I tried to work backwards and verify the magnetic field required by the LHC beam pipes. A circumference of 27km implies a radius R=4300 m. The beam energy E is 7 TeV per proton beam. Considering approximation E approximately equal to pc to get momentum (ultra-relativistic case). Plugging into p=qBr, I am getting a magnetic field of 5.4T as opposed to 8.3T. Clearly, I am doing something wrong. Could someone please point out where I am faltering? Thank you very much.