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Produce Doctor,
a professor doctor,
Dr. Robert C.
Helling from the University
of Munich. And
please give a big hand for his
presentation here on one of the most
confusing topics that I ever had to read
about when I was doing physics, which is
supersymmetry.
Thank you very much, Dr. Holly.
OK.
Thank you for coming to this prime
time talk on day two.
Yes, I am.
My name's rover telling. I'm a physicist
at Munich University and this
talk is by request of a local
brewer. Hacker asked
me to talk about supersymmetry.
So who knows?
These people just got an idea.
I'm over 40. Who else is over 40
for particular,
this lady?
You all know her, but who recognize her?
It's Madonna. Yes, it's
a I can 80s
movie picture.
OK, so what is supersymmetry?
We are talking about particle physics
and supersymmetry or Susie.
And chart is a symmetry that predicts
that for every known species of
particles, there is a new particle
and not a single one
of them has ever been observed.
So why bother?
And I will probably spend
forty five minutes to explain why bother
us?
So I want to explain why my colleagues
have come up with this idea of
supersymmetry
because it solves some of the big,
outstanding problems in particle physics
and theoretical high energy physics and
in general. So but I have to explain
a couple of things. So a brief
introduction of first,
the known players that is the standard
model of particle physics that consists
of matter particles,
namely the leptons of
they all have spin one half.
This is the spin.
That's the angular momentum, the
intrinsic angle angle, the momentum of
the particle. Most well known of this,
these particle is the electron
here depicted as E.
And there are also neutrinos you might
have heard of about those because there
were some rumors that they could
travel faster than light that turned out
to be a problematic
cable.
But these two?
So this one is everyday
physics and chemistry.
This one is very light.
They have heavy, the electron is heavier
partners, and there are also neutrinos
for these part, and it's called This is
the meal on. This is the town.
And then in addition.
So these guys make up the hull
of an atom, and the
core of the nucleus
of an atom is made up
out of quarks and neutrons.
And those consist out of quarks, namely
of these up and down quarks, but that
form more types of quarks called
chom strange bottom and top.
And then there are
four forces in the universe.
One is gravity that doesn't matter for
elementary particles.
The others are mediated
by particles again.
Those have spin one, and the
most well-known is the gamma particle,
or the photon that's responsible for
electromagnetism.
But that's also the W and
the Z vector boson that
mediates the weak
interaction that is responsible for beta
decay.
And there are gluons that actually keep
these quarks together in the nucleus
then.
And then since this
year, we know that there is actually
another particle of spin zero
and that's called the Higgs boson.
And this year, the Nobel Prize was given
for the discovery of actually for the
prediction of this particle.
So that is
the standard model. These are the
particles that we have all by now seen,
and they fit well into this model
called the standard model.
Now come supersymmetry
and for each and every one of those,
there's a new partner.
So now we're talking about the minimally
supersymmetric star model that minimally
refers to. We're adding as little
as possible.
So for these, X equals
one half particles we add
as equals zero particles called this
leptons.
You get their names by adding an X.
So that's the electron, that's
the smidgeon. And that's the star
as well as the squawks.
And then to these
force particles that are
fermions with SW equals one half
called the photo for the photon,
the winos and the Xenos for the W
and the Z. You see the way adding an
igloo we know are actually several one
for the gluons plus Higgs,
you know.
And to make things internally consistent,
this doesn't quite work.
We have to add another pair of Higgs and
Higgs xeno to make things work.
So this is the minimally supersymmetric
standard model, and I will be talking
mostly about this
set up of elementary particles.
These. Has covered these hypothetical,
and then there's an important principle
and quantum physics that
particles are fields.
So there's the this is the
electromagnetic field, but it's described
by photon particle
and the fields are again particles.
So I will and the rest
of the talk. Use this synonymously.
OK, so I claimed there
are open problems that
are solved by assuming supersymmetry
is a symmetry of nature.
And I have five of them listed here.
The first is actually very close
to my heart.
Up when I'm actually doing research,
that's the mathematics of quantum field
theory.
But unfortunately, I won't talk about
this.
I'm
the next one.
This will take quite a while to explain
it's called naturalness.
Susie provides a solution
to the natural problem, and to explain
this, I have to go on a small detour.
I have to explain how we
theoretical physicist in
the 21st century view
these force fields, in particular
the electromagnetic field.
So this is how everybody learns what
electromagnet magnetism is.
You have a wonderful generator and that
makes your hair go up and you have
charges and force fields.
And this is this electromagnetism 101.
But I want I.
I ask you to believe me
that there is a completely different
point of view that actually talking about
the same thing than electric
and magnetic fields, and that goes like
this. So
let's assume so.
This is space the hammer CCH
dumped to a bahnhof plant and blown,
and at each point in space,
that's a virtual or internal
plane attached to each point in space.
So far, five by five.
My point is dying, but for five by
five points, I've drawn these spheres.
Not not spheres, actually, that whole
planes and
they have a rotational symmetry.
I can rotate the plane around the
origin, so let's do that.
So now I hope everybody can see that
these guys are rotating around the origin
and rotating.
Yeah, yeah. You got it.
Get an idea, at least the people in the
front row.
But the important thing is, so now
they're all rotating in the same way,
they are all rotating in parallel.
But you can rotate them independently.
So now this starts, then the others come
on. And so you see that
each one is rotating
separately from the other.
