why is the higgs boson
it's what
gives everything mass if we weren't made
of massive particles we'd fly around at
the speed of light some people would
like that
but you'd never join together to form
bodies again so it's very important that
we've got masses
at first sight everything should go at
the speed of light and you've got to
stop things going at the speed of light
otherwise they're all whizzing apart not
interacting
so you have to put a term in which
allows for a mass
which will slow it down a bit
but different particles have got
different masses you know if you just
think of the standard particles in the
universe the electron for example and
say the quarks the top quark
there's a difference of about a factor
of 350 000 between the mass of the
electron and the mass of the of the top
quark and yet those are in the same
family of particles that make up the
standard model and why
it's a particle it's also what we call a
field which means it sort of you know it
permeates all regions of space it's one
of those things which is very esoteric
off the end of the maths that most
people can deal with and off the end of
the math that most theoretical physics
people can deal with the particle is
just the
the end product if you like the big
thing you talk about that that particle
physicists are interested in is the
field the field is the is the concept of
this object that permeates the whole
universe if it's
found it gives a basis for cosmology and
masses of particles so that we become
more secure in our ideas of what the
universe is made of this is the
difference between the field and the
particle the particles if you like are
the fluctuations the oscillations in
that background field so it's the
equivalent of with electromagnetism we
think of the electromagnetic field
pervading the universe
its fluctuations are the photons the
photons of light are the fluctuations in
that field and that's what the
equivalent of the bows on the particles
are they're they're the fluctuations in
this field and then you so you can
imagine you need quite a lot of energy
to get the feel to get excited enough to
produce those bosons in the first place
and that's what the collision of the
protons can do for you what happens when
two protons collide at tremendous
energies that makes the higgs boson show
its face
well i guess you know you just
so the way the higgs has appeared in
this is it's do you create that you get
this collision you create particles
which then can annihilate and and you
get a series of events happening now if
you get enough of those then rare stuff
can happen
okay and what's one of the rare things
that happens that may have happened we
think is that a higgs particle decayed
into two photons and that's what we've
detected but in a way that only the
higgs would have done so that's how
we've detected it
can i make a suggestion then why aren't
we searching for the higgs field why are
we searching for the particles if
they're so hard to find because the
field is even harder
that's the problem that
so we're hoping that by by finding the
particles we'll actually gain some
information about the field i cannot
explain it simply to the general public
because it is
well i would use the word recondite and
that means that it's so obscure that you
have to go and look up the words and the
meaning in a dictionary
and that is the difficulty you have to
use a mathematical language which is
rather obscure
in order to get to grips with it and you
have to have a mental picture i mean the
one that's used you'll find my
colleagues love this
is a mexican hat can i bring my hat into
this at this point
well this is where the higgs lives the
higgs lives on on this hat and you
imagine there's a potential that runs
down and then has a minimum around here
my finger is the is the higgs
so you start out and it's in this point
here this this hat is that is what we
call the higgs potential it sort of
controls what the higgs doing so you
know just think of the of the higgs has
been like a little ball on this hat and
it's rolling around say so at the top
here
okay it's unstable because
you know the excitations are unstable
because if you nudge it a little bit
it's going to fall down the hat
okay now
that happens it rolls down you get what
process what we call spontaneous
symmetry breaking then the head higgs
ends up down here
okay and then the excitations
around that point here this point at the
bottom of the hill if you like at the
bottom of the hat those are what we call
the higgs particle and it's some the
properties of the excitations around
this point also give mass to everything
else that doesn't mean anything to you
but to people in the field they would
know roughly whether i got it right for
a start i'm not sure i got it right and
whether
this is the right physics and it is the
oscillation in a
in a symmetric well which has a certain
symmetry which causes the higgs boson so
the higgs particle is a is a very
unstable particle and that's part of the
issue right if it was really stable
they'd be all out there and you'd just
be able to find them so
let me give you an idea of how difficult
it is to to generate them there are
on average 200 million collisions of a
second between the protons and the uh
going one way and the other way so two
protons smashed together
and that's happening 200 million times a
second right this
the the accelerator has been running for
about best part of a year
200 million collisions a second
do you know how many higgs have been
detected how many potentially have been
detected in this this data
in some of the channels three
three higgs
so these are small statistics right
because they're very difficult to
produce these particles and then and
then be guaranteed that you be fairly
confident that you've seen it because
they they you need a lot of energy to
produce them and then they decay very
rapidly and you have to be fairly
confident that you understand the decay
products in order to reconstruct what
you think is that is the is the higgs in
the first place
so there's there are many protons
colliding and very relatively few higgs
being produced there's lots of other
stuff being produced which is far easier
there was
a conservative mp william waldergrave
who asked for people to write one page
of a4 to explain the higgs boson to the
public and there was a competition and
somebody won it
and you can't really do that that's what
