An Analysis of Some Refractive Error Trends in US Air Force Pilots and Navigators

Refractive error trends with age in US Air Force pilots and navigator

Best practice for motor imagery: a systematic literature review on motor imagery training elements in five different disciplines

<p>Abstract</p> <p>Background</p> <p>The literature suggests a beneficial effect of motor imagery (MI) if combined with physical practice, but detailed descriptions of MI training session (MITS) elements and temporal parameters are lacking. The aim of this review was to identify the characteristics of a successful MITS and compare these for different disciplines, MI session types, task focus, age, gender and MI modification during intervention.</p> <p>Methods</p> <p>An extended systematic literature search using 24 databases was performed for five disciplines: Education, Medicine, Music, Psychology and Sports. References that described an MI intervention that focused on motor skills, performance or strength improvement were included. Information describing 17 MITS elements was extracted based on the PETTLEP (physical, environment, timing, task, learning, emotion, perspective) approach. Seven elements describing the MITS temporal parameters were calculated: study duration, intervention duration, MITS duration, total MITS count, MITS per week, MI trials per MITS and total MI training time.</p> <p>Results</p> <p>Both independent reviewers found 96% congruity, which was tested on a random sample of 20% of all references. After selection, 133 studies reporting 141 MI interventions were included. The locations of the MITS and position of the participants during MI were task-specific. Participants received acoustic detailed MI instructions, which were mostly standardised and live. During MI practice, participants kept their eyes closed. MI training was performed from an internal perspective with a kinaesthetic mode. Changes in MI content, duration and dosage were reported in 31 MI interventions. Familiarisation sessions before the start of the MI intervention were mentioned in 17 reports. MI interventions focused with decreasing relevance on motor-, cognitive- and strength-focused tasks. Average study intervention lasted 34 days, with participants practicing MI on average three times per week for 17 minutes, with 34 MI trials. Average total MI time was 178 minutes including 13 MITS. Reporting rate varied between 25.5% and 95.5%.</p> <p>Conclusions</p> <p>MITS elements of successful interventions were individual, supervised and non-directed sessions, added after physical practice. Successful design characteristics were dominant in the Psychology literature, in interventions focusing on motor and strength-related tasks, in interventions with participants aged 20 to 29 years old, and in MI interventions including participants of both genders. Systematic searching of the MI literature was constrained by the lack of a defined MeSH term.</p

A Next-Generation Liquid Xenon Observatory for Dark Matter and Neutrino Physics

The nature of dark matter and properties of neutrinos are among the mostpressing issues in contemporary particle physics. The dual-phase xenontime-projection chamber is the leading technology to cover the availableparameter space for Weakly Interacting Massive Particles (WIMPs), whilefeaturing extensive sensitivity to many alternative dark matter candidates.These detectors can also study neutrinos through neutrinoless double-beta decayand through a variety of astrophysical sources. A next-generation xenon-baseddetector will therefore be a true multi-purpose observatory to significantlyadvance particle physics, nuclear physics, astrophysics, solar physics, andcosmology. This review article presents the science cases for such a detector.<br

