What are pentaquarks
Quarks and leptons are the fundamental particles that make up matter and we think they're fundamental simply because we haven't found anything
smaller inside them no other constituents
Quarks make up the protons and neutrons that form atomic nuclei which are orbited in turn by electrons
Which are a type of lepton
now you can find leptons singly in the universe but quarks always come linked up by one of the
fundamental forces the strong force in particles that we call hadrons
Usually this is a combination of a quark and antiquark in a particle
we call a meson or else a combination of one quiet with two other quarks to make a baryon and
Protons and neutrons are examples of baryons
now the reason why quarks quite literally stick together in this way is because they have a property called color charge and
color charge is associated to the strong force in exactly the same way that an electric charge is
Associated to the electric force acts as a source for the force to act on in the case of the color charge though
There's actually three types and we label these red green and blue
now particles inside
hadrons
occupy colorless objects which means to say that the quarks inside a meson or baryon their color charges cancel each other out
So overall, the object is neutral and it doesn't experience the strong force
Now there's no reason why you should only get two or three quarks to form a hadron in principle
You could get any number at all. As long as they all link up in a combination whose color charges cancel each other out and
scientists have been looking for evidence of particles containing more quarks for years and years and years in
2003 we saw the first hints of a tetra quark
Particle containing four quarks and the discovery was confirmed in 2008 in
2015 the LHC B experiment discovered pentaquarks, a particle containing five quarks
Since then we've analyzed nine times as much data on LHC B
We've scrutinized our pentaquark signals further and we've learned much more about them
It turns out that LHC B is actually a really good environment for studying pentaquarks. And that's because the Large Hadron Collider
Collides its particle beams together 40 million times a second inside the experiment and in these collisions
Quarks and antiquarks are created that quickly form all types of hadrons
Including the super rare super elusive pentaquarks, giving us a chance on LHCb to study them
The only catch is that a pentaquark is not stable it decays quickly
So we can't see it directly with our experiment. So instead we have to look for pentaquarks by finding the particles that they decay to
So far on LHCb
We've been looking for pentaquarks that decay to a J/psi meson or a proton because these are particles that we can identify
Really well on LHC B, and that allows us to isolate
select and analyze these events from the LHC collisions in order to be able to search for
pentaquarks. Our data consists of signal and
background, but you can distinguish it by looking at the combined mass of the J/psi meson and the proton. If the mass
Accumulates at a particular characteristic value, then you have signal if you have a background combination and the mass is pretty random
when we looked at our data, we saw three Peaks each one of these Peaks corresponds to a new and
distinct pentaquark signal
Now this is really exciting because we don't know very much about
Pentaquarks and that in turn means we don't know that much about the behavior of the strong force that forms them
so for example
We don't even know if a pentaquark is made of a meson and a baryon that
Sit loosely together or if it's made of a really tightly held bundle of five quarks
but what we do know is that we have the experimental apparatus to study this further. Our
observation has shown us that we have the ability to
investigate
Pentaquarks. So although we don't know the answer yet, by the time we've analyzed more data we should be able to say something definitive
About how a pentaquark is formed and what sticks it together
Longer term you might be wondering why pentaquarks are so interesting or what relevance this has for your life
so in answer to that, I'd just like to point out the last time we really
Investigated a charge - the electric charge - which led to the discovery of electricity
Which was investigated in great detail by Michael Faraday here in the Royal Institution
Then this led to applications that have really revolutionized our lives in every aspect
So, who knows what is going to come out of our investigations of this color charge and the strong force?
We have no idea, but it's going to be really exciting to find out