So this movie that you see here
is actually a depiction
of an electromagnetic wave
traveling here from once this
southwest to northeast.
So here it goes again.
OK.
And I claim, and I
have to ask you to believe
this. I cannot explain this further that
electromagnetism is nothing
but the description of these rotations.
So you have a description of these
rotations.
I'm talking in an equivalent
way about electromagnetism.
This is actually a representation of
Maxwell's equations.
If you happen to know what those are.
So in particular, there is some somewhere
in these rotation. That's the Coulomb law
that describes the force between two
charges.
But I'm claiming
this is contains all the information
about the electromagnetism, how all these
planes rotate.
OK. So and and the point is
not only electromagnetism is about
of this type.
So electromagnetism is a rotation
of a plane. Here you see the plane
rotating, but also the weak
force. Remember Decay,
K, W and Z bosons?
This is also about rotations, but those
this force is not about rotations
of a plane.
This rod rotations in a
three dimensional space.
So if you like of a sphere, so this
sphere here is rotating about different
axes and that's and coating
the weak force.
So weak force.
So technically, it's not the this
group that rotation was assumed to.
There's also the strong force that is
about rotations in a complex, three
dimensional space, and I don't have a
better picture of this than hyperspace.
But the principle the mathematics is the
same is just high dimensional.
OK, so that is I claim
these these are all the forces
in the universe.
Maybe, except gravity are just
rotations of some sort of internal spaces
that are attached to each point in space.
OK.
These are the forces. Now comes the Higgs
effect. So what so you told you a Higgs
particle Nobel Prize 2013?
I explain to you what the Higgs effect is
very simple.
In addition to the plane, there's a
little blue ball in the plane,
and the Higgs field
just tells you where in the plane
the ball is. So right now, it's in the
origin, right?
But I can move in principle.
I can move the ball around to any other
point in the plane.
And the notion where the ball is that
is the Higgs field in the same
spirit as the rotation of the plane is
electromagnetism.
And now we add something to this plane,
we add a potential energy, so kind of
landscape, so let's turn that on.
So this now looks a bit like the
bottom of a champagne bottle.
So I've added some potential LNG,
but this is still rotational asymmetric.
So now rotational symmetry is still
intact. Now you have these champagne
bottles with a blue ball in
the origin, and this thing is still
protection symmetric.
The wave goes
through Hamburg.
Hello.
OK, but of course, the ball at the tip
of the champagne bottle is not the
minimal energy configuration
the ball wants to be further down.
You can gain energy by bringing the ball
down.
So let's do that.
What now you see the balls
at the bottom?
So and of course, there's more than one
possibility to put the ball at the
bottom. There's a whole ring of possible
places where the ball can lie and a
minimal energy configuration.
And each one of them, each
choice for possession
of the ball on the bottom
breaks the rotational symmetry.
Wherever I place the ball, the symmetry
is broken.
So now if I rotate these planes
with the ball, as this happens
here, I have to drag the ball around
and that costs energy and
this energy.
This turns out to
be the mass that is given, so the
symmetry is broken.
And this is how mass is created.
The mass is actually the energy it
costs to drag the ball
around when the electromagnetic wave
goes through this configuration
with the broken symmetry, and that is the
Higgs effect. This is how the Higgs
effect gives mass to elementary
particles.
And so, OK, so
when I said this happens in
electromagnetism, this is actually not
true, I lie to you
in electromagnetism, the symmetry is
not broken and the photon is
mass remains massless.
That's good because otherwise it couldn't
travel long distance.
You couldn't see me of the photon where
massive it would decay before it reaches
the photon that comes from me or from the
screen would decay and would not be there
if it would be massive, but it's massive
so you can see the screen.
But the Higgs effect takes place
for the weak interaction.
Remember, that was the one with the
rotating ball, but then with the ball,
I couldn't draw the the potential, so I
chose to use this representation.
But it happens for the
for the weak interaction.
And this Higgs effect makes these
Z and W bosons that
mediate this force.
It gives them a mass of roughly 100
gig electron volts could get electron
volts or electron volts.
Is the energy unit the particle physics
physicists use? That's very convenient,
so this is an important number.
Remember this one hundred GeV?
OK, and this mass
corresponds to the distance that the
ball has from the center.
So. So that's kind of the radius of
the of the motion of the ball that I have
to drag around. The further it's out
there, the more difficult
it gets to direct the ball around.
OK, so so that was the Higgs effect
and gauge interaction, so
such interactions are called gauge
interactions.
German speakers call them, I
call.
OK.
OK, so now
for something completely different.
That was my first explanation, this is
how electromagnetism and his friends
work. Now comes a different concept
that's called ring normalization.
So now I'm
for second. I'm back to the old picture.
This is supposed to be an electron and
this is supposed to be
the antiparticle of an electron positron.
This is just like the electron
just with positive charge instead of
negative charge. This has nothing to do
with the super fast.
This is all standard model
physics and the
wiggly lines have drawn.
Here is the cooling field.
That's the electromagnetic field
that drags the
this violet ball towards the Red
Bull. And everybody learned
in school that this force
that the force of
attraction between the balls
is proportional to the charge of the
electron and it scales
inversely with the square of the
distance. That's cool, MS Law.
Everybody should have learned this in
high school at some point, hopefully.
