cc >> Jim Lattis: Well tonight
for our monthly guest speaker, I'm pleased to introduce
professor Francis Halzen. Francis has been the head of
Neutrino Astronomy here for quite some years, and the
Ice Cube project is nearing a really important point in this
current construction season and he's going to give us, tonight,
a talk about the Ice Cube Neutrino Telescope and what he
calls First Light, but it isn't actually light, it's neutrinos
actually. So, Francis.
Francis Halzen: Thank you for not mentioning how long we
have been doing this. [LAUGHTER]
In my case, it's over 20 years. I understand this is the fourth
talk of a series, and so this is usually what I talk about, but a
lot of this has been covered. So I will quickly go over the
previous talks as an introduction, and then I'm going
to talk to you about our first attempts to actually do some
science. And so since am I a professor,
there will be a test afterwards. [LAUGHTER]
And so I'll first review the three previous lectures.
You know by know that we don't know what a telescope is.
We are building a particle physics detector which we
thought we knew how to do and we actually know how to do because
it will be finished by this weekend.
So that I will remind you of this endeavor to build this huge
detector. Then I will tell you why it's
maybe astronomy, maybe not. And I will remind you a little
bit about the technology. But most of my talk, you will
have heard most of this by now, most of my talk will be about
the first science that we are trying to do with this detector.
My usual apology, there is no nice pictures in this talk.
There are no penguins. This is the last beautiful
picture. This is Antarctica for us.
This is an actual picture of the geographic South Pole.
If you look at the wrong direction and you don't see ice
cube or the South Pole station, you see this.
And you are standing on three kilometers of ice.
And that's our interest in Antarctica.
It says here ultra-transparent ice.
In fact, if you take this glacier, you're standing at the
South Pole, you are moving 10 meters a year on the glacier
that comes of the west Antarctic mountain range.
And if you go all the way to the coast, you can see this glacier
and so you have to imagine that we are at the South Pole, this
is three kilometers thick and we are building a detector right in
the middle of this. And this is why I'm standing
here. We actually discovered that
light travels 100 to 300 meters in this ultra-pure ice.
It was a total surprise, especially to us.
In fact, you have to realize we would never have started this
project if we had had glaciology books that said that this number
was more like eight meters. When people measure the
transparency of tap water, light travels about two meters before
going extinct. In distilled water, it goes
about eight meters. If you make bubble free ice and
test it in the lab, light travels eight meters.
Fortunately, we didn't know any of this or we would never have
started. So we are particle physicists so
we had the blessing of being totally ignorant.
[LAUGHTER] But we discovered to our
surprise that this ice actually is so transparent that
you cannot compete with it with things you make in the lab.
You couldn't make a solid that's as transparent as this ice.
It's ultra-pure condensed of some hundred thousand years ago
that fell on Antarctica. So it's ultra-pure and that's
what counts. So that's why I'm here.
Now comes the review. What are neutrinos?
In two slides. In high school you were told
that the world is made of protons and neutrons, and the
protons and neutrons make nuclei like alpha particles, helium,
uranium. And then when you put electrons
around it, they make atoms. And that's what you learned and
that was not your money's worth, wherever you learned this,
because we wouldn't be here if it were not for the fact that
there is also a neutrino. And how do we know this?
We know this since the 1930s because when a neutron decays,
it decays into a proton and an electron, and if there were no
neutrino, whenever the proton goes this way, the electron goes
that way. It's billiard ball physics.
In fact they noticed that occasionally the proton and the
electron would go that way which means something else has to go
that way. And they say, well, it's a
particle and it's saves momentum conservation.
And in fact it doesn't interact with anything.
And so that was it. It was like a mathematical
trick. And so the neutrino was born.
But you have to remember that the neutrino is kind of an agent
that makes nuclear physics possible.
Without changing neutrons into protons, there's no nuclear
physics, there are no nuclear reactors along Lake Michigan,
there is no sun that burns and there are no stars that explode.
So we wouldn't have sunlight, and we wouldn't be here because
the stuff we are made of is made by nuclear reactors in stars.
So the neutrino is important, but people realized that it was
just like light. It had no mass, no electric
charge, no nothing. So it was just like photons
except photons don't go through walls and neutrinos do.
That's the only difference. And so that may be good actually
because if they go through walls maybe they come out of the inner
cores of black holes and that allows you to do astronomy you
cannot do with slide. That was kind of the fake idea.
