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hep-ex/9503009 10 Mar 1995
Limits on WWZ and WW couplings from WW and WZ production in pp collisions at s=1.8 TeV
Abstract
Direct limits are set on WWZ and WWγ three-boson couplings in a
search for WW and WZ production with high transverse momentum in
pp¯ collisions at s = 1.8 TeV, using the Collider Detector at
Fermilab. The results are in agreement with the SU(2) × U(1) model
of electroweak interactions. Assuming standard model WWγ
couplings, the limits are interpreted as direct evidence for a nonzero
WWZ coupling at subprocess energies near 500 GeV. Alternatively,
assuming identical WWZ and WWγ couplings, bounds
-0.11<κ<2.27 and -0.81<λ<0.84 are obtained at
95% C.L. for a form factor scale 1000 GeV.
... The diboson processes have been studied at the Tevatron since the beginning of Run I. Most of the Run I studies were statistics-limited and focused on setting limits on anomalous trilinear gauge boson couplings [208][209][210][211][212][213][214][215][216][217][218][219][220][221][222] and diboson production cross sections [223]. The CDF collaboration also reported first evidence for WW production and measured a WW production cross section of W W = 10.2 +6. 3 5.1 (stat) ±1.6 (syst) pb in`⌫`⌫ final states (`is an electron or muon, ⌫ is a neutrino) [224]. ...
The Tevatron collider led the World energy frontier program in particle physics during the late 20th and early 21st centuries. During this exciting period the standard model of particle physics was in its final stages of development and the search for physics beyond the standard model became one of the main research topics. In this review article we summarize the design and performance of the Tevatron collider and its two detectors, CDF and D0, as well as their evolution. Highlights of the Tevatron scientific results are provided, including the discovery of the top quark and measurements of its properties, studies and discoveries of the particles containing heavy quarks, precision studies of the strong and electroweak forces, searches for beyond the standard model particles and interactions, as well as the hunt for the Higgs boson.
The Tevatron collider led the particle physics energy frontier program during the late 20th and early 21st century. In the history of particle physics, it bridged the era of foundation of the Standard Model (SM) in the 70′s and 80′s to the era of completion of the SM and of searches for physics beyond the SM in the 2000′s. Major physics “hits” of the Tevatron, such as the discovery of the top quark, the observation of matter-antimatter oscillations in the heavy quark sector, the precision measurement of the W boson mass, and the evidence of Higgs boson production and decay into fermions, played critical role in shaping modern particle physics. This paper focuses on those hits, discussing them in the context of the Tevatron program and highlighting their impact on the progress in particle physics.
This note presents recent results obtained using the DELPHI detector at the Large Electron-Positron collider (LEP) at CERN in Geneva. The LEP machine, which ran at the Z peak from 1989 to 1995, was upgraded with superconducting radio-frequency cavities in 1995–6 in order to increase the available beam energy.
The title implies an impossibly broad field, as the Standard Model includes the fermion matter states, as well as the forces and fields of SU (3) × SU (2) × U (1). For practical purposes, I will confine myself to electroweak unification, as discussed in the lectures of M. Herrero. Quarks and mixing were discussed in the lectures of R. Aleksan, and leptons and mixing were discussed in the lectures of K. Nakamura. I will essentially assume universality, that is flavor independence, rather than discussing tests of it.
Limits on the anomalous WW gamma and WWZ couplings are presented from a simultaneous fit to the data samples of three gauge boson pair final states in <p(p)over bar> collisions at root s = 1.8 TeV: W gamma production with the W boson decaying to e nu or mu nu, W boson pair production with both of the W bosons decaying to e nu or mu nu, and WW or WZ production with one W boson decaying to e nu and the other W boson or the Z boson decaying to two jets. Assuming identical WW gamma and WWZ couplings, 95% C.L. limits on the anomalous couplings of -0.30<Delta kappa<0.43 (lambda=0) and -0.20<lambda<0.20 (Delta kappa=0) are obtained using a form factor scale Lambda = 2.0 TeV. Limits found under other assumptions on the relationship between the WW gamma and WWZ couplings are also presented. [S0556-2821(98)50615-7]
We summarize an extensive Tevatron (1984–2011) electroweak physics program that involves a variety of W and Z boson precision measurements. The relevance of these studies using single and associated gauge boson production to our understanding of the electroweak sector, quantum chromodynamics and searches for new physics is emphasized. We discuss the importance of the W boson mass measurement, the W/Z boson distributions and asymmetries, and diboson studies. We highlight the recent Tevatron measurements and prospects for the final Tevatron measurements.
