22 research outputs found
Tevatron Run II combination of the effective leptonic electroweak mixing angle
Drell-Yan lepton pairs produced in the process pp→â.,"+â.,"-+X through an intermediate γ∗/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin2θefflept using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9-10 fb-1 of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin2θefflept=0.23148±0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin2θW, or equivalently the W-boson mass MW, using the zfitter software package yields sin2θW=0.22324±0.00033 or equivalently, MW=80.367±0.017 GeV/c2
Tevatron Constraints on Models of the Higgs Boson with Exotic Spin and Parity Using Decays to Bottom-Antibottom Quark Pairs
Combined constraints from the CDF and D0 Collaborations on models of the
Higgs boson with exotic spin J and parity P are presented and compared
with results obtained assuming the standard model value J(P) = 0(+).
Both collaborations analyzed approximately 10 fb(-1) of
proton-antiproton collisions with a center-of-mass energy of 1.96 TeV
collected at the Fermilab Tevatron. Two models predicting exotic Higgs
bosons with J(P) = 0(-) and J(P) = 2(+) are tested. The kinematic
properties of exotic Higgs boson production in association with a vector
boson differ from those predicted for the standard model Higgs boson.
Upper limits at the 95% credibility level on the production rates of
the exotic Higgs bosons, expressed as fractions of the standard model
Higgs boson production rate, are set at 0.36 for both the J(P) = 0(-)
hypothesis and the J(P) = 2(+) hypothesis. If the production rate times
the branching ratio to a bottom-antibottom pair is the same as that
predicted for the standard model Higgs boson, then the exotic bosons are
excluded with significances of 5.0 standard deviations and 4.9 standard
deviations for the J(P) = 0(-) and J(P) = 2(+) hypotheses, respectively
Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element V-tb
We present the final combination of CDF and D0 measurements of cross
sections for single-top-quark production in proton-antiproton collisions
at a center-of-mass energy of 1.96 TeV. The data correspond to total
integrated luminosities of up to 9.7 fb(-1) per experiment. The
t-channel cross section is measured to be sigma(t) = 2.25(-0.31)(+0.29)
pb. We also present the combinations of the two-dimensional measurements
of the s- vs t-channel cross section. In addition, we give the
combination of the s + t channel cross section measurement resulting in
sigma(s+t) = 3.30(-0.40)(+0.52) pb, without assuming the standard model
value for the ratio sigma(s)/sigma(t). The resulting value of the
magnitude of the top-to-bottom quark coupling is vertical bar V-tb
vertical bar = 1.02(-0.05)(+0.06), corresponding to vertical bar V-tb
vertical bar > 0.92 at the 95% C. L
Observation of s-Channel Production of Single Top Quarks at the Tevatron
We report the first observation of single-top-quark production in the s
channel through the combination of the CDF and D0 measurements of the
cross section in proton-antiproton collisions at a center-of-mass energy
of 1.96 TeV. The data correspond to total integrated luminosities of up
to 9.7 fb(-1) per experiment. The measured cross section is sigma(s) =
1.29(-0.24)(+0.26) pb. The probability of observing a statistical
fluctuation of the background to a cross section of the observed size or
larger is 1.8 x 10(-10), corresponding to a significance of 6.3 standard
deviations for the presence of an s-channel contribution to the
production of single-top quarks
Tevatron Run II combination of the effective leptonic electroweak mixing angle
Drell-Yan lepton pairs produced in the process p (p) over bar ->
l(+)l(-) + X through an intermediate gamma*/Z boson have an asymmetry
in their angular distribution related to the spontaneous symmetry
breaking of the electroweak force and the associated mixing of its
neutral gauge bosons. The CDF and D0 experiments have measured the
effective-leptonic electroweak mixing parameter sin(2) theta(lept)(eff)
using electron and muon pairs selected from the full Tevatron
proton-antiproton data sets collected in 2001-2011, corresponding to
9-10 fb(-1) of integrated luminosity. The combination of these
measurements yields the most precise result from hadron colliders,
sin(2)theta(lept)(eff) = 0.23148 +/- 0.00033. This result is consistent
with, and approaches in precision, the best measurements from
electron-positron colliders. The standard model inference of the
on-shell electroweak mixing parameter sin(2) theta(W), or equivalently
the W-boson mass M-W, using the ZFITTER software package yields sin(2)
theta(W) = 0.22324 +/- 0.00033 or equivalently, M-W = 80.367 +/- 0.017
GeV/c(2)