(soft, jazzy, orchestral music)
My name is Steve Boggs,
I'm the Chair of the
Physics Department here
at Berkeley and I'm
really excited that Berkeley
can help host the Breakthrough
Prize Symposium this year and,
of course, I'm very excited
for the physicists who won
today, so Berkeley had,
in addition to, of course, our
involvement in Daya Bay with
Ken Bue Luc, who we're very
proud of, congrtulations
Ken Bue, Berkeley has had
substantial involvement in both
snow, which you'll hear about
a little bit more today,
and in chem lands, so that
was Stuart Friedman who
passed away, unfortunately,
a couple of years ago but
very heavily on our minds today in today's
awards presentations so.
The discussion this afternoon
is on the future of particle
experimental physics and
oddly we had no idea about the
selections this year when we
chose that subject so I think
we did a good job picking
that topic, and so we're gonna
hear about the full spectrum
of particle physics, not just
the nutrinos but they're
certainly a critical part of that
so the way that we're going
to structure this today,
we're going to have 15
minute presentations by five
different speakers, we'll
have time for very brief
questions for each speaker
afterwards and then if there's
time at the end we'll bring
them up for a panel so that
we'll have to play that by
ear and see how time goes
when we get to the end, so
our first speaker today is
Nima Arkani-Hamed who is coming from the
Institute of Advanced Physics,
he is a particle theorist
and he won the Breakthrough
Prize in 2012, so I think
a good person to start off
our presentation so, Nima?
- Thanks a lot.
Well it's always fantastic
to be back here at Berkeley
and our topic today is the
future of particle physics so
what I want to, I'll be talking
about motivations for great,
big circular colliders, maybe
100 kilometer scale colliders
that can operate as Higgs
Factories in a first run as
E+/E- machines, and 100 TeV
proton proton colliders after
that, but since the topic is
the future of particle physics
I want to spend, this is very
important for the subject,
I want to spend a few minutes
talking about why there
is a future for particle physics, okay?
It's not a fully obvious question,
people say, "Look, before
"the LHC we had a very good
expectation that we would
"see something like the HIggs,
a new particle, the Higgs
"or something like it," and
now when we go beyond we don't
know where the next mile post
is, we don't know for sure
whether the next colliders
are going to discover
new particles so how can we
possibly justify continuing?
It's a very important question
and we have to confront it
head on if we're going to
talk about the subject and
part of the misconception
is what particle physics is
actually about.
One of the sort of popular
pictures for what it is,
is that it's a study of the
basic building blocks of matter.
That's one aspect of it, but
it's not the most interesting
aspect of it, the most
interesting aspect of it,
it's not merely the study of
the building blocks of matter,
we study these elementary
particles ultimately because
we care about what they tell
us about the fundamental
laws of nature, and what we
discovered in the early part
of the 20th century, is that
the story of the fundamental
laws is most effectively told
by studying the interactions
of the elementary particles at
the highest possible energies
and are governed by the still
mysterious union of the ideas
of space time, and quantum
mechanics, the two big
revolutions of the early part
of the 20th century that we
all understand well enough
to construct this fantastic
edifice of the standard model
of particle physics but which
leaves us with many really
fundamental paradoxes left
as we go to the 21st century,
so saying this all again,
is it true that new physics
means new particles?
If our definition of new
physics is that we have to
guarantee before going
to the next frontier that
we're going to discover new
particles, we should quit
right now, 'cause we can't guarantee that.
That's the honest statement.
But new physics does
not mean new particles,
we care about new
particles because there are
standard for something more important,
we care about new phenomenon
and new principles.
That's what' we really care
about and from that point
of view, we're actually in
an incredibly interesting
almost unprecedented situation
in the history of our
development, in the
development of our subject.
That can be sort of
summarized by this slogan,
a big summary of what we
learned in the early part
of the, in the 20th century
is whatever the underlying
laws of physics are,
compatibility with the pictures of
space time and quantum
mechanics guarantees that
at long enough distances we'll
have elementary particles,
the physics will described
by elementary particles
interacting in the simplest possible way,
with three particles coming
together at points in space time
and that the elementary
particles have to be picked from
a menu of spins, of particles
pf spins zero, one-half,
one, three-halves and two.
