List of baryons

This is a list of baryons, which are the family of subatomic particles with a baryon number of 1. The term baryon is usually used to refer to triquarks — baryons made of three quarks. "Exotic" baryons made of four quarks and one anti-quark, known as the pentaquarks, are also listed, but their existence is not generally accepted. Each baryon have a corresponding antiparticle (anti-baryon) where quarks are replaced by their corresponding antiquarks and their corresponding anti-quarks replaced by quarks. For example, a proton is made of two up quarks and one down quark, and the anti-proton is made of two up antiquarks and one down antiquark.

Baryons are a subset of the hadrons (which are the particles made of quarks) and participate in the strong interaction.

Overview

File:Barion decuplet.svg

Combinations of three u, d or s-quarks forming baryons with a spin-3⁄2 form the baryon decuplet.

Baryons are classified into groups according to their isospin values and quark content. There are six groups of triquarks — nucleon (
N
), Delta (
Δ
), Lambda (
Λ
), Sigma (
Σ
), Xi (
Ξ
), and Omega (
Ω
). The rules for classification are defined by the Particle Data Group. These rules consider the
u
,
d
and
s
quarks to be light and the
c
,
b
, and
t
to be heavy. The rules cover all the particles that can be made from three of each of the six quarks (up, down, strange, charm, bottom, top) — even though baryons made of top quarks are not expected to exist because of the top quark's short lifetime — but not pentaquarks.^[1]:

Baryons with three
u
and/or
d
quarks are
N
's (isospin 1⁄2) or
Δ
's (isospin 3⁄2).
Baryons with two
u
and/or
d
quarks are
Λ
's (isospin 0) or
Σ
's (isospin 1). If the third quark is heavy, its identity is given by a subscript.
Baryons with one
u
or
d
quark are
Ξ
's (isospin 1⁄2). One or two subscripts are used if one or both of the remaining quarks are heavy.
Baryons with no
u
or
d
quarks are
Ω
's (isospin 0), and subscripts indicate any heavy quark content.
Baryons that decay strongly have their masses as part of their names. For example, Sigmas (
Σ
) and Omegas (
Ω
) do not decay strongly, but Deltas (
Δ
(1232)), and charmed Xis (
Ξ⁺
_c(2645)) do.

Quarks carry charge, so knowing the charge of a particle indirectly gives the quark content. For example, the rules above say that the
Σ
_b contains a bottom and some combination of two up and/or down quarks. A
Σ⁰
_b must be one up quark (Q=2⁄3), one down quark (Q=−1⁄3), and one bottom quark (Q=−1⁄3) to have the correct charge (Q=0).

The number of baryons within one group (excluding resonances) is given by the number of isospin projections possible (2 × isospin + 1). For example there are four
Δ
's, corresponding to the four isospin projections of the isospin value I = 3⁄2:
Δ⁺⁺
(I_z = 3⁄2),
Δ⁺
(I_z = 1⁄2),
Δ⁰
(I_z = −1⁄2), and
Δ⁻
(I_z = −3⁄2). Another example would be the three
Σ
_b's, corresponding to the three isospin projections of the isospin value I = 1:
Σ⁺
_b (I_z = 1),
Σ⁰
_b(I_z = 0), and
Σ⁻
_b(I_z = −1).

Relation between isospin and up and down quark content

Up and down quarks each carry isospin 1⁄2. Due to Pauli's exclusion principle, quarks of the same flavor must have their isospin aligned. Three aligned up and down quarks would make a particle with isospin 3⁄2, while two up quarks (who must be aligned) and a strange quark would make a particle with isospin 1.

Particles of isospin 3⁄2 can only be made by a mixture of three aligned u and d quarks (Δs):

The four
Δ
s are:

Δ⁺⁺
(uuu),
Δ⁺
(uud),
Δ⁰
(udd),
Δ⁻
(ddd)

Particles of isospin 1 are made of two aligned u quarks, two aligned u and d quarks, or two aligned d quarks (Σs).

The nine
Σ
s are:

Σ⁺
(uus),
Σ⁰
(uds),
Σ⁺
(dds),

Σ⁺⁺
_c (uuc),
Σ⁺
_c (udc),
Σ⁰
_c (ddc),

Σ⁺
_b (uub),
Σ⁰
_b (udb),
Σ⁻
_b (ddb)

Particles of isospin 1⁄2 can be made of two aligned u quarks and one unaligned d quark, or two aligned d quarks and one unaligned u quarks (Ns). They can also be made of one u or d quark (Ξs).

