They Built the Quietest Place on Earth to Find Dark Matter

Brian Keating (0:00)

Welcome, everybody. This is a very special and urgent lecture episode featuring my friend and professor at my alma mater, Rick Gaitskell. Joining us from Brown University, Rick is the spokesperson of the LZ collaboration, which stands for Lux Zeppelin, which is located at the Sanford facility in America.

Denny Sanford was a friend. He lived here in La Jolla. I met him many times. We have some conversations together. It's really wonderful that you guys have done so much to celebrate this great contributor to philanthropy and also to our understanding of the cosmos. So Rick, I'm really excited. You're gonna talk to us about one of the most exciting announcements in very recent history. And that has to do with an event that was announced just about a week ago. So this is really urgent and emergent, as I said. So Rick, please take it away.

Rick Gaitskell (0:52)

Brian, thanks so much. It's marvelous to see you. So the Lux Zeppelin experiment is the sort of latest in a line of dark matter direct detection experiments that I've been involved in over the last 40 years. It always helps me to gain a little bit of perspective looking backwards as well as, as you say, what we've announced from the work of Lux Zeppelin just in the last week or so.

It is always a little sobering that if you sort of just consider what's happened in the last three years, for instance, the universe has actually expanded measurably in the sense that it's about a fifth of a part per billion, which I always find quite remarkable.

SPEAKER_3 (1:36)

You know, just the universe continues relentlessly doing its thing.

Rick Gaitskell (1:40)

But from a dark matter perspective, we've been improving our sensitivity, looking for so many, or testing so many different models of dark matter. And as you'll see, you know, in a moment, just how extensive that testing has been. And then, one factor is my weight, which actually for once has fluctuated down and not up, which, you know, for three years, it's not bad.

I am going to take the opportunity always to sort of remind people a little bit about why we're still engaged in looking for dark matter particles, even given that we've been looking for them for 40 years. And then, of course, as you said, we are actually sitting on an event. An event has shown up in the LZ. Now, as anybody who sort of follows more closely rare event searches, you know, one has to recognize that a single event is simply at the start, if you like, and either statistically or in terms of our growing understanding of the conditions that might have contributed to the event that the interpretation could either be that we're going to see subsequent events consistent with a dark matter hypothesis or it could be, we're going to see events consistent with some other more exotic, but mundane at the same time background. As experimental physicists is something we're absolutely focused on always in search. The talk or discussion, there are so many abbreviations, buzzwords, acronyms these days.

SPEAKER_3 (3:30)

I think I'm going to forgo the usual jokes I make about some of these.

Rick Gaitskell (3:33)

Other than to mention when people hear the word WIMP for Weakly Interacting Massive Particle, which is after all these significant number of years, that we've been trying to test such a hypothesis. You have to understand that 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, which were massive compact Taylor objects.

SPEAKER_3 (3:56)

So there was a very deliberate, I think, sort of element of humor in the WIMP MACHO.

Rick Gaitskell (4:02)

Now, MACHOs have actually been something that we've managed to test that particular hypothesis, and it is significantly, the amount of dark matter that could be satisfied using a MACHO hypothesis is very much smaller, and certainly will not solve the entire dark matter issue. Now, the other thing I'm going to do a little bit of is I will end up mentioning supersymmetry, but again, I'm not going to get too heavily into the acronyms. Anyway, let's move on. The other thing is, as you will see, these slides in fact do not have any AI used in their preparation, certainly with respect to prettification.

SPEAKER_3 (4:43)

Wow.

Rick Gaitskell (4:44)

There is an interesting aspect of AI in rare event searches when it comes to the analysis chain. While this is something that like many scientific experimental, that we are doing a great deal of investigation in, we also have to subject the any points in the analysis where AI has been used. We have to be very rigorous about understanding how it's working, which is not always the way that people choose to use AI. We're a very constrained case, so we are excited to see what can be done in terms of making better and better use of data that we're taking. But equally, as you might imagine, if we're talking about a single event, we would not be in a situation where an analysis chain simply popped an event out of magic because of an AI component, and that was what we stood behind. It simply, as you might imagine, would not work like that, and that's not something that... The other thing that I have to, let's not talk about the AI. Let's talk about the natural intelligence that we have. This is a large scientific collaboration, relatively speaking. There are over 250 authors on the latest paper that we've done. This is a photograph taken from a collaboration meeting here at Brown a year or two ago, but we have regular collaboration meetings, as you might imagine. This work takes or combines the input of a broad range of people, both DOE institutions here in the US and also universities and labs from other parts of the world, including the United Kingdom.