Thebeta−particle(orβor[math]β−[/math])isnothingelsethanourgoodfriendtheelectron.
Itwascalledlikethatbecausewhenradioactivitywasdiscovered,wedidnotyetunderstandwhatwashappeningexactly…andonlylaterweunderstoodthatthe“radiation”calledα,[math]β[/math]and[math]γ[/math]whererespectivelyHelium−4nuclei,electronsandphotons.
Theβ+istheantiparticleoftheelectron,i.e.thepositron,whichisidenticaltotheelectronexceptithasapositivecharge.