2021 was
finally when we first published our results.
Results from a laboratory in Illinois suggest that there's new evidence
from the behavior... Fermilab's muon G minus two experiment
...this experiment at Fermilab in Batavia It's called a muon, muons muons
a muon is basically a heavy electron, Muons
they have a small wobble, This is actually potentially
huge news.
In 2021, we published our first results
based on the first campaign about our precision called run one.
This was a data set collected in 2018.
It still gives me goosebumps to think about that time
when we presented to the world what we found out
this was anticipated by the international physics community
and still is. That was just the beginning for us
and the world was very excited to know what was going to come from us next
and the quest still continues.
This year, we're releasing
the results of the next two years of running the experiments.
So it's runs two and three. In 2019 and 2020, we collected more data.
This has four times the amount of data of the first publication.
We ended up collecting a huge amount of data that needed to go
through various stages of our own understanding
before we could deliver the result and present that to the world.
And so we had loads on our shoulders to deliver.
So that brings us to our current publication.
So a muon is basically a heavy electron.
It's got a mass 200 times higher than the electron's mass.
They are unstable,
so they live only a short amount of time, like two millionths of a second.
They are relatively easy to produce in accelerator laboratories
and also we can do many test with them to see if we understand nature.
In the G minus two experiment,
we're measuring what's called the muon's anomalous magnetic moment.
Which just means it's the part that's different from two.
So that's why we say muon G minus
two and G is a factor related to the magnetic moment.
Because the muon has a charge and it's spinning,
that means it produces its own magnetic moment.
The reason why we're studying muons is that they can probe the standard model
so they can test particles and interactions.
The g minus two experiment essentially revolves around a huge magnet.
The magnet used for the muon g minus two experiment is a superconducting magnet.
It has a 50 foot diameter.
We run more than 5000 amps through it, which produces a field of approximately
1.45 Tesla, which is about
30,000 times the magnetic field of the earth.
So it's a very strong magnet.
Although we're using the same magnet as the Brookhaven experiment,
this time we've done a more precise job
of making the magnetic field incredibly uniform.
We shimmed the magnet very precisely so that the magnetic field
would be as uniform as possible, they wrapped it in what we call the parka,
which is the white insulation that you see over the blue magnet.
Obviously bringing it to Fermilab, we also produce more muons
so in that way we were able to take a lot more data. We have state of the art
calibration systems and many techniques were improved in many cases.
So in the end we will have similar statistical
and systematic effects, which means that we will have used
the best possible techniques to extract the measurements from our data.
We aim for measuring the magnetic anomaly of the muon
to the precision of 140 parts per billion.
When you try to measure circumference of Earth
by counting your footsteps while you are walking
heel to toe, then you have to count those number of footsteps
really, really precisely.
You have to remember those numbers really well.
If you miss a few tens of steps, then you immediately lose this precision.
So we blind
ourselves to the actual true value of the measurement
that we're making in order to reduce our biases.
We don't want to be accidentally making analysis choices
that will bias the results of what we've done before. Yes,
so leading up to the unblinding,
we were all super anxious.
Right? We've been doing this analysis for a long time.
We don't have any idea what the number is going to be. Right.
We've done the whole thing without knowing
how to calculate the final number here because we've been blind.
So we,
we all sat there in the room getting together, opening up the envelope,
and then we have to punch it in the computer, get it on the plot.
And then there's this palpable relief as we see the number pop up there.
And phew! It agrees with our last result.
The new generation is taking over.
Yes! They did it.
So agreeing with the previous result is like the kind of bare minimum.
But we've done so much work in terms of the years of collecting data
and all the analysis, hard work that we've done to really shrink down
our uncertainties.
And we ended up with an uncertainty that's about half of the previous result.
So before this measurement, we had measurements from Brookhaven
and our experiment at Fermilab, run one from 2018.
So you can see that those two measurements agree
within their uncertainties, but the uncertainties are quite large.
When you see a new result we're agreeing with the previous ones,
but with much smaller error bars, meaning that the uncertainty shrunk right down
and we're making this measurement a lot more precisely now.
And then here at the bottom of the plot you have the world average,
so now this world average is the most precise ever measurement of muon
G minus two.
So we're
really proud of this achievement to get to this level of precision,
but we're not done yet.
There's about three times as much data we've already collected.
We're starting the analysis of that,
and we're aiming for a couple of years time to be putting out a new result
where we're hoping to push this current level of uncertainty down
by about another factor of two.
And at that point, we'll be able to compare with the theoretical prediction
and we'll be putting it to its toughest test.