OK, cool.
I'm sorry this everybody knows.
OK, so now
this this picture, this was classical
physics. This is the first to learn in
school, but the world is a quantum world
and it's more complicated.
The upshot of of of quantum mechanics is
that the charge of the electron actually
depends on the distance at
which you look at it.
And this comes about as follows.
So quantum mechanics says the vacuum
is not empty.
Oh, not a lot of bottle
for some.
OK. You fell asleep.
No problem.
You were OK.
Everything OK,
OK. Back to quantum physics.
Quantum physics says the vacuum
is full of virtual pairs
of particle particles
and the antibiotics. They pop out of
nothing and annihilate again.
So I've drawn a couple of those here.
You see the original electron, the
original positron. But there are a couple
of other electron positron pairs
that have popped out of the vacuum for a
split second.
But these particles are also charged.
Posit the the red
one is positive and the the the
purple one is negative.
The other way round red, negative,
purple positive.
And they also see the electromagnetic
field of this electron.
So the purple one likes to
go towards the Red Bowl, and the Red Bull
likes to go away from it.
So, so, so they align a little bit
in this field. You see that
the purple one's always closer to the red
ball in the virtual positron
electron pair, then the electron.
So that causes
something like a polarization of the
vacuum and that yields
shielding effect. So now this
positron that was supposed to see
the electric field of this electron not
only sees the electric field of this
electron that I've drawn here, but it
sees also the electric field of all
these other virtual particles and because
they are aligned in the original field.
Turns out, the field at this particle
size is actually a little bit weaker
because it's shielded by these
other pairs, and
this shielding effect is stronger.
The stronger the the first field is
because the stronger the so
stronger because you are closer.
So when you're closer than the alignment
is even stronger and the shielding effect
is even stronger, and you can
subsume this by saying
actually, so I total all
these that charge and the shielding into
a new charge called the re normalized
charge. And that is then
the charge that depends on the distance.
Ah, so now the electric
field e is proportional
well at distance AH is proportional
to the charge corresponding
to the particular distance.
Here are is this or some here to here.
Divide it by all squared.
That's the upshot of your normalization.
That's a quantum version of the rule of
law.
So now how does Q of our look like
so so that that's called running
couplings because the well,
the charge is
special.
Well, I mean, it's one example of
coupling and it's
running because it depends on the
distance.
And a similar effect applies not only
to the charge of particles, but also
for other properties of the particles,
for example of the mass, also the mass of
a particle like five and 11
K.V. for an electron.
That's not the full truth that depends on
the distance, the distance
at which I measure the mass
and for almost all properties.
This dependance of.
Are logarithmic.
So there is a coefficient called beta,
the so-called beta function times
the logarithm of our logarithm, as you
know, the function that grows very slowly
with R and this
coefficient theta depends
on particular types of of
the particles that are participating
in this shielding. So you have to
you can calculate this actually and
depends on all the types of particles
that can pop up from the vacuum.
And also another property of
a particle is the shape.
Remember, the champagne bottle
are the shape of the potential,
and that happens to depend
not logarithmic Li like the charge
or the mass, but it depends quadratic
li on the distance. So it goes more like
some coefficient times are squared
and our squared is a function that
is much more sensitive to our than the
logarithm you change.
Our little bit logarithm stays mostly
the same.
We change our little bit, but the square
of that change is actually quite a bit
so. And because the mass
of the W inset bosons, remember they
came from the ball that it was not in the
center, but somewhere in this potential.
So the result is that the
mass of these particles is very sensitive
to the distance at which I measure them.
And and for particle physics
units, one
is actually quite a small mass.
And if it were in fact
quite dramatically sensitive to the
distance, it's very unnatural
to be so small.
Based on order of magnitude estimate,
you would actually expected to be
17 orders of magnitude bigger.
So the natural size would be more the
Planck. Such plans to have 10 to the 19
GB, rather than the 10 to the two G.V.
that it actually is as
a question.
When you say the mass.
The point is it cannot be quadratic
because it would be a good one, just one
distance, and if you change this in a
little bit, it would be completely
different.
And that's not what we observe.
So
this smallness of of this
mass is not natural.
We would expect it to be much, much
bigger based on
this type of argument.
So we have to explain why
nature can maintain the small mass
of one hundred easy
and simple. And that's the naturalness
problem. Explain how the mass can
be. Hundreds of small
and supersymmetry provides
a solution to this problem.
How does it work?
Well, it works because
the coefficient there was this alpha
coefficient.
It was this number in front that
says, how was
the coefficient of this r squared
in supersymmetric theories?
The original standard model particles
and their super partners contribute
exactly the same amount, but with
opposite signs to this alpha.
So if as if I'm not only
electrons and positrons popping
out of the vacuum, but as well so
electrons and positrons
are that effect cancels and
there's a zero in front of this r
squared.
So this quadratic running
of the mass of the W and Z bosons
goes away for exactly
supersymmetric theories because in
supersymmetry, the effect of the
different types cancel.
So that would be an explanation
of the naturalness and well of the
smallness of the size and the naturalness
would be saved if this if
nature would have, in addition to
electrons and positrons, their
superpowers.
Well, that that would be too
nice to be true because
supersymmetry predicts that besides
the spin
on the other properties of the partner
particles, so the selections for the
electrons
are actually the same.
