What is Pion?
[[File:Quark structure pion.svg|thumbnail|300px|right|One [[up quark]] (u) and one [[down quark|down antiquark]] are one combination to make a pion]]A '''pion''', '''π meson''', or '''pi meson''' is a type of [[meson]], made of one [[up quark]] (u) and one [[antimatter|down antiquark]] (d̅). Mesons are a category of [[subatomic particles]], which are composed of one [[quark]], and one [[antimatter|antiquark]]. There are six types of quarks (called ''flavours'') but only two ''flavours'' go together to make a pion. These flavours are called [[up quark|up]] and [[down quark|down]]. Quarks have [[electric charge|charge]], so two quarks of the same flavour (both up or both down) make a [[neutral]] pion. But when the two quarks have different flavours (up and down), the pion will have a charge. This charge is [[positive charge|positive]] when an up quark pairs with a down antiquark. The charge is [[negative charge|negative]] when a down quark pairs with an up antiquark. Pions do not exist for a long time. ([[mean lifetime|On average]], charged pions exist for around 26 [[nanosecond]]s; neutral pions last a tiny fraction of this). Pions are significant to our lives because they are one of the ways for [[strong force]] [[force|interaction]]s to take place between [[nucleon]]s like the [[proton]]s and [[neutron]]s of ordinary [[matter]]. These interactions hold the [[Nucleus (physics)|nucleus]] together. Pions are the lightest [[hadron]]s (particles made up of quarks) and pions with a positive or negative charge are the mesons with the longest ''mean lifetime'' (the average time that passes before they ''decay'' into [[lepton]]s). == Three Types of Pions == The three types of pion have the Greek letter [[pi]] in their symbols: ::π<sup>+</sup> for the positively charged pion ::π<sup>–</sup> for the negatively charged pion, and ::π<sup>0</sup> for the neutral pion. The ([[superscript]]) <sup>+</sup>, <sup>–</sup>, or <sup>0</sup> simply refers to the [[electromagnetism|(electromagnetic) charge]] of the pion. <!--π