Related Clues:

• Particle has complicated route between two points
• Nearly massless subatomic particle
• It contains an up quark and two down quarks
• New and revised interpretation of routine output from cyclotron?
• Urine not analysed for tiny particle
• Heartless upstart right to cut gas for which there's no charge
• Particle beginning to trigger inside nerve cell
• Urine not flowing? It should pass right through you!
• Time to enter cell — it's free of charge
• Particle of dirt ultimately found in nerve cell
• Nationalist in routine wrangling — one has almost zero impact
• Turn one out, identifying particle
• Proton partner