This sounds all good until you hear the rest of the story.
[LAUGHTER] In fact, the person who
discovered the neutrino as a mathematical object said that I
have done a terrible thing, I have invented a particle that
cannot be detected. [LAUGHTER]
And when we were in the beginning trying to build
AMANDA I would always tell my collaborators we're going to
prove him right. [LAUGHTER]
It never went over very well. Now this slide you have seen
before, I'm sure. It gives you an introduction in
two slides again to multi-wavelength astronomy.
This is the explosion of the cap, 1,054.
When this happened, you could read your newspaper, or whatever
they wrote in, for three weeks during the day.
And so that's what it looks like now, a Hubble picture.
There is a pulsar in the center, and this is a picture of the
explosion a thousand years later.
And so that's the same picture in infrared and in ultraviolet.
So the next case this is a -- picture taken with a satellite.
And you see this picture is only a few years old, and you see the
streams of high energy particles coming out that have never been
seen before. And so what we want to do
is take a picture of the crab, the neutrinos.
Although we're almost sure that the crab doesn't emit any
neutrinos, and if it does it will take us 10 years to find
them, but we will find them if they can be found in 10 years,
don't worry. This is the excuse we went
around the world with. You know, as soon as we told
--, we went around saying we can build a neutrino telescope.
So isn't this great? Look, whenever we build a
telescope, look at all these surprising discoveries we made.
And so you know we build this and we don't know what we'll see
but it will be great. [LAUGHTER]
Just like in the past. And I said this once in the
wrong place, in Washington. And someone came over and said,
you know, it was from the Office of Management and Budget, and he
said, what you're saying is that you're going to take government
money, gamble with it and we'll see what comes out.
Doesn't sound very good. I said, what do I say instead?
And this is what he told me. [LAUGHTER]
There are administrators with a sense of humor.
Okay, so you get the idea. The summary is almost finished.
The last thing is how we detect neutrinos.
Now, I told you neutrinos for 20 years were a mathematical
concept until this man, Reines, he had to wait another 20 years
to get a Nobel Prize for it, but he knew that neutrinos are
produced where there are nuclear reactors.
He went to the Savannah River nuclear reactor and put a small
detector about a meter. And you see here it's basically
water and photomultipliers. And so he put it close to a
nuclear reactor. And you have this enormous flux
of neutrinos so you can do it with a small detector.
And he did it. Got a Nobel Prize for it.
He told me that as soon as he detected neutrinos he had the
idea that you could do astronomy with it.
In 20 years nobody had told about it.
But it's strange, once you know something is real you suddenly
get this idea that nobody had had before.
And in fact he was not the only one.
Someone else had the idea, and a man in Russia named Markov
had the idea. All in the 1960s.
This experiment was 1956. Unfortunately, this beautiful
dream went home when people started doing some calculations
and realized that you needed a kilometer scale detector.
So what we need is this detector but instead of one meter, one
kilometer. That's all.
And so since the 1970s we have been trying to do this.
And actually, next weekend, unless something goes wrong,
it will be a reality. In fact we have a detector
that's much bigger than a kilometer cube even if we don't
get the next two strings in. So this is Markov who had the
idea of how to detect these neutrinos.
So this is what he wrote in his paper in 1960: We propose to
install detectors deep in a lake or in a sea to determine the
direction of charged particles with the help of radiation.
It doesn't matter. You understand this.
That's what I will explain in a minute.
But why did it take so long? It is because he talked about
water which was the wrong medium.
And so we had the idea in '87 after people had been trying
this in water, forget it. We are going to do this in ice,
not knowing that ice may not be very transparent.
And so you heard the story. We drill holes in the ice, put
light sensors in it and all this is beautiful and easy.
And so that's the idea. You go a mile deep under the
glacier at the South Pole. You go a mile deep and put a
kilometer cube worth of light sensors.
It's totally dark so you can't detect light, and here comes
your neutrino. And what does it do?
It goes right through your detector.
It has already gone through the earth, it goes through your
detector, but these are light sensors.
So here is a, it's called a photomultiplier and it detects
light. Buy it in Japan for a thousand
dollars and put five thousand of them in the ice.
