Particle Physics Booklet - Particle Data Group - Lawrence Berkeley ...

10. Electroweak model and constraints on new physics 179
Table 10.5: Values of �s 2 Z , s2 W , αs, andM H [in GeV] for various
(combinations of) observables. Unless indicated otherwise, the top
quark mass, mt = 170.9±1.9 GeV, is used as an additional constraint
in the fits. The (†) symbol indicates a fixed parameter.
Data �s 2 Z s 2 W αs(M Z) M H
All data 0.23116(13) 0.22292(28) 0.1183(15) 90 +27
−22
All indirect (no mt) 0.23118(14) 0.22283(34) 0.1183(16) 112 +110
− 52
Z pole (no mt) 0.23121(17) 0.22311(59) 0.1198(28) 90 +114
− 44
LEP 1 (no mt) 0.23152(21) 0.22376(67) 0.1213(30) 170 +234
− 93
SLD + MZ 0.23067(29) 0.22201(54) 0.1183 (†) 33 +27
−17
A (b,c)
FB + MZ 0.23193(28) 0.22484(76) 0.1183 (†) 389 +264
−158
MW + MZ 0.23100(23) 0.22262(48) 0.1183 (†) 67 +38
−28
MZ 0.23128(6) 0.22321(17) 0.1183 (†) 117 (†)
QW (APV) 0.2314(14) 0.2233(14) 0.1183 (†) 117 (†)
QW (e) 0.2332(15) 0.2251(15) 0.1183 (†) 117 (†)
νμ-N DIS (isoscalar) 0.2335(18) 0.2254(18) 0.1183 (†) 117 (†)
Elastic νμ(νμ)-e 0.2311(77) 0.2230(77) 0.1183 (†) 117 (†)
e-D DIS (SLAC) 0.222(18) 0.213(19) 0.1183 (†) 117 (†)
Elastic νμ(νμ)-p 0.211(33) 0.203(33) 0.1183 (†) 117 (†)
αs(MZ)=0.1198 ± 0.0028, is very sensitive to such types of new physics
as non-universal vertex corrections. In contrast, the value derived from
τ decays, αs(MZ)=0.1174 +0.0018
−0.0016 , is theory dominated but less sensitive
to new physics. The two values are in remarkable agreement with each
other. They are also in agreement with other recent values, such as
from jet-event shapes at LEP [215] (0.1202 ± 0.0050) the average
from HERA [216] (0.1198 ± 0.0032), and the most recent unquenched
lattice calculation [217] (0.1183 ± 0.0008). For more details and other
determinations, see our Section 9 on “Quantum Chromodynamics” in this
Review.
Using α(MZ)and�s2 Z as inputs, one can predict αs(MZ)assuming grand unification. One predicts [218] αs(MZ)=0.130 ± 0.001 ± 0.01 for
the simplest theories based on the minimal supersymmetric extension
of the SM, where the first (second) uncertainty is from the inputs
(thresholds). This is slightly larger, but consistent with the experimental
αs(MZ) =0.1183 ± 0.0015 from the Z lineshape and the τ lifetime, as
well as with other determinations. Non-supersymmetric unified theories
predict the low value αs(MZ)=0.073 ± 0.001 ± 0.001. See also the note
on “Supersymmetry” in the Searches Particle Listings.
The data indicate a preference for a small Higgs mass. There is
a strong correlation between the quadratic mt and logarithmic MH terms in �ρ in all of the indirect data except for the Z → bb vertex.