485 research outputs found
Constraining Spin-One Color-Octet Resonances Using CDF and ATLAS Data
In this paper, we study the production of spin-one color-octet resonances
(colorons) at hadron colliders in a model independent way. We use dijets data
measured by CDF (at \sqrt{s}=1.96 TeV and L=1.13 TeV and L=315 1/nb) collaborations at the Tevatron and the LHC
respetively to impose limits on the coupling of colorons to fermions. We show
that CDF data still produce the more stringent limits on the coloron coupling
constant.Comment: Version accepted for publication in EPJC. Two paragraphs expanded and
new references adde
Flavor Physics and the Triviality Bound on the Higgs Mass
The triviality of the scalar sector of the standard one-doublet Higgs model
implies that this model is only an effective low-energy theory valid below some
cut-off scale . The underlying high-energy theory must include flavor
dynamics at a scale of order or greater in order to give rise to the
different Yukawa couplings of the Higgs to ordinary fermions. This flavor
dynamics will generically produce flavor-changing neutral currents and
non-universal corrections to Z -> b b-bar. We show that the experimental
constraints on the neutral D-meson mass difference imply that must be
greater than of order 21 TeV. We also discuss bounds on from the
constraints on extra contributions to the K_L - K_S mass difference and to the
coupling of the Z boson to b-quarks. For theories defined about the
infrared-stable Gaussian fixed-point, we estimate that this lower bound on
yields an upper bound of approximately 460 GeV on the Higgs boson's
mass, independent of the regulator chosen to define the theory.Comment: 11 pages, 2 embedded figures, LaTeX; references and discussion of CP
violation adde
Topped MAC with extra dimensions?
We perform the most attractive channel (MAC) analysis in the top mode
standard model with TeV-scale extra dimensions, where the standard model gauge
bosons and the third generation of quarks and leptons are put in D(=6,8,10,...)
dimensions. In such a model, bulk gauge couplings rapidly grow in the
ultraviolet region. In order to make the scenario viable, only the attractive
force of the top condensate should exceed the critical coupling, while other
channels such as the bottom and tau condensates should not. We then find that
the top condensate can be the MAC for D=8, whereas the tau condensation is
favored for D=6. The analysis for D=10 strongly depends on the regularization
scheme. We predict masses of the top (m_t) and the Higgs (m_H), m_t=172-175 GeV
and m_H=176-188 GeV for D=8, based on the renormalization group for the top
Yukawa and Higgs quartic couplings with the compositeness conditions at the
scale where the bulk top condenses. The Higgs boson in such a characteristic
mass range will be immediately discovered in H -> WW^(*)/ZZ^(*) once the LHC
starts.Comment: REVTEX4, 24 pages, 21 figures, to appear in PRD. The title is changed
in PRD. One reference added, typos correcte
Minimal Composite Higgs Model with Light Bosons
We analyze a composite Higgs model with the minimal content that allows a
light Standard-Model-like Higgs boson, potentially just above the current LEP
limit. The Higgs boson is a bound state made up of the top quark and a heavy
vector-like quark. The model predicts that only one other bound state may be
lighter than the electroweak scale, namely a CP-odd neutral scalar. Several
other composite scalars are expected to have masses in the TeV range. If the
Higgs decay into a pair of CP-odd scalars is kinematically open, then this
decay mode is dominant, with important implications for Higgs searches. The
lower bound on the CP-odd scalar mass is loose, in some cases as low as
100 MeV, being set only by astrophysical constraints.Comment: 33 pages, latex. Corrections in eqs. 3.21, 3.23, 4.1, 4.5-10. One
figure adde
Dynamical chiral symmetry breaking in gauge theories with extra dimensions
We investigate dynamical chiral symmetry breaking in vector-like gauge
theories in dimensions with () compactified extra dimensions, based on
the gap equation (Schwinger-Dyson equation) and the effective potential for the
bulk gauge theories within the improved ladder approximation. The non-local
gauge fixing method is adopted so as to keep the ladder approximation
consistent with the Ward-Takahashi identities.
Using the one-loop gauge coupling of the truncated KK
effective theory which has a nontrivial ultraviolet fixed point (UV-FP)
for the (dimensionless) bulk gauge coupling , we find that there
exists a critical number of flavors, ( for
for SU(3) gauge theory): For , the dynamical
chiral symmetry breaking takes place not only in the ``strong-coupling phase''
() but also in the ``weak-coupling phase'' ()
when the cutoff is large enough. For , on the other hand,
only the strong-coupling phase is a broken phase and we can formally define a
continuum (infinite cutoff) limit, so that the physics is insensitive to the
cutoff in this case.
We also perform a similar analysis using the one-loop ``effective gauge
coupling''. We find the turns out to be a value similar to
that of the case, notwithstanding the enhancement of the
coupling compared with that of the .Comment: REVTEX4, 38 pages, 18 figures. The abstract is shortened; version to
be published in Phys. Rev.
Problematising parentâprofessional partnerships in education
The value of, and need for, parentâprofessional partnerships is an unchallenged mantra within policy relating to âspecial educational needsâ. In spite of this, partnerships continue to be experienced as problematic by both parents and professionals. This paper brings together the different perspectives of two disability researchers: one a parent of a disabled child while the other was a teacher for 20 years of children with the label autism. The paper deconstructs the concept of partnership and then, drawing on the expertise of parents, suggests how enabling and empowering parentâprofessional relationships might be achieved
Problematising parentâprofessional partnerships in education
The value of, and need for, parentâprofessional partnerships is an unchallenged mantra within policy relating to âspecial educational needsâ. In spite of this, partnerships continue to be experienced as problematic by both parents and professionals. This paper brings together the different perspectives of two disability researchers: one a parent of a disabled child while the other was a teacher for 20 years of children with the label autism. The paper deconstructs the concept of partnership and then, drawing on the expertise of parents, suggests how enabling and empowering parentâprofessional relationships might be achieved
Single Top Production as a Window to Physics Beyond the Standard Model
Production of single top quarks at a high energy hadron collider is studied
as a means to identify physics beyond the standard model related to the
electroweak symmetry breaking. The sensitivity of the -channel mode,
the -channel -gluon fusion mode, and the \tw mode to various possible
forms of new physics is assessed, and it is found that the three modes are
sensitive to different forms of new physics, indicating that they provide
complimentary information about the properties of the top quark. Polarization
observables are also considered, and found to provide potentially useful
information about the structure of the interactions of top.Comment: References added and minor discussion improvements; results
unchanged; Version to be published in PR
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