Comments on: The Top Quark Mass

By: John Martin

John Martin — Wed, 31 Dec 1969 19:00:00 +0000

http://elasticity2.tripod.com/
On above site I give formula for the field structures of particles and atoms. The particle formula is based on the mass of the electron as this is the most accurately known particle mass. This indicates that a mass of 174GeV is the correct figure for the top quark.

By: D R Lunsford

D R Lunsford — Wed, 31 Dec 1969 19:00:00 +0000

Peter, the reason your b-log is so well received is very simple – the topic is physics as it once was practiced, with excursions into math for variety. You seem to me to be close to unique in having a mathematician’s sensibility and depth combined with a physicist’s common sense. It really shows in all your writing.

By: Peter

Peter — Wed, 31 Dec 1969 19:00:00 +0000

Glad to hear you enjoy the weblog and thanks for the encouraging words. I’ve been surprised how much attention it has gotten.

The string theory situation is a rather weird one and the public discussion of the theory has been almost all coming from its promoters. I hope I’m redressing that situation a bit, and that people will look at both sides of the story and make up their own minds.

By: raj

raj — Wed, 31 Dec 1969 19:00:00 +0000

FWIW, I am not a physicist by profession (although I did undergrad and graduate work in physics many years ago, and continue to follow some of the literature), I wanted to let you know that I enjoy your blog very much. I am particularly interested in your criticisms of string theory. It has gotten such hype in the popular press, but I have yet to see anything that appears to make sense about it. I read Brian Greene’s book and, although I found it interesting (particularly the first quarter, relating to quantum mechanics and general relativity), I hate to say it but it did seem more than a bit unpersuasive.

Regardless, I do enjoy the blog, and I would encourage you to keep it up.

By: Peter

Peter — Wed, 31 Dec 1969 19:00:00 +0000

Hi Thomas,

A good recent reference for all this is chapter 5 of some lectures by Sally Dawson, hep-ph/0303191.

In the SM there is no tree-level restriction on the Higgs mass. However, increasing the Higgs mass requires increasing the quartic Higgs coupling, and perturbation theory breaks down if this gets too large. For perturbation theory to be valid the Higgs mass can’t be more than a few hundred Gev.

In the MSSM you have to introduce a second Higgs field (otherwise the anomaly from the superpartners of the first one are uncanceled). You can show that, at tree level, the lightest neutral Higgs should have mass less than that of the Z. Taking into account one-loop effects the upper bound goes up. It depends on the extra parameters in the theory (e.g. tan \beta, the ratio of vacuum expectation values of the two Higgs), but overall it has to be less than 140 Gev.

By: Thomas Larsson

Thomas Larsson — Wed, 31 Dec 1969 19:00:00 +0000

Is a light Higgs compatible with the ordinary standard model?

I have seen somewhere that the tree-level prediction from the SM for the Higgs mass is m_H = m_Z = 91 GeV; that’s the same with or without SUSY. The big difference is that the uncertainty in the radiative corrections is much smaller with SUSY, so the upper bound gets much tighter. So a light Higgs wouldn’t really be a proof for SUSY, but the absense would be a proof against it.

OTOH, I have seen an argument by Frank Wilczek that a light Higgs would be problematic for the ordinary SM, but I don’t remember the details.

The discovery of sparticles at the LHC would be a proof SUSY though, and would be a pretty strong indication that the string line of though is on the right track. But that doesn’t seem to be too likely, does it?

By: D R Lunsford

D R Lunsford — Wed, 31 Dec 1969 19:00:00 +0000

Tony Smith’s analysis: http://www.innerx.net/personal/tsmith/TQvacua.html

He gets these numbers as ratios of volumes within Shilov boundaries (as I understand it).