3,121 research outputs found
Anomalous Gauge Interactions of the Higgs Boson: Precision Constraints and Weak Boson Scatterings
Interaction of Higgs scalar (H) with weak gauge bosons (V=W,Z) is the {\it
key} to understand electroweak symmetry breaking (EWSB) mechanism. New physics
effects in the HVV interactions, as predicted by models of compositeness,
supersymmetry and extra dimensions, can be formulated as anomalous couplings
via a generic effective Lagrangian. We first show that the existing electroweak
precision data already impose nontrivial indirect constraints on the anomalous
HVV couplings. Then, we systematically study VV --> VV scatterings in the TeV
region, via Gold-plated pure leptonic decay modes of the weak bosons. We
demonstrate that, even for a light Higgs boson in the mass range 115GeV < m_H <
300GeV, this process can directly probe the anomalous HVV interactions at the
LHC with an integrated luminosity of 300fb^{-1}, which further supports the
``No-Lose'' theorem for the LHC to uncover the EWSB mechanism. Comparisons with
the constraints from measuring the cross section of VH associate production and
the Higgs boson decay width are also given.Comment: Version in Phys. Lett. B (v3: minor typos removed, v2,v4: fix Latex
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Unitarity of Little Higgs Models Signals New Physics of UV Completion
The ``Little Higgs'' opens up a new avenue for natural electroweak symmetry
breaking in which the standard model Higgs particle is realized as a
pseudo-Goldstone boson and thus is generically light. The symmetry breaking
structure of the Little Higgs models predicts a large multiplet of
(pseudo-)Goldstone bosons and their low energy interactions below the
ultraviolet (UV) completion scale TeV, where
is the Goldstone decay constant. We study unitarity of the Little Higgs
models by systematically analyzing the high energy scatterings of these
(pseudo-)Goldstone bosons. We reveal that the collective effect of the
Goldstone scatterings via coupled channel analysis tends to push the unitarity
violation scale significantly below the conventional UV scale
as estimated by naive dimensional analysis (NDA).
Specifically, , lying in the multi-TeV range for TeV. We interpret this as an encouraging sign that the upcoming LHC may
explore aspects of Little Higgs UV completions, and we discuss some potential
signatures. The meanings of the two estimated UV scales (from
unitarity violation) and (from NDA) together with their implications
for an effective field theory analysis of the Little Higgs models are also
discussed.Comment: To match Phys.Lett.B version (9pp, only minor rewording
Phase Transitions of Charged Scalars at Finite Temperature and Chemical Potential
We calculate the grand canonical partition function at the one-loop level for
scalar quantum electrodynamics at finite temperature and chemical potential. A
classical background charge density with a charge opposite that of the scalars
ensures the neutrality of the system. For low density systems we find evidence
of a first order phase transition. We find upper and lower bounds on the
transition temperature below which the charged scalars form a condensate. A
first order phase transition may have consequences for helium-core white dwarf
stars in which it has been argued that such a condensate of charged helium-4
nuclei could exist.Comment: 20 pages, 3 figures. Version accepted for publication in JHE
Supersymmetric radiative corrections at large tan beta
In the minimal supersymmetric extension of the Standard Model (MSSM), fermion
masses and Yukawa couplings receive radiative corrections at one loop from
diagrams involving the supersymmetric particles. The corrections to the
relation between down-type fermion masses and Yukawa couplings are enhanced by
tan beta, which makes them potentially very significant at large tan beta.
These corrections affect a wide range of processes in the MSSM, including
neutral and charged Higgs phenomenology, rare B meson decays, and
renormalization of the CKM matrix. We give a pedagogical review of the sources
and phenomenological effects of these corrections.Comment: 10 pages, 1 figure, to appear in the proceedings of 30 Years of
Supersymmetry, Minneapolis, Minnesota, October 13-27, 2000; references adde
A 125 GeV SM-like Higgs in the MSSM and the rate
We consider the possibility of a Standard Model (SM)-like Higgs in the
context of the Minimal Supersymmetric Standard Model (MSSM), with a mass of
about 125 GeV and with a production times decay rate into two photons which is
similar or somewhat larger than the SM one. The relatively large value of the
SM-like Higgs mass demands stops in the several hundred GeV mass range with
somewhat large mixing, or a large hierarchy between the two stop masses in the
case that one of the two stops is light. We find that, in general, if the
heaviest stop mass is smaller than a few TeV, the rate of gluon fusion
production of Higgs bosons decaying into two photons tends to be somewhat
suppressed with respect to the SM one in this region of parameters. However, we
show that an enhancement of the photon decay rate may be obtained for light
third generation sleptons with large mixing, which can be naturally obtained
for large values of and sizable values of the Higgsino mass
parameter.Comment: 14 pages, 4 figures. Corrected small typos and added reference
Dynamical stabilization of runaway potentials at finite density
We study four dimensional non-abelian gauge theories with classical moduli.
