181 research outputs found
Effects of polarisation on study of anomalous VVH interactions at a Linear Collider
We investigate the use of beam polarisation as well as final state
polarisation effects in probing the interaction of the Higgs boson with a pair
of heavy vector bosons in the process , where is
any light fermion. The sensitivity of the International Linear Collider (ILC)
operating at GeV, to such () couplings is examined
in a model independent way. The effects of ISR and beamstrahlung are discussed.Comment: To appear in the proceedings of 2007 International Linear Collider
Workshop (LCWS07 and ILC07), Hamburg, Germany, 30 May - 3 Jun 2007. 4 pages,
LaTeX, 1 eps figure. requires ilcws07.cls. included in submissio
Looking for the Top-squark at the Tevatron with four jets
The scalar partner of the top quark is relatively light in many models of
supersymmetry breaking. We study the production of top squarks (stops) at the
Tevatron collider and their subsequent decay through baryon-number violating
couplings such that the final state contains no leptons. Performing a
detector-level analysis, we demonstrate that, even in the absence of leptons or
missing energy, stop masses upto 210 \gev/c^2 can be accessible at the
Tevatron.Comment: 4 pages, 4 embedded figures, RevTe
Signatures of anomalous VVH interactions at a linear collider
We examine, in a model independent way, the sensitivity of a Linear Collider
to the couplings of a light Higgs boson to gauge bosons. Including the
possibility of CP violation, we construct several observables that probe the
different anomalous couplings possible. For an intermediate mass Higgs, a
collider operating at a center of mass energy of 500 GeV and with an integrated
luminosity of 500 fb is shown to be able to constrain the vertex
at the few per cent level, and with even higher sensitivity in certain
directions. However, the lack of sufficient number of observables as well as
contamination from the vertex limits the precision with which the
coupling can be measured.Comment: Typeset in RevTeX4, 16 pages, 12 figures; V2: minor changes in title
and Sec. II and III; V3: version appeared in PRD with minor correctio
Nonstandard, strongly interacting spin one tt̅ resonances
Examining theories with an extended strong interaction sector such as axigluons or flavour universal colorons, we find that the constraints obtained from the current data on tt̅ production at the Tevatron are in the range of TeV and thus competitive with those obtained from the dijet data. We point out that for large axigluon/coloron masses, the limits on the coloron mass may be different than those for the axigluon even for . We also compute the expected forward-backward asymmetry for the case of the axigluons which would allow it to be discriminated against the SM as also the colorons. We further find that at the LHC, the signal should be visible in the tt̅ invariant mass spectrum for a wide range of axigluon and coloron masses that are still allowed. We point out how top polarisation may be used to further discriminate the axigluon and coloron case from the SM as well as from each other
A generalized linear mixed model for longitudinal binary data with a marginal logit link function
Longitudinal studies of a binary outcome are common in the health, social,
and behavioral sciences. In general, a feature of random effects logistic
regression models for longitudinal binary data is that the marginal functional
form, when integrated over the distribution of the random effects, is no longer
of logistic form. Recently, Wang and Louis [Biometrika 90 (2003) 765--775]
proposed a random intercept model in the clustered binary data setting where
the marginal model has a logistic form. An acknowledged limitation of their
model is that it allows only a single random effect that varies from cluster to
cluster. In this paper we propose a modification of their model to handle
longitudinal data, allowing separate, but correlated, random intercepts at each
measurement occasion. The proposed model allows for a flexible correlation
structure among the random intercepts, where the correlations can be
interpreted in terms of Kendall's . For example, the marginal
correlations among the repeated binary outcomes can decline with increasing
time separation, while the model retains the property of having matching
conditional and marginal logit link functions. Finally, the proposed method is
used to analyze data from a longitudinal study designed to monitor cardiac
abnormalities in children born to HIV-infected women.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS390 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Living on the edge in a spacetime with multiple warping
The Randall-Sundrum warped braneworld model is generalised to six and higher
dimensions such that the warping has a non-trivial dependence on more than one
dimension. This naturally leads to a brane-box like configuration alongwith
scalar fields with possibly interesting cosmological roles. Also obtained
naturally are two towers of 3 branes with mass scales clustered around either
of Planck scale and TeV scale. Such a scenario has interesting phenomenological
consequences including an explanation for the observed hierarchy in the masses
of standard model fermions.Comment: 14 Pages, Latex, 2 figures, To appear in Phys.Rev.
Electromagnetic leptogenesis at the TeV scale
We construct an explicit model implementing electromagnetic leptogenesis. In
a simple extension of the Standard Model, a discrete symmetry forbids the usual
decays of the right-handed neutrinos, while allowing for an effective coupling
between the left-handed and right-handed neutrinos through the electromagnetic
dipole moment. This generates correct leptogenesis with resonant enhancement
and also the required neutrino mass via a TeV scale seesaw mechanism. The model
is consistent with low energy phenomenology and would have distinct signals in
the next generation colliders, and, perhaps even the LHC.Comment: 14 pages, 2 eps figure
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