I am an engineering graduate who tries to change the field of study into Physics because of my interest towards the high energy physics (HEP) – Theory. I applied for about 15 universities for Fall 2018 (all USA universities) which have very good researches in HEP but got rejections from all these universities. According to the feedback from two of the 15 universities I applied, being my first and second degree in engineering has been the minus point of my application ( I am B.Sc. Engineering graduate and I have completed an M.Phil degree in Electronics Engineering). Due to my rejections, I applied for some middle-ranked universities later and got admitted to a PhD program in physics in one of those universities in the USA(800-1000 world rank) with a full financial support package. I am going to go there because I do not need to miss the oppertunity to start my career as a physist as early as possible. However, I am going to go to that university with the intention to change the university soon. I need to change that university due to two reasons. The primary reason is that HEP is not an area of research in that university. The second reason is that I need to go to a top-ranked physics graduate programme. So I am going to apply for Fall 2019 admission cycle again. When I apply for Fall 2019 I am applying as a physics graduate student. I believe that will strengthen my application as well.
What I need to know is that is it possible to change PhD programme within the first year as I intended and what should I consider when reapplying. I have second upper-class in my previous undergraduate and graduate studies and 850 physics GRE score. I hope to retake GRE and increase my score before applying again. If that matters I am from a South Asian country.
If someone can provide me with answers or share their experiences I am very grateful.