
The Nobel Prize in Physics 2015: Takaaki Kajita And Arthur B. McDonald - sasvari
http://in.reuters.com/article/2015/10/06/nobel-prize-physics-idINKCN0S00ZZ20151006
======
adekok
I worked on SNO for my masters, helping to build the water purification
systems. The goal was one atom of impurity per cubic metre of water. It made
distilled water look filthy. :)

Everyone knew that if we got it to work, Arthur would win the Nobel Prize. He
worked _very_ hard on it, and was a good leader.

Congratulations to him.

~~~
apetresc
Maybe I'm confused, but it seems like he won the prize for completely
unrelated work. Does the prize committee award it for the full lifetime work
and simply pick one nominal project to credit, or has Arthur McDonald simply
done _two_ Nobel-worthy projects in his lifetime?

~~~
adekok
[http://www.nobelprize.org/nobel_prizes/physics/laureates/201...](http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/press.html)

"for the discovery of neutrino oscillations, which shows that neutrinos have
mass”

Which indicates that he won it for work resulting from the SNO experiment.

~~~
apetresc
Wait, so the water purification project led to the discovery that neutrinos
have mass?

EDIT: Oh okay, I get it now. The project wasn't about building water
purification systems, they just needed really really pure water to run
particle-related experiments. Got it!

------
bobmichael
Technical document explaining the scientific background here:
[http://www.nobelprize.org/nobel_prizes/physics/laureates/201...](http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/advanced-
physicsprize2015.pdf)

------
pkrumins
I can't wait to see laureates' Nobel Lectures. Each year laureates give a down
to earth lecture about their findings - how they started, how they found the
results, what motivated them to work on these problems, etc. Very interesting
to see laureates explain this themselves.

Click on the laureate names, then choose "Nobel Lecture" to watch the videos.

For example,

[http://www.nobelprize.org/nobel_prizes/physics/laureates/201...](http://www.nobelprize.org/nobel_prizes/physics/laureates/2013/higgs-
lecture.html)

For Higg's lecture a few years ago, etc.

------
Maro
[https://en.wikipedia.org/wiki/Neutrino_oscillation](https://en.wikipedia.org/wiki/Neutrino_oscillation)

Neutrino oscillation is a quantum mechanical phenomenon whereby a neutrino
created with a specific lepton flavor (electron, muon or tau) can later be
measured to have a different flavor. The probability of measuring a particular
flavor for a neutrino varies periodically as it propagates through space.

First predicted by Bruno Pontecorvo in 1957,[2] neutrino oscillation has since
been observed by a multitude of experiments in several different contexts.
Also, it turned out to be the resolution to the long-standing solar neutrino
problem.

Neutrino oscillation is of great theoretical and experimental interest, since
observation of the phenomenon implies that the neutrino has a non-zero mass,
which was not included as part of the original Standard Model of particle
physics.

------
JTon
Quote from the embedded video:

> In order to do this we had to build a detector the size of a 10 story
> building, 2 kilometers underground. In a mine, Creighton Mine, near Sudbury,
> Ontario... and we had the advantage of a thousand tonnes [of heavy water] on
> loan from Canada's reserves of heavy water. The value of which was on the
> order of 300 million dollars. We used that for about 10 years, measuring
> neutrinos roughly 1 [per] hour. By having this very sensitive detector we
> were able to make measurements that others could not. But it took [a]
> team... on the order of 150 people to accomplish this scientific
> measurement.

Pretty astounding work, if you ask me. The dedication of these people should
be applauded.

------
sanxiyn
This seems to be awards for two neutrino observatories, Super-Kamiokande and
SNO(Sudbury Neutrino Observatory). Note that the Nobel Prize in Physics 2002
was also awarded to neutrino observations.

------
redmaverick
Is it fair to give the Nobel prize to a single/two persons in 2015? Usually it
is a team of people all working together collectively to solve a common
problem.

~~~
jeffwass
I was actually involved with the experimental setup at SNO, however tiny in
the grand scheme.

Btw, my contribution was in the front end particle detectors, when I was an
undergraduate student. This was 20 yrs ago so a bit fuzzy on he details. But
basically, people on my team (University of Pennsylvania high energy physics
dept) designed analog ASIC's that effectively connected directly to the SNO
photomultiplier tube outputs to process the tiny electrical signals, IIRC
often from only a few hundred or thousand electrons. There were two chips they
designed. An integrator (SNOINT) which was like a preamp and identified how
strong the signal was, and a discriminator (SNOD) which identified accurate
timing information of the pulses.

We required IIRC about 10,000 of these chips, and the fabrication process had
a very low yield (about 30% had all functionality working). So my job entailed
setting up an automated test station, simulating all functionality of the
photomultiplier inputs, and interfacing with a computer to run the suite of
tests and identify good/bad in about 30-60s. We had a good process and hired a
bunch of part-time workers who would run through the tests to identify the
good chips.

I was quite jealous of some of my colleagues who worked with the actual
production circuit boards, and got to travel to SNO itself and go down into
the mine to set them up in production.

Fun times though. We also built Fermilab and CERN detector electronics, and
even for the cancelled superconducting supercollider. That job basically
taught me electronics and data acquisition, and led to my next job as a joint
hardware/software engineer.

------
bmm6o
Is there an easy explanation for why the oscillation implies mass?

~~~
zakk
You need to know two facts:

1) A massless object will travel at the speed of light. A massive object, on
the other hand, as long as it may accelerate, will always travel at smaller
speeds.

2) When you are travelling at the speed of light you don't experience time, it
is completely frozen. If you could ride a photon time would freeze. This is
the notion of proper time, in physicists' terms. Think of the twins paradox,
it's similar, albeit not identical...

So if a neutrino were massless, as predicted by the Standard Model, it
wouldn't experience time and it wouldn't oscillate. Oscillating requires time.

It follows that, as oscillations are observed, the neutrino must experience
time, and have a mass.

This mass is quite tiny, we don't know its value, we just know upper bounds.

------
sidcool
I would love someone to do an ELI5 of their research.

~~~
dagw
Here's the official ELI5 (or ELI12, which is probably what you really want):

[http://www.nobelprize.org/nobel_prizes/physics/laureates/201...](http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/popular-
physicsprize2015.pdf)

edit: and here is the official ELIAPhysicsGradStudent:
[http://www.nobelprize.org/nobel_prizes/physics/laureates/201...](http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/advanced-
physicsprize2015.pdf)

------
ycitera
I probably will get down-voted for my ignorance, but is this as meaning-less
as the Nobel Peace Prize?

------
dang
We changed the URL from
[http://www.nobelprize.org/nobel_prizes/physics/laureates/201...](http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/index.html)
to one that gives some background.

------
singold
OT: In spanish Kajita sounds like Cajita (little box), so there's a joke about
this being a PR campaing of McDonalds.

Also Kajita should be happy because of this achievement :P

~~~
kragen
Well, it _looks_ like it should sound like "cajita", as in "cajita feliz"
("happy meal"), but actually his name is pronounced [kadʒita], not [kaxita];
think "callita", like a small digging stick, but pronounced with a Rioplatense
accent. Japanese transliteration is misleading in Spanish!

(You could kind of make the same complaint about pronouncing "tomato" as
[tə'meɪɾoʊ], since the second vowel in the Nahuatl word is very clearly [a],
but I think you can make a reasonable case that "tomato" is an English word
with several centuries of history whose pronunciation has simply changed,
while Kajita is not a Spanish word, but rather the name of a Japanese guy
who's in fact not even dead yet. So if you pronounce it [kaxita], you're just
mispronouncing it, that's all.)

