I Strassler Hidden Valleys Viable?

[jtlz]

How viable are Hidden Valleys? Did LHC take any effort to look for them? What are the constraints in the searches? Any actual model how they interact?

If they were real.. can Hidden Valley particles even be in the MeV and we could miss them?

 

[jedishrfu]

Here's an article on hidden valley particles:

https://phys.org/news/2016-05-dark-hidden-valley.html

and an article from CERN where it looks like the LHC is doing experiments in that area:

https://home.cern/about/physics/dark-matter

 

[ohwilleke]

I'm not very upbeat on this prospect which stinks of "God of the gaps" reasoning. There is nothing compelling in the data that these are needed to explain and any major tweak of the SM should be producing anomalies all over the place, not just in an isolated area. Measurements that are sensitive to the global structure of the SM like muon g-2 and top quark and Higgs boson decay branching fractions should be affected but there is no obvious sign that we are missing something that big.

 

[PAllen]

How is this different from Dark Sector ideas, or is it similar? There are low energy searches being done for Dark Sector models:

https://arxiv.org/abs/1804.00661
https://arxiv.org/abs/1801.07867

 

[Haelfix]

Those models are amongst the earliest theoretical forebears of the modern 'dark sector' model building. There are some differences in detail, but they describe a framework in which large classes of particles can evade detection in detectors, and the phenomenological consequences thereof... Dark matter phenomenology was of course one of the primary applications, but it's more general than that. They are of course now part of model building lore, as they tend to produce rather exotic detector signatures.

You basically have an adhoc hidden or dark gauge group that is not charged under the SM quantum numbers, but that can only weakly communicate to the SM through for instance some new heavy state (or say a 'portal'). Particles in this sector need not be very massive (and indeed can be quite light), and there is usually at least one particle that is stable.

Interesting phenomenology occurs when we assume the dynamics are confining.

 

[ohwilleke]

A good example of how sensitive everything in the Standard Model is to everything else is a recent post by Jester on rare Kaon decay measurements (the most recent of which match the Standard Model with some modest tension). The branching fraction of this rare but otherwise unexceptional decay is sensitive to 1 PeV BSM particles. And, this isn't an outlier. The "every possible path contributes" aspect of quantum physics and SM physics calculations means that a significant deviation almost anywhere propagates almost everywhere. So, if we aren't seeing problems with SM predictions almost everywhere (and in fact, we see just the opposite, consistency almost everywhere), this is pretty strong proof the the whole edifice is sound and complete.

So, why propose a Hidden Valley if would have so minute an observable impact on anything?

 

[jtlz]

A good example of how sensitive everything in the Standard Model is to everything else is a recent post by Jester on rare Kaon decay measurements (the most recent of which match the Standard Model with some modest tension). The branching fraction of this rare but otherwise unexceptional decay is sensitive to 1 PeV BSM particles. And, this isn't an outlier. The "every possible path contributes" aspect of quantum physics and SM physics calculations means that a significant deviation almost anywhere propagates almost everywhere. So, if we aren't seeing problems with SM predictions almost everywhere (and in fact, we see just the opposite, consistency almost everywhere), this is pretty strong proof the the whole edifice is sound and complete.

So, why propose a Hidden Valley if would have so minute an observable impact on anything?

Last week I was thinking what was the most sensitive experiment or theoretical tool that can shows hints of any new unknown physics. I was thinking of the small mass of the Higgs boson and small value of the Higgs field and the naturalness problem but realized this is invariant to a new physics because if there were supersymmetry.. it can hide all unknown physics except the supersymmetric particles.

So I wrote this thread about Hidden Valley experiments to know where it could hide.

So is the rare Kaon decay the most sensitive yet that can unravel any new particle or forces of nature?

What is the most sensitive test ever that can unravel indirectly or at least show the existence of for example any dark matter particle, any new scalar field, any larger symmetry group physics, or combination of them like SU(7) Higgs that cause quark confirment, any preons, any compactified calabi-yau manifolds,, any superstring or LQG.. or even causal fermion system? Hidden Valleys, and others?

What new physics can occur that won't affect say the rare kaon decay measurements?

 

[Haelfix]

A good example of how sensitive everything in the Standard Model is to everything else is a recent post by Jester on rare Kaon decay measurements (the most recent of which match the Standard Model with some modest tension).
So, why propose a Hidden Valley if would have so minute an observable impact on anything?

The point is that hidden valley and dark sector models *do* have an observable impact on things. It is precisely this feature that makes them interesting. They of course won't have a 'naive' looking detection profile in a experiment (and indeed must satisfy all exclusion bounds on direct and indirect searches of dark matter, collider signatures etc) but will tend to have 'exotic' signatures. Things like high jet multiplicities, lepton jets, unusual cascade dynamics coupled with missing energy, displaced vertices and things like that. The whole point was that maybe our current experiments were missing things precisely b/c we weren't looking in the right place. As far as the virtues of the 'dark matter' models, they are of course designed to answer the various cosmological problems we have, as well as to provide the correct thermal history, suitable dark matter candidates and so forth.

 

[jtlz]

Hi folks. We need higher energy and momentum to act as high energy probe or microscope to explore small scale from the debroglie momentum being inversely proportional to wavelength. So we need very high momentum to produce small wavelength to probe say the Planck scale.

I'd like to know if it is theoretically possible to have something (a fundamental force, new BSM object, a new non-SM particle) that doesn't obey the formula. Meaning it can probe the Planck scale without high momentum small wavelength focused at that small point?

In particle accelerators. We use high energy collisions not only to reach the mass-energy to produce the particles but also to probe using high energy at smaller scale.

Are there not say an inverse unparticle decelerators that can use low energy to probe big scale. Remember this new particle doesn't obey the rules of SM and QFT. I just want to know if the universe or multiverse can create this possibility with its almost infinite possibilities of parameter spaces and all kinds of laws of physics.

Any reference along this line?

 

[nikkkom]

If "this new particle doesn't obey the rules of QFT", then you need a completely new, mathematically consistent set of rules explaining how that works.

 

[MathematicalPhysicist]

If "this new particle doesn't obey the rules of QFT", then you need a completely new, mathematically consistent set of rules explaining how that works.

I am not sure that QFT is mathematically consistent... assuming electron's mass to be zero, even though it doesn't actually zero, come on!