That's something that can
be determined almost from
pure thought, once you
know these basic principles
of relativity and quantum mechanics.
That's something we knew
on theoretical grounds
and the story of the Higgs
is essentially part of the
completion of this story,
we discovered the Higgs
on July 4th, 2012, that
turned that red zero into a
black zero, we finally
saw an elementary particle
of spin zero, plays a crucial
role in allowing us to connect
the physics of massive
particles at very long distances
to massless particles at
very short distances where
their interactions are so
incredibly constrained by
these general principles, and
that's what's so important
about the Higgs, it's the
first really new elementary
particle we've seen, we've never
seen an elementary particle
of spin zero before and it's
existence is tied up with all
sorts of other mysteries.
On the one hand if we
posit that it exists,
the kinematics of how to
describe it are well controlled
by our understanding of
relativity and quantum mechanics,
but, on the other hand, from
many points of view, it's very
mysterious that it should exist at all.
Here is a famous one, if we
look at something as simple
as the energy in the vacuum
of the universe, we add up
the half H bar omega for
all the harmonic oscillators
for the particle and box
modes for every particle
in the universe, it has
contributions which are enormous,
sensitive to very high energy scales.
The leading contribution is
the energy density of the
vacuum, that should curl up
the universe, by all rights,
to a size of 10 to the minus
33 centimeters, and it hasn't.
That's the cosmodule
concept problem, but there's
a sub-leading piece to
that, which has to do with
the dependence of the mass
of the elementary particles
on the Higgs, that should
give the Higgs an enormous
mass, 32 orders of magnitude
bigger, or 16 orders of
magnitude bigger as a
mass than we've observed,
and these are both associated,
this is the cosmodule
concept problem, this is
the hierarchy problem and
it affects the Higgs in that
sub-leading term precisely
because the HIggs is a
particle of spin zero that has
the opportunity to have a mode that fills
the entire universe.
Here's another aspect of it,
which more clearly illustrates
why spin zero is a problem.
We understand why particle
like the photon is massless,
because of a discontinuous
difference between the number
of degrees of freedom of
massless and massive particles
with spin, a massless particle
of spin has two degrees
of freedom, a massive has
three, and so there's no way
that it interactions with
virtual particles in the vacuum
can discontinuously convert
a massless spin one particle
to a massive one.
Not true for spin zero
particles, have exactly the same
number of degrees of
freedom for massive and
massless, we have no
good understanding why
the interaction with the
virtual particles in the vacuum
don't give the Higgs an enormous mass.
So, it's the first really new
elementary particle we've seen
and in this sense, it's
really new physics.
It's a new phenomenon.
We've never seen anything
like it before and you
don't discover something
new, that you've never
seen before, especially
one that's tied up with
the drama about quantum fluctuations in
the vacuum and just walk away from it.
So the first, it's really
new physics, we've never
seen anything like it.
Many people think it's a
harbinger of some profound
new principles at work in
the quantum vacuum and so
experimentally, we just
have to look at it closely.
Sol there's very obvious
questions associated with it,
and we've never seen a point like scaler.
The picture of the HIggs
that we get from the LHCs
looks roughly elementary,
in other words, it's size
is a little bit smaller than
it's natural compton wave
length, okay?
But not so much smaller
and there's a very natural
question, how point like is it?
That's something for experiment to answer.
That's a question that
today we know the LHC will
not answer, they won't
do so much better than
it's done already.
Just to drive this point
home, what we know with LHC
resolution today, and what
we're likely to know through
the final run of the LHC, is
that the Higgs could be about
as elementary as a pion.
A pion was a spin zero particle
and it's also a relatively
light compared to it's
compton wavelength, okay?
So it has a size which is
smaller, about five times smaller,
than it's actual compton wavelength.
The size that's set
for example by the mass
of the room adds on.