So in particular, I would predict
that the electron also has the
same mass as the Electron 511
K.V..
But of course, I told you nobody has
seen this supersymmetric partner particle
in particular. We would have known if
there were a boson, so that could
be a part in the particle at five hundred
twelve. Sorry, I'm on the same question.
11. Now it's Typhon.
11 This, too, is wrong.
So if there would be another particle
with the same mass as the electron, I
mean, we produce electrons all
the all the time, and we have never
produced any of these foreign particles.
So so that that cannot be true.
I mean, supersymmetry that predicts the
partner particles have the same mass must
be wrong.
And the way out is there's
also a Higgs effect.
So the symmetry breaking effect from the
ball rolling away from the center
that breaks supersymmetry.
So supersymmetry is also a broken
symmetry like this rotational
symmetry in nature.
But we have to do this in a way to
preserve this naturalness
that the supersymmetry brings.
So how does that work?
So, so there's some way to break Susy,
like with the ball
and then the super partners of of all the
known particles can have larger mass
than the known particles, and
then the quadratic running is back
because the canceling is not exact
anymore,
but only up to about the
mass of the super partner.
So up from that mass on
there again, particles
and super PACs, and then the cancelation
kicks in again.
Is that clear?
So for masses below
the mass of super fast, the super planets
are invisible and there is quadratic
running, but for higher energies
or for higher masses where the super
partners are,
the cancelation effectively works again.
So we would expect that the running
happens. There is quadratic running, but
only up to the mass.
Of the super partners,
and that means since the mass that we
observe of the billions that bulldozers
have 100 GV, if this
explanation of natural naturalist works,
then this would suggest that super
partners also have masses
in this range of 100 G.V..
OK, that was the point with the
naturalness that was actually the
strongest point for supersymmetry.
There's another point called unification
of cage interaction, so I explained what
gauge interactions are gauge interactions
are these things with rotations?
And I told you are three in nature.
There is the electromagnetic force, which
is one, there's the weak force and
there's the strong force.
And we measured their values
while this the we
measured how strong actually
what we measure is the electric charge,
and that's a measure of how strong the
electromagnetic field is.
And so so this is
actually a measure of the distance
here. So we are here at
long distances away.
We measured the values of the three
of the three charges
here, here and here, and
I told you we can compute the coefficient
of this logarithmic running this beta.
And so we can extrapolate from our
distance scale to other distance scales
are here. So I told you this log
of Q, well, this is
effectively a measure of the distance.
Get a logarithm of the distance.
So this gives you a straight
line and you see that they're almost
meet in the point. Well, not quite
right.
The intersection of the three lines is
pretty close, but it's not in one point.
So pretty close already.
Quite surprising if you have three
generals, straight lines, they
their interactions are all over the
place. But here they almost meet at the
same point. But with supersymmetry,
the coefficient is a little bit different
because the supersymmetric partners
contribute with supersymmetry.
These lines happen to meet all the same
points at some distance scale or
some energy scale 60
10 to the 16.
In this graph, all
the charges happen to be the same,
although at our distance 'cause they're
very different.
So how can this be? So the idea is
that actually these are not three
different forces, but
that this is a single force
that comes about from a rotation
and an even higher dimensional space than
the hyperspace I was showing with Han
and Chewbacca.
Because this braking mechanism, so now I
have tried to draw
the brake and say, here is the blue ball,
but now in the sphere.
And if the blue, if the blue ball sits
here, then a rotation of the
ball around the axis
that goes through this point is still
a symmetry of this configuration.
So the original ball had rotations
about three axes as a symmetry.
But after I placed the
ball here, there's still one
axis where the symmetry
remains and
the rotation about the two other axes
are broken.
So by placing the ball here,
I do not completely remove the symmetry,
but I make it smaller.
Symmetry only rotation about one axis
rather than three axis is the rotation
of this. So the idea is
if I go back.
So also here is the Higgs effect.
So this is the mass of this additional
Higgs particle.
And then there are three independent
remaining symmetries that
after this point, become
one big rotation group while this
rotation group is actually rotation in a
10 dimensional space.
Again, I cannot draw this,
but that is the idea.
So, so this is how this comes about that.
The three lines meet in one point.
They all come from the same symmetry,
highest symmetry.
But this is not the only indication
of this higher symmetry.
Actually, there are more. So this diagram
is called a weight diagram.
I'm going to explain this says all the
particles that we know fit nicely
into groups of particles that transform,
according to this being our symmetry.
So many people believe that
this symmetry is actually a symmetry of
nature.
I mean, at high energies where
the breaking of the symmetry
is undone. And there are also the fact
that the neutrinos have masses and that
there are masses are roughly in the right
range is also an indication that
this thing is going on.
And I showed you this unification.
The meeting of the three lines and one
point happens only with the supersymmetry
without supersymmetry does not happen.
It's ruled out by a current observation.
So if you if you want this,
you need supersymmetry.
The next open
problem that is solved by Susie comes
from a completely different angle of
physics so far, I've talked about
particle physics.
Now let's talk about astrophysics.
This is a galaxy
and we've I mean this picture from Hubble
Space Telescope.
And so as you know, the galaxy is
actually a disk, and we're viewing this
disk from almost from the sign here.
This this one. So the this and this
disk is rotating around an axis that
is almost vertically in this
picture.
