Welcome back everyone to Seeker+, this is the last episode in our 3 part series on the Higgs Boson.
In episode 1 I covered how we knew to look for it and even talked about some juicy drama
among scientists.
In episode 2 we discussed why we needed the Large Hadron Collider to look for it and how
this complex amazing machine was broken by a baguette wielding pigeon.
Definitely check those out if you need to catch up.
And now, finally, with the Standard Model mapped out and the LHC up and running, let’s
talk about how scientists actually found the Higgs Boson.
Here’s the thing, it’s actually impossible to observe the Higgs Boson.
Welp, thanks for tuning in, goodbye!
No, I’m kidding, of course that’s not the end of the story.
I didn’t waste your time just to tell you this whole thing was pointless.
The Higgs Boson decays incredibly fast.
it has a lifespan of just 1 zeptosecond, to 10-21 seconds.
No instrument we can make can snap an image of it fast enough.
The scientists at the LHC already knew that before they even started, but they didn’t
spend all those years and billions of euros just to have a steady paycheck.
The Higgs itself may be impossible to detect, but it is possible to see what it turns into
when it decays.
It prefers to decay into particle-antiparticle pairs that have a similar mass to itself.
Remember the Higgs is chonky and scientists were expecting a particle up to 140 times
the mass of the proton.
That means the particles it will most likely decay into is a bottom quark and an antibottom quark.
A bottom quark is a heavier relative of the quarks that make up protons and neutrons.
More than half the time the Higgs Boson decays into a bottom-antibottom pair, but that doesn’t
mean that’s the only thing scientists were on the lookout for.
The Higgs boson also decays into pairs of W bosons and other particles we haven’t
talked about yet like Muons and Tauons.
That’s assuming a collision of 2 protons makes a Higgs Boson at all, which isn’t
a guarantee.
One of the tough things to wrap your head around with particle physics, along with pretty
much everything else, is how much it’s governed by probabilities.
I said earlier that protons are made up of quarks, antiquarks, and gluons and their exact
makeup is constantly changing.
When they collide you never know exactly what is going to hit what and what the energy of
the collision will be.
There’s a certain probability that a collision will create a Higgs Boson, and when it does
there's a certain probability the boson will decay into a bottom-antibottom pair, or W
bosons, or something else.
To make things more complicated, these particles could pop out anyway, even without decaying
from a Higgs boson.
The key is to calculate how often you’d expect to see these particles if a Higgs Boson
weren't created.
Then you compare your calculations to your data.
I cannot stress enough just how much data the detectors at the LHC put out.
Before the LHC opened the largest database in the world held a grand total of 6 petabytes.
A petabyte is a million gigabytes, by the way.
The LHC creates about a billion collisions every second, and at that rate it can generate
a petabyte of data PER SECOND.
It would have taken just 6 seconds to fill up the world’s largest database in 2007.
That is way too much information to store, so scientists have to design algorithms that
keep the data they’re looking for and throw the vast majority away.
Even with sending most of the data straight to the recycle bin the LHC today generates
about 90 petabytes of data per year.
All that information is crucial for particle physicists who want to be certain they’re
not mistaking a random blip for a world-changing discovery.
They’re looking for a statistical distribution of products, but with anything involving probability
there’s some wiggle room in the outcomes.
A coin toss may have a 50/50 chance of coming up heads or tails, but if you flipped a coin
100 times it wouldn't be weird if it landed heads 53 times and tails the other 47.
In statistics the greek letter sigma represents random fluctuation, with 1 sigma being the
amount of randomness you expect to see.
5 sigma means it’s almost impossible that your data could be explained by random chance.
That’s like tossing a coin a hundred times and it coming up heads 99 times.
Sure, it could happen, but it’s almost guaranteed something fishy is going on with your coin.
When the scientists at CERN examined the data from billions and billions of collisions,
they concluded the particles they saw at the energies they saw could not be accounted for
without a particle like the Higgs Boson to a certainty of 5 sigma.
They revealed this monumental finding to the public on July 4th, 2012, and there was much
rejoicing.
Still, they wanted to be extra sure this wasn’t some Higgs-like impostor, so they analyzed
4 times more data.
Finally, after looking at over two and a half quadrillion collisions, they decided that
was probably enough for them to confidently say they had found the bona fide Higgs Boson.
With that the last puzzle piece of the standard model was put in its place.
So we’re done here, right?
We know everything?
We can focus our brain power on life’s other great mysteries like why toast always lands
butter side down?
Or why loving someone doesn’t always mean they’ll love you back?
Sorry that got a little real there.
No, of course not.
Finding the Higgs Boson doesn’t mean there’s nothing left to discover in particle physics.
In fact, the Higgs Boson actually hints at more questions, some tantalizing and some terrifying.
Based on the data from the ATLAS and CMS detectors, which were in surprisingly good agreement,
the Higgs Boson has a mass of about 125 billion electron volts.
That particular value is puzzling for a lot of different reasons.
Some physicists were surprised it wasn’t much higher, and have suggested that it could
indicate there are a lot more particles at higher energies we haven’t discovered.
This idea, known as supersymmetry, may mean we’ve found fewer than half the particles
out there, and only 1 of 5 Higgs Bosons.
This mass is also right at a precarious value.
Scientists have theorized that the Higgs Field could become unstable and change drastically,
radically altering the mass of all the particles moving through it and basically destroying
the universe.
They’ve calculated that if the mass of the Higgs boson is below a certain threshold that
won’t happen, and if it’s above a certain threshold, it would have already happened.
Want to guess where the actual mass of the Higgs Boson falls?
Pretty much right in the middle.
Try not to think about it, I’m sure the end will come quickly if the universe unravels.
The Higgs Boson could also help us find, well, most of the rest of the universe.
95% of it is made up of dark matter and dark energy.
Dark matter is matter that we know must be there, based on our observations of the universe,
but it doesn’t seem to interact with normal matter in any other way.
A big candidate for dark matter are WIMPs, or Weakly Interacting Massive Particles.
Because these particles interact via the weak force, and because the Higgs Boson is such
a sociable particle that likes to mingle with just about everyone, maybe we’ll be able
to see dark matter interacting with regular matter via the Higgs Boson.
Likewise Dark Energy is energy we know must be there, expanding spacetime and stretching
the cosmos out.
Maybe the energy of the Higgs field could be responsible for it in some way.
We don’t know, we’ll just have to keep searching.
Almost immediately after the discovery of the Higgs Boson was announced, scientists
got straight back to work looking for the next major breakthrough in particle physics.
Finding something after almost 50 years of searching was nice, but what they’re really
hoping to see next is something they’re not looking for.
Something totally unexpected that will raise new questions, requiring brilliant minds and
incredible technology to come together once again.
The LHC has actually been shut down for the last 3 years as technicians upgraded the beams
and detectors.
Barring any pigeon saboteurs, it should start up again this month and be running full-time
by May, once again probing a little deeper into the nature of our existence.
Hey thanks for tuning in to this Seeker+ on the Higgs Boson, I hope you all enjoyed it.
If you did, be sure to let us know, you can find us on twitter @seeker and I’m there
too @huggetout.
Feel free to share any ideas you might have for what you’d like to learn about, and
until then thanks for joining us on Seeker+.