That's about the picture
of the galaxy that we're
going to get, that's about
the picture of the Higgs
that we're going to get from
the LHC so it's possible
that even though it looks
like it's an elementary
spin zero particle, and there
aren't a lot of other friends
around, that it's about
as elementary as the pion.
Be great to know if
the HIggs is composite.
It'll be great to know
if the Higgs is something
like a pion, but it's
implications whether it is
or isn't are gigantic, right?
I mean if it is, it's
another layer of the onion,
it's very important, we'll
have to understand it.
If it isn't, it's much more
theoretically dramatic, right?
Then we really are in
completely uncharted territory
of the sort that we haven't seen before.
We have to decide this
question, not theoretically,
but experimentally.
There's lots of theories
that make the Higgs something
like a pion, but we'd like
to know experimentally
whether that's possible, okay?
So, in order to do that, we
just have to study it, okay?
So we have to, instead of
having the fuzzy picture,
this is the picture of the
Higgs that we'll get from
a Higgs Factory, okay?
By looking at how the Higgs
interacts with other particles,
almost literally like
looking at it, instead of
with photons bouncing off
of it, you see how Higgs
decays to, couples to
two Z particles, okay?
That's going to give
us a picture that looks
much, much more like this, okay?
It'll increase the resolution
compared to what we get
from the LHC by a factor of
10 or 20 or 30 and that's
what's needed, for example,
if we do this at Higgs Factory
we'll know for sure whether
the Higgs is like a pion
or not, okay?
And if it is like a pion,
there'll be deviations in
the strength of it's
interactions, compared to that
of a point like picture, and
if not, not, but we'll know
definitively the answer to
that very important question.
Here's a quick plot just to
give you an idea of the leap
in position that you can get
at a Higgs Factory versus
what you can expect from
the LHC, and I won't have
time to go through it in
detail, but across the board
it's a factor of 10 or 20, and
in some of the most important
coupling constants, namely
the coupling of the HIggs
to two Z particles, it's
almost a factor of 30,
better than you can do with the LHC.
It's fortuitous that the
one you do the best with,
that this machine is the
one that has the deepest
theoretical significance,
and is the cleanest measure
of whether the Higgs is composite or not.
All right?
Now, there's one more
important question associated
whether the Higgs is point
like or not, which is
the following: Does the
HIggs look point like
to itself, okay?
It might look point like
to other things and yet
not look point like to itself.
In fact, the self interaction
of an elementary particle
is perhaps the most basic
process we can talk about
in quantum field theory and
yet no elementary particle
other than the Higgs
can experience it, okay?
We thing that gluons can
interact with each other,
Ws interact with each other,
but they always change
the quantum number, they
change a color or flavor
or some quantum number.
The only particle that even
has a chance to interact
with itself is an elementary
spin zero particle,
so we have to go look does
it interact with itself?
It's a brand new kind of
interaction we've never seen
in nature before, the most
basic simple possible one,
and the LHCs not going to
be able to tell us even
whether this interaction
exists, never mind measure
it, okay?
That's what you need,
for that you need to make
hundreds of millions,
billions of Higgs particles,
enough so that this process
happens at a sufficiently
high rate that you can
actually see it and measure it,
and that's ultimately
that's the actual rock solid
physics case, I mean that's
one of many things that
go into 100 TeV proton
proton collider will do,
produce enough Higgs particles
to be able to actually
see that process and perhaps
measure it to the five
percent level, five to ten
percent people, people are
fighting right now about
whether it's five percent
or 15 percent, my bet is
that eventually it'll settle
down closer to five percent
or even better as people
start being more imaginative
with how they go about
doing this, okay?
So it goes from not knowing
whether this interaction
exists at all, to being able
to actually see it, right?
So those are the most basic
questions about the Higgs,
this totally, this new object,
we have a very fuzzy picture
of it from the LHC, we're
bound to continue to have
a relatively fuzzy picture
of it from the LHC and that's
what these facilities are
going to allow us to do.
Of course, 100 TeV collider
does something else,
it blasts into the energy
frontier and that's
something that we've
been doing for a hundred
years or 50 years, depending
on how you count and
so there's absolutely no
reason to stop doing it now.
