Quote:
Originally Posted by CraigS
Been thinking about your question here, Rob .. my pure guess would be that one (or both) the two pieces of information you presented may not be founded in accurate assumptions (??)
I'm not sure I understand the overall problem posed by the Standard Model (SM) not making an accurate prediction of the HB mass, either (??).
It looks to me as though it is expected (by the author) that the SM should be capable of being extrapolated both up and down the energy scale (ad infinitum ?). I'd question the rationale behind this expectation. The SM theory seems to have been constructed after the discovery of particles (from particle accelerator experiments) … who is to say that it is accurate beyond the range over which we know it to be useful ?
I think this aspect is why they're excited about 'new physics' emerging.
I can't see why 125 GeV would be seen as being outside the range of usefulness of the SM. If the HB is discovered at this mass range, to me, it would seem to be well within the applicability range of the SM ? Perhaps they're saying that the HB can only exist at this range if SUSY is found to be valid … (I'm not sure this rationale is logical, however).
Sorry I can't be of more help on this one.
Cheers
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Rob and Craig,
The problem with a low Higgs boson mass is that it can create
fine tuning problems.
It's difficult to explain without going into some very deep theory but one of the principles of Quantum field theory (QFT) is to define and sum all the momentum changes as a particle goes from an initial quantum state to a final quantum state. This can lead to divergences (the UV catastrophe) where the summed momentums become infinite.
To avoid such infinities the theory needs to be
renormalizable.
Quantum electrodynamics and Quantum chromodynamics are examples of renormalizable theories.
Quantum gravity is not renormalizable which is why no one has been able to unify gravity to the other forces.
A problem with a low Higgs mass is that renormalization can add mass to the Higgs boson. To avoid this the theory needs to be very finely tuned.
If SUSY exists then the problem goes away as the infinite terms are cancelled out.
Unfortunately technical papers describing this issue are very complicated and require a knowledge of the mathematical aspects of QFT.
This is one of the "simpler" explanations (warning high maths content).
http://www.weizmann.ac.il/particle/n...e/chapter1.pdf
Regards
Steven