And so once in a while, actually about once in a million times,
instead of going through the ice, a neutrino, ice is made of
protons and a bit of oxygen, a neutrino will crash head on into
a proton. And then a nuclear reaction
happens. And nuclear reactions produce
light. And in fact, in the cases we are
most interested in, it does this in a very interesting way.
It actually produces a slash of nuclear particles, but among
these particles there is this muon and this muon can travel a
long way. And when it travels through your
detector, it leaves this wake of light and it's blue light and
you use your sensors to map this wake.
From this wake you never see the muon, but this wake tells you
where the muon came from and the neutrino comes from the same
direction. So you know to only detect
neutrinos, you know where they come from and you have a
telescope. You know where they come from,
somewhere on the other side of the earth.
So from the South Pole we are looking at the sky above us,
looking for neutrinos that travel to the earth.
So if you didn't quite get this, let me explain this a bit
better. Blue light from a nuclear
reaction, actually, you have to realize this is a very faint
nuclear reaction. And most of the time what we
detect is not a lot of light. In fact, typically we detect 10
photons. That's all.
And these light sensors typically detect one photon.
So we require that eight of them fire and that's what we call an
event. Okay?
So it's not as easy as it sounds.
This is a nuclear reactor, not a neutrino.
And you see it's covered with water.
And all the nuclear particles coming out of the nuclear
reactor, including very few muons, they made the water glow
just like these particles make the ice glow.
And so this is the color of the light we see in the ice.
And so where does this wake come from?
The wake, first of all I already explained, it's very important.
This muon at high energy travels kilometers so we can actually
see neutrinos outside our detector.
And so the detector is actually much bigger than the kilometer
cube instrument with photomultipliers.
But the wake is what gives away the direction of the neutrino,
and that's what makes the astronomy possible.
And this is the physicist's explanation, but this is the one
that's easy to understand. This is the muon.
The muon travels at the speed of light or very, very close.
So it tickles the atoms in the ice and the atoms emit light.
But that light is slowed down in the ice.
So it's going at the speed of light in ice which is
significantly less than the speed of light.
So it goes at the speed of light but the light waves go out less
than the speed of light which means you get a wake.
And if you measure this wake with our photomultipliers, you
know where the duck is going. That's it.
Okay, so we started somewhere in the early '90s, in fact I gave
my first talk to this audience when it was still in Ponderosa
Steakhouse. And so we started at that time,
we were thinking about building a detector we called AMANDA.
So this is the South Pole, and this detector was completed by
the year 2000. And it's the same story.
You go 1500 meters deep and then there was 500 meters worth of
photomultipliers and we started trying to do this.
We knew this detector was much too small.
When you read the proposal it says we want to test whether we
can build a kilometer cube detector.
And in fact we give the price. And if you correct for
inflation, it's exactly what we spent.
We're very proud of this. So now we see neutrinos with
AMANDA. And I can remember the day I saw
the first neutrino event from AMANDA.
It was one of the great thrills of my life.
I won't say where it hangs because it may upset a lot of
people. But this is a neutrino.
And once you find it, you know it's a neutrino.
You can bet your house on it. So you see, remember you want to
see a track coming through the ice.
It comes from the bottom, from under the detector.
Each of these dots is a photomultiplier tube.
So the length of this track, you track from about here to
Ponderosa Steakhouse, it's about that far.
And you see the way we are going to look at a lot of these
events, that's my job here tonight, you see these colored
dots. Whenever you see a colored dot
it means that the photomultiplier detected one
photon. So you see these little dots,
that's one photon. The red is early, the purple is
late. So you follow the rainbow and
that tells you the direction where the track is going.
And when you see big dots, it means that the photomultiplier
detected a lot of photons. You can see the size of a dot
here so this dot is like 12 photons.
But you see without looking at the size of the dots, anyone can
tell that this track comes in here and goes out 300 meters
later at the top. That's a neutrino.
So it worked. So then we started, we proposed
in 1999, in fact a year before AMANDA was finished we knew this
work. And we proposed the ice cube.
And this you can seen many times by know was the inevitable
Eiffel Tower. And this is the AMANDA detector
which worked for nine years until it became insignificant
and we turned it off a year ago. And so it's just a kilometer
cube filled with 5,160 photomultiplier tubes between
one and a half and two and a half kilometers.
And what it does is, in fact it's almost complete so we know
this was good precision, it detects 220 neutrinos per day,
but it also detects 1.7, almost a billion cosmic muons per day.