The two
N
s are:

p⁺
(uud),
n⁰
(udd)

The twelve
Ξ
s are:

Ξ⁰
(uss),
Ξ⁻
(dss),

Ξ⁺
_c (usc),
Ξ⁰
_c (dsc),

Ξ⁺⁺
_cc (ucc),
Ξ⁺
_cc (dcc),

Ξ⁰
_b (usb),
Ξ⁻
_b (dsb),

Ξ⁺
_cb (ucb),
Ξ⁰
_cb (dcb),

Ξ⁰
_bb (ubb),
Ξ⁻
_bb (dbb)

Particles of isospin 0 can be made two unaligned u and d quarks (Λs), or of no u or d quarks at all (Ωs):

The three
Λ
s are:

Λ⁰
(uds),

Λ⁺
_c (udc),

Λ⁰
_b (udb)

The ten
Ω
s are:

Ω⁻
(sss),
Ω⁰
_c (ssc),
Ω⁺
_cc (scc),
Ω⁻
_b (ssb),
Ω⁰
_cb (scb),
Ω⁻
_bb (sbb)

Ω⁺⁺
_ccc (ccc},
Ω⁺
_ccb (ccb),
Ω⁰
_cbb (cbb),

Ω⁻
_bbb (bbb)

Baryons (triquarks)

This list details all known and predicted ground triquark states. Resonances (excited states) have not been included, but can be found in their individual particle group page. Antiparticles are also not listed in the table; however, they simply would have all quarks changed to antiquarks, and their baryon number (B),charge (Q), strangeness (S), charm (C), and bottomness (B′) quantum numbers would have their signs flipped.

All the particle listed have baryon numbers of +1. Particles with ^† next to their names have been predicted by the standard model but not yet observed. Isospin (I) , spin (J), and parity (P) values with * have not been established, but are predicted by the quark model.^[2]^[3]