If 100 TeV seems crazy, I'll
just remind you that it's
only two times more powerful
than the super conducting
super collider, which is
something we're going to do
30 years ago, okay?
So it's pathetic if the human race cannot
50 years after we've first
started doing about it,
go a factor of two compared
to what we could do back then.
This is not crazy technology,
it's not, you know, it's not
la-ti-da thinking, this is
something that we can do
and there's absolutely no
reason we shouldn't keep
doing it, but by going to these
higher energies we'll have
power to produce new
particles at 10 times,
roughly 10 times the
reach of the LHC in mass,
more like five, okay?
Five to 10 times reach
of the LHC in mass and
importantly, the probe of
the quantum fluctuations
in the vacuum, scales like
the square of the energy
of the machine, so given
this is a probe of those
quantum fluctuations
with the power 100 times
larger than the LHC, okay?
So, there are various ways
and if you want to speak
more professionally about
some very concrete physics
questions that these machines
are going to tell us something
quite robust about, if you ask
the question for a long time
we wondered what breaks
electro weak symmetry and
now we know the answer, it's
that the Higgs particle,
the Higgs field getting an
expectation rather breaks
the electro weak symmetry,
the next obvious question
from there is how is electro
weak symmetry restored
as you go to much higher energies?
Or as you go to much higher
temperatures in the early
universe, okay?
So that question about the
nature of the phase transition
to restore electro weak
symmetry is something that we
like to explore experimentally,
and anything with effects
the nature of this phase
transition is bound to give you
percent level deviations in
the couplings of the HIggs,
as well as new particles
that are accessible to the
100 TeV collider.
There are questions involving
why the HIggs particles
like to begin with, the
infamous or famous depending
on how you think about it,
question of naturalness.
This is something that was
a huge motivation for the
construction of the LHC,
we haven't seen any of the
particles that were suggested
by these arguments yet, okay?
It's not obvious that means
that they're not there,
there's something a little
bit wrong with the way we're
thinking about it, or there's
something a lot wrong with
the way we're thinking about
it, we just don't know,
the only way we can
decide is to go and look.
I want to point out something
that David Gross keeps
emphasizing whenever we
talk about these things that
never in history has it been
true that to understand physics
at an energy scale E it's suffice to go to
the energy scale E, you
go to 10 E, you go to 10 E
so that things aren't confused
and you're not in transition
regions and you really get a
picture of what's going on.
That's really what happened with QCD.
The characteristic scale
of QCD is 300 MEV and
if we're stuck at 300 MEV
doing experiments there,
there's no way in hell
we would figure out that
there's quarks and guans
underneath the whole thing,
that needed just to go to two
or three GV in order to see
that the picture emerge, okay?
And finally the idea that
dark matter might be weakly
interacting particles, the
very simplest picture for
what dark matter could be,
their mass is something
that's not accessible to the
LHC, it's not, it's just tough.
The simplest pictures of
dark matter have these
particles weigh one TeV
or three TeV, they cannot
be produced at the LHC,
but they will be produced
in 100 TeV proton proton collider.
All right, so there are
some technical things that
I don't have time to go
into, but let me just finish
by making the most obvious remark,
that here we're talking
about the long term,
two or three decade future
of particle physics,
but right now we're
probably entering, or in
the most exciting phase
of the running of the LHC
and almost all of us in this
field are spending most of our
waking moments worrying and
thinking about it and being
excited about it, but I want
to emphasize that no matter
what we see at the LHC, the
fact that we haven't seen
anything already tells us
that we have a solid argument
for proceeding and making
plans for this next
generation of accelerators,
and that's both in
the pessimistic and the optimistic cases.
The pessimistic case where
we see nothing but the Higgs,
then we're humbled as
theorists, certainly, many of us
okay, we need to study this
particle experimentally,
we have a fuzzy picture from
the LHC so we have to go
and look at it.
Let's say we do see new particles,
euphoria, hallelujah, right?
