Does the graviton count as a currently known Standard Model particle?
If it turns out that dark energy does not have a "source" at all but is just a cosmological constant, does this resolve as No?

@ArmandodiMatteo A graviton would NOT count as a currently known Standard Model particle. Only the 61 known particles (with the possible exception of an anti photon) would resolve to YES. Any other particle, including the graviton or a cosmological constant will resolve as NO. (One other grey area being any hypothetical quanta of spacetime would not count as a particle and would not trigger a NO unless it was the source of the phenomena as opposed to just part of the mechanism itself)

@JoeCharlier "with the possible exception of an anti photon"
Nitpick: us being mistaken about whether the photon is its own antiparticle probably shouldn't be treated any differently than us being mistaken about whether the Z boson (or the Higgs boson, or the gluon) is its own antiparticle.
TBF if it turned out that the photon and the antiphoton were distinct, it'd mean we're so badly confused about everything that this question should probably just resolve as N/A

When you say "found among" do you mean exclusively, as in, no new particles from outside the standard model are involved, or do you mean "are standard model particles involved in any way?"?

For example, if it turns out that there's a coupling between SM particles and a new particle, and this coupling is essential for DE, does the market resolve YES or NO?

(E.g. https://arxiv.org/abs/0706.4427)

Growing neutrinos and cosmological selection

The time evolution of a cosmological scalar field can be stopped by an increasing mass of the neutrinos. This leads to a transition from a cosmological scaling solution with dynamical dark energy at early time to a cosmological constant dominated universe at late time. The trigger for the transition is set at the time when the neutrinos become non-relativistic. The characteristic mass scale for dark energy is thus related to the neutrino mass, the only known particle physics scale in its vicinity. This explains the ``why now problem'' for dark energy. We present a particle physics realization of this ``growing matter'' scenario. It is based on the very slowly varying mass of a superheavy scalar triplet field whose expectation value dominates the light neutrino masses.

My estimates:

DE is a fully SM effect: <1%

DE is pretty much entirely driven by BSM particles: 95%

DE is driven by some weird coupling like the paper above: 5%

This market gets cancelled because there is no consensus: >90%.

Tl;dr market is overpriced but I'm not going to correct it because I think it will be NAd.

@Fion If any currently unknown particles are involved at all I will resolve this to NO. Certainly the chance of this not resolving is very high, but I was more interested in peoples guess aside from that.

@JoeCharlier I don't get this market. There is no known link between DE and particle physics. DE is entirely explained from gravity AFAIK. It is just the cosmological constant and doesn't need any particle to explain.

@AdamTreat Gravity caused by the Earth is due to its mass. The Earths mass largely comes from the atoms that make it up. The mass of those atoms are mostly protons, neutrons and electrons. Protons and Neutrons are made up of up and down quarks.

Thus the gravity of Earth derives mainly from 3 standard model particles: up quark, down quark and the electron.

This question ask people to conjecture whether the source of the dark energy affect will derive from one of the 61 currently known standard model particles.

If it derives from, even partially, a new particle or from no particle at all I will resolve this question as NO.

@AdamTreat it's certainly one hypothesis that DE is "just" a cosmological constant, and one that matches data at least as well as any competitor. But all the theorists I knew when I was working in the field were of the opinion that a pure cosmological constant is not theoretically sound. Why does the universe have this really tiny cosmological constant? And why does the vacuum energy not create a massive cosmological constant?

You can't even really invoke anthropics, at least not in the usual way. Because then the "constant" would need to have some spatial dependence.

Finally, I don't think anybody really believes that gravity is truly a classical phenomenon. The universe is quantum, and black holes have serious problems in classical GR. So at some point we're going to need a particle physics explanation of all of gravity, including the CC.

@JoeCharlier <nitpick>Around 99% of the mass of nucleons (which in turn are around 99.9% of the mass of the Earth) is from chromodynamic stuff, not from the individual quarks.</nitpick> (But of course, the gluon being one of the currently known Standard Model particles, this doesn't really affect your point.)