And now what you can do by using the
Doppler effect, you can
measure the rotation
velocity of this disk because you know,
when you when the ambulance
comes towards you, the sound
is higher in pitch than when it goes away
from you. Everybody knows the fact called
Doppler effect that also happens for
light and from
observing the frequency.
Or if you like the color of the light of
the stars here, you can determine
the velocity at which
these stars are coming towards us or
moving away. So if this galaxy rotates,
say this way, then the stars here are
coming towards us and the stars here are
moving away from us and this can be
measured.
Right. So are
people observe this for many, many
galaxies.
And the other thing you can do is you can
just look at the picture and kind of
count how many stars are in this galaxy?
Well, not you, but people can.
People have no idea how many,
how many stars in this galaxy, and they
also have no idea how big the stars are
because astronomers again from the
color of the star can determine
the mass of the star.
So you can
see you can actually determine the mass
distribution in this galaxy from looking
at how bright it is.
And so astronomy, that's something that
astronomers can do.
And since the rotation
is balanced so that the centrifugal force
from the rotation is balancing
the gravitational pull
of all the other stars towards the center
of the galaxy by
computing how much mass there is, you
know how strong the gravitational pull
on, say, this star here,
and that determines how fast it has to
go around the center of the galaxy.
So.
So when I say that this disk is rotating,
it doesn't mean that it's uniformly
rotating so that the speed of rotation
can depend on the radius.
Like in the in the Solar System, the
speed at which the planets
fly around the Sun depends on the
distance of the planets from
from the star.
So, uh, so stars
orbit the center of the galaxy, and let's
let's draw a diagram.
I draw this rotation velocity v
against the radius, the distance
from the center of the galaxy.
And I told you from
estimating the mass in the galaxy,
you can predict the velocity
of the star, the velocity of the stars
as a function of the radius.
So that gives you a curve that roughly
looks like this.
And you can measure it using the Doppler
effect and what you measure.
Looks like this.
So obviously, there's something wrong
with your prediction.
So it turns out, I mean, this is the true
thing, and this was predicted on the mass
that you see. So how can this be wrong?
How can you be so wrong?
Well, the only solution is
that you're not seeing all the mass.
Actually, you need more than five times
of the mass of the stars that you see
in the galaxy to get this
rotation curve.
So this curve of velocities that
is almost flat rather than
decaying like this.
So the conclusion is there must be more
mass in this galaxy than
the mass of the of the
atoms in the stars.
And further, from looking
at the details of this curve,
you can determine
what this mass properties of
where the smallest comes about.
So you have to
people conclude that this mass has to
be in the form of heavy, stable particles
so that are only subject
to gravity and the weak force, but not
electrically charged, all strongly
interacting because so high,
so heavy. It means that
they are moving slowly.
They are moving at relativistic speeds
that move much slower than the speed of
light in this galaxy.
Furthermore,
they must go through the stars and
everything that happens in the galaxy
without
interacting with them without
scattering with them, because otherwise
they would also be kind of aligned
with the stars and they are not aligned
with the stars.
And so that determines these the
properties of this particle.
So there has to be there has to be.
And of course, it has to be stable
because these galaxies have been around
for a long, long time
and they wouldn't be
there anymore if these particles that
make up this additional mass would have
decayed in the meantime.
So.
So there has to be have is a heavy
particle that is stable
and not interacting,
not not
having any significant interaction with
the matter of the stars.
And such are such
particles called the WIMP weakly
interacting massive particle.
And I should say no WIMPs are
among the known species of particles.
So in the standard model, there is no
particle that that would work
as a wimp first.
Some of them are not heavy enough,
like the neutrinos would be wonderful
WIMPs, except that they are much too
light and the heavier
particles
wouldn't be kind of non-interactive
with the stars.
So there has to be an additional particle
that makes up this dark matter
in the galaxy. And it turns out
supersymmetry provides exactly such a
particle
because of the following reason.
So far, I haven't told you about this,
but supersymmetric particles have a
property called all parity.
Parity is something that can be either +1
or minus one, and it's +1
for all the known particles and
minus one for all the particle,
the super partners that would have still
be to be found and
and that is conserved.
So the product of this
party?
In a particle interaction has to be
conserved, and that means
you can only create new particles in
pairs because the square.
So each one would contribute a factor of
minus one. So that's plus
one.
So here.
So this is a process that you have to
read from left to right, there are two
quarks interacting giving a W
boson and that decays now into
these guys a supersymmetric partners and
decays into two each.
One having minus one is our party.
And then these decay further.
So this one decays by emitting a new
neutrino. That's an ordinary particle.
So and decay,
there has to be an odd number of new
particles in the product so that
here there's one.
There's a slept on and that again sends
out an electron and there's
also a remaining
supersymmetric partner particle.
So, so when they're created that
created in pairs and when they
decay.
If there is a supersymmetric partner
particle in a decade before the
decay, that has to be one after the
decay. So the total number of super
partners in the process always has to be
an even number.
And that means if I have a super partner
and it decays it all the products,
there's always another super partner.
And if I have the lightest super partner
called the LSP the lightest
supersymmetric particle, it cannot decay
any further because there is no mass, no
energy it can decay into,
and it cannot decay into only stanozolol
modeling particles because that would
violate this parity.
So that makes the light super partner
stable and therefore
such a LSP lightest supersymmetric
particle has accepted the properties
that we need to explain the dark
matter and the rotation of galaxies.
