Astudy in which the researchers, but not the participants, are aware of the treatment or condition to which the participants have been assigned is called a study

It's called a blind study. It essentially means that the researches are fully aware of the what the participants are going through, but the participants are "blind" to the details of the study. This allows researchers to get a complete and honest understanding of the results of the study without worrying about the participant's beliefs or thoughts getting in the way.