Baryons (triquarks)
Particle	Symbol	Quark content	Rest mass MeV/c²	Isospin I	Spin(Parity) J^P	Q	S	C	B′	Mean lifetime s	Commonly decays to
Proton ^[4]	p / p⁺ / N⁺	u u d	938.272 023 ± 0.000 080[a]	1⁄2	1⁄2⁺	+1	0	0	0	Stable^[b]	Unobserved
Neutron ^[5]	n / n⁰ / N⁰	d d u	939.565 360 ± 0.000 081[a]	1⁄2	1⁄2⁺	0	0	0	0	885.7 ± 0.8^[c]	p⁺ + e⁻ + ν _e
Delta ^[6]	Δ⁺⁺ (1232)	u u u	1232 ± 1	3⁄2	3⁄2⁺	+2	0	0	0	6×10⁻²⁴ ^[7]	p⁺ + π⁺
Delta ^[6]	Δ⁺ (1232)	u u d	1 232 ± 1	3⁄2	3⁄2⁺	+1	0	0	0	6×10⁻²⁴ ^[7]	π⁺ + n⁰ or π⁰ + p⁺
Delta ^[6]	Δ⁰ (1232)	u d d	1 232 ± 1	3⁄2	3⁄2⁺	0	0	0	0	6×10⁻²⁴ ^[7]	π⁰ + n⁰ or π⁻ + p⁺
Delta ^[6]	Δ⁻ (1232)	d d d	1 232 ± 1	3⁄2	3⁄2⁺	−1	0	0	0	6×10⁻²⁴ ^[7]	π⁻ + n⁰
Lambda ^[8]	Λ⁰	u d s	1 115.683 ± 0.006	0	1⁄2⁺	0	−1	0	0	2.60×10⁻¹⁰ ^[7]	p⁺ + π⁻ or n⁰ + π⁰
charmed Lambda ^[9]	Λ⁺ _c	u d c	2 286.46 ± 0.14	0	1⁄2* ⁺	+1	0	+1	0	(2.00±0.06)×10⁻¹³	See Λ⁺ _c Decay Modes
bottom Lambda ^[10]	Λ⁰ _b	u d b	5 620.2 ± 1.6	0*	1⁄2* ^{+^*}	0	0	0	−1	1.409+0.055 −0.054×10⁻¹²	See Λ⁰ _b Decay Modes
Sigma ^[11]	Σ⁺	u u s	1 189.37 ± 0.07	1	1⁄2⁺	+1	−1	0	0	(8.018±0.026)×10⁻¹¹	p⁺ + π⁰ or n⁰ + π⁺
Sigma ^[12]	Σ⁰	u d s	1 192.642 ± 0.024	1	1⁄2⁺	0	−1	0	0	(7.4±0.7)×10⁻²⁰	Λ⁰ + γ
Sigma ^[13]	Σ⁻	d d s	1 197.449 ± 0.030	1	1⁄2⁺	−1	−1	0	0	(1.479±0.011)×10⁻¹⁰	n⁰ + π⁻
charmed Sigma ^[14]	Σ⁺⁺ _c(2455)	u u c	2 454.02 ± 0.18	1	1⁄2* ^{+^*}	+2	0	+1	0		Λ⁺ _c + π⁺
charmed Sigma ^[14]	Σ⁺ _c(2455)	u d c	2 452.9 ± 0.4	1	1⁄2* ^{+^*}	+1	0	+1	0		Λ⁺ _c + π⁰
charmed Sigma ^[14]	Σ⁰ _c(2455)	d d c	2 453.76 ± 0.18	1	1⁄2* ^{+^*}	0	0	+1	0		Λ⁺ _c + π⁻
bottom Sigma ^[15]	Σ⁺ _b	u u b	5 807.8+3.7 −3.9	1*	1⁄2* ^{+^*}	+1	0	0	−1		Λ⁰ _b + π⁺
bottom Sigma^†	Σ⁰ _b	u d b		1*	1⁄2* ^{+^*}	0	0	0	−1
bottom Sigma ^[15]	Σ⁻ _b	d d b	5 815.2 ± 2.7	1*	1⁄2* ^{+^*}	−1	0	0	−1		Λ⁰ _b + π⁻
Xi ^[16]	Ξ⁰	u s s	1 314.83 ± 0.20	1⁄2	1⁄2^{+^*}	0	−2	0	0	(2.90±0.09)×10⁻¹⁰	Λ⁰ + π⁰
Xi ^[17]	Ξ⁻	d s s	1321.31 ± 0.13	1⁄2	1⁄2^{+^*}	−1	−2	0	0	(1.639±0.015)×10⁻¹⁰	Λ⁰ + π⁻
charmed Xi^[18]	Ξ⁺ _c	u s c	2 467.9 ± 0.4	1⁄2	1⁄2* ^{+^*}	+1	−1	+1	0	(4.42±0.26)×10⁻¹³	See Ξ⁺ _c Decay Modes
charmed Xi^[18]	Ξ⁰ _c	d s c	2 471.0 ± 0.4	1⁄2	1⁄2* ^{+^*}	0	−1	+1	0	1.12+0.13 −0.10×10⁻¹³	See Ξ⁰ _c Decay Modes
double charmed Xi^†	Ξ⁺⁺ _cc	u c c		1⁄2*	1⁄2* ^{+^*}	+2	0	+2	0
double charmed Xi^[c] ^[19]	Ξ⁺ _cc	d c c	3 518.9 ± 0.9^[c]	1⁄2*	1⁄2* ^{+^*}	+1	0	+2	0	<3.3×10⁻¹⁴^[d]	Λ⁺ _c + K⁻ + π⁺ ^[d] or p⁺ + D⁺ + K⁻ ^[d]
bottom Xi ^[20]	Ξ⁰ _b	u s b	5 792 ± 3	1⁄2*	1⁄2* ⁺*	0	−1	0	−1	1.42+0.28 −0.24×10¹²^[e]	See Ξ _b Decay Modes
bottom Xi or Cascade B ^[20]^[21]^[22]	Ξ⁻ _b	d s b	5 792.9 ± 3.0	1⁄2*	1⁄2* ^{+^*}	−1	−1	0	−1	1.42×10⁻¹²	See Ξ _b Decay Modes ( Ξ⁻ + J/ψ was also seen)
double bottom Xi^†	Ξ⁰ _bb	u b b		1⁄2*	1⁄2* ^{+^*}	0	0	0	−2
double bottom Xi^†	Ξ⁻ _bb	d b b		1⁄2*	1⁄2* ^{+^*}	−1	0	0	−2
charmed bottom Xi^†	Ξ⁺ _cb	u c b		1⁄2*	1⁄2* ⁺	+1	0	+1	−1
charmed bottom Xi^†	Ξ⁰ _cb	d c b		1⁄2*	1⁄2* ^{+^*}	0	0	+1	−1
Omega^[23]	Ω⁻	s s s	1 672.45 ± 29	0	3⁄2⁺	−1	−3	0	0	(8.21±0.11)×10⁻¹¹	Λ⁰ + K⁻ or Ξ⁰ + π⁻ or Ξ⁻ + π⁰
charmed Omega^[24]	Ω⁰ _c	s s c	2 697.5 ± 2.6	0	1⁄2* ^{+^*}	0	−2	+1	0	(6.9±1.2)×10⁻¹⁴	See Ω⁰ _c Decay Modes
bottom Omega^†	Ω⁻ _b	s s b		0*	1⁄2* ^{+^*}	−1	−2	0	−1
double charmed Omega^†	Ω⁺ _cc	s c c		0*	1⁄2* ^{+^*}	+1	−1	+2	0
charmed bottom Omega^†	Ω⁰ _cb	s c b		0*	1⁄2* ^{+^*}	0	−1	+1	−1
double bottom Omega^†	Ω⁻ _bb	s b b		0*	1⁄2* ^{+^*}	−1	−1	0	−2
triple charmed Omega^†	Ω⁺⁺ _ccc	c c c		0*	3⁄2* ^{+^*}	+2	0	+3	0
double charmed bottom Omega^†	Ω⁺ _ccb	c c b		0*	1⁄2* ^{+^*}	+1	0	+2	−1
Charmed double bottom Omega^†	Ω⁰ _cbb	c b b		0*	1⁄2* ^{+^*}	0	0	+1	−2
triple bottom Omega^†	Ω⁻ _bbb	b b b		0*	3⁄2* ^{+^*}	−1	0	0	−3