So that's another probe of supersymmetry.
And finally, again, something close to my
heart. I'm not going to say anything
about this. That's we are not stuck
with particles. There's also super
strings. And if you ever want to make a
realistic model out of super strings,
that gives you a standard model particles
their own.
The only way we know to do this is
also to actually create the super
symmetric version of the standard model,
but I'm not going to say anything more
about this. So super strings also want
supersymmetry.
OK, so these five problems
out of which I try to explain, three
are all reason
to believe that supersymmetry is actually
a good idea to have.
So let's look for it.
And then what we look for.
So that is and there's unfortunately a
problem
and particularly the breaking of the
super symmetry. Remember, we needed to
break it because we need the
super partners to be heavy.
It comes that's not in
the 120 parameters
to 120 numeric parameters.
You should compare this to the 19
parameters that we have in the standard.
So again, there's not the standard model,
but there is a 19 dimensional space
of standard models. You can you have to
to choose 90 numbers.
Here I've listed the ones of the standard
model, so you have to choose the mass
of the electron, the mass of the other
particles you have to.
There are some mixing angles, blah
blah. In total, there are 19 numbers that
you have to measure.
These 90 numbers determine the standard
model. Unfortunately for
supersymmetry, you need to measure how
many parameters to determine exactly
which incarnation
of the super symmetric of
the minimum supersymmetric started when
you have.
So if you measure something,
for example, of LHC after his
speed spits it, well, first you would
have to measure these how many parameters
or you make an assumption about the
the values of these parameters, and then
you check whether that's realized or not.
So you can turn
this argument around and say that is with
how many parameters there's plenty of
room to avoid detection.
So if you don't see anything, you say,
Oh, maybe the pyramids have different
values and you can go on,
and every measurement that you make
is relative to some choices for some
or at least some of these parameters.
So, so looking for supersymmetry is
actually a hard thing because
you have to determine a lot of numbers.
And our best way to look for it for
supersymmetry is at the Large
Hadron Collider at CERN in Geneva.
So, yeah, I gave you the picture that I
hope you've seen many times before in the
popular press. This is the collider
ring somewhere here.
This is the computing center or the
control center on on the CERN ground,
but they're at several points
in the ring there.
Detectors were actually experiments of
and in particular, there are two of them
here CMS and here Atlas are big
detectors where the
two beams that are running that are
running around in the pipe here
are we're colliding.
So yesterday there was a talk about LHC
that I hope explained this in much more
detail than I can.
So this for the for today, this all
you have to know two detectors called
Atlas and CMS that are different,
but in principle, measuring the same
thing.
And there's another problem with the
Large Hadron Collider, and that's harder
on hydrogen.
This is a type of particle and
protons are
examples of hadrons and protons,
but none of these other things in the
nucleus of an atom.
These are the things that are accelerated
at LHC because
they're easy to accelerate to say it, in
short.
The problem is, remember, in
my list of particles, there were no
protons because they are not
elementary. They consist of quarks, they
consist of three quarks.
And actually because of this ring
normalization effect and particles
popping out of the vacuum.
And these energies that we're looking at,
they're actually of
more or less 2000 particles.
So a proton is a cloud of two thousand
particles, including
the ones that are popping out from the
vacuum that you are accelerating and then
you collide them.
And when you collide two protons at LHC,
you're not colliding to protons, but
actually you pick from
from the from each proton and pick one of
these two thousand particles and
you collide these two,
these two particles and all
the twice one thousand
nine hundred ninety nine roughly
particles just fly through as bystanders.
And that makes this process.
So that's a depiction of such collision.
Very hard to analyze because there's a
lot of garbage flying around.
Also, these collisions happen
while the the the beams have
have a collision energy of 8V.
But the 8V is distributed among
these twice 20 particles, so the
collision happens only with a small
fraction of these 8V.
And we don't know which fraction
because we don't know the details of
the particles.
So we have to look at lots of these
processes. Get rid of the
DBRS and do
statistical analysis on this, and that's
actually quite hard.
So it's not something you turn on.
You see immediately see something.
So that's a picture of of this
atlas detector.
You see a person that gives
you an idea how big this thing is.
This is a well, I mean,
this is from the construction of of the
detector. This is the detector with
the inner part of the detector.
Remove you. You look along the beam pipe
here.
This stuff is actually this empty
space is actually filled with detector.
This is only the outer part of the
detector. And here you see the beam part
like this, and this is part of the
detector, the mean detector.
So to get an idea of how big this is, so
this is a multi-story building.
If you be there several
stories underground
and this is
what this detector measures are.
Actually, this is a simulation.
What you see here, the beam pipe goes
here in the middle.
So some one
beam of protons comes from here.
The other beam of product comes from here
and here they're supposed to collide.
And when they collide, they go through
several shells of detectors and
the innermost shell.
This consists of of a detector type
where you can track the particles
and the next shell.
There, you can only see the energy
that is deposited in the detector and
that's indicated by these yellow
bars. And then some particles named the
muons make only those make
it out of this initial of the detector
and reach the outer part, and there again
tracks where it can detect
them. This is how one such collision
looks like, and there are millions and
millions of those every second.
So this is what you're seeing
are now.
What would super symmetry look like?