Let's say we see some
colored particle that weighs
one and a half TeV, I can
guarantee you 500 theorists
will call it the super
partner of the top quark.
The problem is it will
not produce enough of them
at the LHC to be able to
verify that even couples to
the Higgs, never mind that
it does the job that it's
supposed to do in more detail to solve the
hierarchy problem.
See, and this is not a trivial statement,
rah,rah, rah keep going no matter what!
Have we discovered a 300 gb gullinoes in
the first run of the LHC would be swimming
in these particles by now
and then with millions
of them, that is not so
obvious that this is the next
thing that you want to
do, but now it is because
even if we do see them, we're
going to make a thousand
of them or 10,000 of them,
enough to actually produce
them and claim a discovery
but not enough to be able
to tell us a story about
what's actually going on.
So, and for this you need
actually Higgs Factory that
can confirm that these
couple up with a HIggs,
as well as ultimately,
going to 100 TeV to actually
have a factory and study them in detail.
All right, so, something
particle physicists love to see
is pictures of the planet
with big rings on them, okay?
And I think one of the
most exciting things that's
happened in the past couple
years is that these pictures,
with big rings on them are being drawn.
They're being drawn by our
friends at CERN who are
imagining an 80 kilometer
tunnel going underneath
Lake Geneva, that'll be
this next big step beyond
the LHC and Byee Fung
and his friends in China
that are drawing maps of 50 kilometer and
hundred kilometer rings on
the ground 300 kilometers
northeast of Beijing, okay?
I think this is amazingly
exciting, amazingly important and
worth the putting a lot of
effort into supporting both
things in order to try to make
sure that this, that these
machines actually go from
being a dream to a reality
on the necessary decades time schedule.
And there's the final question
of the cost that always comes
comes up, and I've stolen
this slide from Yu Fung,
the cost of these machines
is 10 billion in your
favorite units, okay?
So, and there's no sugar
coating it, that's how much
they cost, but Ye Fung has
pointed out, a number of times
that the fractional costs of
these projects, compared to
the GDP of any country,. at
any point in the last 30 years
has always been roughly the same.
Roughly 10 to the minus four, okay?
So the SOC, when it was
cancelled was 10 to the minus
four, U.S. GDP, the running
cost of the LHC now is
around three 10 to the
minus four European GDP.
The costs of these projects in China is
of the same order, okay?
This is something human
beings have done before,
by the way Tyco Brahe's
boss, the king of Denmark,
spent eight percent of his GDP
to give him an island, okay?
And this was a really good
idea, because people remember
this guy, except I just didn't,
sorry, but people remember
this guy, this is something
human beings do, right?
There's very few things of
importance that we can do
on this planet before we
shuffle off this mortal coil
and this is one of them,
this is one of them.
Am I putting you on the spot, Yuri?
All right, so let me just
end by saying that certainly,
and not just my view, the
scientific issues that we're
facing today are amongst the
most difficult and profound
ones that fundamental physics
has faced since the 1930s.
And it's fascinating to me that
the questions that have been
raised by the biggest experimental
discoveries of the past
two decades, the discovery of
the accelerating universe and
the HIggs discovery, they both
go to the heart of something
we don't understand about the
combination of these ideas
that were handed down to
us from the first part of
the 20th century, there's
something we don't understand
about the nature of space
time, quantum mechanics
and the vacuum, and both of
these big discoveries are
pointing to a something that
we don't understand there.
In the case of the accelerating
universe, our friends in
astronomy have no difficulty
making the intellectual
case that we have to keep
going, we have to measure W,
we have to really know that
it's a cosmodule constant,
all the more power to them, I
support you 100 percent, okay?
We have a similar case that
we could be making in particle
physics, and we have like tons
of measurements we can make.
There's a big, rich experimental
program revolving around
the Higgs avatar of these same
problems and I believe that
these future circular machines
are the way to go about
doing that, so the scale of
our vision and ambition have
to be commensurate with
what the science demands
and we should be more,
not less aggressive in
pursuing it.
Thank you very much.
(applause)
(soft, jazzy music)