And that's a problem which I'll come back to later.
That's the hard part of the story.
And we'll ignore this at the moment and concentrate on the
220 neutrinos per day. I'll tell you about the muons
later. This is a really annoying
background. Two thousand per second.
They come from a buff. No interest in it.
They're cosmic muons. You have to deal with it.
You have to measure them and reject them.
And that's what we do every second, 2,000 times.
So on top of the ice there is a big computer center that takes
care of this. Where are we?
I've referred to next weekend. Well, here is ice cube looked
from the top. So if you look on top of the
ice. This was the first string
deployed in January 2005. And this is what the detector
looked like a year ago. And in fact as of today, these
strings have been put in, and there are only two more strings
that have to be put in at the center here.
In fact, I have to show some pictures of people drilling.
I mean, the drill was maybe the hardest part of the project.
It's 4.8 megawatts. It drills holes to two and a
half kilometers. Melts the ice in two days.
It moves three and a half centimeters every second.
And it's a masterpiece. So here the drill comes out,
the photomultipliers are ready, 60 to go in the hole.
And then you see them go in, one every 17 meters, one after the
other. And if you looked at my computer
three hours ago, and this is what I was seeing.
This is time versus depth. And this was the drill that
finished the hole about a day ago.
Three hours ago they were drilling hole number six, seven.
And you see they are already at 500 meters there and now
probably close to a kilometer. And then you can see them deploy
a string. These little red dots is each
time you attach a module one of these lines is drawn, and as
time goes on the string sinks in the ice.
You are looking at the data upside down.
And three hours ago the string reached the bottom, reached zero
which means it's at the bottom of the hole.
So by this weekend, this will be finished.
Two more strings to go. Now before we looked at events,
here is, in case you didn't get it, here it is again, the movie.
So look at the bottom here. You'll see a neutrino arrive.
As you know neutrinos are red. [LAUGHTER]
And I think they are red, I'm not sure.
Yes, they are red. They hit an atom, make a muon,
the muon makes light in the detector.
This light is actually transformed in a digital signal.
The digital signal goes up on a cable and goes through the
computer that reconstruct the event.
Okay? You get the idea.
So here we go. At some point we had 22 strings,
and that's what a neutrino looks like.
Then the next year we had 40 strings, and that's what a
neutrino looks like, three of them actually.
They all look the same, right? So here, this is a neutrino that
you see it doesn't make much light.
That's a low energy neutrino. It's one we can barely detect.
It's energy is one TeV. It doesn't matter what a TeV is.
This is the same energy as the Fermilab accelerator in Chicago.
So these are the highest energies we can produce on earth
except they can go a bit higher in Geneva now.
But this neutrino is the same energy as the protons
accelerator, that Fermilab. But this, for us, is wimpy
stuff. This is a real neutrino.
You can think of this, this is a real nuclear explosion.
In fact, it's not a nuclear explosion.
The neutrino makes a nuclear explosion but this muon when it
travels through the detector makes a series of nuclear
explosions. So you see bombs going off.
So you see a lot of light, and this is a high energy neutrino.
In fact I'll show you one, this one, you see red again, you
follow the rainbow, it goes to green, this one is a hundred
times the energy of the Fermilab accelerator.
This one I have to change units. It's 10,000 times the energy of
the accelerator. And we actually don't understand
this event very well. We cannot quite pin down what
made it, but we only have one like it.
And it produced 250,000 photons. Not the eight or ten I was
talking about. So it still may be an
atmospheric neutrino, but its probability
is 10 to the minus three. We have more data by now, we'll
figure this out. But I want to tell you, I always
show this slide and this has nothing to do with me.
Developing this technology was a masterpiece, and so in fact we
made it to the cover of Science magazine without ever having
discovered anything. This has never happened before
as far as I know. But it was in recognition of
having built a kilometer cube detector.
In fact we hadn't at that point, but it was clear we were going
to. We also got elected one of the
Seven Wonders of Modern Astronomy.
That's when we were just building AMANDA.
I am not sure we had seen a neutrino by then.
But the category is kind of questionable.
You see. [LAUGHTER]
Maybe you cannot see this very well.
So let me now go back and use the rest of my time just going
to look at maps. You have the idea, each time you
detect a neutrino, to point this way, you make a dot where it
comes from on the other side of the earth.
