Citation: W.-M. Yao
et al.
(Particle Data Group), J. Phys. G
33
, 1 (2006) (URL: http://pdg.lbl.gov)
QUARKS
QUARKS
QUARKS
QUARKS
The
u
-,
d
-, and
s
-quark masses are estimates of so-called “current-
quark masses,” in a mass-independent subtraction scheme such as
MS at a scale
µ
≈
2 GeV. The
c
- and
b
-quark masses are the
“running” masses in the MS scheme. For the
b
-quark we also
quote the 1S mass. These can be different from the heavy quark
masses obtained in potential models.
uuuu
I
(
JP
) =
1
2
(
1
2
+)
Mass
m
= 1
.
5 to 3
.
0 MeV
[
a
]
Charge =
2
3
e
I
z
= +
1
2
m
u
/
m
d
= 0
.
3 to 0
.
6
dddd
I
(
JP
) =
1
2
(
1
2
+)
Mass
m
= 3 to 7 MeV
[
a
]
Charge =
−
1
3
e
I
z
=
−
1
2
m
s
/
m
d
= 17 to 22
m
= (
m
u
+
m
d
)/2 = 2
.
5 to 5
.
5 MeV
ssss
I
(
JP
) = 0(
1
2
+)
Mass
m
= 95
±
25 MeV
[
a
]
Charge =
−
1
3
e
Strangeness =
−
1
(
m
s
– (
m
u
+
m
d
)/2)
(
m
d
−
m
u
) = 30 to 50
cccc
I
(
JP
) = 0(
1
2
+)
Mass
m
= 1
.
25
±
0
.
09 GeV
Charge =
2
3
e
Charm = +1
bbbb
I
(
JP
) = 0(
1
2
+)
Charge =
−
1
3
e
Bottom =
−
1
Mass
m
= 4
.
20
±
0
.
07 GeV
(MS mass)
Mass
m
= 4
.
70
±
0
.
07 GeV
(1S mass)
HTTP://PDG.LBL.GOV
Page 1
Created: 7/5/2006 10:38
Citation: W.-M. Yao
et al.
(Particle Data Group), J. Phys. G
33
, 1 (2006) (URL: http://pdg.lbl.gov)
tttt
I
(
JP
) = 0(
1
2
+)
Charge =
2
3
e
Top = +1
Mass
m
= 174
.
2
±
3
.
3 GeV
[
b
]
(direct observation of top events)
Mass
m
= 172
.
3
+ 10
.
2
−
7
.
6
GeV
(Standard Model electroweak fit)
p
t
DECAY MODES
t
DECAY MODES
t
DECAY MODES
t
DECAY MODES
Fraction (Γ
i
/Γ)
Confidence level (MeV/
c
)
W q
(
q
=
b
,
s
,
d
)
–
W b
–
ν
anything
[
c,d
]
( 9
.
4
±
2
.
4) %
–
τ ν
τ
b
–
γ
q
(
q
=
u
,
c
)
[
e
]
<
5
.
9
×
10
−
3
95%
–
∆
T
= 1 weak neutral current (
T1
) modes
∆
T
= 1 weak neutral current (
T1
) modes
∆
T
= 1 weak neutral current (
T1
) modes
∆
T
= 1 weak neutral current (
T1
) modes
Z q
(
q
=
u
,
c
)
T1
[
f
]
<
13
.
7
%
95%
–
b
(4
th
Generation) Quark, Searches for
b
(4
th
Generation) Quark, Searches for
b
(4
th
Generation) Quark, Searches for
b
(4
th
Generation) Quark, Searches for
Mass
m
>
190 GeV, CL = 95%
(
p p
, quasi-stable
b
)
Mass
m
>
199 GeV, CL = 95%
(
p p
, neutral-current decays)
Mass
m
>
128 GeV, CL = 95%
(
p p
, charged-current decays)
Mass
m
>
46
.
0 GeV, CL = 95%
(
e
+
e
−
, all decays)
Free Quark Searches
Free Quark Searches
Free Quark Searches
Free Quark Searches
All searches since 1977 have had negative results.
HTTP://PDG.LBL.GOV
Page 2
Created: 7/5/2006 10:38
Citation: W.-M. Yao
et al.
(Particle Data Group), J. Phys. G
33
, 1 (2006) (URL: http://pdg.lbl.gov)
NOTES
[
a
] The ratios
m
u
/
m
d
and
m
s
/
m
d
are extracted from pion and kaon masses
using chiral symmetry. The estimates of
u
and
d
masses are not without
controversy and remain under active investigation. Within the literature
there are even suggestions that the
u
quark could be essentially massless.
The
s
-quark mass is estimated from SU(3) splittings in hadron masses.
[
b
] Based on published top mass measurements using data from Tevatron
Run-I and Run-II. Including also the most recent unpublished results from
Run-II, the Tevatron Electroweak Working Group reports a top mass of
172
.
5
±
1
.
3
±
1
.
9 GeV. See the note “The Top Quark” in the Quark
Particle Listings of this
Review
.
[
c
]
means
e
or
µ
decay mode, not the sum over them.
[
d
] Assumes lepton universality and
W
-decay acceptance.
[
e
] This limit is for Γ(
t
→
γ
q
)/Γ(
t
→
W b
).
[
f
] This limit is for Γ(
t
→
Z q
)/Γ(
t
→
W b
).
HTTP://PDG.LBL.GOV
Page 3
Created: 7/5/2006 10:38