• 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.


PO is now at the Physics Department of Bielefeld University!

New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

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


(propose a free ad)

Site Statistics

205 submissions , 163 unreviewed
5,054 questions , 2,207 unanswered
5,345 answers , 22,719 comments
1,470 users with positive rep
818 active unimported users
More ...

  Significance of $U(1)$ extensions of SM

+ 5 like - 0 dislike

Let's assume $U(1)$ extensions of SM with some detalizations:

1) Fermion sector of SM is extended by adding new very massive fermions;

2) Gauge group of SM is extended by adding new spontaneously $U_{V}(1)$ group with vector meson $V$ as mediator of $U_{V}(1)$ interactions

What's role play massive fermions and $V$ boson in explanation of unanswered phenomenas of modern physics (like baryogenesis, dark matter, neutrino oscillations problem)? Is the value of $V$ boson mass important for given explanation?

This post imported from StackExchange Physics at 2015-10-21 15:10 (UTC), posted by SE-user Name YYY

asked May 17, 2015 in Phenomenology by NAME_XXX (1,060 points) [ revision history ]
recategorized Oct 22, 2015 by Dilaton
You are referring to Z-prime extensions of the SM. See PDG (pdg.lbl.gov/2012/reviews/rpp2012-rev-zprime-searches.pdf) and references therein. Your question is rather broad

This post imported from StackExchange Physics at 2015-10-21 15:10 (UTC), posted by SE-user innisfree

$U(1)_{B-L}$ extensions of the MSSM could provide an explanation for a second higgs, that according to current experimental hints might be sitting at 145 GeV...

1 Answer

+ 4 like - 0 dislike

That is quite a general question, and I can't give you a definite answer if you don't give me some other information. For example, are the SM fermions charged under this interaction? If so, with what charges? What are exactly the gauge representations of the new fermions? How do they appear in the Lagrangian?

You see, there are MANY ways of answering these questions, and each lead to a different model. I could give a good example, for example $U(1)$ being a $B-L$ symmetry that arises naturally in $SO(10)$ or large group GUTs. In this case the extra heavy fermions would be the conjugated right-handed neutrinos, with a heavy Majorana mass. This would lead to an anomaly free theory (as the right-handed neutrinos have the desired charges for that) with a sufficiently heavy right-handed SM singlet to produce a see-saw mechanism to generate low physical masses for the neutrinos.

Other than that, the options are literally infinite, even if the interesting ones are significantly less this means that you can have $U(1)$ symmetries with very different phenomena at low energies.

Also, if you are thinking in supersymmetric model building, some $U(1)$ can be added to enfore an R-symmetry, which has many appealing low energy consequences.

Further reading:




Added in reply to

What about case when SM fermions aren't charged under this new group?

Well in that case I think the only obvious scenario (not unique for sure, but this is the first that comes to mind) is that it might be a dark matter model, as in this case the new matter content does not interact with ordinary matter.

Obviously that this statement depends on other things: how heavy are the new particles? What is the full spectrum of the extra states? Etc I am not an expert in dark matter model building - perhaps you have a few papers and ideas in the back of your mind when you asked the question - so it's hard for me to say what are the exact benefits of this type of models over, say, supersymmetric dark matter candidates.

This post imported from StackExchange Physics at 2015-10-21 15:10 (UTC), posted by SE-user romanovzky
answered May 17, 2015 by romanovzky (40 points) [ no revision ]
Thank you! What about case when SM fermions aren't charged under this new group?

This post imported from StackExchange Physics at 2015-10-21 15:10 (UTC), posted by SE-user Name YYY
No worries, glad I could help. I'll edit the post with some more comments on that possibility as I don't have enough space here.

This post imported from StackExchange Physics at 2015-10-21 15:10 (UTC), posted by SE-user romanovzky

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:
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).
Please complete the anti-spam verification

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

Your rights