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Upsilon meson
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<p>The Upsilon meson (ϒ) is a <a href="/facts/Quarkonium/YxVtcTd3">quarkonium</a> state (i.e. <a href="/facts/Flavour_(particle_physics)/RR7rsuTD">flavourless</a> <a href="/facts/Meson/9R0kIc1q">meson</a>) formed from a <a href="/facts/Bottom_quark/2s4rJRSo">bottom quark</a> and its <a href="/facts/Antiparticle/7Ic43ThI">antiparticle</a>. It was discovered by the E288 experiment team, headed by <a href="/facts/Leon_Lederman/3UT17nBB">Leon Lederman</a>, at <a href="/facts/Fermilab/8yyTx3oj">Fermilab</a> in 1977, and was the first particle containing a bottom quark to be discovered because it is the lightest that can be produced without additional massive particles. It has a <a href="/facts/Mean_lifetime/wLB1zYDP">lifetime</a> of 1.21×10−20 <a href="/facts/Second/jtFxnJXx">s</a> and a mass about 9.46 <a href="/facts/Electronvolt/YMT1fqX9">GeV/<i>c</i>2</a> in the ground state. </p>