Supersymmetry breaking and hidden sector

[kodama]

in gauge mediated supersymmetry breaking, theories say there is a hidden sector that breaks its own symmetries and then communicates it to a messenger field, which then breaks SUSY.

any specific details on the hidden sector and messenger field?

i.e what kind of fermions and bosons make up the hidden sector? what are their masses, is there a fine tuning problem? any prospects of finding any particles of this hidden sector? what energy scale are they expected to be seen by a collider?

same for messenger field.

is this hidden sector also part of the dark matter or are they unstable and decay quickly?

do the fermions of the hidden sector come in 3 generations?

and does each and every fundamental particle in the hidden sector, fermions and bosons, also have superpartners, doubling the number of particles in the hidden sector? what prevents hidden sector from interacting with SM sector say through virtual particles?

how many particles are there in proposed hidden sectors?
same set of questions for this messenger field. is the messenger field bosons or fermions? do these messenger field particles also have superpartners?

any concrete proposals and names for the additional particles of what is in effect a second standard model of particles, but hidden.

how many total number of particles are there when all the particles of the hidden sector plus its susy partners, plus messenger field and its susy partners, are there, or what is the fewest number of additional particles allowed for a consistent theory? plus all the particles of SUSy partners of SM. plus any additional particles created by GUT's if they exist.

what prevents all the additional interactions that can cause disagreement with experiment?

is this plausible based on occam's razor?

isn't the simplest theory just SM + dark matter

 

[mitchell porter]

The conventional reasoning is something like this: If supersymmetry exists, it must be broken (i.e. superpartners have different masses), because we don't see the SM superpartners. Also, there's no good way to break supersymmetry if you only allow yourself superpartners of standard model particles. Therefore, there must be something more. The options are hidden sector + mediation, and BSM single sector.

In hidden sector + mediation, there are extra fields which do not interact with SM forces, thus they are "hidden" and might be part of dark matter. Supersymmetry is directly broken by interactions within this hidden sector, and then induced in the SM sector by interactions between SM and hidden sector. The usual options for the interaction are gauge mediation and gravity mediation. In gauge mediation, there are new fields (messengers) which do interact with SM forces, and with hidden sector forces. In gravity mediation, the interaction goes through something gravitational, like a gravitino.

In BSM single sector, the SM is either part of something bigger like a supersymmetric GUT, or emerges from something deeper like a supersymmetric preon theory. Supersymmetry is directly broken at this bigger/deeper level, and remains broken at the level of SM physics.

The most common idea for how to directly break supersymmetry is gaugino condensation - the superpartners of the gauge bosons of some BSM force form a vacuum condensate. A hidden sector might consist of "dark gluons" and "dark gluinos"; the dark gluinos could condense and break supersymmetry, and the dark gluons could form dark glueballs that are part of the dark matter.

The hidden sector particles don't interact directly with standard model particles because they aren't charged under standard model forces, and vice versa. The standard model has strong force and electroweak force. A particle feels the strong force if it has color charge, it feels electroweak force if it has "weak isospin" or "hypercharge". (Electromagnetic charge is a specific combination of these.) In my example, dark gluinos don't have any of these quantum numbers, but they have "dark color", so they interact with dark gluons; but none of the standard model particles have dark color charge, so they don't interact with dark gluons.

This is not so unprecedented; in the standard model, leptons don't have ordinary color charge and don't interact with gluons. But all the fermions in the standard model have hypercharge, so they all have electroweak interactions and there's no isolated subsector within the SM akin to a hidden sector. (Though sterile right-handed neutrinos would be like that.)

E8xE8 heterotic string theory rather naturally gave models of gravity mediated supersymmetry breaking. In the field theory limit, it reduces to two supersymmetric E8 GUTs coupled by gravity. The idea was that the SM comes from one of them, and gaugino condensation occurs in the other.

 

[kodama]

any sort of speculation proposals of what sort of particles would make up this hidden sector? i.e their masses, spin, charges etc?

if this hidden sector is non-existent how does this impact SUSY as a theory of nature?

 

[mitchell porter]

There would be dozens of proposals. But the hidden SUSY-breaking sector is a bit like the Higgs sector before 2012 - theory says it should be there, but that doesn't constrain its nature very much. It just has to be a set of superfields whose internal dynamics breaks supersymmetry. The simplest possibility is what I described - a set of strongly coupled super-Yang-Mills fields (spin-1 gauge bosons with spin-1/2 gaugino superpartners) that encode some BSM symmetry group. There might also be a bunch of chiral superfields (spin-1/2 fermions with spin-0 scalar superpartners) charged under this new force. Over the years, the mathematical study of supersymmetry has yielded a growing list of examples.

So to make a supersymmetric theory of everything, choose a set of superfields charged under a GUT symmetry group that will break down to the standard model, choose another set of superfields whose internal dynamics are known to break supersymmetry, and ensure that these two sectors interact. Your overall theory will have a certain number of free parameters; now it's up to you to see if there are any possible values of those parameters consistent with reality. If you're more ambitious, do all this within string theory, which happens to naturally accommodate this paradigm. For example, the GUT sector can come from one stack of branes, the SUSY-breaking hidden sector can come from another nearby stack of branes, and the messengers are massive strings that connect the two stacks.

Here is an example of such model-building. I selected it for three reasons: it gives a concrete example of the hidden sector's composition (see the start of Part II), it tries to explain an actual observation (galactic X-rays of a specific energy), and it assumes SUSY-breaking at very high energies (so superpartners won't be seen at the LHC). That is an unusual, maybe even a unique combination... Meanwhile, this paper examines how hidden sector glueballs can be a problem for early universe cosmology. It might be more typical - the hidden sector is discussed in very generic terms, and its impact on anything observable is indirect at best.