We report on the measurement of W-boson pair-production with the L3
detector at LEP at a centre-of-mass energy of 161.34 GeV. In a data
sample corresponding to a total luminosity of 11 pb-1, we
select four-fermion events with high invariant masses of pairs of
hadronic jets or leptons. Combining all final states, the measured total
cross section for W-pair production is: sigmaWW =
2.89+0.81-0.70 (stat.) +/- 0.14 (syst.) pb. Within
the Standard Model, this corresponds to a mass of the W boson of:
MW = 80.80+0.48-0.42 (exp.) +/- 0.03
(LEP) GeV. Limits on anomalous triple-vector-boson couplings are
derived.
Electroweak radiative one-loop corrections to the process γγ→W+W- with photon and W-boson polarizations are calculated within the two-Higgs-doublet model extension of the standard model, and the relevant analytical results for the nonstandard Higgs bosons contributions to the helicity amplitudes are given. The relative difference between the predictions of the two-Higgs-doublet model and minimal standard model for a light salar MH1 and heavy MH2 and MΦ easily exceed ±20% for WTWT pair production in the central angular region at high energy, and even larger for WLWL pair production. The angular dependence corrections owing to the nonstandard Higgs boson get larger, where box diagrams constitute the dominant part of the radiative corrections.
We present results from a search for anomalous WW and WZ production in ppbar
collisions at sqrt(s) = 1.8 TeV. We used ppbar->evjjX events observed during
the 1992-1993 run of the Fermilab Tevatron collider, corresponding to an
integrated luminosity of 13.7 +- 0.7 pb^-1. A fit to the transverse momentum
spectrum of the W boson yields direct limits on the CP-conserving anomalous
WWgamma and WWZ coupling parameters of -0.9 < delta kappa < 1.1 (with lambda =
0) and -0.6 < lambda < 0.7 (with delta kappa = 0) at the 95% confidence level,
for a form factor scale Lambda = 1.5 TeV, assuming that the WWgamma and WWZ
coupling parameters are equal.
Evidence of anomalous WW and WZ production was sought in pp¯ collisions at a center-of-mass energy of s=1.8 TeV. The final states WW(WZ)-->munu jet jet+X, WZ-->munuee+X and WZ-->enuee+X were studied using a data sample corresponding to an integrated luminosity of approximately 90 pb-1. No evidence of anomalous diboson production was found. Limits were set on anomalous WWgamma and WWZ couplings and were combined with our previous results. The combined 95% confidence level anomalous coupling limits for Lambda=2 TeV are -0.25
We augment a previous discussion of the production of pairs of gauge
bosons with a study of the reactions pp and
p¯p-->WZ0X or WγX. As before, these depend upon
trilinear boson couplings and the high-energy behavior is controlled by
gauge cancellations. In particular, the (hard) photon production is
sensitive to the magnetic-moment parameter κ for the W. We also
discuss the related neutrino reactions, νe-->WZ0 or
Wγ, which may be of interest in very-high-energy cosmic-ray
physics.
Amplitudes for the production of electroweak-gauge-boson pairs (any combination of γ, Z, or W±) in association with up to two jets are given. The gauge bosons may be either real or virtual with subsequent decays into charged or neutral leptons. The amplitudes are presented in a form directly amenable to numerical evaluation. Representative cross sections are given for Fermilab Tevatron, CERN Large Hadron Collider, and Superconducting Super Collider center-of-mass energies.
