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Select a Force:
Mediating Boson: Relative Strength: Effective Range
of the Force:
Strong Nuclear Gluon 1 10-17 cm.  This is about the same
size as a proton. 
Electromagnetic Photon 1/137th Essentially, this force operates over an infinite distance.
Weak Nuclear W± & Z 10-13 10-20 cm.  This is about 1/1000th the size of a proton. 
Higgs Higgs Unkown Unkown
Beta Minus decay:
a free neutron converts into a proton and emits an electron plus an electron anti-neutrino.  In fact, as the neutron comprises an up and two down quarks, it is one of the down quarks that changes into an up quark due to the interaction with a W- boson to form the proton.  The W- then decays into the electron and electron anti-neutrino.  Beta minus decay always produces an electron emission plus an electron anti-neutrino. 

Beta Plus decay:
a proton in the nucleus converts into a neutron and emits a positron and an electron neutrino.  Again, one of the two up quarks in the neutron changes into a down quark emitting a W+ that decays into  the positron and electron neutrino.  Beta plus decay always produces a positron emission plus an electron neutrino. 

Weak Nuclear Force - The W± & Z Bosons

The weak interaction involves the exchange of W-, W+ and Z Bosons.  The W- boson is the anti-particle of the W+, while the neutral Z boson is its own anti-particle.  Being so massive, each weighs much more than an atom of iron, the range of the force is very small.  When a particle emits or absorbs a Z boson, which has no electrical charge, only the spin, momentum, and energy are altered.  Emitting or absorbing a W boson can change one quark or lepton type into another. 

Electron/Neutrino Conversion:
An electron, for example, can convert into an electron neutrino, or a positron can convert into an electron anti-neutrino, by emitting or absorbing a W boson. 
Because the weak interaction is so weak, it proceeds slowly; for example, a neutral pion decays with a life of about 10-16 seconds via the electromagnetic force, while a charged pion decays in about 10-8 seconds and a free neutron lives for about 15 minutes before decaying, all via the weak interaction .  The weak interaction is crucial to the formation of stars as it allows protons to turn into neutrons.  This permits the formation of deuterium nuclei (one neutron and one proton) from hydrogen nuclei (one proton).  Generally, it is critical to the fusion process that forms heavier nuclei from lighter nuclei.   The force acts only on left-handed fermions and right-handed anti-fermions.  Only gravity and the weak interaction act on neutrinos. 


Standard Model

Forces & Bosons -