My hardcore science geeks out there probably
know about Super-Kamiokande, or Super-K, as
its friends call it.
The 15-story tall tank of water buried 1,000
meters under a mountain in Japan has been
instrumental for detecting and studying neutrinos,
reshaping the standard model of particle physics
while it was at it.
Now the Japanese government has approved Hyper-Kamiokande which will be,
you guessed it, even bigger. So big that it may rewrite the standard model yet again.
Before we get to the particle physics-changing
event that Hyper-K could detect in theory,
let’s first talk about what it’s being
designed to detect.
Hyper-K, like Super-K before it, will hunt
for neutrinos.
Neutrinos are incredibly elusive and hard
to spot, because they very rarely interact
with anything.
Billions and trillions of the ultra-lightweight
and chargeless particles pass through us at
nearly the speed of light every second , and
honestly I’ve never noticed.
But here’s the beauty of the word “almost.”
Neutrinos almost never interact with other
matter, which is another way of saying they
sometimes do!
So if you can get a lot of matter and just
stare at it for awhile, and I mean all
of it, eventually you should see the telltale
sign of a neutrino interaction.
The telltale sign in question is something
known as Cherenkov Radiation.
Cherenkov radiation occurs when a charged
particle travels faster than the speed of
light through a dielectric medium like water.
Think of it almost like a sonic boom, but
instead of a conical shock wave of air, the
moving charged particle generates a cone of
blue light.
If you were paying very close attention, you
noticed that I said Cherenkov radiation is
generated by charged particles, but neutrinos
have no charge.
However, neutrinos come in three types or
“flavors”; electron, muon, and tau.
On the rare occasion that a neutrino does
interact with water, it will convert into
one of these other subatomic particles based
on its flavor.
Electrons, muons, and tau particles are charged,
and will briefly emit a cone of Cherenkov
light until they slow down below the speed
of light in water.
The end result sensors can detect is a faint
flash of a blue ring of light.
Super-K uses 50,000 metric tons of ultra-pure
water watched by 11,000 golden bulbs called
Photo Multiplier Tubes that take that faint
light and convert it into an electrical current. Thanks
to its huge size and sensitivity, it can detect
neutrinos from the sun, our atmosphere, or
even from a particle accelerator on the other
side of Honshu that shoots neutrinos at it
from hundreds of kilometers away.
In 1998, just two years after it began operating,
it observed that neutrinos oscillate, meaning
they switch between their three flavors as
they travel.
This discovery altered the standard model
and won one Japanese researcher the Nobel prize.
Super-K has achieved so much, so what could an
even bigger detector with over five times the
water and four times the Photo Multiplier Tubes
hope to accomplish?
How about explaining why stuff is here at
all.
Scientists believe Hyper-K will be able to
make more precise measurements that will reveal
the different speeds neutrinos and their antimatter
counterparts, anti-neutrinos, cycle through
their three flavors.
This difference could be the key to explaining
why more matter than antimatter was created
when the universe began, instead of being
made in equal parts that annihilated each
other completely.
And if physicists are really, really, really
lucky, Hyper-K will observe the decay of a
proton.
Right now the standard model says it’s impossible,
but if Hyper-Kamiokande does observe a proton
decay, then our understanding of the entire
universe changes.
It would mean that three of the four fundamental
forces stem from a single fundamental force
when time began.
It would be the final piece that’s been
missing from the puzzle of grand unified theories
that otherwise seem to fit together so perfectly.
Hyper-K should be able to see a proton decay
if their average lifetime is 10^34 years.
That’s a 1 with 34 zeros after it.
Hopefully it does, because if the ultra-huge
Hyper-K doesn’t detect it, that means the
average life of a proton must be at least
10 times longer.
But we’re getting ahead of ourselves, Hyper-K
isn’t even built yet.
Let’s let them actually construct it, then
pull up a chair and stare at 260,000 metric
tons of water.
Or as I call it, Tuesday.
Fun fact: while Super-K used ultra-pure water for decades, in 2019, researchers added gadolinium
to make it more sensitive to antineutrinos.
To test the water filtration with the new
element, scientists made two testbeds with
the acronyms EGADS and GADZOOKS! because scientists cannot resist cheesy acronyms.
If you liked this episode, let us know in
the comments below and check out this Focal
Point on the international race to find the
ghost particle.
Make sure to subscribe, thanks for watching.
And I’ll see you next time.