As they, most of them, all of them as far as we know, are
produced in the atmosphere, you find a totally uniform sky.
They come from everywhere. So this is after we operated
AMANDA for one year. And so we had 600 neutrinos in
one year. And so you look at this map, by
the way these are muons, this is this annoying background coming
from the southern hemisphere. And so if you look at that, you
can see this here. This is the type of thing you're
looking for. This is the atmosphere, and this
is a star that you see through the atmosphere.
It's actually a statistical fluctuation.
We knew that. We expected to see a fluctuation
like that in this map. We understand statistics.
Nobody got excited. In fact, we took data for
another four years and you get this map.
And there's actually a hole in the sky where this X has
appeared and now there's an X somewhere else, it doesn't
matter. But you get the idea as time
goes on, it's like in the old days when you developed a
picture in the darkroom you just see it become clearer and
clearer, except for us it takes years.
And remember AMANDA was a hundred times too small to see
anything we anticipated. And so we were establishing the
technology. So here this was AMANDA's final
sky plot, and it delivered a beautiful sky with nothing in it
as it was supposed to do, almost 7,000 events.
Then we went to ice cube and this is ice cube of two years
ago. And it delivered by now of
instead of 7,000, in one year it produced more events than AMANDA
in its eight years of existence. And you see 14,000 neutrinos in
this map. These are the neutrinos.
Now, I am not going to discuss this, but this detector is so
powerful that we begin to be able to look at the northern
sky. We begin to find neutrinos in
this huge and annoying background of atmospheric muons.
And so at the moment, is there an interesting point in this
map? There always is.
It's there. There's no way you can see it.
I know where it is. You have to find it by computer.
And so now we understand this detector.
And this is what our sky map will look like in five years.
I'm a theorist so you can run a computer program, and you can
see here you will see the sources appear.
You see these sources? That's what I think we'll see
first. It's almost inevitable.
Let me try to explain this. Since 1932 people have realized
that about the only thing that can energetically produce
galactic cosmic rays is a supernova explosion.
Actually like the cap, they look like a cap although the cap is
not a good one. And so detectors have been
looking for these in gamma rays. And this is an experiment that
mapped the galactic plain in gamma rays at the energies we
are working. So there you see the candidate
sources except they look like any other gamma ray sources.
There is no way to prove that these produce cosmic rays.
But we have. In fact, if you take a lot of
particle physics courses, then you can derive this identity.
That's for every two gamma rays they see, we have to see a
neutrino and an antineutrino which we cannot tell apart.
So basically, if these are the sources of the cosmic rays,
which everybody already believes although there is no evidence
for it, then we have to see one neutrino for every gamma ray
they see, and that gives us this map.
And you know you can see the sources we see arise.
It's incredibly easy. And in fact, you can ask what
about this map we just saw? So of course here it is.
I couldn't resist plotting this out and there are the candidate
sources, they are now in a different coordinate frame, but
the biggest one is this star here.
And you see this cluster of red dots.
And so this is maybe the beginning of a very beautiful
future. However, these red dots here are
two sigma fluctuations. So there's nothing to get
excited about. But this is on track to in five
years, in fact the predictions are that we should get to where
we would declare we have discovered something to which we
have agreed on a minimum statistical significance.
This could take as little as three years.
It could take forever. If it takes forever then this
man will be very unhappy because he's the one who
predicted in 1934 that supernova remnants make cosmic rays,
this is Zwicky, and unfortunately he will not be
around but I'm sure wherever he is when he sees these sources
appear on the map he will smile. He won't look like this.
So I have been telling you about this annoying ongoing muon sky,
and so that's the end of the story.
This is the detector. If you looked at the detector at
any time, this is of course you realize when you see these
events, these develop at the speed of light.
So I clearly have the speed of light significantly slowed down.
And so instead of coming at 2,000 seconds, they come at like
one every few seconds. So you get one event after the
other. But there's something
interesting. Look at these events.
These are just like neutrino events.
They are also muons like the muons made by neutrinos.
A muon is a muon. But look here, the red is there
and the green is here. So they go the wrong way.
2,000 a second, you measure them, throw them away.
How do they get there? Well, cosmic rays hit the
atmosphere everywhere, make pions and these pions decay into
these annoying muons which you can see here.
So you get constantly bombarded by these muons.
