Particle Collider Event Display
How to use the collider event display
- Choose an event type and click Collide. Protons meet at the centre and the products fly out through the tracker (inner cylinder), the calorimeters (the ring that lights up) and the muon chambers (outer cylinders).
- Charged particles curve in the magnetic field: tighter curves mean lower momentum. Raise the field to see them curl more.
- For Z and Higgs events, the invariant mass is rebuilt from the leptons' momenta, which is how those particles are found in real data.
Frequently asked questions
What are the parts of the detector?
From the inside out: a tracker that records the paths of charged particles, calorimeters that stop particles and measure their energy (light-coloured towers), and muon chambers on the outside, which only muons reach. Neutrinos leave without a trace and show up as missing energy.
What is invariant mass?
The mass of the particle that decayed, computed from the energies and momenta of its decay products: m² = E² − p². Two muons from a Z boson give about 91 GeV; four leptons from a Higgs give about 125 GeV. Plotting it for many events shows a peak at the particle's mass above a smooth background.
Is this real collision data?
No. The events are generated at random to look like typical LHC events: soft tracks from the proton remnants, back-to-back jets, or a heavy particle decaying to leptons with the right mass. Real events are messier, with pile-up from several collisions at once.
Why do tracks curve?
A charged particle in a magnetic field feels a force at right angles to its motion and follows a circle of radius r = p ÷ (qB). Measuring the curvature gives the momentum, and the direction of the curve gives the sign of the charge.
It says WebGL is turned off.
The 3D view needs WebGL, which every current browser has. It can be switched off by hardware acceleration being disabled in the browser settings, or by a very old graphics driver. Turn hardware acceleration on, or try another browser.
Is anything uploaded?
No. The simulation is drawn by your own browser with WebGL; nothing is sent anywhere, and it keeps working offline once the page has loaded.