A next-generation liquid xenon observatory for dark matter and neutrino physics

The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector

Fingerprints of High Energy Physics Beyond Colliders

Hints of new physics Beyond the Standard Model (BSM) range from dark matter and the strong CP problem to grand unification and the origin of the matter-antimatter asymmetry. Historically, colliders have been the principal engines of discovery, but with no new physics discovered at the Large Hadron Collider (LHC) except the expected Higgs, and decades until the next collider may be built, a few questions naturally arise: What if there is no new physics until very high scales? How can we discover high energy physics which may hide at energies far above the reach of next-generation colliders? This dissertation focuses on answering these questions in three parts.Part (I) discusses early-Universe cosmology and model building guided by hints from Standard Model parameters as measured by the LHC, particularly Higgs Parity phenomenology. Higgs Parity is a two Higgs doublet mirror extension of the Standard Model that provides an explanation for the peculiar vanishing of the Higgs quartic coupling at very high energies due to quantum corrections from Standard Model particles. Higgs Parity comes in many rich variations, but all share the key mechanism of making the Standard Model Higgs a pseudo- Goldstone boson at the Higgs quartic scale, thereby giving the Standard Model Higgs a vanishing mass and hence vanishing quartic coupling at this scale. The phenomenology of these variations of Higgs Parity are discussed in Chapters 1-3. We find that Higgs Parity admits a natural dark matter candidate in the mirror electron, which can be detected from its scattering with protons due to unavoidable kinetic mixing between the mirror photon and our photon (Ch. 1); generation of dark radiation from the decay of mirror glueballs that can be detected by CMB Stage IV (Ch. 2); and generation of our observed matter-antimatter asymmetry via leptogenesis associated with warm and hot sterile neutrino dark matter (Ch. 3). In all Higgs Parity models, future precision measurements of the top quark mass, strong coupling constant, and Higgs mass will hone in on the precise scale at which the Higgs quartic vanishes and hence predict the aforementioned signals. The reader will thus find signal plots in this part of the dissertation that indicate how the various Higgs Parity signals change as a function of these Standard Model parameters. Finally, Part (I) concludes with discussion on physics inspired by, or in similar spirit to, Higgs Parity: general cosmological constraints on sterile neutrino dark matter in left-right symmetric theories (Ch. 4) and Higgsino dark matter in Intermediate Scale Supersymmetry models (Ch. 5). Part (II) focuses on astrophysical probes of BSM physics at energies and couplings unreach- able at current colliders. We first turn to Nature’s own accelerator, supernova shocks, to search for undiscovered CHarged Massive Particles (CHAMPs) that may make up a compo- nent of dark matter (Ch 6). Such undiscovered particles with minuscule electric charges are well motivated in particle physics (kinetic mixing between the photon and a dark photon), and in cosmology. For example, a particle with electric charge about one trillionth that of an electron can be thermally produced via freeze-in in the early Universe with a relic abundance matching that of the dark matter we see today. Typically, such small electrically charged particles are too weakly interacting or too massive to be discovered at colliders. However, the plasma of the interstellar medium provides a unique laboratory to search for such particles. We trace the dynamics of CHAMPs in the Milky Way and their acceleration by supernova shocks and find this Fermi-accelerated component of dark matter can provide unique experimental signatures typically absent from dark matter moving at virial speeds, such as from their Cherenkov light produced in water or ice. From this analysis, we disfavor CHAMP dark matter with mass less than 10^5 GeV and charge greater than 10^-9 e. In the following chapter, we examine how Magnetic White Dwarfs (MWDs) can generate leading constraints on the coupling of low mass axions to photons (Ch. 7). Axions — well- motivated particles that arise in many theories beyond the Standard Model, such as from the breaking of a global U (1) or from string compactifications — are extremely weakly coupled to Standard Model particles and are thus difficult to probe. However MWDs possess enormous static (B ? 100 MG) and large scale (coherence ? 1R?) magnetic fields that can provide another unique laboratory to test the axion-modified Maxwell equations. In particular, we calculate the axion-induced polarization of MWD starlight arising from the conversion of photons leaving the MWD atmosphere and converting to axions in the MWD magnetosphere. Taking into account astrophysical polarizations and uncertainties, we exclude, at 2σ, axion- photon couplings greater than 5.4 × 10^−12 GeV^−1 for axion masses below 3 × 10^−7 eV. Part (III), which concludes this dissertation, considers other novel signals of high energy physics from the sky, namely gravitational waves. Gravitational waves provide a particularly promising way of studying ultra-high energy physics since gravitational waves produced in the early Universe can travel unimpeded through the primordial plasma and be detected today, carrying information about the BSM physics that sourced them. Moreover, it is often the case that the higher the scale of the BSM physics, the stronger the gravitational wave signal. In contrast, with state-of-the-art technology, a collider far larger than the size of the solar system is needed to reach energies approaching grand unification scales. We first study the gravitational wave signals from a stochastic cosmic string background experiencing an exotic equation of state in the early Universe known as kination, which can arise from the rotation of an axion field (Ch. 8). We find that the change in the expansion rate of the Universe due to the rotation of the axion field imprints a unique triangular peaked gravitational wave spectrum that encodes enformation about the duration and energy scale of the kination era. We determine the parameter space where current and future gravitational wave detectors can distinguish the kination cosmology from the standard ΛCDM cosmology. In the final chapter (Ch. 9), we investigate more generally the gravitational wave signals from hybrid topological defects such as cosmic strings bounded by magnetic monopoles or domain walls bounded by cosmic strings. We show that many grand unification paths generate hybrid topological defects in the early Universe that decay via gravitational waves from the ‘eating’ of one defect by the other via the conversion of its rest mass into the other defect’s kinetic energy. We calculate these gravitational wave ‘gastronomy’ signals and show how observation of these relic gravitational wave signatures can be used to distinguish many unification paths, providing extraordinary insight into ultra-high energy physics

Dark Radiation Constraints on Heavy QCD Axions

The naturalness problem of PQ symmetry motivates study of the heavy QCD axion, with masses $m_a >$ 1 MeV generated at scales above the QCD scale, and low values of the PQ symmetry breaking scale, $f_a$. We compute the abundance of such axions in a model-independent way, assuming only that they freeze-out after reheating from inflation, and are not subsequently diluted by new physics. If these axions decay between neutrino decoupling and the last scatter era of the Cosmic Microwave Background (CMB), they dilute the neutrinos and their abundance is constrained by CMB measurements of the energy density in dark radiation, $N_{\rm eff}$. We accurately compute this bound using a numerical code to evolve the axion momentum distribution, including many key processes and effects previously ignored. We assume that the only relevant axion decays are to final states involving Standard Model particles. We determine regions of $(m_a, f_a)$ that will give a signal in $N_{\rm eff}$ at CMB Stage 4 experiments. We similarly compute the $N_{\rm eff}$ bound and CMB Stage 4 signal for heavy axions that can decay to light mirror photons. Finally, we compute the bounds on heavy axions with mass below 1 MeV that decay after the era of CMB last scatter, from their contribution to cold or hot dark matter or $N_{\rm eff}$ at this era

A Heavy QCD Axion and the Mirror World

We study the mirror world with dark matter arising from the thermal freeze-out of the lightest, stable mirror particle -- the mirror electron. The dark matter abundance is achieved for mirror electrons of mass 225 GeV, fixing the mirror electroweak scale near $10^8$ GeV. This highly predictive scenario is realized by an axion that acts as a portal between the two sectors through its coupling to the QCD and mirror QCD sectors. The axion is more massive than the standard QCD axion due to additional contributions from mirror strong dynamics. Still, the strong CP problem is solved by this "heavy" axion due to the alignment of the QCD and mirror QCD potentials. Mirror entropy is transferred into the Standard Model sector via the axion portal, which alleviates overproduction of dark radiation from mirror glueball decays. This mirror scenario has a variety of signals: (1) primordial gravitational waves from the first-order mirror QCD phase transition occurring at a temperature near 35 GeV, (2) effects on large-scale structure from dark matter self-interactions from mirror QED, (3) dark radiation affecting the cosmic microwave background, and (4) the rare kaon decay, $K^+ \rightarrow (\pi^+ + \rm{axion})$. The first two signals do not depend on any fundamental free parameters of the theory while the latter two depend on a single free parameter, the axion decay constant