you're asking me to do one page of a4
written simply and talk about mrs
thatcher moving through a party and
everybody coming towards her and
making a mess around well i can give you
an analogy for how the how the higgs
mechanism works and so so the the the
mechanism the analogy people normally
use is is they say well imagine a room
i don't know in hollywood or something
right and the room's empty and you get
some superstar like i don't know brad
pitt walks into that room and
there's no one in the room so he can
walk about freely there's no problem
okay now you go later on the day and the
room is filled with people
okay
that's let's call them higgs people if
you like right now brad pitt walks into
that room and he can't so easily move
about because everywhere he goes he gets
surrounded by these these higgs people
who sort of want to talk to him want to
be with him you know want to associate
themselves with him and so if you like
it's difficult for him to move about
it's like he's got sort of
you know a lot of mass if you like
that's the analogy of the higgs
mechanism really it's like you know you
fill permeate space with with this
particle so rather than being here it's
down here
and then that gives mass that
everything else sort of sort of absorbs
the mass from that that's not it at all
you have to talk about
broken gauge symmetry and different
groups and all sorts of things which are
too abstract
for even undergraduates we don't teach
them that it is a difficult subject for
undergraduates you need a
schooling in this subject before it
makes any sense what happened last week
what happened last week well
i don't want to say that they discovered
the higgs boson because they didn't
discover it
but there was a smoking gun shall we say
so last week was the sort of the
preliminary set of data that's that's
really important right because there's a
risk that everyone will say this is it
now it's all done this is a preliminary
set of data which is kind of the
culmination of the initial runs that
were done throughout this year up until
i think about october
runs of the lhc protons going around the
lhc and looking at the collisions
and two groups announced results two of
the experiments the atlas experiment and
the cms experiment and both were
specifically looking for signatures of
the higgs particle
and they've both seen
what looked like excess events that
means events above what the background
would be and above what you would
naturally think you should get from the
standard model
and
these events are at a over a certain
mass range as i said about 125 times the
mass of the proton
and what they're hoping is that
as more and more data is taken the
significance of these events well it
will either grow so they'll see more and
more of these events building building
building above the background like a
volcano rising up
or if these events are not really due to
a higgs what they'll see over the course
of the next few months is these events
basically disappearing back into the
background noise again i guess what
would have been more interesting is if
they hadn't found it right because then
we'd be thinking oh right okay where did
all this mass come from so of course
it's the higgs particle that's after
peter higgs the
particle physicist in edinburgh i got
higgs here if i can find it this is
1964
peter higgs
broken symmetries that's the paper where
he comes up with a version which is
written in the language of particle
theorists which is lagrangians and
covariant derivatives and all sorts of
frightening mathematics and it's
frightening for me
because i'm not used to this language
this work was done back in the 1960s
okay it it actually i was thinking about
this earlier today that it just shows
you you know that you work on the
topical things you work on the exciting
things in the 1960s people were working
on the standard model and of course they
realized there was this problem with the
masses of the gauge particles and they
knew they had to come up with a
mechanism to give the gauge particles
masses the standard model had them all
massless so not surprisingly it wasn't
just peter higgs working on this there
was a group uh brout and anglais were
working on it in belgium and then there
was a group of three people working on
it in in at imperial college including a
good friend of mine tom kibble
and the paper they were working
independently of each other on different
aspects of it
and in fact the papers all appeared
within a few months of each other in
fact almost a few weeks of each other it
will always be known as a higgs
mechanism in the community and it will
be outrageous if he's not rewarded but
if the higgs boson hasn't been
discovered
no prizes will be awarded so it's
contingent it depends on whether they
actually see it if they do see it
it's going to be somebody in that group
who do you give the credit to it i
remember at one stage when it used to be
called the higgs kibble mechanism and
then it became the higgs mechanism
and who knows where i mean
it looks of course it looks like it's
got to go to hicks if if a prize is
given um but
there's this crazy rule i think in the
nobel panel which is meant to go to no
more than three people
well brought sadly died earlier this
year
um historically the order in terms of
publications is brought in anglais
then higgs and then kibble and his
collaborators
and so um
you've potentially got higgs and anglais
and then you've got the three
collaborators so
it's a difficult call i'm not going to
call it
but one of the three of them should get
it
i think they should abandon this three
people maximum and give it to the whole
five of them
yeah it was such an exciting time brady
i mean you know
you must be picking up on it right in
particle physics it's just
great time right with the neutrinos
and then you've got the spherical
electrons and you've got the lhc just
producing this amazing data yeah we were
all excited and then we it was all a bit
of a damp squib for us because we went
over to watch it all on a big screen we
did watch it on the internet and it was
it was
it wasn't great because uh
the internet connection was rubbish not
not nottingham but it's said so we had
it all hooked up onto a big screen you
know like and uh the stream was just
rubbish and it's kind of ironic because
the guys at cern invented the internet
and yet the internet connection wasn't
working very well