1,424 research outputs found
A Very Narrow Shadow Extra Z-boson at Colliders
We consider the phenomenological consequences of a hidden Higgs sector
extending the Standard Model (SM), in which the ``shadow Higgs'' are uncharged
under the SM gauge groups. We consider a simple U(1) model with one Higgs
singlet. One mechanism which sheds light on the shadow sector is the mixing
between the neutral gauge boson of the SM and the additional U(1) gauge group.
The mixing happens through the usual mass-mixing and also kinetic-mixing, and
is the only way the ``shadow '' couples to the SM. We study in detail
modifications to the electroweak precision tests (EWPTs) that the presence of
such a shadow sector would bring, which in turn provide constraints on the
kinetic-mixing parameter, , left free in our model. The shadow
production rate at the LHC and ILC depends on . We find that
observable event rate at both facilities is possible for a reasonable range of
allowed by EWPTs.Comment: 10 pages, 7 figures. Note and refs. adde
Testing Realistic Quark Mass Matrices in the Custodial Randall-Sundrum Model with Flavor Changing Top Decays
We study quark mass matrices in the Randall-Sundrum (RS) model with bulk
symmetry . The Yukawa couplings are
assumed to be within an order of magnitude of each other, and perturbative. We
find that quark mass matrices of the symmetrical form proposed by Koide
\textit{et. al.} [Y. Koide, H. Nishiura, K. Matsuda, T. Kikuchi and T.
Fukuyama, Phys. Rev. D {\bf 66}, 093006 (2002)] can be accommodated in the RS
framework with the assumption of hierarchyless Yukawa couplings, but not the
hermitian Fritzsch-type mass matrices. General asymmetrical mass matrices are
also found which fit well simultaneously with the quark masses and the
Cabibbo-Kobayashi-Maskawa matrix. Both left-handed (LH) and right-handed (RH)
quark rotation matrices are obtained that allow analysis of flavour changing
decay of both LH and RH top quarks. At a warped down scale of 1.65 TeV, the
total branching ratio of t \ra Z + jets can be as high as for symmetrical mass matrices and for
asymmetrical ones. This level of signal is within reach of the LHC.Comment: 30 pages, 6 figures. Reference added, typos corrected, discussions in
Sec. IV B expanded. Version conforms to the published versio
Phenomenology from a U(1) gauged hidden sector
We consider the phenomenological consequences of a hidden Higgs sector
extending the Standard Model (SM), in which the matter content are uncharged
under the SM gauge groups. We consider a simple case where the hidden sector is
gauged under a U(1) with one Higgs singlet. The only couplings between SM and
the hidden sector are through mixings between the neutral gauge bosons of the
two respective sectors, and between the Higgs bosons. We find signals testable
at the LHC that can reveal the existence and shed light on the nature of such a
hidden sector.Comment: 5 pages, 2 figures. Talk given at the Lake Louise Winter Institute
2007, Feb. 19-24, Alberta, Canad
Discrete Dirac Neutrino in Warped Extra Dimensions
We implement Dirac neutrinos in the minimal custodial Randall-Sundrum setting
via the Krauss-Wilczek mechanism. We demonstrate by giving explicit lepton mass
matrices that with neutrinos in the normal hierarchy, lepton mass and mixing
patterns can be naturally reproduced at the scale set by the constraints from
electroweak precision measurements, and at the same time without violating
bounds set by lepton flavour violations. Our scenario generically predicts a
nonzero neutrino mixing angle , as well as the existence of
sub-TeV right-handed Kaluza-Klein neutrinos, which partner the right-handed
Standard Model charged leptons. These relatively light KK neutrinos may be
searched for at the LHC.Comment: 20 pages, 4 figure
Constraints on New Scalars from the LHC 125 GeV Higgs Signal
We study the implications the recent results from the LHC Higgs searches have
on scalar new physics. We study the impact on both the Higgs production and
decay from scalars with and without colour, and in cases where decoupling do
and do not happen. We investigate possible constraints on scalar parameters
from the production rate in the diphoton channel, and also the two vector boson
channels. Measurements from both channels can help disentangle new physics due
to colour from that due to charge, and thus reveal the nature of the new scalar
states.Comment: 23 pages, 8 figures; references addded, typos corrected. Published in
PR
Complex-Distance Potential Theory and Hyperbolic Equations
An extension of potential theory in R^n is obtained by continuing the
Euclidean distance function holomorphically to C^n. The resulting Newtonian
potential is generated by an extended source distribution D(z) in C^n whose
restriction to R^n is the delta function. This provides a natural model for
extended particles in physics. In C^n, interpreted as complex spacetime, D(z)
acts as a propagator generating solutions of the wave equation from their
initial values. This gives a new connection between elliptic and hyperbolic
equations that does not assume analyticity of the Cauchy data. Generalized to
Clifford analysis, it induces a similar connection between solutions of
elliptic and hyperbolic Dirac equations. There is a natural application to the
time-dependent, inhomogeneous Dirac and Maxwell equations, and the
`electromagnetic wavelets' introduced previously are an example.Comment: 25 pages, submited to Proceedings of 5th Intern. Conf. on Clifford
Algebras, Ixtapa, June 24 - July 4, 199
A linear programming approach to Markov reward error bounds for queueing networks
In this paper, we present a numerical framework for constructing bounds on
stationary performance measures of random walks in the positive orthant using
the Markov reward approach. These bounds are established in terms of stationary
performance measures of a perturbed random walk whose stationary distribution
is known explicitly. We consider random walks in an arbitrary number of
dimensions and with a transition probability structure that is defined on an
arbitrary partition of the positive orthant. Within each component of this
partition the transition probabilities are homogeneous. This enables us to
model queueing networks with, for instance, break-downs and finite buffers. The
main contribution of this paper is that we generalize the linear programming
approach of [1] to this class of models
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