Helicity (particle physics)

Helicity is a very big word that describes how some tiny particles in the world move around. You know how tiny things like atoms are made up of even smaller parts called particles, right? Well, some of these particles like electrons or photons have something called "spin".

Spin is kind of like how a top spins around and around. You know how a top can spin in one direction or the other, right? Well, particles can do that too - they can spin clockwise, or they can spin counterclockwise.

Now, when a particle spins, it also moves forward like it's traveling through space. But the way it moves forward is also important. It could be moving in the same direction as the spin, or it could be moving in the opposite direction. That's where helicity comes in - it tells us which way the particle is moving in relation to its spin.

Think of it like a race car going around a track. The car can go either clockwise or counterclockwise around the track, just like a particle can spin either clockwise or counterclockwise. But it can also be going forwards or backwards relative to its direction around the track, just like a particle can be moving in the same or opposite direction as its spin. Helicity tells us which way the particle is going relative to its spin and helps scientists understand how particles move and interact with each other.