Introducing a chemical potential for a flavor charge causes moduli to become
unstable and start condensing. We show that the moduli condensation in the
presence of a chemical potential generates nonabelian field strength
condensates. These condensates are homogeneous but non-isotropic. The end point
of the condensation process is a stable homogeneous, but non-isotropic, vacuum
in which both gauge and flavor symmetries and the rotational invariance are
spontaneously broken. Possible applications of this phenomenon for the gauge
theory/string theory correspondence and in cosmology are briefly discussed.Comment: revtex4, 4 pages; v.2: journal versio
Generalized screening theorem for Higgs decay processes in the two-doublet model
The radiative corrections to the decay processes of the neutral (-even)
Higgs boson () into a longitudinal gauge boson pair, {\it i.e.}, and are analyzed in
the two-Higgs doublet model by assuming that all of the Higgs boson masses are
much greater than the and bosons'. These calculations are motivated to
see if one could see potentially large virtual effects to these decay rates due
to the charged and -odd neutral Higgs boson masses ( and ,
respectively) which are supposed to be larger than . It is pointed out
that, although the radiative corrections to the decay width depend sensitively in general on and
, there occurs a screening effect, {\it i.e.,} cancellation in leading
terms once we set , so that the radiative corrections tend to be
minimized. It is also pointed out that the decay rate is fairly insensitive to the other heavier Higgs masses and is
possibly a good measuring tool of the Higgs mixing angle. The mechanism of
these screening phenomena in the Higgs decays is explained on the basis of a
new screening theorem, which we postulate with reference to the custodial
symmetry in the Higgs potential.Comment: 42 pages, latex, 9 figure
Constraining parameter space in type-II two-Higgs doublet model in light of a 126 GeV Higgs boson
We explore the implications of a 126 GeV Higgs boson indicated by the recent
LHC results for two-Higgs doublet model (2HDM). Identifying the 126 GeV Higgs
boson as either the lighter or heavier of CP even neutral Higgs bosons in 2HDM,
we examine how the masses of Higgs fields and mixing parameters can be
constrained by the theoretical conditions and experimental constraints. The
theoretical conditions taken into account are the vacuum stability,
perturbativity and unitarity required to be satisfied up to a cut-off scale. We
also show how bounds on the masses of Higgs bosons and mixing parameters depend
on the cut-off scale. In addition, we investigate whether the allowed regions
of parameter space can accommodate particularly the enhanced di-photon signals,
ZZ* and WW* decay modes of the Higgs boson, and examine the prediction of the
signal strength of Z{\gamma} decay mode for the allowed regions of the
parameter space.Comment: To be published in JHEP, 20 pages, 11 figures, Figures and results
are updated for the recent LHC result
Gluino Decay as a Probe of High Scale Supersymmetry Breaking
A supersymmetric standard model with heavier scalar supersymmetric particles
has many attractive features. If the scalar mass scale is O(10 - 10^4) TeV, the
standard model like Higgs boson with mass around 125 GeV, which is strongly
favored by the LHC experiment, can be realized. However, in this scenario the
scalar particles are too heavy to be produced at the LHC. In addition, if the
scalar mass is much less than O(10^4) TeV, the lifetime of the gluino is too
short to be measured. Therefore, it is hard to probe the scalar particles at a
collider. However, a detailed study of the gluino decay reveals that two body
decay of the gluino carries important information on the scalar scale. In this
paper, we propose a test of this scenario by measuring the decay pattern of the
gluino at the LHC.Comment: 29 pages, 9 figures; version published in JHE
Constraints on CP violation in the Higgs sector from the parameter
We discuss the relation between the CP symmetry and the custodial
symmetry in the Higgs sector. In particular, we show that CP violation in the
Higgs-gauge sector is allowed only if the custodial symmetry is broken.
We exploit these facts to constrain CP violation using the experimental bounds
on . CP nonconservation in the Higgs-fermion interactions can also be
constrained in a similar way although a possible exception is pointed out.Comment: 19 pages, 2 figures (not included), SLAC-PUB-619
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