Baryons

• There is another whole class of unstable particles known as 'hyperons' , whose masses are each greater then that of protons.
• The first hyperon was found in cosmic rays named as Λ⁰ hypron , a neutral decaying particle.
• Charged particles seen in the decay were identified as proton and π^- meson, indicating a process

  Λ⁰ →p+π^-

• Anti-Λ⁰ hypron decay to an anti proton and π⁺-meson.
• The family of hyprons wit greatedt number of members is Σ-family.
• First if it to be observed is Σ⁺ with mass about 2328m_e , and two prominent decat schemes are

  Σ⁺→p+π⁰ ; Σ⁺→n+π⁺

• Σ^- has just one set of decay products

  Σ^-→n+π^-

  its mass being slightly greater than Σ⁺ and is 2341 m_e.

• Neutral Σ hyperon decays as

  Σ⁰→Λ⁰+γ

  its mass is 2328m_e

• The Σ hyperon form a triplet Σ⁺,Σ^- and Σ⁰. A corresponding triplet of anti Σ hyperon also exists.
• The anti particle of Σ⁺ can not be Σ^- because the two have slightly different masses, whereas particle anti particle must have exactly same masses.
• Another group of members belonging to hyperon family is Ξ hyperon originally called cascade particles.
• Theit negative and neutral forms have been observed with decay processes

  Ξ^-→Λ⁰+π^-

  Ξ⁰→Λ⁰+π⁰

  Their masses are about 2582 m_e

• Anti Ξ hyperons have been detected.
• Togather with nucleons (p and n) , the hyperons form the family of baryons.

Baryons(B=+1, L_e=L_μ=L_τ=0)

Particle	Symbol	mean life (s)	spin	S	Y	I	I3	Mass MeV/c2
Nucleon	n	stable	1/2	0	+1	1/2	-1/2	938.3
	p	886					+1/2	936.6
Lambda	Λ0	2.6×10-10	1/2	-1	0	0	0	1116
Sigma	Σ+	8.0×10-11	1/2	-1	0	1	+1	1189
	Σ0	6×10-20					0	1193
	Σ-	1.5×10-10					-1	1197
Xi	Ξ0	2.9×10-10	1/2	-2	-1	1/2	+1/2	1315
	Ξ-	1.6×10-10					-1/2	1321
Omega	Ω-	8.2×10-11	3/2	-3	-2		0	1672

• There is a sequence of decay for Ω^- baryon

  Ω^-→Ξ⁰+π^-→Λ⁰ +π⁰ ....

  Final result of decay is proton , two electrons and two photons.