12,420 research outputs found
Nonlinear sequential designs for logistic item response theory models with applications to computerized adaptive tests
Computerized adaptive testing is becoming increasingly popular due to
advancement of modern computer technology. It differs from the conventional
standardized testing in that the selection of test items is tailored to
individual examinee's ability level. Arising from this selection strategy is a
nonlinear sequential design problem. We study, in this paper, the sequential
design problem in the context of the logistic item response theory models. We
show that the adaptive design obtained by maximizing the item information leads
to a consistent and asymptotically normal ability estimator in the case of the
Rasch model. Modifications to the maximum information approach are proposed for
the two- and three-parameter logistic models. Similar asymptotic properties are
established for the modified designs and the resulting estimator. Examples are
also given in the case of the two-parameter logistic model to show that without
such modifications, the maximum likelihood estimator of the ability parameter
may not be consistent.Comment: Published in at http://dx.doi.org/10.1214/08-AOS614 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Higgs-- Coupling at High and Low Energy Colliders
There is no tree-level flavor changing neutral current (FCNC) in the standard
model (SM) which contains only one Higgs doublet. If more Higgs doublets are
introduced for various reasons, the tree level FCNC would be inevitable except
extra symmetry was imposed. Therefore FCNC processes are the excellent probes
for the physics beyond the SM (BSM). In this paper, we studied the lepton
flavor violated (LFV) decay processes and
induced by Higgs-- vertex. For
, its branching ratio is also related to the
, and vertices. We categorized the BSM
into two scenarios for the Higgs coupling strengths near or away from SM. For
the latter scenario, we took the spontaneously broken two Higgs doublet model
(Lee model) as an example. We considered the constraints by recent data from
LHC and B factories, and found that the measurements gave weak constraints. At
LHC Run II, will be confirmed or set stricter limit on
its branching ratio. Accordingly,
for general chosen parameters. For the positive case,
can be discovered with
pair samples at SuperB factory, Super -charm factory and new Z-factory.
The future measurements for and
will be used to distinguish these two
scenarios or set strict constraints on the correlations among different Higgs
couplings, please see Table II in the text for details.Comment: 18 pages, 10 figures, 2 table; more references added; more
discussions about cancellation in the amplitude added accoeding to the
referee's suggestion
Localization of gauge vector field on flat branes with five-dimension (asymptotic) AdS spacetime
In order to localize gauge vector field on Randall-Sundrum-like
braneworld model with infinite extra dimension, we propose a new kind of
non-minimal coupling between the gauge field and the gravity. We propose
three kinds of coupling methods and they all support the localization of zero
mode. In addition, one of them can support the localization of massive modes.
Moreover, the massive tachyonic modes can be excluded. And our method can be
used not only in the thin braneword models but also in the thick ones.Comment: Added acknowledgments to the refree. Appeared on JHE
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