And the answer is the smoking gun for
supersymmetry is that you don't see it
in which sense, well, I explain to you
that the LSP, the lightest
supersymmetric particle, doesn't interact
with matter, so it's invisible
to the detector. It just flies out of the
detector and you don't see it.
You only see the rest of the particles,
but you see that the remaining particles
seem to violate momentum
conservation and
momentum conservation. This view
is hard to determine because see, there
is no detector along the beam pipes, so
most of the stuff just flies
in. Still, in the compartment is not
detected, but if you view
the detector head on, so now this is
again looking along the
beam pipe, you see that here is
stuff going here.
Is stuff going on here, stuff going.
But everything is a little bit more to
the right than to the left.
There's nothing to the left.
And both of them are to the right.
So since the beam has
no momentum transfers to
the beam. This means in
this collision, there must have been
something that went this way
with lots of energy
to balance the
tendency of all the rats to go to the
right. So this means here
some particle has been created that we
don't see, and this is what supersymmetry
would look look like.
You would see an imbalance of energy.
So this is what this is.
The. We are looking for
and there are some other more subtle
effects that also indicate supersymmetry,
and our expectation for LHC was I
remember a couple of years ago before the
LHC was turned on, I heard talks that
said all within actually five minutes.
If not, then in
a week we discover supersymmetry.
That was the expectation of particle
physicist for the LHC.
But when it was actually turned on and I
actually was going, even the Fuhrer
had to land.
And we have not seen any direct evidence
for supersymmetry at LHC, although we
expected to see it there.
So
in a more technical way, these
are this is actually a picture from
from publication, from this
one, from the steam detector.
This is what they publish about
supersymmetry.
These are bounds
that you're supposed to read like this.
This is an enormous scale and energy
scale, and these are all types
of different supersymmetric partner
particles that and
also different processes in which they
would would have been created.
And you're supposed to read this as if
super points exist.
They have to be heavier than bluh
in order that we wouldn't have seen them
so far.
So all these are so-called mass
bound. So you see that
the super partners would be have to be
heavier while depending on the type and
the process, then these numbers
and I explain in the beginning that we
would have expected them at 100 GB, which
is here.
So
there's obviously a problem.
So now what?
As you know, there are known unknowns and
unknown unknowns, as this famous
philosopher explained.
So what can we do? So I mean the easy,
the easy way to wiggle out to say this,
to say, Oh, there's still room in the
parameter space. We can tune some of the
under-20 parameters in such
a way that
that are compatible with the bounds that
we obtained from the experiments.
The other possibility is to say, Well,
maybe this was only the simplest version.
I accept this is the minimal
supersymmetric version.
We can also come up with extra
stuff, even more particles, and
in these more contrived models,
again, there's even more wiggle room to
say, Well,
this could explain why we haven't seen it
so far. But of course, these more
complicated models are more baroque and
even harder to
well motivated.
Or simply
the high-energy v scale supersymmetry
that would have explained Naturalis is
not in its nature, a solution to
naturalness.
And but then
so do we have to forget Suzy?
Well, maybe not.
But if Susy is not realized in nature
and these solutions to look
for some other regions parameter
space, this would mean would have to come
up with new solutions
to these five problems that Suzy is
actually solving for us.
And I have to say not
any good alternative candidate
here is known.
There are some for naturalness, but there
there are even weaker physiological
basis than supersymmetry.
So my take-home message is,
are I trying to explain
that supersymmetry offers solutions to
some of the most pressing open questions
in particle physics?
But unfortunately,
it's not as easy as we had hoped.
We haven't seen it, although we expected.
But there's hope for the next round of
LHC. Currently, LHC
is not running.
It's
while people put in more stuff to
make it run at even higher energies and
higher collision rates.
So we hope that within
version two of LHC,
more collisions at higher energy that
those reveals supersymmetry and if not,
then we have to come up with other
ideas.
So
thanks for lot.
So
we have
we have about 10, 10 minutes here for
questions if you have any questions,
if you can use the two microphones in the
in the two aisles and
I'll go form
two neat, neat lines.
And we'll start with
this gentleman here and then work
one two one two.
So you said that the WIMP candidates
would have to interact weekly as well,
but at most weekly
at most weekly?
Yes.
If oh, so it's possible that they
would not partake in the week interaction
because I was thinking that you have some
events in the universe, which
are very extreme manifestations of the
weak interactions like supernovae
where you get an enormous number of
neutrinos and enormous densities
of neutrinos.
And if if we should not
expect some sort of effect between
WIMPs and neutrinos from a
supernova, which would be observable
well, whether they
have to partake in some interaction,
otherwise we couldn't.
We could never create those particles.
So that's the first thing.
And then you are mixing things up.
So indeed, a supernova is a very
big energy concept.
But the when
I said these are high energies, even this
10 to the 19 TV Planck scale
this as a mass from every
day scale that's mg
microgram now. So I mean,
me doing this is a much
higher energy process
than any any plunks go process.
The problem is when I do this, I'm
not a single particle,
but by that consists
of two 10 to the twenty
three particles and they share this
energy and again, a supernova.
I mean, that's a whole star exploding.
So yes, it has much, much higher
energy, but distributed among
all the particles that make up the star.
So yes
and no, thanks.
Well, it's actually the question.
This gentleman over here.
OK.
And my question is, if there are such
particles which do not interact
electromagnetically with other parts but
have mass?
