3,590 research outputs found
|Vub| from exclusive B and D decays
We propose a model-independent method to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vub| from exclusive B and D decays. Combining information obtainable from BâĎlν¯l, BâK*νν¯, DâĎl¯νl, and DâK*l¯νl, a determination of |Vub| is possible, with an uncertainty from theory of around 10%. Theoretical uncertainties in the BâK*llÂŻ decay rate are discussed
Solutions of the Regge Equations on some Triangulations of CP^2
Simplicial geometries are collections of simplices making up a manifold
together with an assignment of lengths to the edges that define a metric on
that manifold. The simplicial analogs of the Einstein equations are the Regge
equations. Solutions to these equations define the semiclassical approximation
to simplicial approximations to a sum-over-geometries in quantum gravity. In
this paper, we consider solutions to the Regge equations with cosmological
constant that give Euclidean metrics of high symmetry on a family of
triangulations of CP^2 presented by Banchoff and Kuhnel. This family is
characterized by a parameter p. The number of vertices grows larger with
increasing p. We exhibit a solution of the Regge equations for p=2 but find no
solutions for p=3. This example shows that merely increasing the number of
vertices does not ensure a steady approach to a continuum geometry in the Regge
calculus.Comment: 11 pages, uuencoded revtex w/ embedded ps figure. Replaces a
submission which had corrupted ps fil
New Vector-Like Fermions and Flavor Physics
We study renormalizable extensions of the standard model that contain
vector-like fermions in a (single) complex representation of the standard model
gauge group. There are 11 models where the vector-like fermions Yukawa couple
to the standard model fermions via the Higgs field. These models do not
introduce additional fine- tunings. They can lead to, and are constrained by, a
number of different flavor- changing processes involving leptons and quarks, as
well as direct searches. An interesting feature of the models with strongly
interacting vector-like fermions is that constraints from neutral meson mixings
(apart from CP violation in neutral kaon mixing) are not sensitive to higher
scales than other flavor-changing neutral-current processes. We identify order
1/(4 pi M)^2 (where M is the vector-like fermion mass) one-loop contributions
to the coefficients of the four-quark operators for meson mixing, that are not
suppressed by standard model quark masses and/or mixing angles.Comment: 25 pages, 3 figures, several issues are added, accepted in JHE
Measures of metacognition on signal-detection theoretic models
Analysing metacognition, specifically knowledge of accuracy of internal perceptual,
memorial or other knowledge states, is vital for many strands of psychology, including
determining the accuracy of feelings of knowing, and discriminating conscious from
unconscious cognition. Quantifying metacognitive sensitivity is however more challenging
than quantifying basic stimulus sensitivity. Under popular signal detection theory (SDT)
models for stimulus classification tasks, approaches based on type II receiver-operator
characteristic (ROC) curves or type II d-prime risk confounding metacognition with
response biases in either the type I (classification) or type II (metacognitive) tasks. A new
approach introduces meta-dâ˛: the type I d-prime that would have led to the observed type
II data had the subject used all the type I information. Here we (i) further establish the
inconsistency of the type II d-prime and ROC approaches with new explicit analyses of
the standard SDT model, and (ii) analyse, for the first time, the behaviour of meta-dâ˛
under non-trivial scenarios, such as when metacognitive judgments utilize enhanced or
degraded versions of the type I evidence. Analytically, meta-dⲠvalues typically reflect the
underlying model well, and are stable under changes in decision criteria; however, in
relatively extreme cases meta-dⲠcan become unstable. We explore bias and variance of
in-sample measurements of meta-dⲠand supply MATLAB code for estimation in general
cases. Our results support meta-dⲠas a useful measure of metacognition, and provide
rigorous methodology for its application. Our recommendations are useful for any
researchers interested in assessing metacognitive accuracy
Comment on from Exclusive Semileptonic B and D Decays
The prospects for determining from exclusive B semileptonic decay
are discussed. The double ratio of form factors is calculated using chiral perturbation theory.
Its deviation from unity due to contributions that are non-analytic in the
symmetry breaking parameters is very small. Combining experimental data
obtainable from (B->rho l nu), (B->K* l l) and (D->rho l nu) can lead to a
model independent determination of with an uncertainty from theory
of about 10%.Comment: 14 pages, 3 figs, minor typos corrected, to appear in Phys. Lett.
Blind insight: metacognitive discrimination despite chance task performance
Blindsight and other examples of unconscious knowledge and perception demonstrate dissociations between
judgment accuracy and metacognition: Studies reveal that participantsâ judgment accuracy can be above chance
while their confidence ratings fail to discriminate right from wrong answers. Here, we demonstrated the opposite
dissociation: a reliable relationship between confidence and judgment accuracy (demonstrating metacognition) despite judgment accuracy being no better than chance. We evaluated the judgments of 450 participants who completed an AGL task. For each trial, participants decided whether a stimulus conformed to a given set of rules and rated their confidence in that judgment. We identified participants who performed at chance on the discrimination task, utilizing a subset of their responses, and then assessed the accuracy and the confidence-accuracy relationship of their remaining
responses. Analyses revealed above-chance metacognition among participants who did not exhibit decision accuracy.
This important new phenomenon, which we term blind insight, poses critical challenges to prevailing models of metacognition grounded in signal detection theory
Current and voltage based bit errors and their combined mitigation for the Kirchhoff-law-Johnson-noise secure key exchange
We classify and analyze bit errors in the current measurement mode of the
Kirchhoff-law-Johnson-noise (KLJN) key distribution. The error probability
decays exponentially with increasing bit exchange period and fixed bandwidth,
which is similar to the error probability decay in the voltage measurement
mode. We also analyze the combination of voltage and current modes for error
removal. In this combination method, the error probability is still an
exponential function that decays with the duration of the bit exchange period,
but it has superior fidelity to the former schemes.Comment: 9 pages, accepted for publication in Journal of Computational
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