The process of peer review involves evaluation of the experiment by experts, who typically give their opinions anonymously. Some journals request that the experimenter provide lists of possible peer reviewers, especially if the field is highly specialized. Peer review does not certify correctness of the results, only that, in the opinion of the reviewer, the experiments themselves were sound (based on the description supplied by the experimenter). If the work passes peer review, which occasionally may require new experiments requested by the reviewers, it will be published in a peer-reviewed scientific journal . The specific journal that publishes the results indicates the perceived quality of the work. 
As you can see, there is no 'proof' or absolute 'truth' in science. The closest we get are facts, which are indisputable observations. Note, however, if you define proof as arriving at a logical conclusion, based on the evidence, then there is 'proof' in science. I work under the definition that to prove something implies it can never be wrong, which is different. If you're asked to define hypothesis, theory, and law, keep in mind the definitions of proof and of these words can vary slightly depending on the scientific discipline.