91 research outputs found

### The No-Higgs Signal: Strong WW Scattering at the LHC

Strong WW scattering at the LHC is discussed as a manifestation of
electroweak symmetry breaking in the absence of a light Higgs boson. The
general framework of the Higgs mechanism -- with or without a Higgs boson -- is
reviewed, and unitarity is shown to fix the scale of strong WW scattering.
Strong WW scattering is also shown to be a possible outcome of five-dimensional
models, which do not employ the usual Higgs mechanism at the TeV scale.
Precision electroweak constraints are briefly discussed. Illustrative LHC
signals are reviewed for models with QCD-like dynamics, stressing the
complementarity of the W^{\pm}Z and like-charge W^+W^+ + W^-W^- channels.Comment: 16 pages, talk presented at Physics at LHC, July 13 - 17, 2004,
Vienna, Austria, to be published in the proceeding

### The Direct Limit on the Higgs Mass and the SM Fit

Because of two $3\sigma$ anomalies, the Standard Model (SM) fit of the
precision electroweak data has a poor confidence level, $CL= 0.02$. Since both
anomalies involve challenging systematic issues, it might appear that the SM
could still be valid if the anomalies resulted from underestimated systematic
error. Indeed the $CL$ of the global fit could then increase to 0.71, but that
fit predicts a small Higgs boson mass, $m_H=45$ GeV, that is inconsistent at
95% CL with the lower limit, $m_H>114$ GeV, established by direct searches. The
data then favor new physics if the anomalous measurements are both excluded or
both retained, and the Higgs boson mass cannot be predicted until the new
physics is understood. The validity of the SM could however be maintained by a
propitious combination of statistical fluctuation and systematic error. The
current data do not allow a definitive conclusion.Comment: 12 pages, 4 figures, presented at the Workshop on Electroweak
Precision Data and the Higgs Mass, DESY-Zeuthen, February 28 - March 1, 2003;
typos in table 3 corrected, discussion of products of CL's generalized;
kinder, gentler abstrac

### Quantum corrections from nonresonant WW scattering

An estimate is presented of the leading radiative corrections to low energy
electroweak precision measurements from strong nonresonant WW scattering at the
TeV energy scale. The estimate is based on a novel representation of
nonresonant scattering in terms of the exchange of an effective scalar
propagator with simple poles in the complex energy plane. The resulting
corrections have the form of the corrections from the standard model Higgs
boson with the mass set to the unitarity scale for strong WW scattering.Comment: 12 page

### Chiral Suppression of Scalar Glueball Decay

Because glueballs are SU(3)_{Flavor} singlets, they are expected to couple
equally to u,d, and s quarks, so that equal coupling strengths to \pi^+\pi^-
and K^+K^- are predicted. However, we show that chiral symmetry implies the
scalar glueball amplitude for G_0 \to \qbq is proportional to the quark mass,
so that mixing with \sbs mesons is enhanced and decays to K^+K^- are favored
over \pi^+\pi^-. Together with evidence from lattice calculations and from
experiment, this supports the hypothesis that f_0(1710) is the ground state
scalar glueball.Comment: 9 pages; This revision reconciles posting (approximately) with
published version. Posting contains figures that are omitted in the
publicatio

### Gauge invariant formulation of strong WW scattering

Models of strong $WW$ scattering in the $s$-wave can be represented in a
gauge invariant fashion by defining an effective scalar propagator that
represents the strong scattering dynamics. The \sigma(qq \ra qqWW) signal may
then be computed in U-gauge from the complete set of tree amplitudes, just as
in the standard model, without using the effective $W$ approximation (EWA). The
U-gauge ``transcription'' has a wider domain of validity than the EWA, and it
provides complete distributions for the final state quanta, including
experimentally important jet distributions that cannot be obtained from the
EWA. Starting from the usual formulation in terms of unphysical Goldstone boson
scattering amplitudes, the U-gauge transcription is verified by using BRS
invariance to construct the complete set of gauge and Goldstone boson
amplitudes in $R_{\xi}$ gauge.Comment: single LaTeX file, no figures, 12 page

### Strong WW scattering in unitary gauge

A method to embed models of strong $WW$ scattering in unitary gauge
amplitudes is presented that eliminates the need for the effective $W$
approximation (EWA) in the computation of cross sections at high energy
colliders.The cross sections obtained from the U-gauge amplitudes include the
distributions of the final state fermions in $ff \rightarrow ffWW$, which
cannot be obtained from the EWA. Since the U-gauge method preserves the
interference of the signal and the gauge sector background amplitudes, which is
neglected in the EWA, it is more accurate, especially if the latter is
comparable to or bigger than the signal, as occurs for instance at small angles
because of Coulomb singularities. The method is illustrated for on-shell
$W^+W^+ \rightarrow W^+W^+$ scattering and for $qq \rightarrow qqW^+W^+$.Comment: 14 pages, Latex with 2 epsf-embedded postscript figure

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