^[a]The masses of the proton and neutron are known with much better precision in atomic mass units than in Electron volt/c², due to the relatively poorly known value of the elementary charge. In atomic mass unit, the mass of the proton is 1.00727646688(13) u while that of the neutron is 1.00866491560(55) u.
^[b] At least 10³⁵ years. See proton decay.
^[c] For free neutrons; in most common nuclei, neutrons are stable.
^[d] Some controversy exists about this data. See references
^[e] This is actually a measurement of the average lifetime of b-baryons that decay to a jet containing a same sign
Ξ
^∓
ℓ
^∓ pair. Presumably the mix is mainly
Ξ
_b, with some
Λ
_b.

Exotic baryons (pentaquarks)

This lists details pentaquarks reported to exist. However, other groups have looked for them and reported to have found nothing. The existence of pentaquarks is generally not accepted.

Exotic baryons (pentaquarks)
Particle	Symbol	Quark content	Rest mass MeV/c²	Isospin I	Spin(Parity) J^P	Q	S	C	Commonly decays to
Theta^† ^[25]	Θ⁺ (1540)	u u d d s	1 533.6±2.4	0	?^?	+1	+1	0	K⁰ + p⁺ or K⁺ + n⁰
Charmed Theta^† ^[26]	Θ⁰ _c (3100)	u u d d c	3 099(8)	0	?^?	0	0	−1
Phi^† ^[27]	Φ⁰ (1860)	s s d d u	1 862±2	3⁄2	?^?	0	−2	0

^† Data is controversial to the point that many do not consider these particles discovered. See references.

References

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^ W.-M. Yao; et al. (2006). "Particle summary tables - Baryon" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-25. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ J. G. Körner, M. Krämer, and D. Pirjol (1994). "Heavy Baryons". Progress in Particle and Nuclear Physics. 33: 787–868. Retrieved 2008-04-25.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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^ W.-M. Yao; et al. (2006). "Particle listings -Neutron" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ ^a ^b ^c ^d W.-M. Yao; et al. (2006). "Particle listings - Delta(1232)" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ ^a ^b ^c ^d ^e "Physics Particle Overview - Baryons". Retrieved 2008-04-20.
^ W.-M. Yao; et al. (2006). "Particle listings - Lambda" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ W.-M. Yao; et al. (2006). "Particle listings - Charmed Lambda" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ W.-M. Yao; et al. (2006). "Particle listings - Bottom Lambda" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ W.-M. Yao; et al. (2006). "Particle listings - Sigma⁺" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ W.-M. Yao; et al. (2006). "Particle listings - Sigma⁰" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
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^ ^a ^b ^c W.-M. Yao; et al. (2006). "Particle listings - Charmed Sigma(2455)" (PDF). Journal of Physics G. 33 (1). Particle Data Group. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ ^a ^b T. Aaltonen; et al. (2007). "First Observation of Heavy Baryons
Σ
_b and
Σ^∗
_b" (PDF). Phys. Rev. Lett. 99. CDF Collaboration. Retrieved 2008-04-20. {{cite journal}}: Explicit use of et al. in: |author= (help)
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^ V. M. Abazov; et al. (2007). "Direct observation of the strange b baryon Xi(b)-". Physical Review Letters. 99: 052001. Retrieved 2008-04-25. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ T. Aaltonen; et al. (2007). "Observation and mass measurement of the baryon Xi(b)-". Physical Review Letters. 99: 052002. Retrieved 2008-04-25. {{cite journal}}: Explicit use of et al. in: |author= (help)
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