Shouldn't they concentrate in the center
of a galaxy and change again?
The rotation a little bit.
No, no. Because of momentum conservation.
They just fly.
I mean, they don't. They only feel the
mass. They just fly around on
on big orbits. Nothing kind of.
There's no friction that makes them
fall into. So let me go back to my
picture of the galaxy.
No.
Back, back, back, back, back, back, back,
back, back, back, back, back, back,
back, back, back.
Here's my picture of a galaxy.
The the fact that the galaxy
is a disk comes actually from
the friction.
So it starts out.
I mean, early in cosmic evolution, there
was just stuff flying around.
So it was more or less
about three dimensional
thing.
But then it has rotation,
so it has angular momentum.
And because the stars,
they actually feel each other.
I mean, the stars, I mean, they interact
gravitationally and they're heavy enough
to have significant gravitational force.
This complicated
gravitational pull of all the millions of
stars among them
that acts like friction
and that this friction makes this
three dimensional bulb
kind of decay and fall back.
And the fact that there's angular
momentum that has to be conserved that
cannot be radiated off makes it actually
go into a disk because the disk is the
configuration with the given angle, the
momentum of the kind of lowest,
lowest energy. So if they don't retract
they, they don't do this.
They don't have the friction.
They would just fly around and orbits
like
they're used to, you say.
Gravity is not enough to build those
concentrations.
No, these because these are again, single
particles. I mean, they're they're tiny,
tiny particles. These are star stars
have significant gravity.
But these particles?
And shouldn't those supersymmetric
particles have affect to the
HAWKINS' radiation if they constantly?
So if you
have it in the in the I mean, hawking
radiation
we look at, it sounds like this
particular question needs to be taken.
OK, so let's go.
We'll take one answer is no,
no hawking radiation.
This is you. Remind me of my old physics
teacher at university.
No, you're wrong.
We'll take questions here from the VÃ‰CU
here.
It's up to you.
It's my it's not my phone on.
I don't know about.
You just want to come forward to this.
No. No, it
works.
Works, OK?
I always thought the advantage of the
LHC is that we accelerate
protons.
And now you say, well, proton is
free quarks and a speck of dust on the
actual collision takes place between only
a small part of them.
So why didn't you establish the electrons
in the first place and accumulate
all the energy to this one, lepton?
Well, that was my first point that
was encoded in my answer.
It's that easy to accelerate.
Well, you can see you.
Well, the problem is you want to
accelerate them in the ring.
And the fact that
so people did that with the electrons
in the past, the predecessor left,
did this with electrons.
But the electrons, when you put them
on a circular orbit, they radiate
off electromagnetic waves, they lose
energy. Also, when you pull them on
the ring and they lose
more energy than you pump in by
the acceleration. So if
you want to accelerate electrons at these
high energies that cannot do this in a
ring, have to do this in a straight
accelerator called Linear Accelerate.
And actually, the next thing that
physicists would like to build is such a
linear accelerator that would be like 30
km pipes,
straight pipes colliding.
Actually, there was a proposal to build
one here at DC, so that would have reach
from pin it back.
I am torn to the DC
area in Bonn and then another 15
kilometers in the other direction.
Not small.
This gentleman here?
Yeah. In the diagram that is just
like next slide.
So you?
Yeah. Next one.
Yeah, this one, you just show like an
interaction with like supersymmetry
particle and you see that
there is like a neutrino like ejected
on the top.
Yeah, but couldn't we like see those
neutrinos who like, detect them somehow?
No, we don't see them as well.
OK, so they haven't been seen
or like.
Well, I mean, not in a particle and not
in such a particle detector.
They are detectors for neutrinos, but
they are completely, completely
different. Yeah. No, I don't.
But we could like have like some
somewhere in the Earth, and we would like
to see them coming from like those points
in the galaxy or somewhere.
So like seeing an excess
of neutrino?
Yeah. But. Remember, you're creating just
one.
Yeah.
Compared to like the song, it's enough to
detect you.
Yeah, yeah.
OK, so we're just about out of time
here. Do we have any questions from the
internet?
No. OK.
Maybe this lady in the back.
Yeah, OK. We'll take one more here for
this lady, and then I'll call it quits.
OK, I have no clue, and I tried to get a
basic understanding of this dark matter
concept. So as
I understood it, it had
there should be mass.
But this there is nothing that emits
anything that we could measure.
Is that right?
Well, that we see, I mean, we just see
light. So we only see stuff that emits
light, namely stars.
OK, what is light?
Oh, that's a complicated light.
So light. I mean, when you look at it,
I mean, go outside.
No clouds stars.
You see the light from the stars.
So that's what we see.
I mean, that's our information about the
galaxy, the light from the stars that
reaches us.
And this comes from stars and we know
what stars are made out of.
OK, so it's only light.
Yeah, OK.
OK, thanks.
OK.
Was that do you feel appropriately
enlightened,
come to me afterwards, and maybe I can
give you a longer version of
the Sense, OK? Well, this if
there are any further questions,
Dr. Helling will take up cheerfully.
Take your questions in the lounge
so I can place it.
No, that's too loud.
That's a lot.
I just thought that all this probably
also neatly explains why
I failed.
Q Can I try to
find out? About 20 some odd years ago,
it was embarrassing.
Thank you very much.
They can't focus, please.