Here, to tell you how annoying this gets, here in four
microseconds you see five of these muons go through the
detector. And it's very easy to fool
yourself in this mess and reconstruct a fake neutrino some
way or another. But we managed to do this.
Remember, they are a million times more frequent than
neutrinos. So if you mess this up one in a
million times you have no experiment.
So we are doing this now like one in a billion times we make
mistakes. I think you get the idea.
The muons come from above, which is from below at the South Pole,
and the neutrinos come through the earth.
So what we are going to do, I explained this already, but here
several billion, oops that's not right.
Atmospheric muons, yeah seven billion per year and about
400,000 neutrinos a year. So what we decided at some
point, I'll tell you why in a minute, we decided we are not
seeing anything this way, the detector is too small, let's
look up where we have billions of events.
They shouldn't point any where but let's look up.
And so you cannot see the dots anymore.
You cannot see a billion dots on a screen.
This is actually a probability distribution you are looking at,
but you may think of it as a billion dots.
In fact this is four billion dots.
And we looked at this and you got the idea these muons come
through the ice from above and they tell us about the direction
of this cosmic rays which are produced in our galaxy.
So the first thing we saw was the moon.
You know wherever the moon is, the flux of the cosmic rays is
absorbed. And you know the moon is a half
of degree on the sky. And here is the moon.
It makes a deep hole in our detector of less than one
degree, it's about 10 standard --.
So we saw the moon. So now the next thing what we
actually wanted to see was this. The cosmic rays are attached to
our galaxy so we try to see the solar system move through the
wind of the cosmic rays. Because our detector is on
earth, so six months we are moving into the cosmic rays and
six months we are moving out. We didn't see it.
What we did actually see, so we thought maybe our detector
doesn't work, what we did see is let's try if we can see the sun
go around, the earth going around the sun.
And there it is. Beautiful dipole.
This, by the way, has also never been seen before.
So we now know that the earth moves.
We have seen the moon and we know that the earth moves.
So anything can happen next. [LAUGHTER]
But this detector worked beautifully.
In fact, we have much better than a degree resolution now.
So here is the map. And so what we saw is, so we
didn't see any of these fancy motion of the solar system but
we saw that there's a big excess of cosmic rays coming from one
direction in the sky. Now cosmic rays are charged.
They are not neutrinos, they are not light, they are not supposed
to make a map. In fact among friends I can tell
you that all this structure in this map we know by know is
real. Nobody knows what this is.
The only thing, in fact you can see this is with 22 strings,
this is with 40 strings and I have seen 59 strings and you see
how all this structure reappears in these maps.
They look identical. The only clue we have is that
detectors in the north, the Vela detector I mentioned
before, it also has annoying muons that it mapped.
And our access, in fact in the latest map, the hot spot in this
map points right at Vela, which is the closest supernova to the
earth. And so is this the explanation?
Not possible. There's no way 10 TeV cosmic
rays can travel in straight line to the galactic field from Vela
to here. Not possible.
So it's like there is no galactic field between us and
there. So this is not an explanation
but I don't have one. We promise surprises, well, this
is the first one. And so this is, there is
something wrong with our understanding of the magnetic
field or there's something wrong with the fusion of charged
particles in the galaxy. God knows.
So keep tuned. But if we detected Vela, we have
already proven Zwicky's theory. But we don't claim this yet.
The only thing we claim is that we discovered something
we don't understand. Okay, so that's the end of my
talk. So everybody, the first question
is always will we discover atmospheric earth, atmospheric
we have, will we discover cosmic neutrinos?
And a few years ago there was a web page, this is always in
Britain right, where you could bet on big projects like what's
the probability that LIGO detects cavitational waves,
AMANDA detects cosmic neutrinos, and others--.
And in fact they gave six to one that AMANDA discovered cosmic
neutrinos, which is crazy. But six to one.
In fact, we started betting on LIGO where they gave 500 to one.
And I thought that was a good bet so when we started betting
on it they took the page down. [LAUGHTER]
You see the normalization here.
Finding Elvis alive was a hundred to one, and the
Loch Ness Monster is 66 to one. I would actually have bet on the
Loch Ness Monster instead of AMANDA.
[LAUGHTER] But after this talk,
after the question period, I'll be in the back of the room,
cash only, I give on Ice Cube two to one.
[LAUGHTER] Thank you.
[APPLAUSE]