We present a measurement of the inclusive jet cross section in {ital {bar p}p} collisions at {radical}{ital s} =1.8 TeV at the Fermilab Tevatron using the Collider Detector at Fermilab. Good agreement is seen with the predictions of recent next-to-leading-order ({ital O}({alpha}{sub {ital s}}{sup 3})) QCD predictions. The dependence of the cross section on clustering cone size is reported for the first time. An improved limit on {Lambda}{sub {ital c}}, a term characterizing possible quark substructure, is set at 1.4 TeV (95% C.L.).
An order-alphas calculation of pp(-)-->W+/-Z+X is presented. Results are given for the total cross section and differential distributions for the Fermilab Tevatron, CERN Large Hadron Collider, and Superconducting Super Collider energies. The calculation utilizes a combination of analytic and Monte Carlo integration methods which makes it easy to calculate a variety of observables and to impose experimental cuts.
Possible experiments with high-energy colliding beams of electrons and positrons are discussed. The role of the proposed two-pion resonance and of the three-pion resonance or bound state is investigated in connection with electron-positron annihilation into pions. The existence of a three-pion bound state would give rise to a very large cross section for annihilation into pi0+gamma. A discussion of the possible resonances is given based on consideration of the relevant widths as compared to the experimental energy resolution. Annihilation into baryon-antibaryon pairs is investigated and polarization effects arising from the nonreal character of the form factors on the absorptive cut are examined. The density matrix for annihilation into pairs of vector mesons is calculated. A discussion of the limits from unitarity to the annihilation cross sections is given for processes going through the one-photon channel. The cross section for annihilation into pairs of spin-one mesons is rather large. The typical angular correlations at the vector-meson decay are discussed. A neutral weakly interacting vector meson would give rise to a strong resonant peak if it is coupled with lepton pairs. Effects of the local weak interactions are also examined. The explicit relation between the e2 corrections to the photon propagator due to strong interactions and the cross section for annihilation into strongly interacting particles is given.
We discuss the production of pairs of weak bosons in those processes where electrons or quarks annihilate. Besides comparing and extending previous calculations for e+e-→W+W-, we consider e+e-→Z0Z0, pp and pp̅ →W+W-X or Z0Z0X. It is emphasized that (1) the rate of production of Z0 pairs is comparable to that of W pairs and that (2) W-pair production with colliding proton beams may be the best way to see high-energy cancellations in cross sections, the hallmark of renormalizability in gauge theories.
We report on a study of W + photon production in approximately 20
pb-1 of p-p¯ collisions at s = 1.8 TeV recorded with the
Collider Detector at Fermilab. Our results are in good agreement with
standard model expectations and are used to obtain limits on anomalous
CP-conserving WWγ couplings of -2.3<Δκ<2.2 for
λ = 0 and -0.7<λ<0.7 for Δκ = 0 at 95%
C.L. We obtain the same limits for CP-violating couplings. These results
provide limits on the higher-order electromagnetic moments of the W
boson of 0.8<gW<3.1 for qeW = 1
and -0.6<qeW<2.7 for gW = 2 at
95% C.L.
The production and event topology of three-jet events produced in
pp¯ collisions at √s =1.8 TeV have been studied with the
Collider Detector at Fermilab at the Tevatron Collider. The
distributions of the three-jet angular variables (ψ* and
cosθ*) and of the variables describing the energy
sharing between jets (x3 and x4) are found to
agree well with tree-level QCD calculations. These distributions are
predicted to have different shapes for different initial-state
subprocesses (quark-antiquark, quark-gluon, and gluon-gluon). The data
are consistent with the small expected contribution from quark-antiquark
initial states, in agreement with theoretical expectations.
The process ppBAR --> e-nu-gamma + X is studied as square-root s = 630 GeV. The observed signal is used to extract a direct measurement of the parameters-kappa and lambda which define the magnetic dipole and electric quadrupole moments of the W boson and therefore the WW-gamma coupling. We find kappa = 1(-2.2)+2.6 and lambda = 0(-1.8)+1.7 and their 95% confidence limits -3.5 < kappa < 5.9 and -3.6 < lambda < 3.5. The results are model independent and in good agreement with the standard model values, kappa = 1 and lambda = 0.