Quantcast
  • Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.

News

New features!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback

Attributions

(propose a free ad)

Site Statistics

123 submissions , 104 unreviewed
3,547 questions , 1,198 unanswered
4,552 answers , 19,366 comments
1,470 users with positive rep
411 active unimported users
More ...

Status of the little hierarchy problem

+ 6 like - 0 dislike
346 views

What is the current thinking on the little hierarchy problem in light of a potential Higgs mass above 120 GeV? A few years ago, at least, I remember various phenomenologists saying that this at least makes life rather difficult for the MSSM.

This post has been migrated from (A51.SE)
asked Dec 12, 2011 in Theoretical Physics by Aaron (420 points) [ no revision ]
retagged Apr 19, 2014 by dimension10
The newest paper with "little hierarchy problem" in the title is one from May 2011 by Feldman, Kane, Kuflik, Lu: http://arxiv.org/abs/arXiv:1105.3765 - those gravitinos and moduli around 30 TeV do solve it, aside from other problems. Another 2011 paper: http://arxiv.org/abs/arXiv:1104.3171

This post has been migrated from (A51.SE)

1 Answer

+ 5 like - 0 dislike

I don't think there is a little hierarchy problem in general (this is why I never regarded it as a real problem; it is a somewhat mild issue only in the most minimal SUSY theory).

The origin of the little hierarchy is that in the MSSM, at tree-level, the Higgs cannot be heavier than 90 GeV or so (see hep-ph/9709356 for a still relevant review). So in light of the LEP bound (115 GeV) one has to get a pretty decent contribution (to the quartic coupling) from loops. To make the loops sufficiently large one needs the stop to be somewhat heavier than the top. But that comes back to hunt you since it destabilizes the Higgs mass. Typically, for a Higgs around 120-130 I believe one would have to live with tuning at the per mil level (more optimistically, one could perhaps get 10^{-2}).

However, innocuous additions to the MSSM allow for heavier Higgs particles at tree-level. For instance, one can add a singlet (this leads to the so called NMSSM) or one could add an additional gauge group that is broken at the TeV scale (this enhances the quartic coupling through new D-terms). One can cook models where there is virtually no tuning whatsoever.

Note that there is no model independent bound on the stop mass, it could easily be 300-400 GeV in some scenarios. Therefore, in the presence of additional tree-level terms in the Higgs potential, there is no tuning.

(It should be added, though, that in many models beyond the MSSM one looses gauge coupling unification...)

This post has been migrated from (A51.SE)
answered Dec 13, 2011 by Zohar Ko (650 points) [ no revision ]
I remember the NMSSM. But, well, ick, no? And your last comment (if you want various charged stuff floating around) sort of spoils the point of the whole thing. But now I guess I'm getting more opinionated :).

This post has been migrated from (A51.SE)
In fact, the stop mass can be 200 GeV or perhaps even lower; as you say, it's model-dependent. Hopefully the story of stop mass limits (or signals?) will change very quickly over the next year.

This post has been migrated from (A51.SE)
Matt: Yes I agree, there is also the famous small window for the stop mass below 200 GeV. Aaron: I don't know why you say the NMSSM is more ugly than the MSSM. They look comparable in complexity to me. Also the NMSSM does not introduce any new charged fields. It jeopardizes unification for a different reason, a Landau pole for a Yukawa coupling....

This post has been migrated from (A51.SE)
I guess there's two ways of looking at it -- you could say you're doubling the number of fields out there, why not throw in another two? Or you could say, oh my god, you're doubling the number of fields, and you want to throw in another chiral, too, because you're still not fitting the real world? I never was a good phenomenologist....

This post has been migrated from (A51.SE)
I am also not a true phenomenologist, although I spend a lot of time thinking about pheno. To me all these models look equally complex, I would not judge something just because it has one more field...

This post has been migrated from (A51.SE)
And also my basic claim about fine tuning in the MSSM is true. There is even a whole paper about this today arXiv:1112.2703...

This post has been migrated from (A51.SE)

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
p$\hbar$ysicsOverf$\varnothing$ow
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
To avoid this verification in future, please log in or register.




user contributions licensed under cc by-sa 3.0 with attribution required

Your rights
...