null hypothesis tests basically try to calculate the probability of a data set given the null hypothesis. What you really want is the probability of a hypothesis given the data set. So in that case, you want to estimate the probability of theories of physics, such as those that include the particle and those that don't.