Shape versus Volume: Making Large Flat Extra Dimensions Invisible

Much recent attention has focused on theories with large extra compactified dimensions. However, while the phenomenological implications of the volume moduli associated with such compactifications are well understood, relatively little attention has been devoted to the shape moduli. In this paper, we show that the shape moduli have a dramatic effect on the corresponding Kaluza-Klein spectra: they change the mass gap, induce level crossings, and can even be used to interpolate between theories with different numbers of compactified dimensions. Furthermore, we show that in certain cases it is possible to maintain the ratio between the higher-dimensional and four-dimensional Planck scales while simultaneously increasing the Kaluza-Klein graviton mass gap by an arbitrarily large factor. This mechanism can therefore be used to alleviate (or perhaps even eliminate) many of the experimental bounds on theories with large extra spacetime dimensions.Comment: 9 pages, LaTeX, 5 figure

Kaluza-Klein States versus Winding States: Can Both Be Above the String Scale?

When closed strings propagate in extra compactified dimensions, a rich spectrum of Kaluza-Klein states and winding states emerges. Since the masses of Kaluza-Klein states and winding states play a reciprocal role, it is often believed that either the lightest Kaluza-Klein states or the lightest winding states must be at or below the string scale. In this paper, we demonstrate that this conclusion is no longer true for compactifications with non-trivial shape moduli. Specifically, we demonstrate that toroidal compactifications exist for which all Kaluza-Klein states as well as all winding states are heavier than the string scale. This observation could have important phenomenological implications for theories with reduced string scales, suggesting that it is possible to cross the string scale without detecting any states associated with spacetime compactification.Comment: 8 pages, LaTeX, no figure

Higgs Descendants

We define a Higgs descendant $\chi$ to be a particle beyond the standard model whose mass arises predominantly from the vacuum expectation value of the Higgs boson. Higgs descendants arise naturally from new physics whose intrinsic mass scale is unrelated to the electroweak scale. The coupling of $\chi$ to the Higgs boson is fixed by the mass and spin of $\chi$, yielding a highly predictive setup in which there may be substantial modifications to the properties of the Higgs boson. For example, if the decay of the Higgs boson to $\chi$ is kinematically allowed, then this branching ratio is largely determined. Depending on the stability of $\chi$, Higgs decays may result in a variety of possible visible or invisible final states. Alternatively, loops of $\chi$ may affect Higgs boson production or its decays to standard model particles. If $\chi$ is stable dark matter, then the mandatory coupling between $\chi$ and the Higgs boson gives a lower bound on the direct detection cross section as a function of the $\chi$ mass. We also present a number of explicit models which are examples of Higgs descendants. Finally, we comment on Higgs descendants in the context of the excesses near 125 GeV recently observed at ATLAS and CMS.Comment: 9 pages, 7 figures; version to appear in Phys. Rev. D; v3 typos correcte

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-d′: 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-d′ under non-trivial scenarios, such as when metacognitive judgments utilize enhanced or degraded versions of the type I evidence. Analytically, meta-d′ values typically reflect the underlying model well, and are stable under changes in decision criteria; however, in relatively extreme cases meta-d′ can become unstable. We explore bias and variance of in-sample measurements of meta-d′ and supply MATLAB code for estimation in general cases. Our results support meta-d′ as a useful measure of metacognition, and provide rigorous methodology for its application. Our recommendations are useful for any researchers interested in assessing metacognitive accuracy

Probing a Secluded U(1) at B-factories

A secluded U(1) gauge field, kinetically mixed with Standard Model hypercharge, provides a `portal' mediating interactions with a hidden sector at the renormalizable level, as recently exploited in the context of WIMP dark matter. The secluded U(1) symmetry-breaking scale may naturally be suppressed relative to the weak scale, and so this sector is efficiently probed by medium energy electron-positron colliders. We study the collider signatures of the minimal secluded U(1) model, focusing on the reach of B-factory experiments such as BaBar and BELLE. In particular, we show that Higgs-strahlung in the secluded sector can lead to multi-lepton signatures which probe the natural range for the kinetic mixing angle of 10^(-2)-10^(-3) over a large portion of the kinematically accessible parameter space.Comment: 14 pages, 3 figure

CP Violation from 5-dimensional QED

It has been shown that QED in (1+4)-dimensional space-time, with the fifth dimension compactified on a circle, leads to CP violation (CPV). Depending on fermionic boundary conditions, CPV may be either explicit (through the Scherk--Schwarz mechanism), or spontaneous (via the Hosotani mechanism). The fifth component of the gauge field acquires (at the one-loop level) a non-zero vacuum expectation value. In the presence of two fermionic fields, this leads to spontaneous CPV in the case of CP-symmetric boundary conditions. Phenomenological consequences are illustrated by a calculation of the electric dipole moment for the fermionic zero-modes.Comment: 11 pages, 2 figure

Shadows of the Planck Scale: The Changing Face of Compactification Geometry

By studying the effects of the shape moduli associated with toroidal compactifications, we demonstrate that Planck-sized extra dimensions can cast significant ``shadows'' over low-energy physics. These shadows can greatly distort our perceptions of the compactification geometry associated with large extra dimensions, and place a fundamental limit on our ability to probe the geometry of compactification simply by measuring Kaluza-Klein states. We also discuss the interpretation of compactification radii and hierarchies in the context of geometries with non-trivial shape moduli. One of the main results of this paper is that compactification geometry is effectively renormalized as a function of energy scale, with ``renormalization group equations'' describing the ``flow'' of geometric parameters such as compactification radii and shape angles as functions of energy.Comment: 7 pages, LaTeX, 2 figure

Dark Matter and Dark Forces from a supersymmetric hidden sector

We show that supersymmetric "Dark Force" models with gravity mediation are viable. To this end, we analyse a simple string-inspired supersymmetric hidden sector model that interacts with the visible sector via kinetic mixing of a light Abelian gauge boson with the hypercharge. We include all induced interactions with the visible sector such as neutralino mass mixing and the Higgs portal term. We perform a detailed parameter space scan comparing the produced dark matter relic abundance and direct detection cross sections to current experiments.Comment: 40 pages, 11 figures comprising 21 plots. 4Mb total size. v2: figures and references updated; typos removed; some extra explanations added. Matches version published in PR

The value of Bayesian statistics for assessing credible evidence of animal sentience

Determining what constitutes practically relevant, statistically significant evidence for animal sentience, under the precautionary principle, could be enhanced through Bayesian statistics. A Bayesian approach allows the incorporation of multiple evidence sources through prior probabilities, the tracking of changing evidence across time, and a principled means of adjusting evidentiary bars via Bayes factors

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 participants’ 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