Weakly interacting massive particle

There's different kinds of dark matter, as we'll talk about, different kinds of searches.

He and his teams have been looking for WIMPs, weakly interacting massive particles.

For a long time, WIMPs were the leaders as the theoretical candidates for dark matter.

They're not the only ones out there.

Yeah

...

there are WIMPs, like you mentioned, weakly interacting massive particles, and you also briefly mentioned, you know, supersymmetry is an idea that may have something to do with that.

So are WIMPs part of supersymmetry? Are they related somehow?

Uh-

WIMPs, WIMPs were around for a while, right?

Yeah, weakly-

Weakly

Now, for decades, when astrophysicists modeled these lenses, they assumed the dark matter was made of standard heavy particles.

Like WIMPs.

Right.

In the analogy, they assumed the glass bottle was completely smooth.

It could be a particle which is quite heavy.

If you think about our atomic nucleus, the protons, which are one of those particles inside, if it's a particle that's about that size or a bit heavier than that, that's, uh, what we typically call WIMPs, weakly interacting massive particles, but WIMP is of course something you can easily remember.

So I work, um, in a field which is called direct detection, where we're really trying to see the direct interaction of dark matter with ordinary matter.

And so what I'm looking at is things that are heavier than the proton, and we do that with liquid xenon detectors.

Right.

It's not necessarily a surprising dark matter type.

It's just not the vanilla WIMP we're typically looking for.

We're looking for one specific thing which we're optimized, but we have a lot of other searches we can do at the same time.

It is a mathematically elegant, heavy-hitting player in modern cosmology.

Right, because the traditional view of dark matter usually revolves around WIMPs-

Yeah

... right? Weakly interacting massive particles.

Exactly.

WIMPs are these heavy, sluggish ghost-like particles that basically barely interact with anything.

They just sort of hang out.

Yeah, pretty much.

The, the talk, uh, or our discussion, there are so many, uh, [chuckles] abbreviations, buzzwords, uh, acronyms, uh, these days.

I, I, I think I'm gonna forego the usual jokes I make about some of these, other than to mention when people hear the word WIMP for weakly interacting massive particle, which is after all these significant, uh, you know, number of years that we've been trying to test such a hypothesis, you have to understand that, uh, physicists do have a little bit of a sense of humor, and the WIMP acronym actually came about at a time when dark matter could also be solved by MACHOs-

[chuckles]

...which were massive compact halo objects.

And there was a very deliberate, I think, sort of sl- element of, uh, humor in the WIMP MACHO.

Now, MACHOs have actually been something that we've managed to test the hy-- that particular hypothesis, and it is significantly, um, we-- with the, the amount of dark matter that could be satisfied using a MACHO, uh, uh, hypothesis is, is, is, is, is very much smaller, uh, and certainly would not solve the, uh, the entire, uh, dark matter issue.

Now, the other thing I'm gonna do a little bit of is I will end up mentioning supersymmetry, but again, I, I'm not gonna get too heavily into the, uh, the acronyms.

... and, and that's what we've been doing.

For a long time, the prevailing theoretical models assumed we were hunting for something that would interact directly with that heavy nucleus.

But relying on that specific physical collision assumes we know what we are hunting, right? For decades, the focus was entirely on WIMPs, weakly interacting massive particles.

The assumption was that a WIMP, being relatively heavy, would occasionally crash directly into the dense nucleus of a xenon atom, and this setup would produce two very distinct signals.

Yeah, the dual signal mechanism was the cornerstone of dark matter searches for thirty years.

But those WIMP searches came up completely empty.

The heavy bowling ball never hit the nucleus, which forced a massive paradigm shift in the physics community.

The focus pivoted away from these heavy WIMPs toward lighter, far more elusive candidates, primarily axion-like particles and dark photons.

Yes, but hunting for these lighter particles fundamentally breaks the physical mechanism the detector relies on.

And so if you see something that's way different from the energies that you would associate with all the background things that you know about, you, you get interested.

And so this was da- data from, I think, 2023 actually, that they've been analyzing for a very long time now, of an incident that had a much higher energy than they could account for by any background thing And so, and it's right in the, in the range where we, where the theorists would predict that you'd find one of these WIMPs, right? The massively or the weakly interacting massive particle, which could be the thing that makes up dark matter.

So this obviously isn't, you know, th- first of all, their, their, their kind of error bars or the possibility that this is one of the background things is still, it's like a two or two and a half sigma detection.

So it's still like, you know, a 1% chance or something like that, that it's a background thing, which is too big to say you've made a discovery.

It's, I can't remember exactly.

Well, there's a-

They're not WIMPs, but it's like a gamma something.

There, there are some other experiments.