Citation: S. Navas et al. (Particle Data Group), Phys. Rev. D 110, 030001 (2024)

I (J P ) = 1( 21 + ) Status:

Σ0

∗∗∗∗

COURANT 63 and ALFF 65, using Σ 0 → Λe + e − decays (Dalitzdecays), determined the Σ 0 parity to be positive, given that J = 1/2
and that certain very reasonable assumptions about form factors aretrue. The results of experiments involving the Primakoff effect, fromwhich the Σ 0 mean life and Σ 0 → Λ transition magnetic moment
come (see below), strongly support J = 1/2.

Σ 0 MASS
The fit uses Σ + , Σ 0 , Σ − , and Λ mass and mass-difference measurements.
VALUE (MeV)EVTS

DOCUMENT ID

TECNCOMMENT

1192.642± 0.024 OUR FIT• • • We do not use the following data for averages, fits, limits, etc. • • •1 WANG
1192.65 ± 0.020 ± 0.014
3327
97 SPEC Σ 0 → Λ γ →(p π − ) (e + e − )1 This WANG 97 result is redundant with the Σ 0 -Λ mass-difference measurement below.

mΣ − − mΣ 0VALUE (MeV)EVTS

DOCUMENT ID

TECNCOMMENT

4.807± 0.035 OUR FIT Error includes scale factor of 1.1.
4.86 ± 0.08 OUR AVERAGE Error includes scale factor of 1.2.
4.87 ± 0.1237
DOSCH65 HBC
5.01 ± 0.1212
SCHMIDT
65 HBCSee note with Λ mass
4.75 ± 0.118
BURNSTEIN 64 HBCmΣ 0 − mΛ
VALUE (MeV)EVTS

DOCUMENT ID

TECN

76.959± 0.023 OUR FIT
76.966± 0.020 ± 0.013 3327

WANG

97

SPEC

76.63 ± 0.28

SCHMIDT65

HBCCOMMENT

Σ0 → Λγ →(p π − ) (e + e − )• • • We do not use the following data for averages, fits, limits, etc. • • •76.23 ± 0.55
109
COLAS
75 HLBC Σ 0 → Λ γ
208

See note with Λ mass

Σ 0 MEAN LIFE
These lifetimes are deduced from measurements of the cross sections forthe Primakoff process Λ → Σ 0 in nuclear Coulomb fields. An alternative expression of the same information is the Σ 0 -Λ transition magnetic
moment given in the following section. The relation is (µ Σ Λ /µ N )2 τ =1.92951 × 10−19 s (see DEVLIN 86).

https://pdg.lbl.gov

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Citation: S. Navas et al. (Particle Data Group), Phys. Rev. D 110, 030001 (2024)

VALUE (10−20 s)

DOCUMENT ID

7.4± 0.7 OUR EVALUATION+ 1.7
6.5 −1.1TECNCOMMENTUsing µ Σ Λ (see the above note).
2 DEVLIN

86

SPECPrimakoff effect

3 PETERSEN

7.6± 0.5± 0.7
86 SPEC Primakoff effect• • • We do not use the following data for averages, fits, limits, etc. • • •2 DYDAK5.8± 1.3
77 SPEC See DEVLIN 86
2 DEVLIN 86 is a recalculation of the results of DYDAK 77 removing a numerical approximation made in that work.
3 An additional uncertainty of the Primakoff formalism is estimated to be < 5%.

µ(Σ 0 → Λ) TRANSITION MAGNETIC MOMENT
See the note in the Σ 0 mean-life section above. Also, See the “QuarkModel” review.
VALUE (µN )DOCUMENT ID

TECNCOMMENT

1.61± 0.08 OUR AVERAGE+ 0.17
4 DEVLIN
1.72 −86 SPEC Primakoff effect0.19
51.59± 0.05 ± 0.07
PETERSEN
86 SPEC Primakoff effect• • • We do not use the following data for averages, fits, limits, etc. • • •+ 0.25
1.82 −0.18

4 DYDAK77

SPECSee DEVLIN 86

4 DEVLIN 86 is a recalculation of the results of DYDAK 77 removing a numerical approximation made in that work.
5 An additional uncertainty of the Primakoff formalism is estimated to be < 2.5%.

Σ 0 DECAY MODES

Γ1
Γ2
Γ3ModeFraction (Γi /Γ)Λγ
Λγ γ
Λ e+ e−<Confidence level

100 %
[a]

3%
5 × 10−390%[a] A theoretical value using QED.
Σ 0 BRANCHING RATIOSΓ Λ γ γ /Γtotal

Γ2 /Γ

VALUE

CL%

DOCUMENT ID<0.0390COLASTECN75HLBCΓ Λ e + e − /Γtotal

Γ3 /Γ
See COURANT 63 and ALFF 65 for measurements of the invariant-mass spectrum ofthe Dalitz pairs.

VALUE

DOCUMENT ID

0.00545

FEINBERG

https://pdg.lbl.gov

Page 2

COMMENT58

Theoretical QED calculation

Created: 5/31/2024 10:15

Citation: S. Navas et al. (Particle Data Group), Phys. Rev. D 110, 030001 (2024)

Σ 0 REFERENCES
WANG
DEVLINPETERSEN
DYDAK
COLAS
ALFF
DOSCH
SCHMIDTBURNSTEIN
COURANTFEINBERG

9786867775
656565646358

PR D56 2544
PR D34 1626
PRL 57 949
NP B118 1
NP B91 253
PR 137 B1105
PL 14 239
PR 140 B1328
PRL 13 66
PRL 10 409
PR 109 1019

https://pdg.lbl.gov

M.H.L.S. Wang et al.
(BNL-E766 Collab.)
T. Devlin, P.C. Petersen, A. Beretvas(RUTG)
P.C. Petersen et al.
(RUTG, WISC, MICH+)
F. Dydak et al.
(CERN, DORT, HEIDH)
J. Colas et al.
(ORSAY)
C. Alff et al.
(COLU, RUTG, BNL) P
H.C. Dosch et al.
(HEID)
P. Schmidt(COLU)
R.A. Burnstein et al.
(UMD)
H. Courant et al.
(CERN, UMD) P
G. Feinberg(BNL)

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