Click Below to
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
The standard model does not explain what causes particles and some bosons to have masses.  In particular, the Electroweak theory shows that the weak nuclear force and the electromagnetic force are manifestations of the same underlying force at very high temperatures, so why is the photon massless while the intermediate vector bosons, the W+, W- and Z, are very heavy at around 90 times the proton mass?  There must have been a spontaneous symmetry breaking as the hot universe cooled.  Current theory attributes the symmetry breaking to the Higgs Field which requires a new particle and force mediator which is called the Higgs boson.  It proposes that space is filled with the background Higgs field, called the Higgs condensate, and it is interaction with this background field that generates mass.  Think of when you walk through water; your legs feel much heavier than when you walk through air.  On the other hand, there is very little difference when moving a knife blade, edge first, through air or water.  A photon or gluon is rather like the knife blade, so does not acquire mass from the Higgs field, whereas the intermediate vector bosons are more like your leg, and do acquire mass.  The Higgs has zero spin, no charge and is its own antiparticle. 

It is named for Peter Higgs who first proposed the mechanism in 1964.  A number of other researchers also suggested it around the same time, but Higgs seems to have won the naming game!  He and Francois Englert received the Nobel physics prize for the discovery in 2013.  The Higgs mechanism also gives mass to leptons and quarks, and explains why the
W+, W- and Z intermediate vector bosons all have mass, while the photon and the gluons do not. 

Higgs - The Higgs Boson



Standard Model

Forces & Bosons -
The CMS and the ATLAS groups at the Large Hadron Collider both announced that they found evidence of a new boson on July 4th 2012.  CMS found the mass to be 125.3 0.6 GeV, while the Atlas team found the mass to be 126.5 GeV.  It appears to be "consistent with" the expected bahaviour of the Higgs Boson with both experiments quoting a confidence level of 5 sigma (equivalent to less than one part in one million of an error).  By July 31st 2012, Atlas had improved their results to 5.9 sigma (equivalent to less than one part in five hundred million of an error).  Thus, it was generally confirmed that a new boson had been discovered, but it was not confirmed as being the Higgs. 

By mid 2013, following extensive analysis of the experimental data, it had become clear that it was a Higgs boson though it seems that there is a long way to go to determine what kind of Higgs boson it is.  The data from both detectors was analyzed to ensure that the quantum properties of the boson were consistent with the properties predicted by physics.